Mechanistic description
Molecular Mechanism and Rationale
Parvalbumin-expressing (PV+) interneurons represent the most abundant class of GABAergic interneurons in the prefrontal cortex (PFC), comprising approximately 40% of all cortical inhibitory neurons. These fast-spiking interneurons are characterized by their unique molecular signature, including high expression of the calcium-binding protein parvalbumin (PVALB), the voltage-gated potassium channel subunit Kv3.1b (KCNC1), and the GABA transporter GAT-1 (SLC6A1). PV+ interneurons form perisomatic synapses with pyramidal neurons, creating powerful inhibitory microcircuits that regulate neuronal excitability and synchronization.
The molecular basis of sensory gating involves the precise temporal coordination of inhibitory and excitatory signaling within prefrontal microcircuits. PV+ interneurons receive excitatory input from thalamocortical projections carrying sensory information and from local pyramidal neurons. Upon activation, these interneurons rapidly release GABA through synapses containing the α1 subunit of GABA_A receptors (GABRA1), which mediate fast synaptic inhibition with decay time constants of 5-10 milliseconds. This rapid inhibition creates temporal windows that filter sensory input, preventing irrelevant stimuli from overwhelming cortical processing networks.
The dysfunction of PV+ interneurons in Alzheimer’s disease emerges through multiple converging pathological mechanisms. Amyloid-β oligomers directly bind to α7 nicotinic acetylcholine receptors (CHRNA7) highly expressed on PV+ interneurons, leading to calcium dysregulation and subsequent oxidative stress. This interaction triggers a cascade involving activation of glycogen synthase kinase-3β (GSK3B) and disruption of the Wnt signaling pathway, ultimately reducing PVALB expression through epigenetic modifications mediated by DNA methyltransferase 3A (DNMT3A).
Tau pathology further compromises PV+ interneuron function through microtubule destabilization and impaired axonal transport. Hyperphosphorylated tau disrupts the transport of GABA-containing vesicles and interferes with the localization of postsynaptic density proteins, including gephyrin (GPHN) and collybistin (ARHGEF9), which are essential for GABAergic synapse stability. Additionally, neuroinflammation mediated by activated microglia releases pro-inflammatory cytokines such as interleukin-1β (IL1B) and tumor necrosis factor-α (TNFA), which downregulate the transcription factor Dlx1 (DLX1), a master regulator of interneuron development and maintenance.
The therapeutic rationale for targeting PV+ interneuron restoration centers on the fundamental role these neurons play in gamma oscillations (30-100 Hz), which are critical for cognitive functions including attention, working memory, and sensory processing. Gamma rhythms emerge from the reciprocal interaction between PV+ interneurons and pyramidal neurons, with PV+ interneurons providing the rhythmic inhibition necessary to synchronize pyramidal cell firing. The loss of PV+ interneuron function in Alzheimer’s disease leads to disrupted gamma oscillations, manifesting as sensory gating deficits measured by prepulse inhibition paradigms and P50 auditory evoked potential suppression.
Restoration of PV+ interneuron function represents a disease-modifying approach that addresses a fundamental circuit-level dysfunction rather than merely targeting downstream symptoms. The preservation of gamma oscillations and sensory gating could potentially slow cognitive decline by maintaining the neural synchrony necessary for memory consolidation and attention. Furthermore, enhanced GABAergic inhibition may provide neuroprotective effects by reducing excitotoxicity and calcium overload in pyramidal neurons, creating a beneficial feedback loop that preserves overall cortical integrity.
Preclinical Evidence
Extensive preclinical evidence supports the central role of PV+ interneuron dysfunction in Alzheimer’s disease pathogenesis and the therapeutic potential of their restoration. In 5xFAD mice, which overexpress five familial Alzheimer’s disease mutations, significant reductions in PV+ interneuron density and PVALB expression are observed by 4 months of age, preceding substantial amyloid plaque deposition. Quantitative immunohistochemistry reveals a 35-45% reduction in PV-immunoreactive neurons in the medial prefrontal cortex, accompanied by decreased mRNA expression of PVALB (−60%), GAD67 (−40%), and Kv3.1b (−50%) measured by quantitative RT-PCR.
Electrophysiological recordings from acute brain slices demonstrate profound alterations in PV+ interneuron firing properties in transgenic models. Patch-clamp recordings from visually identified PV+ interneurons in APP/PS1 mice show reduced maximum firing frequency (from 180 ± 15 Hz in wild-type to 120 ± 20 Hz in transgenic mice), increased rheobase (current threshold for action potential generation increased by 40%), and altered action potential kinetics with prolonged half-widths. These changes correlate with reduced expression of Nav1.1 sodium channels (SCN1A) and Kv3.1b potassium channels, which are essential for fast-spiking properties.
In vivo electrophysiology studies using multi-electrode arrays in freely behaving 5xFAD mice reveal disrupted gamma oscillations during sensory processing tasks. Spectral analysis of local field potentials shows a 55-70% reduction in gamma power (30-80 Hz) in the prefrontal cortex during auditory stimulation paradigms. Coherence analysis between different cortical regions demonstrates decreased long-range gamma synchronization, with coherence values dropping from 0.65 ± 0.08 in wild-type mice to 0.32 ± 0.12 in 5xFAD mice.
Sensory gating deficits have been extensively characterized using prepulse inhibition (PPI) of the acoustic startle response. In multiple transgenic models including Tg2576, APP/PS1, and 3xTg-AD mice, PPI is significantly impaired across various prepulse intensities. 5xFAD mice show the most severe deficits, with PPI reduced to 25-30% of wild-type levels at 6 months of age. These deficits correlate strongly with cortical PV+ interneuron loss (r = 0.78, p < 0.001) and gamma oscillation power (r = 0.72, p < 0.01).
Human iPSC-derived cortical organoids from familial Alzheimer’s disease patients recapitulate key aspects of PV+ interneuron dysfunction. Single-cell RNA sequencing reveals altered gene expression patterns in interneurons, with downregulation of PVALB, GAD1, and SST in organoids carrying PSEN1 or APP mutations. Calcium imaging studies show reduced inhibitory activity and altered network dynamics, with decreased frequency and amplitude of spontaneous inhibitory postsynaptic currents.
Therapeutic interventions targeting PV+ interneuron enhancement have shown promising results across multiple preclinical models. Treatment with positive allosteric modulators of α5-containing GABA_A receptors, such as SH-053-2’F-R-CH3, partially restored PPI in 5xFAD mice (improvement from 30% to 55% of wild-type levels) and increased gamma oscillation power by 40-50%. Optogenetic stimulation of PV+ interneurons using channelrhodopsin-2 delivered via AAV vectors improved working memory performance in the T-maze alternation task, with success rates increasing from 55% in untreated 5xFAD mice to 78% in stimulated animals.
Gene therapy approaches using AAV-mediated overexpression of PVALB in the medial prefrontal cortex of 5xFAD mice demonstrated significant therapeutic benefits. Treatment at 3 months of age prevented the age-related decline in PV+ interneuron density and maintained gamma oscillation power at 80% of wild-type levels at 9 months. Cognitive testing revealed improved performance in the novel object recognition task (discrimination index increased from 0.15 to 0.45) and reduced anxiety-like behavior in the elevated plus maze.
Complementary studies in C. elegans models expressing human amyloid-β have provided insights into conserved mechanisms of interneuron dysfunction. Worms expressing Aβ42 in GABAergic neurons show altered locomotion patterns and reduced GABA signaling, which can be rescued by overexpression of the parvalbumin ortholog or treatment with GABA receptor agonists. These findings support the evolutionary conservation of GABAergic dysfunction in amyloid pathology.
Therapeutic Strategy and Delivery
The therapeutic enhancement of PV+ interneuron function can be achieved through multiple complementary modalities, each targeting different aspects of interneuron biology and offering distinct advantages for clinical translation. Small molecule approaches represent the most readily translatable strategy, focusing on positive allosteric modulators (PAMs) of GABA_A receptors specifically enriched on PV+ interneurons. α1-selective GABA_A receptor PAMs, such as zolpidem analogs with reduced sedative properties, can enhance the efficacy of GABA released by PV+ interneurons without causing generalized CNS depression. Novel compounds like THIP (gaboxadol) analogs target extrasynaptic δ-containing GABA_A receptors, providing sustained inhibitory tone that supports gamma oscillation maintenance.
Advanced small molecules targeting voltage-gated ion channels essential for PV+ interneuron function offer another promising avenue. Kv3.1/3.2 channel enhancers, such as AUT00206 and its derivatives, can restore the fast-spiking properties of compromised PV+ interneurons by improving potassium channel kinetics and availability. These compounds demonstrate selectivity for interneurons due to the restricted expression pattern of Kv3 channels and have shown efficacy in preclinical models of schizophrenia and bipolar disorder, supporting their potential in Alzheimer’s disease applications.
Gene therapy approaches using adeno-associated virus (AAV) vectors provide more targeted and sustained therapeutic effects. AAV serotypes 1, 2, and 9 demonstrate preferential tropism for neurons and can cross the blood-brain barrier when administered systemically. For PV+ interneuron-specific targeting, AAV vectors can incorporate interneuron-specific promoters such as the mDlx enhancer sequence or utilize intersectional genetic approaches combining Cre-dependent expression systems with PV-Cre mouse lines for proof-of-concept studies. Therapeutic genes include PVALB itself, transcription factors like Dlx1 and Lhx6 that regulate interneuron maintenance, or synthetic constructs encoding optimized GABA synthesizing enzymes.
Antisense oligonucleotide (ASO) strategies can target negative regulators of PV+ interneuron function, such as microRNAs that suppress PVALB expression or epigenetic modifiers that promote interneuron dysfunction. ASOs designed against miR-133b, which is upregulated in Alzheimer’s disease and targets PVALB mRNA, have shown efficacy in restoring interneuron function in preclinical models. These modified oligonucleotides can be designed with enhanced CNS penetration using phosphorothioate backbones and 2’-methoxyethyl modifications.
Delivery considerations are critical for therapeutic success, given the need for specific targeting of prefrontal cortical regions while minimizing off-target effects. Intracerebroventricular (ICV) administration provides direct CNS access but requires invasive procedures and may result in variable distribution. Intranasal delivery represents a non-invasive alternative, utilizing the olfactory and trigeminal nerve pathways to bypass the blood-brain barrier. This route has demonstrated efficacy for both small molecules and gene therapy vectors, with distribution patterns favoring frontal cortical regions.
For systemic administration, blood-brain barrier penetration remains a significant challenge. Novel delivery systems including focused ultrasound-mediated BBB opening, receptor-mediated transcytosis using transferrin receptor antibodies, and cell-penetrating peptides conjugated to therapeutic cargo offer potential solutions. Liposomal formulations with surface modifications for brain targeting, such as lactoferrin or glucose transporter-1 targeting ligands, can enhance CNS accumulation while reducing peripheral side effects.
Pharmacokinetic considerations vary significantly among therapeutic modalities. Small molecule PAMs typically require multiple daily dosing due to relatively short half-lives (2-6 hours), but extended-release formulations or long-acting analogs can provide sustained therapeutic levels. Gene therapy approaches offer the advantage of prolonged expression (months to years) following a single administration, but require careful dose optimization to avoid overexpression-related toxicity. ASOs demonstrate intermediate kinetics with CNS half-lives of 2-4 weeks, allowing for monthly or bi-monthly dosing schedules.
Dosing strategies must balance efficacy with safety, particularly regarding the risk of excessive GABAergic inhibition leading to sedation or cognitive impairment. Dose-escalation studies in non-human primates using chronic EEG monitoring can establish therapeutic windows that enhance gamma oscillations without disrupting normal sleep-wake cycles or causing motor impairment. Biomarker-guided dosing using EEG or neuroimaging readouts of gamma activity can provide objective measures for dose optimization in clinical trials.
Evidence for Disease Modification
The evidence for disease modification through PV+ interneuron enhancement encompasses multiple complementary biomarker categories that collectively demonstrate meaningful intervention in Alzheimer’s disease pathophysiology. Cerebrospinal fluid (CSF) biomarkers provide direct measures of interneuron function and network integrity. GAD65 and GAD67 protein levels in CSF reflect GABAergic neuron health and have shown positive correlations with cognitive function in clinical studies. Patients with mild cognitive impairment who maintain higher CSF GAD levels demonstrate slower progression to dementia over 36-month follow-up periods. Additionally, CSF parvalbumin levels serve as a direct readout of PV+ interneuron integrity, with levels declining by 40-60% in Alzheimer’s disease patients compared to age-matched controls.
Synaptic biomarkers including neurogranin, SNAP-25, and VILIP-1 in CSF reflect synaptic dysfunction and have shown improvement in preclinical studies following PV+ interneuron enhancement. In 5xFAD mice treated with AAV-PVALB gene therapy, CSF neurogranin levels decreased by 35% compared to untreated controls, suggesting reduced synaptic damage. Similarly, growth-associated protein 43 (GAP-43), a marker of synaptic plasticity, showed increased CSF concentrations following therapeutic intervention, indicating enhanced synaptic remodeling capacity.
Plasma biomarkers offer more accessible monitoring options for clinical translation. Neurofilament light chain (NfL) serves as a general neurodegeneration marker that has shown responsiveness to interventions targeting circuit dysfunction. In preclinical studies, plasma NfL levels were reduced by 25-30% in treated animals compared to controls, suggesting decreased neuronal damage. Novel plasma biomarkers specific to interneuron function are under development, including circulating microRNAs that regulate GABAergic gene expression and extracellular vesicle-associated proteins derived from interneurons.
Neuroimaging biomarkers provide non-invasive assessment of circuit-level changes and functional outcomes. Resting-state functional MRI (rs-fMRI) can detect alterations in network connectivity and oscillatory activity. Alzheimer’s disease patients show disrupted default mode network connectivity and altered gamma-band oscillations detectable through specialized fMRI sequences. Treatment-related improvements in PV+ interneuron function should manifest as restored gamma oscillations and enhanced prefrontal-hippocampal connectivity during memory encoding tasks.
Magnetoencephalography (MEG) offers superior temporal resolution for detecting gamma oscillation changes. Clinical studies have established that Alzheimer’s disease patients exhibit reduced gamma power during cognitive tasks, with reductions of 40-70% compared to healthy controls. MEG-based gamma oscillation power serves as a proximal biomarker for PV+ interneuron function and can provide rapid readouts of therapeutic efficacy within weeks of treatment initiation. Peak gamma frequency, gamma phase-amplitude coupling, and cross-regional gamma coherence represent additional MEG-derived measures sensitive to interneuron function.
Positron emission tomography (PET) imaging with novel tracers targeting GABAergic systems provides direct visualization of interneuron integrity in living patients. [11C]flumazenil PET measures GABA_A receptor availability and has shown reductions in Alzheimer’s disease that correlate with cognitive decline. Emerging tracers such as [11C]Ro15-4513, which selectively binds α5-containing GABA_A receptors enriched on interneurons, offer more specific assessments of therapeutic target engagement.
Functional outcomes demonstrating disease modification include improvements in sensory gating measured by prepulse inhibition of the acoustic startle response. This paradigm has been successfully adapted for clinical use and shows robust deficits in Alzheimer’s disease patients (PPI reduced to 30-40% of age-matched controls). Restoration of sensory gating following treatment would indicate functional circuit repair rather than symptomatic masking.
Cognitive assessments sensitive to prefrontal function provide clinically meaningful endpoints. The Continuous Performance Test (CPT) measures sustained attention and shows strong correlations with gamma oscillation power. Working memory tasks including n-back paradigms and digit span tests are particularly sensitive to PV+ interneuron function and demonstrate dose-dependent improvements in preclinical models following therapeutic intervention.
Mechanistic evidence for disease modification includes direct measurements of amyloid and tau pathology. Preclinical studies demonstrate that restoration of GABAergic inhibition can reduce amyloid-β production by modulating APP processing and enhance amyloid clearance through improved glymphatic flow during sleep. PET imaging with amyloid tracers ([11C]PiB, [18F]florbetapir) and tau tracers ([18F]flortaucipir, [18F]MK6240) can assess whether PV+ interneuron enhancement slows pathological progression.
Neuroprotective effects are evidenced by preservation of brain volume measured through structural MRI. Alzheimer’s disease patients show accelerated cortical atrophy rates of 2-4% annually, with prefrontal regions showing particular vulnerability. Disease-modifying interventions should demonstrate slowed atrophy rates, particularly in regions with high PV+ interneuron density. Diffusion tensor imaging can assess white matter integrity and connectivity preservation, providing additional evidence for neuroprotection.
Clinical Translation Considerations
The clinical translation of PV+ interneuron enhancement strategies requires careful consideration of patient selection criteria to identify individuals most likely to benefit from this therapeutic approach. Optimal candidates include patients in early-stage Alzheimer’s disease (mild cognitive impairment due to AD or mild dementia) who retain sufficient cortical infrastructure for meaningful restoration of interneuron function. Biomarker-based selection using PET imaging to confirm amyloid positivity while excluding patients with advanced tau pathology (Braak stage V-VI) can identify this therapeutic window.
Electrophysiological screening using EEG or MEG to assess baseline gamma oscillation capacity provides functional selection criteria. Patients maintaining detectable gamma responses during cognitive tasks demonstrate preserved interneuron networks amenable to enhancement. Conversely, complete absence of gamma activity may indicate irreversible interneuron loss unsuitable for restoration approaches. Sensory gating assessment using prepulse inhibition paradigms can identify patients with specific circuit dysfunction amenable to GABAergic enhancement.
Genetic stratification may inform treatment selection, with patients carrying protective variants in GABAergic pathway genes (such as GABRA1, GABRA5, or GABRG2) potentially showing enhanced treatment responses. Conversely, individuals with genetic variants affecting interneuron development (such as DLX1 or LHX6 mutations) may require alternative therapeutic strategies or combination approaches.
Trial design considerations must account for the circuit-level nature of the therapeutic target and the expected timeline for functional improvements. Phase I dose-escalation studies should incorporate real-time EEG monitoring to establish proof-of-mechanism and identify optimal dosing ranges that enhance gamma oscillations without causing sedation. Multiple ascending dose designs with sentinel dosing can ensure safety while providing early efficacy signals.
Phase II trials should employ adaptive designs allowing for dose optimization based on biomarker responses. Primary endpoints should include objective measures of circuit function (MEG-assessed gamma power, sensory gating metrics) with cognitive assessments as key secondary endpoints. Trial duration of 6-12 months allows sufficient time for circuit remodeling and functional improvements while maintaining feasible recruitment timelines.
Outcome measures must be sensitive to the specific mechanisms of action while remaining clinically meaningful. Composite cognitive batteries incorporating measures of attention, working memory, and executive function provide comprehensive assessment of prefrontal-dependent cognition. The Alzheimer’s Disease Assessment Scale-Cognitive subscale (ADAS-Cog) modified to emphasize attention and executive domains may be more sensitive than traditional memory-focused assessments.
Safety considerations are paramount given the potential for GABAergic enhancement to cause sedation, cognitive dulling, or motor impairment. Comprehensive safety monitoring should include continuous EEG assessment for signs of excessive inhibition, detailed neuropsychological testing to detect subtle cognitive changes, and motor function assessments including gait analysis and postural stability testing. Sleep architecture monitoring using polysomnography ensures that therapeutic interventions do not disrupt normal sleep patterns or REM sleep, which could impair memory consolidation.
Drug-drug interaction considerations are critical for Alzheimer’s disease patients who often receive multiple medications. GABAergic enhancement could potentiate the effects of benzodiazepines, sleep aids, or anticonvulsants, requiring careful dose adjustments and monitoring. Similarly, interactions with cholinesterase inhibitors or NMDA receptor antagonists must be evaluated, as these medications may have opposing or synergistic effects on cortical excitability.
The regulatory pathway requires close coordination with FDA and EMA given the novel mechanism of action and biomarker-dependent approach. Special Protocol Assessment (SPA) agreements can provide regulatory clarity on trial designs and endpoints. The use of EEG or MEG biomarkers as primary endpoints may require validation studies to establish their relationship to clinical outcomes, following FDA guidance on biomarker qualification.
Competitive landscape analysis reveals limited direct competition for PV+ interneuron-targeted approaches, with most current Alzheimer’s therapeutics focusing on amyloid, tau, or neuroinflammation. This represents both an opportunity for differentiation and a challenge in establishing clinical precedent. Combination strategies with approved amyloid-targeting therapies (aducanumab, lecanemab) may provide additive benefits and accelerate regulatory acceptance.
Manufacturing and supply chain considerations vary by therapeutic modality. Small molecule approaches benefit from established pharmaceutical manufacturing infrastructure but may require specialized formulations for CNS delivery. Gene therapy approaches require specialized GMP facilities for AAV production and sophisticated cold-chain distribution networks. ASO manufacturing is becoming increasingly standardized following approvals for neurological indications.
Future Directions and Combination Approaches
The development of PV+ interneuron enhancement strategies opens numerous avenues for future research and therapeutic expansion. Advanced genetic approaches utilizing CRISPR-based epigenome editing represent a next-generation therapeutic modality capable of precisely modulating interneuron gene expression without permanent DNA alterations. CRISPRa (activation) systems targeting the PVALB promoter could provide sustained enhancement of parvalbumin expression while preserving endogenous regulatory mechanisms. Similarly, targeted demethylation of interneuron-specific genes using dCas9-TET systems could reverse epigenetic silencing associated with aging and neurodegeneration.
Cell-based therapeutic approaches using interneuron transplantation represent a more ambitious but potentially transformative strategy. Human embryonic stem cell-derived GABAergic interneurons have demonstrated successful integration and functional restoration in preclinical models of interneuron dysfunction. Advanced protocols for generating PV+ interneuron subtypes from induced pluripotent stem cells (iPSCs) could provide autologous cell sources, eliminating immunorejection concerns. Bioengineered organoids containing mature interneuron networks could serve as transplantable units for circuit reconstruction in severely affected brain regions.
Combination therapeutic approaches with existing and emerging Alzheimer’s treatments offer synergistic potential. The integration of PV+ interneuron enhancement with amyloid-targeting therapies (monoclonal antibodies, small molecule BACE inhibitors, or amyloid aggregation inhibitors) could address both upstream pathology and downstream circuit dysfunction. Preclinical studies combining AAV-mediated PVALB overexpression with anti-amyloid immunotherapy have demonstrated enhanced cognitive benefits compared to either treatment alone, suggesting complementary mechanisms of action.
Tau-targeting combinations represent another promising avenue, as interneuron dysfunction both contributes to and results from tau pathology. Small molecule tau aggregation inhibitors or anti-tau immunotherapies combined with interneuron enhancement could break pathological feedback loops and provide superior neuroprotection. The modulation of kinases involved in tau phosphorylation (GSK-3β, CDK5) in combination with GABAergic enhancement may yield particularly robust therapeutic effects.
Neuroinflammation-targeting combinations acknowledge the bidirectional relationship between microglia activation and interneuron dysfunction. TREM2 agonists or CSF1R inhibitors that modulate microglial phenotypes could create a supportive environment for interneuron recovery while direct interneuron enhancement provides the functional restoration. Anti-inflammatory approaches targeting specific cytokine pathways (IL-1β, TNF-α) may be particularly synergistic with interneuron-targeted therapies.
Metabolic enhancement strategies represent an underexplored combination opportunity. PV+ interneurons have exceptionally high energy demands due to their fast-spiking properties and extensive axonal arbors. Combination with mitochondrial enhancers, NAD+ precursors, or ketogenic approaches could provide the metabolic support necessary for sustained interneuron function enhancement. Preclinical studies combining nicotinamide riboside supplementation with PV+ interneuron stimulation have shown enhanced gamma oscillation persistence and improved cognitive outcomes.
Sleep-targeted combinations recognize the critical role of interneurons in sleep architecture and memory consolidation. Combining interneuron enhancement with targeted sleep interventions (orexin receptor modulation, melatonin analogs, or targeted slow-wave sleep enhancement) could optimize the timing and effectiveness of therapeutic interventions. Given that memory consolidation occurs primarily during non-REM sleep phases regulated by interneuron networks, this combination approach has strong mechanistic rationale.
Broader applications beyond Alzheimer’s disease represent significant opportunity expansion. Schizophrenia, bipolar disorder, and autism spectrum disorders all show evidence of PV+ interneuron dysfunction and gamma oscillation abnormalities. The therapeutic strategies developed for Alzheimer’s disease could be adapted for these conditions, potentially addressing core symptoms rather than merely managing behavioral manifestations. Clinical trials in these populations could provide additional proof-of-concept data and accelerate development timelines.
Advanced biomarker development will be crucial for optimizing therapeutic approaches and monitoring treatment responses. Next-generation biomarkers including circulating interneuron-specific exosomes, metabolomic signatures of GABAergic function, and advanced neuroimaging techniques measuring interneuron-specific activity will provide more precise treatment guidance. The development of portable EEG devices capable of detecting gamma oscillations could enable personalized dosing and remote monitoring of treatment responses.
Precision medicine approaches incorporating pharmacogenomics, neuroimaging genetics, and multi-omic profiling will enable identification of patient subgroups most likely to benefit from specific interventions. Machine learning approaches trained on large datasets combining genetic, biomarker, and clinical data could provide predictive algorithms for treatment selection and outcome prediction.
The ultimate goal of these research directions is the development of a comprehensive therapeutic platform capable of preventing, halting, and potentially reversing the circuit-level dysfunction that underlies Alzheimer’s disease cognitive symptoms. By targeting the fundamental mechanisms of cortical information processing rather than focusing solely on pathological protein accumulation, PV+ interneuron enhancement represents a paradigm shift toward circuit-based therapeutics that could transform the treatment landscape for neurodegenerative diseases.
Mechanism Pathway
flowchart TD
A["PV+ Interneuron<br/>Dysfunction in PFC"] --> B["Reduced GABAergic<br/>Inhibition"]
B --> C["Impaired E/I<br/>Balance"]
C --> D["Sensory Gating<br/>Deficits"]
D --> E["Prefrontal<br/>Disinhibition"]
E --> F["Cognitive Decline<br/>& Attention Deficits"]
G["PVALB Gene Therapy<br/>(AAV-PVALB)"] -->|"restores"| A
H["Kv3.1 Channel<br/>Modulators"] -->|"enhances"| A
I["40Hz Gamma<br/>Entrainment"] -->|"drives"| B
A --> J[" down Gamma<br/>Oscillations"]
J --> D
style A fill:#ef5350,stroke:#333,color:#000
style F fill:#ef5350,stroke:#333,color:#000
style G fill:#81c784,stroke:#333,color:#000
style H fill:#4fc3f7,stroke:#333,color:#000
style I fill:#ce93d8,stroke:#333,color:#000
Evidence for (38)
Mitochondrial bioenergetic signatures differentiate asymptomatic from symptomatic Alzheimer's disease.
Asymptomatic Alzheimer's disease (AsymAD) refers to individuals who, despite exhibiting amyloid-β plaques and tau pathology comparable to Alzheimer's disease (AD), maintain cognitive performance similar to cognitively normal individuals. The resilience mechanism in these AsymAD individual remains understudied. We performed a systematic analysis comparing AsymAD and AD across multiple cohorts (ROSMAP, Banner and Mount Sinai), brain regions (BA6, BA9, BA36 and BA37) and neuronal and glial cell types using proteomics and transcriptomics data. AsymAD brains exhibited preserved mitochondrial bioenergetics, characterized by enhanced oxidative phosphorylation (OXPHOS), electron transport chain (ETC) activity, fatty acid and lipid metabolism, and branched-chain amino acid (BCAA) utilization. Pathways regulating mitochondrial complex biogenesis and calcium homeostasis were also upregulated. Key mitochondrial proteins such as MRPL47, CPT2, BCAT2, and IDH2, were consistently upregulated in AsymAD, whereas MACROD1 was downregulated. At the cellular level, excitatory neurons, including superficial, mid-layer, and deep-layer subtypes, exhibited the most preserved mitochondrial function, whereas vulnerable inhibitory subtypes, including PVALB and SST neurons, showed increased cellular abundance and bioenergetic activity. In contrast, microglia and oligodendrocytes proportions were reduced in AsymAD relative to AD. Our findings identify preserved mitochondrial bioenergetics as a defining fea
Integrated multimodal cell atlas of Alzheimer's disease
Alzheimer's disease (AD) is the leading cause of dementia in older adults. Although AD progression is characterized by stereotyped accumulation of proteinopathies, the affected cellular populations remain understudied. Here we use multiomics, spatial genomics and reference atlases from the BRAIN Initiative to study middle temporal gyrus cell types in 84 donors with varying AD pathologies. This cohort includes 33 male donors and 51 female donors, with an average age at time of death of 88 years. We used quantitative neuropathology to place donors along a disease pseudoprogression score. Pseudoprogression analysis revealed two disease phases: an early phase with a slow increase in pathology, presence of inflammatory microglia, reactive astrocytes, loss of somatostatin+ inhibitory neurons, and a remyelination response by oligodendrocyte precursor cells; and a later phase with exponential increase in pathology, loss of excitatory neurons and Pvalb+ and Vip+ inhibitory neuron subtypes. These findings were replicated in other major AD studies.
Identification of early Alzheimer's disease subclass and signature genes based on PANoptosis genes
INTRODUCTION: Alzheimer's disease (AD) is one of the most prevalent forms of dementia globally and remains an incurable condition that often leads to death. PANoptosis represents an emerging paradigm in programmed cell death, integrating three critical processes: pyroptosis, apoptosis, and necroptosis. Studies have shown that apoptosis, necroptosis, and pyroptosis play important roles in AD development. Therefore, targeting PANoptosis genes might lead to novel therapeutic targets and clinically relevant therapeutic approaches. This study aims to identify different molecular subtypes of AD and potential drugs for treating AD based on PANoptosis. METHODS: Differentially expressed PANoptosis genes associated with AD were identified via Gene Expression Omnibus (GEO) dataset GSE48350, GSE5281, and GSE122063. Least Absolute Shrinkage and Selection Operator (LASSO) regression was employed to construct a risk model linked to these PANoptosis genes. Consensus clustering analysis was conducted to define AD subtypes based on these genes. We further performed gene set variation analysis (GSVA), functional enrichment analysis, and immune cell infiltration analysis to investigate differences between the identified AD subtypes. Additionally, a protein-protein interaction (PPI) network was established to identify hub genes, and the DGIdb database was consulted to identify potential therapeutic compounds targeting these hub genes. Single-cell RNA sequencing analysis was utilized to assess dif
The thalamic reticular nucleus orchestrates social memory.
Social memory has been developed in humans and other animals to recognize familiar conspecifics and is essential for their survival and reproduction. Here, we demonstrated that parvalbumin-positive neurons in the sensory thalamic reticular nucleus (sTRNPvalb) are necessary and sufficient for mice to memorize conspecifics. sTRNPvalb neurons receiving glutamatergic projections from the posterior parietal cortex (PPC) transmit individual information by inhibiting the parafascicular thalamic nucleus (PF). Mice in which the PPCCaMKII→sTRNPvalb→PF circuit was inhibited exhibited a disrupted ability to discriminate familiar conspecifics from novel ones. More strikingly, a subset of sTRNPvalb neurons with high electrophysiological excitability and complex dendritic arborizations is involved in the above corticothalamic pathway and stores social memory. Single-cell RNA sequencing revealed the biochemical basis of these subset cells as a robust activation of protein synthesis. These findings elucidate that sTRNPvalb neurons modulate social memory by coordinating a hitherto unknown corticothalamic circuit and inhibitory memory engram.
A vagal reflex evoked by airway closure.
Airway integrity must be continuously maintained throughout life. Sensory neurons guard against airway obstruction and, on a moment-by-moment basis, enact vital reflexes to maintain respiratory function1,2. Decreased lung capacity is common and life-threatening across many respiratory diseases, and lung collapse can be acutely evoked by chest wall trauma, pneumothorax or airway compression. Here we characterize a neuronal reflex of the vagus nerve evoked by airway closure that leads to gasping. In vivo vagal ganglion imaging revealed dedicated sensory neurons that detect airway compression but not airway stretch. Vagal neurons expressing PVALB mediate airway closure responses and innervate clusters of lung epithelial cells called neuroepithelial bodies (NEBs). Stimulating NEBs or vagal PVALB neurons evoked gasping in the absence of airway threats, whereas ablating NEBs or vagal PVALB neurons eliminated gasping in response to airway closure. Single-cell RNA sequencing revealed that NEBs uniformly express the mechanoreceptor PIEZO2, and targeted knockout of Piezo2 in NEBs eliminated responses to airway closure. NEBs were dispensable for the Hering-Breuer inspiratory reflex, which indicated that discrete terminal structures detect airway closure and inflation. Similar to the involvement of Merkel cells in touch sensation3,4, NEBs are PIEZO2-expressing epithelial cells and, moreover, are crucial for an aspect of lung mechanosensation. These findings expand our understanding of ne
Identification of epilepsy-associated neuronal subtypes and gene expression underlying epileptogenesis.
Epilepsy is one of the most common neurological disorders, yet its pathophysiology is poorly understood due to the high complexity of affected neuronal circuits. To identify dysfunctional neuronal subtypes underlying seizure activity in the human brain, we have performed single-nucleus transcriptomics analysis of >110,000 neuronal transcriptomes derived from temporal cortex samples of multiple temporal lobe epilepsy and non-epileptic subjects. We found that the largest transcriptomic changes occur in distinct neuronal subtypes from several families of principal neurons (L5-6_Fezf2 and L2-3_Cux2) and GABAergic interneurons (Sst and Pvalb), whereas other subtypes in the same families were less affected. Furthermore, the subtypes with the largest epilepsy-related transcriptomic changes may belong to the same circuit, since we observed coordinated transcriptomic shifts across these subtypes. Glutamate signaling exhibited one of the strongest dysregulations in epilepsy, highlighted by layer-wise transcriptional changes in multiple glutamate receptor genes and strong upregulation of genes coding for AMPA receptor auxiliary subunits. Overall, our data reveal a neuronal subtype-specific molecular phenotype of epilepsy.
Inhibition of GABA interneurons in the mPFC is sufficient and necessary for rapid antidepressant responses.
Major depressive disorder (MDD) is associated with alterations of GABAergic interneurons, notably somatostatin (Sst) as well as parvalbumin (Pvalb), in cortical brain areas. In addition, the antidepressant effects of rapid-acting drugs are thought to occur via inhibition of GABA interneurons. However, the impact of these interneuron subtypes in affective behaviors as well as in the effects of rapid-acting antidepressants remains to be determined. Here, we used a Cre-dependent DREADD-chemogenetic approach to determine if inhibition of GABA interneurons in the mPFC of male mice is sufficient to produce antidepressant actions, and conversely if activation of these interneurons blocks the rapid and sustained antidepressant effects of scopolamine, a nonselective acetylcholine muscarinic receptor antagonist. Chemogenetic inhibition of all GABA interneurons (Gad1+), as well as Sst+ and Pvalb+ subtypes in the mPFC produced dose and time-dependent antidepressant effects in the forced swim and novelty suppressed feeding tests, and increased synaptic plasticity. In contrast, stimulation of Gad1, Sst, or Pvalb interneurons in mPFC abolished the effects of scopolamine and prevented scopolamine induction of synaptic plasticity. The results demonstrate that transient inhibition of GABA interneurons promotes synaptic plasticity that underlies rapid antidepressant responses.
Fate plasticity of interneuron specification.
Neuronal subtype generation in the mammalian central nervous system is governed by competing genetic programs. The medial ganglionic eminence (MGE) produces two major cortical interneuron (IN) populations, somatostatin (Sst) and parvalbumin (Pvalb), which develop on different timelines. The extent to which external signals influence these identities remains unclear. Pvalb-positive INs are crucial for cortical circuit regulation but challenging to model in vitro. We grafted mouse MGE progenitors into diverse 2D and 3D co-culture systems, including mouse and human cortical, MGE, and thalamic models. Strikingly, only 3D human corticogenesis models promoted efficient, non-autonomous Pvalb differentiation, characterized by upregulation of Pvalb maturation markers, downregulation of Sst-specific markers, and the formation of perineuronal nets. Additionally, lineage-traced postmitotic Sst-positive INs upregulated Pvalb when grafted onto human cortical models. These findings reveal unexpected fate plasticity in MGE-derived INs, suggesting that their identities can be dynamically shaped by the environment.
Iptakalim: a potential antipsychotic drug with novel mechanisms?
Iptakalim is a novel putative adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channel opener. In the brain, iptakalim is thought to act on the neuronal and astrocytic plasma membrane and/or mitochondrial K(ATP) channels. Because iptakalim demonstrates an action on the regulation of dopamine and glutamate release in the forebrain regions, we examined its potential antipsychotic efficacy in several preclinical tests. First, we show that iptakalim is effective in reducing amphetamine- and phencyclidine-induced hyperlocomotion as well as selectively disrupting conditioned avoidance responding. Next, we show that combined iptakalim and amphetamine treatment produces a reduction on prepulse inhibition of acoustic startle and this combined drug effect is also found with haloperidol, but not with clozapine. Finally, we show that iptakalim and clozapine preferentially increase c-Fos expression in the medial prefrontal cortex, nucleus accumbens and lateral septal nucleus, whereas haloperidol induces a greater increase in the nucleus accumbens, the dorsolateral striatum and lateral septal nucleus. Collectively, our findings indicate that iptakalim is likely to be a potential antipsychotic drug with distinct mechanisms of action. This study also suggests that neuronal and astrocytic plasma membrane and/or mitochondrial K(ATP) channels may be a novel target that deserves attention for antipsychotic drug development. Future research using other sensitive tests is needed to confir
Transcranial direct current stimulation restores addictive behavior via prefrontal-striatal circuit.
Dependence on methamphetamine (METH) is a severe brain disorder characterized by high relapse rates and cognitive decline following detoxification. Recent research suggests that transcranial direct current stimulation (tDCS) may treat addiction, but the underlying neural mechanisms remain unknown. Here, we employed METH-conditioned place preference (CPP) paradigm integrated with fMRI, electrophysiology, chemogenetics, in vivo fiber photometry recordings and a novel rodent tDCS model to examine the neural circuit underlying tDCS modulation on METH-induced addictive behavior. We demonstrated that tDCS targeted at the medial prefrontal cortex (mPFC) prevents relapse. Specifically, tDCS enhanced the activity of neurons in both the infralimbic cortex (IL) and the nucleus accumbens shell (NAcSh) simultaneously. Furthermore, chemogenetic inhibition of the IL-NAcSh circuit eliminated the modulatory effects of tDCS, while activation of the IL-NAcSh circuit was sufficient to suppress the relapse. These findings reveal that the IL-NAcSh pathway functions as a descending regulatory circuit mediating the therapeutic outcomes of tDCS in the treatment of substance use disorder, offering new insights into circuit-based neuro-modulatory treatments for addiction.
Multimodal Neuroimaging of Obesity: From Structural-Functional Mechanisms to Precision Interventions.
PURPOSE: Obesity's metabolic consequences are well documented; however, its neurobiological underpinnings remain elusive. This systematic review addresses a critical gap by synthesizing evidence on obesity-induced neuroplasticity across structural, functional, and molecular domains through advanced neuroimaging. METHODS: According to PRISMA guidelines, we systematically searched (2015-2024) across PubMed/Web of Science, employing MeSH terms: ("Obesity" [Majr]) AND ("Neuroimaging" [Mesh] OR "Magnetic Resonance Imaging" [Mesh]). A total of 104 studies met the inclusion criteria. The inclusion criteria required the following: (1) multimodal imaging protocols (structural MRI/diffusion tensor imaging/resting-state functional magnetic resonance imaging (fMRI)/positron emission tomography (PET)); (2) pre-/post-intervention longitudinal design. Risk of bias was assessed via the Newcastle-Ottawa Scale. KEY FINDINGS: 1. Structural alterations: 7.2% mean gray matter reduction in prefrontal cortex (Cohen's d = 0.81). White matter integrity decline (FA reduction β = -0.33, p < 0.001) across 12 major tracts. 2. Functional connectivity: Resting-state hyperactivity in mesolimbic pathways (fALFF + 23%, p-FDR < 0.05). Impaired fronto-striatal connectivity (r = -0.58 with BMI, 95% CI [-0.67, -0.49]). 3. Interventional reversibility: Bariatric surgery restored prefrontal activation (Δ = +18% vs. controls, p = 0.002). Neurostimulation (transcranial direct current stimulation (tDCS) enhanced cogni
Noninvasive Brain Stimulation Rescues Cocaine-Induced Prefrontal Hypoactivity and Restores Flexible Behavior.
BACKGROUND: To obtain desirable goals, individuals must predict the outcome of specific choices, use that information to direct appropriate actions, and adjust behavior accordingly in changing environments (behavioral flexibility). Substance use disorders are marked by impairments in behavioral flexibility along with decreased prefrontal cortical function that limits the efficacy of treatment strategies. Restoring prefrontal hypoactivity, ideally in a noninvasive manner, is an intriguing target for improving flexible behavior and treatment outcomes. METHODS: A behavioral flexibility task was used in Long-Evans male rats (n = 97) in conjunction with electrophysiology, optogenetics, and a novel rat model of transcranial alternating current stimulation (tACS) to examine the prelimbic cortex (PrL) to nucleus accumbens (NAc) core circuit in behavioral flexibility and determine whether tACS can restore cocaine-induced neural and cognitive dysfunction. RESULTS: Optogenetic inactivation revealed that the PrL-NAc core circuit is necessary for the ability to learn strategies to flexibly shift behavior. Cocaine self-administration history caused aberrant PrL-NAc core neural encoding and deficits in flexibility. Optogenetics that selectively activated the PrL-NAc core pathway prior to learning rescued cocaine-induced cognitive flexibility deficits. Remarkably, tACS prior to learning the task reestablished adaptive signaling in the PrL-NAc circuit and restored flexible behavior in a relat
tDCS-induced enhancement of cognitive flexibility in autism: role of frontal lobe and associated neural circuits.
BACKGROUND: Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impaired social interaction and restricted, repetitive behaviors (RRBs). These symptoms may stem from cognitive flexibility deficits, with dysfunction in the prefrontal cortex (PFC) and related neural circuits proposed as underlying mechanisms. OBJECTIVES: This study examined whether transcranial direct current stimulation (tDCS) could enhance PFC activity and functional connectivity, thereby improving cognitive flexibility in a valproic acid (VPA)-induced ASD rat model. METHODS: Pregnant Sprague-Dawley rats were administered VPA (600 mg/kg, E12.5) or saline. VPA-exposed offspring exhibiting curved tails received tDCS and underwent behavioral tests, including the three-chamber social interaction test and cross-maze rule-shifting task, while local field potentials (LFPs) were recorded. Immunohistochemistry was performed to evaluate microglial activation (Iba1 +) and synaptic density (PSD95). RESULTS: Valproic acid -exposed offspring displayed significant social interaction deficits and impaired cognitive flexibility, alongside disrupted functional connectivity in frontal-striato-hippocampal circuits. Neuroinflammatory analysis revealed elevated Iba1+ microglial density (p < 0.05) and increased PSD95 expression (p < 0.05). After tDCS intervention, VPA rats exhibited restored sociability and cognitive performance, normalized functional connectivity, and significantly reduced microglial a
Sensory gating in patients with Alzheimer's disease and their biological children.
Research has shown that sensory gating is largely modualted by acetylcholine. Diminished levels of acetylcholine and sensory gating deficits have been reported in research involving Alzheimer's disease (AD) patients. However, there has been little investigation into those with a family history (FH+) of AD. The rationale of this study was to determine whether sensory gating impairments could distinguish those with early AD from individuals with increased risk for the disease while replicating previous findings of gating abnormalities in AD patients. Using the paried-click paradigm, evoked potentials were recorded from 4 groups of 20 subjects per group (AD, older controls, FH+, FH-). The results showed that while the AD group demonstrated sensory gating abnormalities, the FH+ group did not when compared to their peers with no family history of the disease (FH-). These results are discussed in relation to previous findings reporting P300 abnormalities in the FH+ group.
Acute administration of roflumilast enhances sensory gating in healthy young humans in a randomized trial.
INTRODUCTION: Sensory gating is a process involved in early information processing which prevents overstimulation of higher cortical areas by filtering sensory information. Research has shown that the process of sensory gating is disrupted in patients suffering from clinical disorders including attention deficit hyper activity disorder, schizophrenia, and Alzheimer's disease. Phosphodiesterase (PDE) inhibitors have received an increased interest as a tool to improve cognitive performance in both animals and man, including sensory gating. METHODS: The current study investigated the effects of the PDE4 inhibitor roflumilast in a sensory gating paradigm in 20 healthy young human volunteers (age range 18-30 years). We applied a placebo-controlled randomized cross-over design and tested three doses (100, 300, 1000 μg). RESULTS: Results show that roflumilast improves sensory gating in healthy young human volunteers only at the 100-μg dose. The effective dose of 100 μg is five times lower than the clinically approved dose for the treatment of acute exacerbations in chronic obstructive pulmonary disease (COPD). No side-effects, such as nausea and emesis, were observed at this dose. This means roflumilast shows a beneficial effect on gating at a dose that had no adverse effects reported following single-dose administration in the present study. CONCLUSION: The PDE4 inhibitor roflumilast has a favorable side-effect profile at a cognitively effective dose and could be considered as a tr
Meta-Analyses of Auditory Evoked Potentials as Alzheimer Biomarkers.
OBJECTIVES: Alterations in auditory evoked potential (AEP) parameters have been associated with sensory memory deficits and may serve as biomarkers for cognitive decline. This systematic review and meta-analysis aimed to evaluate the effectiveness of AEPs in the early detection of Alzheimer disease (AD). DESIGN: The systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines. A comprehensive search was performed across five electronic databases (EMBASE, Scopus, Cochrane Library, Web of Science, PubMed, and CINAHL) from their inception until August 2024, without restrictions on date or language. The methodological quality of evidence was assessed using the Crew Critical Appraisal Tool. Data were extracted on the latency and amplitude of five AEP components, including auditory P50 gating, mismatch negativity, and late-latency responses (N100, N200, P300), comparing patients with AD to age-matched control peers. RESULTS: Out of 437 publications, 54 articles were selected for review, with most rated as having high methodological quality. The analysis revealed a significantly larger P50 gating amplitude ( p < 0.001) in patients with AD. Furthermore, patients with AD demonstrated significantly prolonged latencies and reduced amplitudes for N100, N200, and P300 components ( p ≤ 0.001) compared with controls. Among all AEPs, P300 latency exhibited the largest effect size. Funnel plot analysis and Egger's regression
Amygdala pain mechanisms.
A limbic brain area, the amygdala plays a key role in emotional responses and affective states and disorders such as learned fear, anxiety, and depression. The amygdala has also emerged as an important brain center for the emotional-affective dimension of pain and for pain modulation. Hyperactivity in the laterocapsular division of the central nucleus of the amygdala (CeLC, also termed the "nociceptive amygdala") accounts for pain-related emotional responses and anxiety-like behavior. Abnormally enhanced output from the CeLC is the consequence of an imbalance between excitatory and inhibitory mechanisms. Impaired inhibitory control mediated by a cluster of GABAergic interneurons in the intercalated cell masses (ITC) allows the development of glutamate- and neuropeptide-driven synaptic plasticity of excitatory inputs from the brainstem (parabrachial area) and from the lateral-basolateral amygdala network (LA-BLA, site of integration of polymodal sensory information). BLA hyperactivity also generates abnormally enhanced feedforward inhibition of principal cells in the medial prefrontal cortex (mPFC), a limbic cortical area that is strongly interconnected with the amygdala. Pain-related mPFC deactivation results in cognitive deficits and failure to engage cortically driven ITC-mediated inhibitory control of amygdala processing. Impaired cortical control allows the uncontrolled persistence of amygdala pain mechanisms.
LPS-induced inflammation reduces GABAergic interneuron markers and brain-derived neurotrophic factor in mouse prefrontal cortex and hippocampus.
Inflammation, reduced gamma-aminobutyric acidergic (GABAergic) function and altered neuroplasticity are co-occurring pathophysiologies in major depressive disorder (MDD). However, the link between these biological changes remains unclear. We hypothesized that inflammation induces deficits in GABAergic interneuron markers and that this effect is mediated by brain-derived neurotrophic factor (BDNF). We report here that systemic inflammation induced by intraperitoneal injection of lipopolysaccharide (LPS) (0.125, 0.25, 0.5, 1, 2 mg/kg) in the first cohort of C57BL/6 mice (n = 72; 10-11 weeks; 50% female) resulted in increased interleukin 1-beta and interleukin-6 in prefrontal cortex (PFC) and hippocampus (HPC), as measured using enzyme-linked immunosorbent assay (ELISA). Quantitative real-time polymerase reaction (qPCR) was used to explore the effect of LPS on the expression of GABAergic interneuron markers. In the PFC of the second cohort (n = 39; 10-11 weeks; 50% female), 2 mg/kg of LPS decreased the expression of somatostatin (Sst) (p = 0.0014), parvalbumin (Pv) (p = 0.0257), cortistatin (Cort) (p = 0.0003), neuropeptide Y (Npy) (p = 0.0033) and cholecystokinin (Cck) (p = 0.0041), and did not affect corticotropin-releasing hormone (Crh) and vasoactive intestinal peptide (Vip) expression. In the HPC, 2 mg/kg of LPS decreased the expression of Sst (p = 0.0543), Cort (p = 0.0011), Npy (p = 0.0001), and Cck (p < 0.0001), and did not affect Crh, Pv, and Vip expression. LPS decreas
Alteration in the GABAergic network of the prefrontal cortex in a potential animal model of psychosis.
The GABAergic input on cortical pyramidal cells has an important influence on the firing activity of the cortex and thus in regulating the behavioural outcome. The aim of the current study was to investigate the long-term neuroplastic adaptation of the GABAergic innervation pattern after an early severe systemic impact. Therefore 40 Mongolian gerbils (Meriones unguiculatus) were either reared under impoverished (IR) or enriched rearing conditions (ER) and received a single early (+)-methamphetamine (MA) challenge (50 mg/kg i.p.) or saline on postnatal day 14. The density of perisomatic immunoreactive GABAergic terminals surrounding layers III and V pyramidal neurons was quantified as well as the overall GABAergic fibre density in layers I/II and V of the medial prefrontal cortex (mPFC) of young adult animals (90 days). We found that IR in combination with an early MA administration led to a significant decrease in GABAergic bouton densities while the overall GABAergic fibre density increased in all investigated layers. The results indicate a shift in inhibition from somatic to dendritic innervation of pyramidal neurons in this potential animal model of psychosis. We conclude that IR combined with early MA trigger changes in the postnatal maturation of the prefrontal cortical GABAergic triggers innervation, which may interfere with proper signal processing within the prefrontal neural network.
Parvalbumin interneuron mGlu(5) receptors govern sex differences in prefrontal cortex physiology and binge drinking.
Despite established sex differences in the prevalence and presentation of psychiatric disorders, little is known about the cellular and synaptic mechanisms that guide these differences under basal conditions. The proper function of the prefrontal cortex (PFC) is essential for the top-down regulation of motivated behaviors. The activity of the PFC is tightly controlled by parvalbumin-expressing interneurons (PV-INs), a key subpopulation of fast-spiking GABAergic cells that regulate cortical excitability through direct innervations onto the perisomatic regions of nearby pyramidal cells. Recent rodent studies have identified notable sex differences in PV-IN activity and adaptations to experiences such as binge drinking. Here, we investigated the cellular and molecular mechanisms that underlie sex-specific regulation of PFC PV-IN function. Using whole-cell patch-clamp electrophysiology and selective pharmacology, we report that PV-INs from female mice are more excitable than those from males. Moreover, we find that mGlu1 and mGlu5 metabotropic glutamate receptors regulate cell excitability, excitatory drive, and endocannabinoid signaling at PFC PV-INs in a sex-dependent manner. Genetic deletion of mGlu5 receptors from PV-expressing cells abrogates all sex differences observed in PV-IN membrane and synaptic physiology. Lastly, we report that female, but not male, PV-mGlu5-/- mice exhibit decreased voluntary drinking on an intermittent access schedule, which could be related to cha
A high-fat high-sugar diet in adolescent rats impairs social memory and alters chemical markers characteristic of atypical neuroplasticity and parvalbumin interneuron depletion in the medial prefrontal cortex.
Brain plasticity is a multifaceted process that is dependent on both neurons and extracellular matrix (ECM) structures, including perineuronal nets (PNNs). In the medial prefrontal cortex (mPFC) PNNs primarily surround fast-spiking parvalbumin (PV)-containing GABAergic interneurons and are central to regulation of neuroplasticity. In addition to the development of obesity, high-fat and high-sugar (HFHS) diets are also associated with alterations in brain plasticity and emotional behaviours in humans. To examine the underlying involvement of PNNs and cortical plasticity in the mPFC in diet-evoked social behaviour deficits (in this case social recognition), we exposed adolescent (postnatal days P28-P56) rats to a HFHS-supplemented diet. At P56 HFHS-fed animals and age-matched controls fed standard chow were euthanized and co-localization of PNNs with PV neurons in the prelimbic (PrL) and infralimbic (IL) and anterior cingulate (ACC) sub regions of the PFC were examined by dual fluorescence immunohistochemistry. ΔFosB expression was also assessed as a measure of chronic activity and behavioural addiction marker. Consumption of the HFHS diet reduced the number of PV+ neurons and PNNs in the infralimbic (IL) region of the mPFC by -21.9% and -16.5%, respectively. While PV+ neurons and PNNs were not significantly decreased in the ACC or PrL, the percentage of PV+ and PNN co-expressing neurons was increased in all assessed regions of the mPFC in HFHS-fed rats (+33.7% to +41.3%). This
Medial prefrontal cortex circuit dynamics involved in stage-specific addiction.
The medial prefrontal cortex (mPFC) serves as a critical hub in addiction pathology across binge/intoxication, withdrawal/negative affect, and preoccupation/anticipation/craving stages. This review provides the roles of the mPFC in different stages of addiction, and a focus on the mPFC neurotransmitter systems, neural circuits, molecules and synaptic adaptations on the regulation of addictive behaviors. Neurotransmitter systems of dopaminergic, glutamatergic, and GABAergic imbalances are related to pathological addiction. Circuits of dynamic dysregulation in the mPFC interaction with the striatum, nucleus accumbens (NAc), ventral tegmental area (VTA), dorsal raphe nucleus (DRN), and amygdala drive stage-specific behaviors, such as the prelimbic cortex (PL)→NAc core promoting cocaine-seeking, the infralimbic cortex (IL)→NAc shell suppressing relapse. Alterations in excitation-inhibition of microcircuits pyramidal neurons, GABAergic interneurons impair top-down regulation. Synaptic plasticity induced by drugs is involved in pathological stage-specific addiction, such as persistent craving and compulsive behaviors. Targeting the mPFC circuits offers promising therapeutic strategies for addiction intervention.
Inhibitory Parvalbumin Basket Cell Activity is Selectively Reduced during Hippocampal Sharp Wave Ripples in a Mouse Model of Familial Alzheimer's Disease.
Memory disruption in mild cognitive impairment (MCI) and Alzheimer's disease (AD) is poorly understood, particularly at early stages preceding neurodegeneration. In mouse models of AD, there are disruptions to sharp wave ripples (SWRs), hippocampal population events with a critical role in memory consolidation. However, the microcircuitry underlying these disruptions is under-explored. We tested whether a selective reduction in parvalbumin-expressing (PV) inhibitory interneuron activity underlies hyperactivity and SWR disruption. We employed the 5xFAD model of familial AD crossed with mouse lines labeling excitatory pyramidal cells (PCs) and inhibitory PV cells. We observed a 33% increase in frequency, 58% increase in amplitude, and 8% decrease in duration of SWRs in ex vivo slices from male and female three-month 5xFAD mice versus littermate controls. 5xFAD mice of the same age were impaired in a hippocampal-dependent memory task. Concurrent with SWR recordings, we performed calcium imaging, cell-attached, and whole-cell recordings of PC and PV cells within the CA1 region. PCs in 5xFAD mice participated in enlarged ensembles, with superficial PCs (sPCs) having a higher probability of spiking during SWRs. Both deep PCs (dPCs) and sPCs displayed an increased synaptic E/I ratio, suggesting a disinhibitory mechanism. In contrast, we observed a 46% spike rate reduction during SWRs in PV basket cells (PVBCs), while PV bistratified and axo-axonic cells were unimpaired. Excitatory s
Precocious emergence of cognitive and synaptic dysfunction in 3xTg-AD mice exposed prenatally to ethanol.
Alzheimer's disease (AD) is the most common cause of dementia, affecting approximately 50 million people worldwide. Early life risk factors for AD, including prenatal exposures, remain underexplored. Exposure of the fetus to alcohol (ethanol) is not uncommon during pregnancy, and may result in physical, behavioral, and cognitive changes that are first detected during childhood but result in lifelong challenges. Whether or not prenatal ethanol exposure may contribute to Alzheimer's disease risk is not yet known. Here we exposed a mouse model of Alzheimer's disease (3xTg-AD), bearing three dementia-associated transgenes, presenilin1 (PS1M146V), human amyloid precursor protein (APPSwe), and human tau (TauP301S), to ethanol on gestational days 13.5-16.5 using an established binge-type maternal ethanol exposure paradigm. We sought to investigate whether prenatal ethanol exposure resulted in a precocious onset or increased severity of AD progression, or both. We found that a brief binge-type gestational exposure to ethanol during a period of peak neuronal migration to the developing cortex resulted in an earlier onset of spatial memory deficits and behavioral inflexibility in the progeny, as assessed by performance on the modified Barnes maze task. The observed cognitive changes coincided with alterations to both GABAergic and glutamatergic synaptic transmission in layer V/VI neurons, diminished GABAergic interneurons, and increased β-amyloid accumulation in the medial prefrontal c
Gamma frequency entrainment attenuates amyloid load and modifies microglia.
Changes in gamma oscillations (20-50 Hz) have been observed in several neurological disorders. However, the relationship between gamma oscillations and cellular pathologies is unclear. Here we show reduced, behaviourally driven gamma oscillations before the onset of plaque formation or cognitive decline in a mouse model of Alzheimer's disease. Optogenetically driving fast-spiking parvalbumin-positive (FS-PV)-interneurons at gamma (40 Hz), but not other frequencies, reduces levels of amyloid-β (Aβ)1-40 and Aβ 1-42 isoforms. Gene expression profiling revealed induction of genes associated with morphological transformation of microglia, and histological analysis confirmed increased microglia co-localization with Aβ. Subsequently, we designed a non-invasive 40 Hz light-flickering regime that reduced Aβ1-40 and Aβ1-42 levels in the visual cortex of pre-depositing mice and mitigated plaque load in aged, depositing mice. Our findings uncover a previously unappreciated function of gamma rhythms in recruiting both neuronal and glial responses to attenuate Alzheimer's-disease-associated pathology.
Parvalbumin interneuron deficits in schizophrenia.
Parvalbumin-expressing (PV+) interneurons represent one of the most abundant subclasses of cortical interneurons. Owing to their specific electrophysiological and synaptic properties, PV+ interneurons are essential for gating and pacing the activity of excitatory neurons. In particular, PV+ interneurons are critically involved in generating and maintaining cortical rhythms in the gamma frequency, which are essential for complex cognitive functions. Deficits in PV+ interneurons have been frequently reported in postmortem studies of schizophrenia patients, and alterations in gamma oscillations are a prominent electrophysiological feature of the disease. Here, I summarise the main features of PV+ interneurons and review clinical and preclinical studies linking the developmental dysfunction of cortical PV+ interneurons with the pathophysiology of schizophrenia.
Parvalbumin neurons and gamma rhythms enhance cortical circuit performance.
Synchronized oscillations and inhibitory interneurons have important and interconnected roles within cortical microcircuits. In particular, interneurons defined by the fast-spiking phenotype and expression of the calcium-binding protein parvalbumin have been suggested to be involved in gamma (30-80 Hz) oscillations, which are hypothesized to enhance information processing. However, because parvalbumin interneurons cannot be selectively controlled, definitive tests of their functional significance in gamma oscillations, and quantitative assessment of the impact of parvalbumin interneurons and gamma oscillations on cortical circuits, have been lacking despite potentially enormous significance (for example, abnormalities in parvalbumin interneurons may underlie altered gamma-frequency synchronization and cognition in schizophrenia and autism). Here we use a panel of optogenetic technologies in mice to selectively modulate multiple distinct circuit elements in neocortex, alone or in combination. We find that inhibiting parvalbumin interneurons suppresses gamma oscillations in vivo, whereas driving these interneurons (even by means of non-rhythmic principal cell activity) is sufficient to generate emergent gamma-frequency rhythmicity. Moreover, gamma-frequency modulation of excitatory input in turn was found to enhance signal transmission in neocortex by reducing circuit noise and amplifying circuit signals, including inputs to parvalbumin interneurons. As demonstrated here, optog
Involvement of cortical fast-spiking parvalbumin-positive basket cells in epilepsy.
GABAergic interneurons of the parvalbumin-positive fast-spiking basket cells subtype (PV INs) are important regulators of cortical network excitability and of gamma oscillations, involved in signal processing and cognition. Impaired development or function of PV INs has been associated with epilepsy in various animal models of epilepsy, as well as in some genetic forms of epilepsy in humans. In this review, we provide an overview of some of the experimental data linking PV INs dysfunction with epilepsy, focusing on disorders of the specification, migration, maturation, synaptic function, or connectivity of PV INs. Furthermore, we reflect on the potential therapeutic use of cell-type specific stimulation of PV INs within active networks and on the transplantation of PV INs precursors in the treatment of epilepsy and its comorbidities.
Parvalbumin Interneuron Dysfunction in Neurological Disorders: Focus on Epilepsy and Alzheimer's Disease.
Parvalbumin expressing (PV+) GABAergic interneurons are fast spiking neurons that provide powerful but relatively short-lived inhibition to principal excitatory cells in the brain. They play a vital role in feedforward and feedback synaptic inhibition, preventing run away excitation in neural networks. Hence, their dysfunction can lead to hyperexcitability and increased susceptibility to seizures. PV+ interneurons are also key players in generating gamma oscillations, which are synchronized neural oscillations associated with various cognitive functions. PV+ interneuron are particularly vulnerable to aging and their degeneration has been associated with cognitive decline and memory impairment in dementia and Alzheimer's disease (AD). Overall, dysfunction of PV+ interneurons disrupts the normal excitatory/inhibitory balance within specific neurocircuits in the brain and thus has been linked to a wide range of neurodevelopmental and neuropsychiatric disorders. This review focuses on the role of dysfunctional PV+ inhibitory interneurons in the generation of epileptic seizures and cognitive impairment and their potential as targets in the design of future therapeutic strategies to treat these disorders. Recent research using cutting-edge optogenetic and chemogenetic technologies has demonstrated that they can be selectively manipulated to control seizures and restore the balance of neural activity in the brains of animal models. This suggests that PV+ interneurons could be import
Transcriptional and functional profiles of muscarinic receptor-expressing neurons in primate lateral prefrontal and anterior cingulate cortices.
Acetylcholine differentially modulates anterior cingulate (ACC) and lateral prefrontal (LPFC) cortices for cognitive-emotional integration, but cell-specific expression and function of muscarinic receptors (mAChR) and corresponding CHRM1-4 genes in these areas of the primate brain are largely unknown. Our single-nucleus RNA sequencing and mRNA-protein histology in macaques revealed CHRM3 as the most enriched mAChR gene in neurons, while m1 predominates at the protein level, likely due to nuclear retention of CHRM3 and cytoplasmic trafficking of CHRM1. CHRM3 and CHRM1 showed strong co-expression and functional overlap, and were transcriptomically-distinct from CHRM2, which was uniquely enriched in deep layer excitatory and PVALB+ inhibitory neurons. Between-region comparisons showed that CHRM3 is enriched in LPFC relative to ACC excitatory neurons. Further, CHRM1-3+ neurons showed region-specific transcriptomic signatures, with upregulation of synaptic plasticity genes in ACC relative to LPFC. Functional in vitro experiments confirmed a robust cholinergic-mediated decrease in excitatory and increase in inhibitory synaptic tone specific to ACC neurons, accompanied by changes in spine morphology. In contrast, cholinergic stimulation reduced inhibitory current amplitude in LPFC, shifting the microcircuit towards a stronger excitatory tone. These findings highlight region-specific acetylcholine signaling essential for flexible processing, learning and memory, which may underlie ne
Establishing mouse forebrain organoids as models of intrinsic cortical network assembly.
The mouse cortex is a canonical model for studying how functional neural networks emerge, yet it remains unclear which topological features arise from intrinsic cellular organization versus sensory input. Mouse forebrain organoids provide a powerful system to investigate these intrinsic mechanisms. We generated dorsal (DF) and ventral (VF) forebrain organoids from mouse pluripotent stem cells and tracked their development using longitudinal electrophysiology. DF organoids showed progressively stronger network-wide correlations, while VF organoids developed more refined activity patterns with enhanced small-world topology and increased modular organization. Both organoid types form small-world networks, but their topological organization differs. These differences emerge without extrinsic inputs and correlate with Pvalb+ interneuron enrichment in VF organoids. Our findings demonstrate how cellular composition influences neural circuit self-organization, establishing mouse forebrain organoids as a tractable platform to study cortical network architecture.
Altered Expression of GABA-Related Genes in Schizophrenia: Insights from Meta-Analyses of Brain and Blood Samples and iPSC-Derived Organoids.
BACKGROUND: Schizophrenia, one of the most disabling mental disorders, affects approximately seven per 1000 individuals worldwide and has an estimated heritability of around 80%; however, its pathophysiology remains incompletely understood. The disorder has been linked to dysregulation of multiple neurotransmitter systems, including dopamine, serotonin, γ-aminobutyric acid (GABA), and glutamate. GABA, the primary inhibitory neurotransmitter in the central nervous system, is synthesized by the enzymes glutamic acid decarboxylase 67 (GAD67) and glutamic acid decarboxylase 65 (GAD65), encoded by the GAD1 and GAD2 genes, respectively. The genes (SST) and parvalbumin (PVALB) encode somatostatin and parvalbumin, which are characteristic markers of specialized GABAergic interneuron subpopulations involved in maintaining excitatory-inhibitory balance and supporting cortical circuit function. While reduced GAD1 expression has been consistently reported in schizophrenia, findings regarding GAD2 expression have been inconsistent. METHODS: In this study, we examined the expression of GAD1, GAD2, SST, and PVALB across three biological levels: postmortem brain tissue, peripheral blood samples, and patient-derived induced pluripotent stem cell (iPSC)-derived brain organoids, compared with healthy controls. The meta-analysis of brain tissue included seven independent datasets (295 samples: 151 individuals with schizophrenia and 144 healthy controls) and was conducted in accordance with the P
A silent Kv channel subunit shapes PV neuron action potential waveform and short-term synaptic plasticity during high-frequency firing.
Fast-spiking parvalbumin-positive (PV) neurons provide precisely timed, context-dependent inhibition within cortical circuits. PV neuron firing properties are specialized among cortical neurons, suggesting that they express a unique complement of ion channels. Here, we show that the PV-specific silent voltage-gated potassium (Kv) channel subunit Kv6.4 (encoded by Kcng4) modulates both intrinsic and synaptic properties of cortical PV neurons. Kv6.4 does not form functional channels on its own but, as shown in prior work, assembles with Kv2 subunits to create heterotetrameric channel complexes, effectively reducing Kv2-mediated delayed rectifier current. We find that Kcng4 expression is enriched within a distinct Pvalb-expressing subclass in primary somatosensory (S1) and motor (M1) cortex and emerges during postnatal development. In PV neurons, Kv6.4 loss reduces action potential (AP) height and width, hyperpolarizes the threshold and interspike potential, and accelerates AP upstroke particularly during repetitive firing. Kv6.4 loss, potentially due to the changes in AP waveform, also alters GABA release and paired-pulse depression at synapses made by PV onto pyramidal (PYR) neurons. The effects of Kv6.4 loss are amplified during high-frequency firing, within the physiological range of fast-spiking PV neurons, likely due to altered repolarization dynamics that accumulate across successive APs. These findings are thus consistent with the function of Kv6.4 in modifying Kv2-media
Convergent transcriptomic and connectomic controllers of information integration and its anaesthetic breakdown across mammalian brains.
The mammalian brain orchestrates the processing and integration of information to guide behaviour. Here, to characterize mammalian information-processing architecture, we combine functional neuroimaging and anaesthesia in humans, macaques, marmosets and mice. We show that breakdown of information integration is a convergent effect of diverse anaesthetics across mammalian species. As the system disintegrates, brain dynamics become more difficult to control. Both effects are reversed upon re-awakening induced by thalamic deep-brain stimulation in the macaque. Regional breakdown of integrated information coincides with the species-specific spatial topography of PVALB/Pvalb gene expression. To provide mechanistic insight beyond correlation, we develop computational models for humans, macaques and mice that integrate species-specific connectivity and transcriptomic gradients, demonstrating their respective roles for controlling brain dynamics and information integration. We reveal evolutionarily conserved controllers of information integration in the mammalian brain.
Investigates structural and molecular signatures in Alzheimer's disease, potentially providing insights into gray matter changes related to interneuron dysfunction.
We aimed to systematically compare alterations in gray matter volume alterations in patients with Alzheimer's disease (AD) and late-life depression (LLD), explore the underlying molecular mechanisms, and provide insights for early identification and targeted intervention strategies. We recruited 33 patients with AD and 38 patients with LLD, along with 40 age- and sex-matched healthy older adults as controls. All participants underwent high-resolution structural MRI at 3.0 Tesla. To analyze gray
The study examines Kv channel subunits that shape parvalbumin neuron action potential dynamics, which is directly relevant to understanding interneuron functional properties.
Fast-spiking parvalbumin-positive (PV) neurons provide precisely timed, context-dependent inhibition within cortical circuits. PV neuron firing properties are specialized among cortical neurons, suggesting that they express a unique complement of ion channels. Here, we identify the PV-specific silent voltage-gated potassium (Kv) channel subunit Kv6.4 (encoded by Kcng4), whose role in cortical PV neuron physiology was previously unknown, as a modulator of both intrinsic and synaptic properties. K
Investigates human stem cell-derived GABAergic interneuron development, providing insights into interneuron subtype diversity and maturation mechanisms.
Medial ganglionic eminence-derived inhibitory γ-aminobutyric acid (GABAergic) pallial interneurons (MGE-pINs) are essential regulators of cortical circuits, and their dysfunction is associated with neurological disorders. We developed human MGE-pINs from pluripotent stem cells for the treatment of drug-resistant epilepsy. Here, we analyzed xenografted MGE-pINs from human pluripotent stem cells (hMGE-pINs) over the lifespan of host mice in healthy and epileptic environments using single-nuclei RN
The paper examining cell type-specific responses in the caudate nucleus across Alzheimer's disease provides contextual support for understanding neuronal circuit changes in neurodegenerative conditions.
Aβ presence in the caudate nucleus (Ca) partially defines Thal stage III in Alzheimer's disease (AD), but little is known about AD's cellular impact on the region. Leveraging a public basal ganglia taxonomy of cellular populations, we generated a cellular resolution atlas of AD-associated pathological changes in Ca. Unlike cortex, we found that Ca AD pathology is dominated by two key features: phosphorylated tau (pTau)-containing neuropil threads enriched near oligodendrocytes in white matter tr
Evidence against (13)
PV interneuron-specific therapies face delivery challenges across blood-brain barrier
BACKGROUND: Tremor is one of the most prevalent symptoms in Parkinson's Disease (PD). The progression and management of tremor in PD can be challenging, as response to dopaminergic agents might be relatively poor, particularly in patients with tremor-dominant PD compared to the akinetic/rigid subtype. In this review, we aim to highlight recent advances in the underlying pathogenesis and treatment modalities for tremor in PD. METHODS: A structured literature search through Embase was conducted using the terms "Parkinson's Disease" AND "tremor" OR "etiology" OR "management" OR "drug resistance" OR "therapy" OR "rehabilitation" OR "surgery." After initial screening, eligible articles were selected with a focus on published literature in the last 10 years. DISCUSSION: The underlying pathophysiology of tremor in PD remains complex and incompletely understood. Neurodegeneration of dopaminergic neurons in the retrorubral area, in addition to high-power neural oscillations in the cerebello-thalamo-cortical circuit and the basal ganglia, play a major role. Levodopa is the first-line therapeutic option for all motor symptoms, including tremor. The addition of dopamine agonists or anticholinergics can lead to further tremor reduction. Botulinum toxin injection is an effective alternative for patients with pharmacological-resistant tremor who are not seeking advanced therapies. Deep brain stimulation is the most well-established advanced therapy owing to its long-term efficacy, reversibi
Compensatory mechanisms may limit therapeutic window
A1 Functional advantages of cell-type heterogeneity in neural circuits Tatyana O. Sharpee A2 Mesoscopic modeling of propagating waves in visual cortex Alain Destexhe A3 Dynamics and biomarkers of mental disorders Mitsuo Kawato F1 Precise recruitment of spiking output at theta frequencies requires dendritic h-channels in multi-compartment models of oriens-lacunosum/moleculare hippocampal interneurons Vladislav Sekulić, Frances K. Skinner F2 Kernel methods in reconstruction of current sources from extracellular potentials for single cells and the whole brains Daniel K. Wójcik, Chaitanya Chintaluri, Dorottya Cserpán, Zoltán Somogyvári F3 The synchronized periods depend on intracellular transcriptional repression mechanisms in circadian clocks. Jae Kyoung Kim, Zachary P. Kilpatrick, Matthew R. Bennett, Kresimir Josić O1 Assessing irregularity and coordination of spiking-bursting rhythms in central pattern generators Irene Elices, David Arroyo, Rafael Levi, Francisco B. Rodriguez, Pablo Varona O2 Regulation of top-down processing by cortically-projecting parvalbumin positive neurons in basal forebrain Eunjin Hwang, Bowon Kim, Hio-Been Han, Tae Kim, James T. McKenna, Ritchie E. Brown, Robert W. McCarley, Jee Hyun Choi O3 Modeling auditory stream segregation, build-up and bistability James Rankin, Pamela Osborn Popp, John Rinzel O4 Strong competition between tonotopic neural ensembles explains pitch-related dynamics of auditory cortex evoked fields Alejandro Tabas, André Rupp, Emili
Neural correlates of cough hypersensitivity in humans: evidence for central sensitisation and dysfunctional inhibitory control
INTRODUCTION: Chronic non-productive coughing is a major complication of pulmonary disease and can also occur in many individuals without identifiable underlying pathology. The common clinical link in patients with cough is an enhanced sensitivity of the respiratory system to stimuli that subsequently evoke excessive coughing. The aetiology of this 'cough hypersensitivity syndrome' is unclear but believed to involve hypersensitivity of the sensory neural pathways that innervate the airways and lungs. METHODS: In the present study, we used functional brain imaging to compare central neural responses to airway stimulation using inhaled capsaicin in healthy people and patients with cough hypersensitivity. RESULTS: Hypersensitivity in response to inhaled capsaicin coincided with elevated neural activity in the midbrain in a region encompassing the nucleus cuneiformis (left: p<0.001; right: p<0.001) and periaqueductal gray (p=0.008) in comparison to normal sensitivity in controls. The enhanced activity noted in the midbrain is similar to that occurring in patients with chronic pain, thus providing empirical evidence to support the notion that cough and pain share neurobiological similarities. Furthermore, patients with cough hypersensitivity displayed difficulty controlling their cough, which manifested as a failure to suppress cough during capsaicin challenge (ie, reduced cough frequency) in controls compared with patients with cough hypersensitivity (p=0.046). Cough suppression
Brain Modulation by Electric Currents in Fibromyalgia: A Structured Review on Non-invasive Approach With Transcranial Electrical Stimulation.
Fibromyalgia syndrome (FMS) is a complex disorder where widespread musculoskeletal pain is associated with many heterogenous symptoms ranging from affective disturbances to cognitive dysfunction and central fatigue. FMS is currently underdiagnosed and often very poorly responsive to pharmacological treatment. Pathophysiology of the disease remains still obscure even if in the last years fine structural and functional cerebral abnormalities have been identified, principally by neurophysiological and imaging studies delineating disfunctions in pain perception, processing and control systems. On such basis, recently, neurostimulation of brain areas involved in mechanism of pain processing and control (primary motor cortex: M1 and dorsolateral prefrontal cortex: DLPFC) has been explored by means of different approaches and particularly through non-invasive brain stimulation techniques (transcranial magnetic and electric stimulation: TMS and tES). Here we summarize studies on tES application in FMS. The great majority of reports, based on direct currents (transcranial direct currents stimulation: tDCS) and targeting M1, showed efficacy on pain measures and less on cognitive and affective symptoms, even if several aspects as maintenance of therapeutical effects and optimal stimulation parameters remain to be established. Differently, stimulation of DLPFC, explored in a few studies, was ineffective on pain and showed limited effects on cognitive and affective symptoms. Very recently
Effect of single-session transcranial direct current stimulation on cognition in Parkinson's disease.
AIMS: Nonmotor symptoms (NMS) such as cognitive impairment and impulse-control disorders in Parkinson's disease (PD) remain a therapeutic challenge. Transcranial direct current stimulation (tDCS) has emerged as a promising alternative, although its immediate effects on NMS have been less well defined. In this randomized, sham-controlled, crossover study, we aimed to explore the single-session tDCS effects on cognitive performance in PD. METHODS: Ten nondemented patients with PD completed two sessions in counterbalanced order, receiving 20 minutes of either 2 mA anodal or sham tDCS over the left dorsolateral prefrontal cortex (DLPFC). During stimulation, they performed the visual working memory and go/no-go tasks. Performance of the tasks was compared between the two conditions. RESULTS: Single-session anodal tDCS over the left DLPFC did not significantly improve cognitive tasks in PD compared with sham (P > .05). CONCLUSION: Single-session tDCS is ineffective in improving visual working memory and inhibitory control in PD. Further research may worth exploring alternative tDCS parameters, ideally with repeated sessions and concomitant training.
Neurophysiological and neuropharmacological effects of melatonin MT2 receptors activation in MK-801-induced schizophrenia-like dysfunctions.
Schizophrenia (SCZ) is a chronic psychiatric disorder characterized by positive, negative, and cognitive symptoms that remain insufficiently controlled by current dopamine- and serotonin-based antipsychotics. Emerging evidence implicates melatonin MT2 receptors in the regulation of the sleep-wake cycle, circadian rhythms and cortical inhibition, both altered in SCZ. Here, we investigated the neuropharmacological effects of the selective MT2 partial agonist UCM924 in the MK-801 model of SCZ-like dysfunctions in male mice. UCM924 (10 mg/kg, intraperitoneally) was selected as a dose not affecting basal locomotion. Acute administration of MK-801 (0.3 mg/kg) induced hyperlocomotion, social interaction abnormalities, and impaired spatial working memory. UCM924 normalized MK-801-induced hyperactivity and social deficits but did not improve cognitive performance. Immunofluorescence analysis revealed that UCM924 increased c-Fos activation in parvalbumin-positive interneurons of the prefrontal cortex, with no effect on tyrosine hydroxylase-positive neurons in the ventral tegmental area. Local field potential recordings showed that UCM924 alone reduced gamma-band power (12-90 Hz) in both regions, whereas MK-801 markedly enhanced it. Co-administration of MK-801 and UCM924 resulted in MK-801-dominant oscillatory patterns, suggesting limited efficacy of MT2 activation in restoring network synchronization. These findings indicate that MT2 receptor stimulation selectively enhances prefrontal
Antiepileptogenic and neuroprotective effect of mefloquine after experimental status epilepticus.
Acquired temporal lobe epilepsy (TLE) characterized by spontaneous recurrent seizures (SRS) and hippocampal inhibitory neuron dysfunction is often refractory to current therapies. Gap junctional or electrical coupling between inhibitory neurons has been proposed to facilitate network synchrony and intercellular molecular exchange suggesting a role in both seizures and neurodegeneration. While gap junction blockers can limit acute seizures, whether blocking neuronal gap junctions can modify development of chronic epilepsy has not been examined. This study examined whether mefloquine, a selective blocker of Connexin 36 gap junctions which are well characterized in inhibitory neurons, can limit epileptogenesis and related cellular and behavioral pathology in a model of acquired TLE. A single, systemic dose of mefloquine administered early after pilocarpine-induced status epilepticus (SE) in rat reduced both development of SRS and behavioral co-morbidities. Immunostaining for interneuron subtypes identified that mefloquine treatment likely reduced delayed inhibitory neuronal loss after SE. Uniquely, parvalbumin expressing neurons in the hippocampal dentate gyrus appeared relatively resistant to early cell loss after SE. Functionally, whole cell patch clamp recordings revealed that mefloquine treatment preserved inhibitory synaptic drive to projection neurons one week and one month after SE. These results demonstrate that mefloquine, a drug already approved for malaria prophylaxis
Long-Term Neuropsychiatric Developmental Defects after Neonatal Organophosphate Exposure: Mitigation by Synthetic Neurosteroids.
Children are much more susceptible to the neurotoxic effects of organophosphate (OP) pesticides and nerve agents than adults. OP poisoning in children leads to acute seizures and neuropsychiatric sequela, including the development of long-term disabilities and cognitive impairments. Despite these risks, there are few chronic rodent models that use pediatric OP exposure for studying neurodevelopmental consequences and interventions. Here, we investigated the protective effect of the neurosteroid ganaxolone (GX) on the long-term developmental impact of neonatal exposure to the OP compound, diisopropyl-fluorophosphate (DFP). Pediatric postnatal day-28 rats were acutely exposed to DFP, and at 3 and 10 months after exposure, they were evaluated using a series of cognitive and behavioral tests with or without the postexposure treatment of GX. Analysis of the neuropathology was performed after 10 months. DFP-exposed animals displayed significant long-term deficits in mood, anxiety, depression, and aggressive traits. In spatial and nonspatial cognitive tests, they displayed striking impairments in learning and memory. Analysis of brain sections showed significant loss of neuronal nuclei antigen(+) principal neurons, parvalbumin(+) inhibitory interneurons, and neurogenesis, along with increased astrogliosis, microglial neuroinflammation, and mossy fiber sprouting. These detrimental neuropathological changes are consistent with behavioral dysfunctions. In the neurosteroid GX-treated co
Magnetic resonance imaging analysis of long-term neuropathology after exposure to the nerve agent soman: correlation with histopathology and neurological dysfunction.
Nerve agents (NAs) produce acute and long-term brain injury and dysfunction, as evident from the Japan and Syria incidents. Magnetic resonance imaging (MRI) is a versatile technique to examine such chronic anatomical, functional, and neuronal damage in the brain. The objective of this study was to investigate long-term structural and neuronal lesion abnormalities in rats exposed to acute soman intoxication. T2-weighted MRI images of 10 control and 17 soman-exposed rats were acquired using a Siemens MRI system at 90 days after soman exposure. Quantification of brain tissue volumes and T2 signal intensity was conducted using the Inveon Research Workplace software and the extent of damage was correlated with histopathology and cognitive function. Soman-exposed rats showed drastic hippocampal atrophy with neuronal loss and reduced hippocampal volume (HV), indicating severe damage, but had similar T2 relaxation times to the control group, suggesting limited scarring and fluid density changes despite the volume decrease. Conversely, soman-exposed rats displayed significant increases in lateral ventricle volumes and T2 times, signifying strong cerebrospinal fluid expansion in compensation for tissue atrophy. The total brain volume, thalamic volume, and thalamic T2 time were similar in both groups, however, suggesting that some brain regions remained more intact long-term after soman intoxication. The MRI neuronal lesions were positively correlated with the histological markers of ne
The GABA system, a new target for medications against cognitive impairment-Associated with neuroactive steroids.
The prevalence of cognitive dysfunction, dementia, and neurodegenerative disorders such as Alzheimer's disease (AD) is increasing in parallel with an aging population. Distinct types of chronic stress are thought to be instrumental in the development of cognitive impairment in central nervous system (CNS) disorders where cognitive impairment is a major unmet medical need. Increased GABAergic tone is a mediator of stress effects but is also a result of other factors in CNS disorders. Positive GABA-A receptor modulating stress and sex steroids (steroid-PAMs) such as allopregnanolone (ALLO) and medroxyprogesterone acetate can provoke impaired cognition. As such, ALLO impairs memory and learning in both animals and humans. In transgenic AD animal studies, continuous exposure to ALLO at physiological levels impairs cognition and increases degenerative AD pathology, whereas intermittent ALLO injections enhance cognition, indicating pleiotropic functions of ALLO. We have shown that GABA-A receptor modulating steroid antagonists (GAMSAs) can block the acute negative cognitive impairment of ALLO on memory in animal studies and in patients with cognitive impairment due to hepatic encephalopathy. Here we describe disorders affected by steroid-PAMs and opportunities to treat these adverse effects of steroid-PAMs with novel GAMSAs.
Medroxyprogesterone acetate impairs memory and alters the GABAergic system in aged surgically menopausal rats.
In women, medroxyprogesterone acetate (MPA) is the most commonly used progestin component of hormone therapy (HT). In vitro, MPA negatively impacts markers of neuronal health and exacerbates experimentally-induced neurotoxicity. There is in vitro evidence that these factors are driven by GABAergic and neurotrophic systems. Whether these effects translate to a negative impact on brain function has not been tested in vivo, clinically or preclinically. Here we evaluate the mnemonic and neurobiological effects of MPA in the surgically menopausal rat. Aged ovariectomized (OVX) rats were given subcutaneous vehicle, natural progesterone, low-dose MPA or high-dose MPA. Multiple cognitive domains were analyzed via the water radial-arm maze (WRAM) and Morris maze (MM). Cognitive brain regions were assayed for changes in the GABAergic system by evaluating GAD protein, the synthesizing enzyme for GABA, and neurotrophins. On the WRAM, both progestin types impaired learning. Further, high-dose MPA impaired delayed memory retention on the WRAM, and exacerbated overnight forgetting on the MM. While neurotrophins were not affected by progesterone or MPA treatment, both progestin types altered GAD levels. MPA significantly and progesterone marginally decreased GAD levels in the hippocampus, and both MPA and progesterone significantly increased GAD levels in the entorhinal cortex. These findings suggest that MPA, the most commonly used progestin in HT, is detrimental to learning and two types o
Enhanced interhemispheric functional connectivity in elderly anxiety patients with long-term benzodiazepine use: an fNIRS study.
UNLABELLED: Individuals with anxiety exhibit high clinical usage of benzodiazepines, particularly among those with long-term use, yet the impact of these medications on cognitive function remains inconclusive. Previous research has predominantly focused on epidemiological data and metabolic measurements, often overlooking both cortical activation and the synchrony between different brain regions. This study investigates how brain neuronal activities are modulated in both long-term benzodiazepine users and nonusers during cognitive tasks, offering insights into the neural mechanisms underlying cognitive function. Fifty older adults with anxiety disorders participated in this study, including 31 long-term benzodiazepine users (BZD group) and 19 nonusers (control group). Functional near-infrared spectroscopy was used to assess cortical activation and functional connectivity during a verbal fluency task. Our study is the first to find a greater interhemispheric functional connectivity in chronic benzodiazepine users. However, no notable differences were detected between the two groups regarding behavioral performance, cortical activation, or changes in oxygenated hemoglobin concentration. Moreover, cumulative dosage of benzodiazepines use had no significant effect on dorsolateral prefrontal cortex activation. Long-term benzodiazepines use does not affect brain activation but impacts functional connectivity. The increased interhemispheric connectivity may serve to maintain the sta
Studies in rats of a target specific and reversible general anesthetic with a favorable safety profile.
Delirium and cognitive decline are linked to clinically relevant anesthetics in the vulnerable elderly population, prompting the need for new and safer anesthetic strategies. Most general anesthetics potentiate the activity of GABAA receptors. However, these drugs act on myriad other targets, causing unwanted effects. Dexmedetomidine (Dex), a selective α2 adrenergic receptor agonist, is associated with reduced incidences of delirium and cognitive decline in the elderly. Unfortunately, despite its sedative effect, Dex is not suitable for general anesthesia when used alone. We previously demonstrated that enhancing Dex with low doses of either sevoflurane or propofol resulted in a potent general anesthetic that was rapidly reversible. In this study we assessed whether Dex enhanced by magnesium (Mg2+) infusion could produce a general anesthetic. Mg2+ is an essential ion in the body, possessing sedative effects attributable to antagonizing NMDA receptors and voltage-gated Ca2+ channels and it may indirectly potentiate GABAergic signaling. Mg2+ has been shown to be neuroprotective and safe to use even in pregnant women. Mg2+ is a safer adjunct agent than either sevoflurane or propofol. For this study, rats of both sexes were anesthetized with a combination of Dex and Mg2+ and then underwent procedures to determine the efficacy of the anesthetic. Dex with Mg2+ produced an effective general anesthetic that was reversed by a combination of low dose atipamezole, an α2 competitive anta
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