Figure 8.

Elimination of poorly timed spikes in NM. A, A sound stimulus (top) evoked eighth nerve action potentials (middle, vertical lines) with slightly imperfect phase-locking. When the timing of eighth nerve action potentials is poor, as in the middle responses, the modeled neuron failed to initiate a spike (bottom). Accommodation of voltage threshold is shown by the dotted line. B, On an expanded timescale, a single excitatory input (top) that evokes a subthreshold EPSP (middle) greatly changes the excitability of the neuron. This is represented as the inverse of EPSC threshold (bottom). At the very onset of the EPSP, during the coincidence detection window (gray shaded area), excitability is high. However, it very quickly drops well below control levels (dotted line) during the succeeding time period, decreasing to such an extent as to become refractory (dashed line and stippled area), after which it returns to control levels.