5-HTP disrupts orienting and inhibition performance. A, Average performance over the course of a session during orienting trials (top) and inhibition trials (bottom) for face images. B, Average performance over the course of a session during orienting trials (top) and inhibition trials (bottom) for scrambled control images. Performance during saline sessions is shown in blue, whereas 5-HTP session is shown in green (mean ± SEM; A, B). The gray circles above each time series represent significant differences between 5-HTP and saline at each time point (p < 0.05, Wilcoxon signed rank; A, B). C, The percent change in performance because of 5-HTP relative to saline (mean ± SEM), illustrating that 5-HTP selectively impaired performance on inhibition trials with face images (solid lines) but not those with control images (dashed line). ***p < 0.001; n.s., not significant, ANOVA. Inset, Each shape represents data from individual monkeys; filled shapes depict performance on trials with face images, and open shapes depict performance on trials with control images.