, 2010), where we showed marked differences in saccadic vs. neck electromyographic (EMG) thresholds depending on the size of the characteristic vector. Given this variability, we opted for a fixed stimulation current, and adopted the level used in our previous SEF work (Chapman et al., 2012). Our general experimental setup has been described previously (Chapman et al., 2012). Briefly, the learn more animals were seated in a primate chair with either the head restrained or unrestrained, facing an array of tri-colored (red, green or orange), equiluminant LEDs. The monkeys were trained

as described previously (Chapman & Corneil, 2011) to generate a pro-saccade or an anti-saccade to a peripheral cue depending on the color of a central fixation point (FP; Fig. 1A) for a liquid reward delivered through a head-fixed sipper tube. Trials began with the removal of a diffuse, white background light that prevented dark adaptation. A red or a green FP was then presented directly in front of the monkey. The monkey was required to look at the FP within 1000 ms and hold gaze within a computer-controlled window (radius of 2.5°) for 1250 ms. A red stimulus (the peripheral cue) was then presented randomly to the left or the right of the FP. Cue locations

were fixed at either 10, 15 or 20°, with the eccentricity chosen to be the closest match to the horizontal component of the saccade selleck compound evoked with longer-duration SEF stimulation. The monkeys

had 1000 ms to either look toward (if the FP was red) or away (if the FP was green) from the cue, and fixate for a subsequent 600 ms. The radius of acceptance windows around the correct goal location was 40% of cue eccentricity, to allow for the inaccuracy of anti-saccades in the dark. On anti-saccade trials, an additional green stimulus was illuminated at the correct goal location 300 ms after the correct anti-saccade as reinforcement. A 1000-ms inter-trial interval was provided between each trial. These behavioral constraints were identical for trials with or without ICMS-SEF. Pro- and anti-saccade trials were presented with equal probability with replacement Amobarbital for incorrectly performed trials (i.e. trials where the monkeys did not obtain a reward). Short-duration ICMS-SEF was delivered on two-thirds of all trials, with the other trials designated as control trials. On a given stimulation trial, ICMS-SEF was delivered at a single time-point relative to cue presentation (−1150, −817, −483, −150, 10, 43, 77 or 110 ms, with negative numbers meaning that stimulation preceded cue presentation; Fig. 1A). We define the time preceding cue presentation as the fixation interval, and the time after cue presentation as the post-cue interval.