Figure 5.

Creation of an optimal phase relationship for CTC. (A) EPSCs from an upstream population successfully induce 1 : 1 phase‐locking by periodically driving the E‐cell above its inhibition and triggering an excitatory volley, which is immediately followed by an inhibitory volley. When the circuit is phase‐locked, input pulses arrive when inhibition is low, an optimal condition for CTC. (B–D) EPSCs fail to phase‐lock the network 1 : 1, owing to frequency mismatch. (B) The forcing period is too short to phase‐lock the PING circuit 1 : 1, but it can phase‐lock the PING circuit 2 : 1 – the second pulse arrives when the E‐cell is under too much inhibition to spike, but the third one evokes an excitatory volley. (C) The forcing period is too short to phase‐lock the circuit. As in B, the second pulse arrives too early to evoke an excitatory spike; unlike in B, the third pulse is too late, and arrives under heavy inhibition. (D) The forcing period is too long to phase‐lock the circuit. The E‐cell recovers from inhibition, spikes, and triggers an inhibitory spike before the second pulse arrives. The second pulse arrives under too much inhibition to evoke another excitatory spike.