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Abstract:
Abstract: We investigated the effect of strategic suppression
of reflexive eye movements on external control over fixation using
a fixation offset paradigm. A visual signal at fixation facilitates
the fixation reflex and inhibits eye movements. Certain preparatory
states render the fixation reflex less reactive to visual
stimulation at fixation, as evidenced by a reduction in the
fixation offset effect (FOE). For example, past studies have
suggested that the reduced FOE during anti-saccade tasks results
from the requirement to inhibit reflexive eye movements. We tested
whether suppressing reflexive saccades reduces external control
over ocular fixation using a go-NOGO saccade paradigm. During each
trial, one of two targets appeared in the periphery. Participants
were instructed to saccade to one target (go), but when the other
target appeared they either had to maintain fixation (nogo) or move
their eyes in the direction opposite the target (anti). When nogo
trials were admixed with target-directed saccades a large FOE was
observed compared to when target-directed saccades occurred alone
(Experiment 1); however, when anti-saccades were mixed with
target-directed saccades, a small FOE was observed for both types
of eye movements (Experiment 2). We conclude that suppressing
reflexive eye movements does not reduce external control over
fixation. Further research is necessary to elucidate which other
component of preparing to make an anti-saccade diminishes the
FOE.
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