Synchronous oscillations in the cat retina.

Retinal ganglion cells exhibit oscillatory responses which are precisely synchronized over large distances. Here we examined, with multi-electrode recordings, the time course of synchronization during spontaneous and stimulus-driven oscillatory activity. Spontaneous discharges showed synchronized oscillations at approximately 30 Hz, which were occasionally associated with slower superimposed oscillations in the range of 1-5 Hz. Stationary stimuli or moving gratings induced synchronous oscillations at higher frequencies (mean of 79.0 +/- 20.0 Hz for OFF- and 91.7 +/- 11.7 Hz for ON-responses), with time lags of a few milliseconds. At response onset, the first few oscillatory cycles were occasionally time locked to the stimulus. Thereafter, synchronization became independent of stimulus coordination and was exclusively due to neuronal interactions. Oscillatory modulation emerged rapidly and was sustained throughout the responses while oscillation frequency decreased gradually. This periodic patterning of responses persisted despite brief and local occlusion of stimuli, suggesting that synchronous oscillations emerge from population dynamics and entrain cells even if they are intermittently silenced.