Role of inhibitory neurons in temporal correlations of critical and supercritical spontaneous activity

Experimental and numerical results suggest that the brain can be viewed as a systemacting close to a critical point, as confirmed by scale–free distributions of relevantquantities in a variety of different systems and models. Less attention has received theinvestigation of the temporal correlation functions in brain activity in different, healthyand pathological, conditions. Here we perform this analysis by means of a model withshort and long-term plasticity which implements the novel feature of different recoveryrates for excitatory and inhibitory neurons, found experimentally. We evidence theimportant role played by inhibitory neurons in the supercritical state: We detect anunexpected oscillatory behaviour of the correlation decay, whose frequency depends onthe fraction of inhibitory neurons and their connectivity degree. This behaviour can berationalized by the observation that bursts in activity become more frequent and witha smaller amplitude as inhibition becomes more relevant.