Disinhibitory circuitry gates associative synaptic plasticity in olfactory cortex
Inhibitory microcircuits play an essential role in regulating cortical responses to sensory stimuli. Interneurons that inhibit dendritic or somatic integration in pyramidal neurons act as gatekeepers for neural activity, synaptic plasticity and the formation of sensory representations. Conversely, interneurons that specifically inhibit other interneurons can open gates through disinhibition. In the rodent piriform cortex, relief of dendritic inhibition permits long-term potentiation (LTP) of the recurrent synapses between pyramidal neurons (PNs) thought to underlie ensemble odor representations. We used an optogenetic approach to identify the inhibitory interneurons and disinhibitory circuits that regulate LTP. We focused on three prominent inhibitory neuron classes-somatostatin (SST), parvalbumin (PV), and vasoactive intestinal polypeptide (VIP) interneurons. We find that LTP is gated by the inactivation SST or PV interneurons or by activation of VIP interneurons. Further, activation of VIP interneurons strongly inhibits putative SST-cells during LTP induction, but only weakly inhibit PV-interneurons. Taken together, these findings suggest that VIP-interneurons mediate a disinhibitory circuit that can regulate synaptic plasticity during olfactory processing.