Fig 3. 3 neuron feedforward inhibition circuit.

A: A 3-neuron circuit displaying feedforward inhibition. Neuron 1 provides excitatory input to neurons 2 and 3, while neuron 3 provides inhibitory input to neuron 2. Neuron 3 also has a self-history coupling, denoted by an autaptic loop, which implements a refractory period in this circuit model. B: Leftmost, the effective interaction from neuron 1 to 2 when neuron 3 is unobserved. Subsequent plots decompose this interaction into contributions from neuron 1’s direct input to neuron 2, and its indirect input through neuron 3. The indirect input through neuron 3 also takes account of neuron 3’s self-history interaction. C. Leftmost, the effective interaction (membrane response) from neuron 1 to 2, subsequently decomposed into contributions from the direct interaction and the indirect interaction from 1 to 2.