Figure 2.

Representative effects of ketamine on visual search performance (monkey G, 0.5 mg/kg ketamine). A, Mean (±SE) saccade amplitude for 1 min intervals following the injection of ketamine. The gray shaded area indicates the epoch during which there was a significant decrease in saccade amplitude. The mean (including ±SE) saccade amplitude for the control block is indicated by the horizontal line. B, Mean (±SE) response latency for each minute following the injection of ketamine. C, Mean (±SE) response latency as a function of stimulus luminance difference before and after ketamine administration. D, Mean (±95% CI) response accuracy as a function of stimulus luminance difference before and after ketamine administration. Ketamine increased the proportion of correct trials at intermediate stimulus luminance differences (see Materials and Methods) (p < 0.05, χ² test), shifting the psychometric function to the left. Discrimination threshold was taken as the point at which the Weibull function reached 64% of its maximum (dashed line).