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Abstract:
In normal vision, information is acquired by a series of
fixations that are interrupted by saccadic eye movements. Despite
the spatial and temporal discontinuities caused by this discrete
sequence of inputs from the retina, the visual experience is
integrated into a continuous scene. To separately examine brain
activity associated with rapid pattern movement at onset of
saccades from responses to the stable retinal image during
fixations, we systematically varied saccade size from 5 to 60
degrees, which prolonged the eye movement duration from 42 to 207
msec. EEG, recorded from 32 electrodes in 8 adults, was averaged in
synchrony with saccade onset. Occipital responses exhibited a
negative-positive-negative waveform whose components peaked at
similar latencies (30 to 32 msec; 63 to 74 msec; and 82 to 88 msec)
for all saccade sizes. A later positive-negative complex increased
in latency (161 to 311 msec; 212 to 361 msec) as saccade size
increased. Stability of these component latencies was observed when
measured from the onset of fixation (104 to 118 ms; 154 to 169 ms).
Thus, event related potential (ERP) components generated at saccade
onsets were fixed in latency whereas those elicited at fixation
onset increased in latency proportional to the duration of the
saccade. Topographic analysis of these components will reveal
cortical regions that process the information contained in our
visual experience and thus directly participate in visual
perception.
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