Figure 8.

The coherence and time dependence of voluntary-saccade targeting errors. A, C, Scatter plots of Spearman's rank correlation coefficients (ρ) between the trial-by-trial targeting error 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 targeting error 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. Positive values in A–D imply that the saccade endpoints were further from the chosen target on trials with more easily discriminable stimuli. E–H, Average mistargeting magnitude (z-scored per choice per session) from 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). These plots include only data from correct trials and sessions in which ρ > 0 (from B and D). I–L, Same conventions as in E–H, but using only data from sessions in which ρ < 0. M, N, Best-fitting values of γ₁ (and SEMs) from Equation 6b, which quantifies the relationship between mistargeting magnitude and the strength and duration of the motion stimulus on the given trial, plotted as a function of session number. In both cases, the slope of a weighted linear regression was not significantly different from zero (p > 0.05).