Figure 8.

Suppression and gating by silence and synchrony in AP patterns. A, EPSPs evoked by spontaneous in vivo pattern. APs were evoked only after a period of silence (1 s, bar). Gray dashes at bottom of traces in A–D mark individual stimuli of the in vivo pattern applied to giant terminals. V _m = −70 mV. Similar results have been obtained in four independent experiments. B, Two giant terminals (1 and 2) on the same POm neuron were sequentially stimulated with two different spontaneous in vivo AP patterns. Each pattern had one additional stimulus (asterisk). Except for the first stimulus, the EPSPs remained subthreshold. V _m = −71 mV. Similar results have been obtained in three independent experiments. C, Giant terminals 1 and 2 were simultaneously stimulated with the same spontaneous in vivo patterns as shown in B, with 8 of 10 stimulus patterns yielding stimulus-locked APs. Additional stimuli (asterisk) evoked an AP in the POm neuron. An AP was also evoked by random coincidence when the terminals were not fully depressed (arrow). V _m = −71 mV. D, As in C but the region of the synchronized stimuli (asterisk) enlarged to show summation of the EPSPs evoked from terminal 1 and 2 (dashed line, AP threshold). V _m = −71 mV.