Sparse balance: Excitatory-inhibitory networks with small bias currents and broadly distributed synaptic weights
Fig 6
Asynchronous irregular activity in an E-I network with small input current.
A) Responses of 500 excitatory (red) and 500 inhibitory (blue) units in two networks, one with lognormal (left) and the other with gamma (right) weight distributions. Responses are sparse and distributed across the population. B) Rates (dark) superimposed on the currents (light) for four example cells from each population. Response is infrequent as fluctuations occasionally push the current above threshold. C) Fraction of active units for individual populations (red and blue) and across the entire network (gray). The inhibitory population is more active than its excitatory counterpart. D) Fraction of (simulation) time units spend above threshold for each population and connectivity distribution. This distribution is wide and skewed. Both choices of the connectivity distribution produce qualitatively similar results. (Model parameters: g = 1, JEE = JIE = 1, JEI = 2, JII = 1.2, IE = 2, II = 1, NE = NI = 3000, K = 600, ϕ = [tanh]+).