Figure 11

Illustration of the reason for the SI firing pattern. The figure shows two periods of input-2, with pulses coming in at O and \(O'\). The SI cell is inhibited and cannot fire in the interval OC (and \(O'C'\)), of length c. Point A lies a distance \(T_{1}\) to the right of C, while points \(C'\) and \(A'\) are the images of C and A in the second period. Suppose the SI cell fires at a phase inside the interval CA. Since at least \(2T_{1}\) time must pass until it can fire again, and by assumption \(CO'\) is less than \(2T_{1}\), the SI cell cannot fire again in the same period. It also cannot fire in the interval \(O'C'\), so it will fire again at the first input-1 pulse after \(C'\). Since successive input-1 pulses are separated by \(T_{1}\), the next SI spike will necessarily fall in the interval \(C'A'\). This demonstrates that if the SI cell fires at a phase between C and A in one period, it will also do so in all subsequent periods