Figure 2. Inhibitory roles in learning goal-directed navigation.

A. Place cells overrepresent behaviorally relevant locations such as reward zones and, while place fields tile the entire environment, more place fields cluster around these important locations. B. Vasoactive intestinal polypeptide (VIP)-expressing interneurons target other interneurons (Int.) that provides either perisomatic or dendritic inhibition onto pyramidal cells (Pyr.). In a recent study investigating a local CA1 disinhibitory circuit in goal-directed learning, optogenetically activating VIP interneurons (light blue) was found to induce faster learning of a new reward zone, as demonstrated by increased licking near the reward location [66]. Optogenetic silencing (yellow) led to impaired learning in the same goal-directed navigation task. These findings suggest that new goal learning (and its behavioral expression) is mediated by local inhibition and disinhibition of pyramidal cells. C. Left, consistent with these behavioral changes in B, optogenetic silencing of VIP neurons led to a reduced proportion of place cells with fields near the goal (yellow, inhibitory opsin ArchT in VIP interneurons). Right, in contrast to the observed behavioral effects, VIP optogenetic activation (light blue, excitatory opsin ChR2 in VIP interneurons) did not lead to observable changes in the proportion of goal-representing place cells. These results suggest that transient release of pyramidal cells from local inhibition is necessary, but not sufficient, to induce learning-dependent neuronal reorganization.