Figure 1.

Variant models of a basic organization show variants of a common behavior in which external excitation shifts the network from a synchronous to an asynchronous state. (A) Basic organization of models of a small patch of a cortical layer. The model networks contain recurrently connected excitatory and inhibitory neurons which receive external excitation. (B) Rasters indicating spike times of neurons from a model network (van Vreeswijk and Sompolinsky, 1998; Brunel, 2000; Mehring et al., 2003; Renart et al., 2010). The neurons show some sychronization at low external excitation, but become asynchronous at high external excitation. (C) Rasters indicating spike times of neurons from a variant model network with stronger recurrent connections and more slowly decaying synapses (Harish and Hansel, 2015). Like the model network in (B), the neurons of the variant show some synchronization at low external excitation, but become asynchronous at high excitation. However, this variant model network differs from the model network in (B), because each neuron of this variant in the asynchronous state has periods of sustained firing such that the autocorrelation of the neuron decays more slowly.