Investigating the role of divisive inhibition (gain control) in the dynamics of neocortical networks

Experimental results suggest that there are two distinct mechanisms of inhibition in cortical networks: subtractive and divisive inhibition. Subtractive inhibition shifts the neuronal input-output function to the right without changing the slope, whereas divisive inhibition causes a reduction in slope providing gain control. Notably, recent experiments show that these mechanisms are delivered by different populations of interneurons with a well understood connectivity between them and the pyramidal population. A novel mathematical model of this basic neocortical circuitry was developed to investigate the role of divisive inhibition in network dynamics. In particularly, the theoretical study focuses on the transition from ordered to chaotic behaviour.

The results suggest that the presence of divisive inhibition in the network prevents any abrupt transition from regular to chaotic dynamics across the parameter space. Therefore, new hypotheses arise about the influence of divisive inhibition on the stability of dynamic network activity patterns and the transition from physiological to pathological (epileptic) brain dynamics. Experimental approaches that are used to test these hypotheses will be discussed as well.