Figure 5.

Temporal properties and inhibitory effects of ISN. (A Upper) Large periods of activity (between brackets) interrupted by faster waves. The autocorrelogram (Right) indicates a dominant rhythm of 60 Hz. (Lower) Bursts of IPSPs occurring at a frequency of 80 Hz in another cell. (B) Instantaneous frequencies of IPSPs in a simple ISN (Inset), plotted against time. M spikes (arrows) were evoked (n = 4 trials) by intracellular current injections that increased the frequency of the noise from 30 to 130 Hz. Control IPSPs were either continuous (n = 3, open symbols) or were induced during the quiet state (♦). (C1) Superimposed traces of antidromic M spikes (n = 10) recorded during the quiet (Left) or the noisy (Center) state and their superimposed averages (Right), indicating a 38% reduction during the noisy state (Right). (C2) Same presentation as above of excitatory postsynaptic potentials (arrow) followed by IPSPs (crossed arrow) evoked by auditory stimuli (sound, 500 Hz, 25 cycles, 50 dB). Note a 36% mean reduction during the noisy periods.