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Abstract:
The contributions of spatial and timing information to
performance on the Antisaccade (AS) task (subjects are instructed
to make a saccade in the direction opposite to a peripherally
flashed cue) were examined in 65 undergraduate subjects. The
current study examined saccade programming in AS and prosaccade
(PS) tasks by varying two sources of uncertainty that exist before
cue onset: location and timing of the cue. We varied the number of
cue locations (1, 2, and 4 on the horizontal plane) and the
predictability of the inter-trial interval (ITI), which either
varied randomly (1500 to 3500 ms) or remained constant (2500 ms).
All saccades were recorded at 180 Hz. In the AS trials, saccadic
reaction times (SRT's) significantly increased from 1 to 2 targets,
but not between 2 and 4 targets; SRT's did not increase in the PS
task. In the AS task, errors in saccade direction increased as the
number of cues increased. Decreasing uncertainty of the timing of
cue onset resulted in decreased SRT's in the AS task, but did not
reduce "reflexive" looking errors. Results are interpreted within a
neuro-cognitive model that suggests a different set of programming
and timing requirements and associated structures/pathways for
generating anti- and prosaccades.
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