Figure 3. Movement time effects on putative DA firing. To determine whether putative DA activity was affected by speed of behavioral response, average population histograms were split into fast and slow trials based on movement time within each session and then averaged across sessions. A–D, K, L, Average population histograms for fast and slow movement times for GO (blue), STOP (red), and STOP error (dashed) trials, aligned to port exit (A, B), well entry (C, D), and reward delivery (K, L). E–J, M, N, Population average distributions for effects between fast and slow trials. Arrows depict direction of distribution shift for significant effects. A, B, Activity was aligned to port exit for fast and slow movement times. E–G, Firing rates were compared between fast and slow trial types during the response epoch by calculating trial type indices for GO trials (GO fast – GO slow), STOP trials (STOP fast – STOP slow), and STOP errors (STOP error fast – STOP error slow). During the response epoch, firing was significantly less on slow STOP trials compared to fast STOP trials (F), but there was no difference in firing between fast and slow GO trials (E) or STOP errors (G). C, D, Activity was aligned to well entry for fast and slow movement times. H–J, Firing rates were compared between fast and slow trial types during the post-response epoch by calculating trial type indices described above. During the post-response epoch, firing on fast STOP errors was significantly lower than firing on slow STOP errors (J). There was no significant difference in firing between fast and slow GO (H) or STOP trials (I). K, L, Activity was aligned to reward delivery for fast and slow movement times. M, N, Firing rates were compared between fast and slow trials during the reward epoch by calculating trial type indices for GO trials (GO fast – GO slow) and STOP trials (STOP fast – STOP slow). During the reward epoch, firing was significantly higher on slow STOP trials compared to fast STOP trials (N). There was no significant difference between fast and slow GO trials at the time of reward (M).