What resolves this contention: Whether direct and indirect SPN pathways operate…

What resolves this contention: Whether direct and indirect SPN pathways operate in opposition or are co-activated. The DA-bias study supports an opponent push-pull architecture (DA shifts the balance), while the calcium-imaging study reports concurrent activation of both populations during movement initiation, undermining strict opposition. / We find that increasing and decreasing DA biases striatal activity toward the direct and indirect pathways, respectively, by changing the overall number of SPNs recruited during behavior in a manner not predicted by existing models of DA function. / Concurrent activation of SPNs from both pathways in one hemisphere preceded the initiation of contraversive movements, and predicted the occurrence of specific movements within 500 ms.