My collaborator Robert Guangyu Yang and I will be presenting a poster on our work at the 2014 Society for Neuroscience meeting, on Wednesday, November 19, in the afternoon session. Our poster (WCC 147B) is titled: Gating neural activity by a disinhibitory mechanism in cortical circuit. Our abstract is below:
A disinhibitory circuit has recently been studied across multiple areas in the mouse cortex. The circuit consists of three major types of cortical interneurons that are specialized in their synaptic targets. Specifically, vasoactive intestinal peptide positive (VIP) neurons inhibit somatostatin-positive (SOM) neurons, which in turn inhibit dendrites of pyramidal cells. In this way, VIP neurons disinhibit pyramidal dendrites. In vivo experiments have demonstrated that this disinhibitory circuit is recruited by specific behavioral contexts, such as active sensing or receipt of reinforcement signals. However, the function of this disinhibitory circuit remains unclear. To explore the role of dendritic disinhibition in regulating pyramidal cell activity, we studied simple compartmental neuron models endowed with active dendritic processes such as NMDA spikes. We found that disinhibition can effectively mediate a control pathway that opens the gate for signal propagation. Importantly, this control pathway can operate without interfering with the content coded in incoming signals. We found that neuronal dynamics depend critically on the temporal sparseness of dendritic excitation in the incoming stimulus and of dendritic inhibition from SOM cells. If the control pathway is mediated by disinhibition, it can open the gate to signal propagation without directly exciting the pyramidal cell and therefore avoid being confused with the stimulus input. We studied a cortical circuit model comprised of pyramidal cells and three interneuron types: SOM, VIP, and parvalbumin positive (PV). The circuit is constrained by experimentally-measured connectivity and cellular/synaptic dynamics. We analyzed the dynamical regimes wherein disinhibition can be recruited by top-down control signals, regulating signal propagation and network computations. These extended circuit computations can subserve cognitive operations in tasks that require gating.