Effect of scopolamine on neuronal firing. A, Mean FRs from 135 PFC neurons (dark gray bars represent control; light dark gray bars represent scopolamine) in the delay, stimulus, and ITI epochs of the task. Scopolamine significantly decreased FRs of recorded neurons in both pro-saccade and anti-saccade trials in the delay, stimulus, and ITI epochs. The indicated significance value applies to all comparisons. B, Decreases to normalized FRs for neurons onto which various doses of scopolamine were tested: 5 nA, p = 0.042; 6–20 nA, p = 0.00081; 21–40 nA, p = 0.00021; 41–100 nA, p < 0.0001. C, Recovery of FR upon cessation of scopolamine ejection. Although recovery condition FR was significantly greater than scopolamine condition (p = 0.00024), it did not reach control levels. This includes all cells given a recovery condition and a control mean FR >1 spikes/s. Error bars indicate SEM. *p < 0.05, **p < 0.01, ***p < 0.0001 (Wilcoxon signed rank test with Holm-Bonferroni correction). FRs were normalized as described (see Materials and Methods).