Article Figures & Data
Figures
- Figure 1.
Experimental setup and basic countermanding findings. A, Graphical depiction of the three trial types. During the preparation of the test saccade, which occurs after a sequence of three to six saccades, a stop signal could be given (color change of the fixation point). At various times, a green vertical bar was flashed, which subjects had to localize in space after the trial was ended (using mouse control). Go trials (green) are trials without a stop signal; noncancelled trials (in blue) are trials with a stop signal, but a saccade was made; cancelled trials (in red) are trials with a stop trial during which the saccade was successfully inhibited. B, SRT of a representative subject subdivided by the saccade-sequence length and trial type. SRTs of the noncancelled trials are significantly lower than those of the go trials (p < 0.05). C, Inhibition functions subdivided by sequence length for the same subject. D, SSRT does not vary systematically with sequence length (p > 0.05).
- Figure 2.
Single-subject analysis. A, Localization errors and mean curve (based on a Gaussian moving window of 15 ms) as a function of flash onset relative to saccade onset. Go trials are in green; noncancelled trials are in blue. The black trace shows the planned saccade. The gray bar shows the mean saccade duration. Dashed lines indicate flash locations (−10 and 10°). B, Measured SRT versus predicted SRT, based on a linear regression model (see Materials and Methods), for the go trials. C, Localization errors and mean curve aligned to estimated SRT. Cancelled trials are in red. D, Inhibition functions for each session: the probability of erroneously making a saccade as a function of the SSD. Cancelled trials were subdivided into three approximately equal-sized bins based on the SSD (short SSD, light red; medium SSD, red; long SSD, dark red). E, Localization errors in the cancelled trials aligned to predicted saccade onset for the three subdivisions in SSD.
- Figure 3.
Mean localization curves across all subjects. A, Localization curves of go and noncancelled trials, aligned to saccade onset. B, Localization curves of go, noncancelled, and cancelled trials relative to predicted saccade onset. C, Localization curves of cancelled trials do not differ for short, medium, and long SSDs (p > 0.05). Shaded areas, SEM.
- Figure 4.
A–C, Variability of the localization. Variability increases closer to saccade execution (A), but is close to zero in cancelled trials (B), regardless of SSD (C).
