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Abstract:
Abstract: In active vision, information is obtained at brief
fixations that are separated by saccadic eye movements.
Nonetheless, our visual experience is not of discrete snapshots,
but of a complete and integrated percept. The scope of neural
activity associated with active vision and perception is revealed
in the ERP synchronous with saccade onset. We recorded ERPs
associated with saccades performed between pre- and post- saccade
fields of high or low content in order to isolate saccade from
fixation related activity. The spatiotemporal course of
transcranial current flow at the scalp was examined with scalp
current density analysis. Saccade related activation consisted of a
mid-occipital focus 115 msec after saccade onset, which was
followed (70 msec later) by occipital-parietal activation. It is
suggested that this activation underlies the maintenance of visual
stability and suppression of visual input during saccades.
Activation associated with fixation consisted of dense current
focused over lateral occipital regions 100 ms after saccade
completion, which presumably reflects initial representation of
visual information at fixation. Parietal activation followed by 50
ms and may reflect an internal spatial reference functioning in
perceptual stability as well as the anticipation of subsequent
fixation coordinates. A second lateral occipital focus of
activation, observed 210 ms following saccade completion, may
underlie the active maintenance of fixation. The contributions of
each of these activation patterns to our continuous and integrated
visual experience will be discussed.
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