Population average histograms (top row) and their cumulative histograms (bottom row) of responses to preferred orientation in three different contexts (sample, match, and non-match). A, Averaged response of 24 match–nonmatch modulation neurons showing larger responses to match stimuli. B, Averaged response of six match–nonmatch modulation neurons showing larger responses to nonmatch stimuli. C, Averaged response of six sample–test modulation neurons showing larger responses to sample stimuli. D, Averaged response of eight sample–test modulation neurons showing larger responses to test stimuli. Differential latencies between the sample and match stimulus, sample and nonmatch stimulus, and match and nonmatch stimulus are indicated by closed triangles, open triangles, and arrows, respectively, in the cumulative histograms. The difference of activity between match and nonmatch trials did not reach statistical significance in neurons with sample–test modulation. For the calculation of differential latencies, see Materials and Methods.