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Fig. 12.2. Effect of connection type and decay rate on synchronization. Thirty neurons with full lateral connections, either excitatory or inhibitory, were simulated for 500 iterations (see Figure 12.1 for plotting conventions). Four experiments were conducted where the type of the lateral connections (excitatory or inhibitory) and the synaptic decay rates (&lambda) were altered. All other parameters were the same for all four cases. (a) Excitatory connections with slow decay (&lambda_E = 0.1) result in desynchronized activity. (b) Excitatory connections with fast decay (&lambda_E = 1.0) result in synchronized activity. (c) Inhibitory connections with slow decay (&lambda_I = 0.1) result in synchronized activity. (d) Inhibitory connections with fast decay (&lambda_I = 1.0) result in synchronized activity. Note that in the two synchronized cases (b) and (c), the firing rate is higher in (b): The input activity to the neuron g(t) approaches the threshold faster because of the excitatory lateral input. The results show that synchronization behavior can vary greatly even for the same connection type if the synaptic decay rate differs.