DYNAMIC TRANSITIONS IN GLOBAL NETWORK ACTIVITY INFLUENCED BY THE BALANCE OF EXCITATION AND INHIBITION

The conditions under which spontaneous activity is self-sustaining in network models may be important for understanding information processi ng in brain activity. We explored the influence of the membrane time-c onstant and cellular threshold potential on spontaneous network activi ty through parameter searches in a large-scale neural network of horiz ontally interconnected excitatory and inhibitory units. We show here t hat a wide range of activity patterns and behaviours emerge in a netwo rk where only the threshold potential and membrane time-constant vary. These simulations revealed a region within the parameter space for me mbrane time-constant and threshold potential where the balance of post synaptic excitation and inhibition enables the network to make transit ions rapidly between different activity states. Cross-correlograms sho wed the influence of global excitation and inhibition on the interacti ons of pairs of cells within a subnetwork. These cross-correlations in dicate that, when a balance of excitation and inhibition exists, the c ontribution of the postsynaptic potentials to the membrane potential a nd the integration time determined by the membrane time-constant may p lay a key role in forming spatio-temporal representations.