Figure 2.
Contrast dependence of 60 Hz phase locking in a complex cell. A, Spike rasters. Spike trains are shown wrapped on the 200 msec period of the 5 Hz drifting grating stimulus, yielding 40 cycles from two 4 sec repeats. The stratification of spikes into columns 16.7 msec apart sharpens with increasing spatial contrast in successive rows. B, Cumulative histograms of the same spikes as shown in A, averaged in 1 msec bins across the 40 cycles at each contrast. The power ratio, which is mean 60 Hz power divided by mean power in the 50-70 Hz band, is shown with each contrast. C, Mean spike rate (open circles) and the amplitude of the 60 Hz component of the spike train (filled circles) at each contrast. D, Amplitude spectra of the spike responses to the three highest contrasts (39,59,90%) are pooled for this graph. The dominance of the line at 60 Hz is obvious. Note in B and C that the power ratio increases from 16.4 at 39% contrast to 37.1 at 90% contrast even though the spike rates at these two contrasts are equal. Cell mt8 u025_005.