Responses of primary visual cortical neurons to natural movies in anesthetized cat

First, we computed the inter-spike interval (ISI) histograms of the 88 cells in our database. Twenty-eight cells were excluded from further analysis due to sparse interval data. A large fraction of the remaining 60 cells exhibited a predominance of short ISIs. The maximum value in the histogram in 39 cells was below 2 ms, and was below 4 ms for all but 8 cells. In addition, by inspecting the joint interval histogram of each spike interval versus the subsequent interval, we found these short intervals to be mainly due to spike bursts rather than spike doublets.