Fig. 9.

Responses to pulse trains (9–10 pulses at 100 Hz) before and after the induction of synaptic depression by a tetanus (20 Hz). The stimulus is depicted at the bottom. The 100 Hz train was presented once before tetanus and twice after tetanus, and a single pulse occurred 35 msec after the pretetanus train and the second post-tetanus train. A–C, Low-pass filtered (153 Hz corner) and averaged (n > 3) responses of three neurons. On both the left andright, time-expanded traces show unfiltered responses to the trains. A andB were the most common responses; C was rarely encountered. A, A fast-PSP neuron.B, A slow-PSP neuron. C, A fast-PSP neuron in which synaptic depression does not reduce responses to 100 Hz trains. Arrows indicate facilitation.