Conditional learning increases inhibition of layer 4 excitatory neurons by somatostatin- and parvalbumin-expressing interneurons in the barrel cortex.

Synaptic strength underlies information processing, learning, and memory storage, yet little is known about how learning impacts synaptic inputs and outputs of specific GABAergic interneurons, particularly in the somatosensory cortex. Using a simple conditional learning model in mice, in which whisker stimulation was paired with a tail shock, we investigated plastic changes in inhibition mediated by somatostatin- (SST-), parvalbumin- (PV-), and vasoactive intestinal polypeptide-expressing interneurons (VIP-INs) in the barrel cortex. In vitro patch-clamp recordings and optogenetics revealed that conditional learning increases inhibition of layer 4 (L4) excitatory neurons by SST- and PV-INs. A small fraction of L4 excitatory neurons in the barrel cortex receives inhibition from local VIP-INs; however, learning does not affect this inhibition. Additionally, learning does not alter excitatory inputs to any of the three interneuron types. These findings suggest that enhanced inhibition by SST-INs and PV-INs may improve information processing and memory coding in L4 of the barrel cortex.