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Ari Z Zivotofsky, Liran Zeligman; "Face" stimulus eliminates pro and anti saccade differences. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2910.
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© ARVO (1962-2015); The Authors (2016-present)
Two classic ocular motor paradigms are the pro- and anti-saccade tasks. In the former, the subject is required to make a saccade towards an appearing target while in the later he looks in the opposite direction. Classically, anti-saccades result in more erroneous saccades and longer latency saccades. We hypothesize that if the standard symbolic cue is replaced with a "smiley" like face-drawing rather than a typical symbolic icon it will increase the difficulty in disengaging from fixation and eliminate those differences.
Subjects provided written, informed consent. Trials began with a 2000 ms fixation target in the center of the screen that also serves to indicate the saccade type: a plus sign for pro and a circle for anti. The cue then appears (with equal probability) left or right for 600 ms. Participants are required to direct their gaze, as quickly as possible, ‘‘TOWARDS’’ the cue (pro-saccade task) or ‘‘AWAY’’ from the cue (anti-saccade task). Pro and anti saccades were run either in blocks or randomly interleaved. In the drawn-face variation the symbolic stimulus is replaced with a "smiley" like face-drawing that signals task type and target direction.<br /> Monocular eye movements were recorded at 120 Hz using the ISCAN ETL-400 (ISCAN Inc., Woburn, MA) video system.<br />
21 right-handed undergraduate students between the ages of 20 and 22 (8 males) participated in this experiment. Mean error rates were significantly lower for pro than anti in both block (0.05 vs 0.22) and random (0.12 vs 0.42) in symbolic conditions. No such difference was found in face trials. A similar result was found for saccadic latency. Mean latencies were significantly lower (p<.001) for pro than anti in both block (249 ms vs 329) and random (260 vs 320) in symbolic conditions. No such difference was found in face trials.
The seemingly ubiquitous difference between pro and anti saccades is usually attributed to the "difficulty" inherent in suppressing a reflexive saccade and then producing the anti saccade. Our data, in which the pro advantage disappears in the face-type trials points not to a typical handicap in anti- but a speeding up in pro. When presented with face stimuli subjects have more trouble disengaging resulting in the pro- trials showing results similar to a typical anti- trial.<br />
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