The dorsomedial striatum: an optimal cellular environment for encoding and updating goal-directed learning

Studies in rodents have described a prefrontostriatal network that functions as a learning and memory system to encode and retrieve goal-directed actions. Prelimbic cortex (PL) plays a key role in the encoding process as a form of short-term working memory for specific action-outcome associations that are then encoded in the posterior dorsomedial striatum. Within the latter structure the PL projection is bilateral and assessments of plasticity at the primary cell types suggest learning-related plasticity occurs bilaterally at direct pathway (striatonigral) spiny projection neurons (dSPNs). The activity of dSPNs is regulated by indirect pathway (striatopallidal) neurons (iSPNs) which, via their direct connections, can modulate dSPN plasticity depending on local cholinergic and dopaminergic activity. In so doing, iSPNs appear to select ensembles of dSPNs for regional plasticity while protecting others from such changes.