Abstract
Recent work from this laboratory has indicated that reflexive saccadic eye movements (including express saccades – reaction times < 120 msec) can be influenced by cognitive commands expressed in object-centered coordinates without an accompanying increase in reaction time (Edelman et al, 2007; Edelman et al, in press). We wished to examine whether color information could similarly influence reflexive saccades without increasing reaction time. Two subjects trained to make short reaction time saccades (>= 50% express) made saccades in a reflexive target/non-target task in which target was indicated by the color of the fixation point. Subjects viewed the fixation point for 500-800 msec. Two visual stimuli (1 deg sq), one red and one green, appeared at 10 deg eccentricity from the fixation point, separated in polar angle by 30 deg. Stimuli were centered randomly either to the left or right of the fixation point. The topmost stimulus was red (green) randomly on 50% of trials. The color of the fixation point (i.e. the instruction) varied randomly from trial to trial. To increase variability in RT, the time between fixation point disappearance and target appearance was varied (between 150 msec overlap and 150 msec gap). Subjects were instructed to make saccades to the color-defined target as soon as the stimuli appeared. Data indicated that while the vectors of express saccades were not influenced by the color instruction, with a mean landing point in between the target and non-target, saccades just at the boundary of the express range (120-130 msec) were affected significantly. Reaction time was not increased relative to one-target control trials. Additional experiments are examining whether task training and blocked trial instructions could enhance the effect of instruction on saccade vector.
Meeting abstract presented at VSS 2017