Figure 3: Conditions for signal propagation through a feedforward network with correlated inhibition. (A): Model of a feedforward network with correlated inhibition induced by FFI. (B), Signal propagation of a synchronous input through the network when each group projects only onto the RS population of the following group. Due to the instability of the ground-state of purely excitatory feedforward networks (Tetzlaff et al., 2002), transient random fluctuations in the asynchronous background ac- tivity may occasionally induce spontaneously propagating synchrony, as can be observed here some 50 ms before the stimulus onset. (C), Propagation of an asynchronous input through the same network. The asynchronous input induced elevated firing rates in the first groups. However, the activity rapidly synchro- nized over subsequent groups. (D), Propagation of synchronous input was hardly affected by correlated inhibition, induced by including the FS neurons in the target population of the successive group. E, FFI in the feedforward network prevented asynchronous inputs from inducing synchronous activity in subsequent groups.

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