Brent Doiron, PhD
Department of Mathematics
University of Pittsburgh
host: Adrienne Fairhall
New Cortex. Who dis(inhibition)?
It is now clear that the inhibitory circuitry within cortical networks is very complex, with multiple cell types interacting with one another and pyramidal neurons in complicated and cell specific ways. The theoretical community has been slow to adapt to this new circuit reality, and much of our results are obtained from analysis of simpler recurrent excitatory-inhibitory circuits. Two often cited functional roles of inhibition is to: 1) stabilize the dynamics of recurrently coupled excitatory networks, and 2) enact gain control of excitatory neuron responses to a driving stimulus. In classic excitatory-inhibitory networks mechanisms that place the network in a high gain state necessarily flirt with network instability. We analyze how recurrent networks of pyramidal neurons (PN), parvalbumin-expressing (PV), somatostatin-expressing (SOM), and vasoactive intestinal polypeptide-expressing (VIP) interneurons compartmentalize stability and gain control through distinct inhibitory and disinhibitory pathways. This permits a disassociation of stability and gain control in the circuit. We further show how PC to SOM connections can be crucial in state dependent gain amplification with a simultaneous decrease of shared variability (noise correlations). In sum, by expanding the complexity of inhibitory architecture cortical circuits can navigate distinct functional roles of inhibition through a “division of labor” with the inhibitory circuit. This imparts a robustness to the functional operations of the circuit that is absent in the often fine-tuned reduced excitatory-inhibitory framework.