Figure 11.
Comparison of spontaneous and evoked correlation. A, CCGs for activity evoked by the most effective orientation (top), the least effective orientation (middle), and spontaneous activity (bottom; gray) for an example V1 pair. The spontaneous CCG is larger and broader than that for the best-compromise stimulus. The least effectively oriented stimulus disrupts the broad CCG observed during spontaneous activity. B, Same as in A for a pair for which the CCG of spontaneous activity and activity evoked by the least effective orientation have a similar amplitude; the spontaneous CCG is substantially broader than those for activity evoked by high-contrast stimuli. C, Average CCGs (n = 24 pairs) for spontaneous activity (gray) and activity evoked by ineffective orientations (black). Although the firing rate was stronger for the evoked activity, the CCG peak amplitude was smaller. Vertical calibration is 0.01 coincidences per spike (coinc/spk) for A, 0.02 coinc/spk for B, and 0.01 coinc/spk for C; horizontal calibration is 500 ms. D, Time scale of correlation for spontaneous (gray) and ineffective (black) stimuli. The rCCG curves show that correlation is stronger for the spontaneous activity at all time scales. Error bars indicate SEM.