What resolves this contention: The Alexander/DeLong parallel-loop framework loc…

What resolves this contention: The Alexander/DeLong parallel-loop framework localizes basal-ganglia disorder pathophysiology to striatal dopamine deficits within segregated circuits; the 2023 review reports that striatal DA loss alone is insufficient and extra-striatal DA modulation is causally required for parkinsonian motor deficits. / Parallel, segregated cortico-basal-ganglia-thalamocortical circuits originate in distinct cortical territories and remain functionally segregated through the striatum and thalamus, with motor symptoms in basal-ganglia disorders attributable to disruption of striatal dopaminergic signaling. / Striatal dopamine depletion alone is not sufficient to induce parkinsonism; restoration of extra-striatal dopamine signaling attenuates motor deficits, indicating that PD circuit pathophysiology cannot be localized to a single striatal node within the parallel-loop framework.