Figure 7.

The coherence and time dependence of voluntary-saccade latencies. A, C, Scatter plots of Spearman's rank correlation coefficients (ρ) between the trial-by-trial latency and the coherence (abscissa) or viewing time (ordinate) of the motion stimulus. Points indicate values of ρ computed from individual sessions for monkeys At (A) and Av (C) for correct trials. Arrows are medians. B, D, Histograms of ρ between the trial-by-trial latency and the decision variable inferred from behavior on correct, nonmicrostimulation trials computed for individual sessions for At (B) and Av (D). Arrows indicate median values. Gray bars indicate counts corresponding to H₀: ρ = 0, p < 0.05. Negative values in A–D imply that latencies tended to be shorter (responses were faster) on trials with more easily discriminable stimuli. E–H, Average latencies (z-scored per choice per session) from correct trials in blocks of sessions for both monkeys combined (using the same sessions described for Fig. 4A–D), computed as the mean value in 100-ms-wide bins of viewing time offset in steps of 25 ms for each coherence (see inset in E). The arrow in each panel indicates the mean viewing time used in the given sessions. I, J, Best-fitting values of γ₁ (and SEMs) from Equation 6b, which quantifies the relationship between latency and the strength and duration of the motion stimulus on the given trial, plotted as a function of session number. Lines are linear fits (H₀: slope = 0, p < 0.05 in both cases).