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Abstract:
Abstract: In monkeys, Logethetis and colleagues have shown
that some V1 neurons fire in synchrony with the perceptual
alternations that occur when discrepant stimuli are presented to
the two eyes. To test whether early cortical activity in humans is
similarly influenced by rivalry, we recorded event-related
potentials (ERPs) and event-related optical signals (EROS) from 12
and 19 participants, respectively. Subjects viewed red vertical and
green horizontal gratings to induce rivalry. In the electrical
study, checkerboard probes to the dominant or suppressed eye were
presented either upon the upper or lower half of one of the
gratings, so as to activate either the lower or upper bank of the
calcarine fissure. Difference potentials reflecting this activation
were not modulated by rivalry. However, confirming our previous
results (NeuroReport, 1999, 10:21-25) a slow (70-350 ms),
endogenous positive component was superimposed on the evoked
potentials. In the optical study, the monocular probes were
presented upon the lateral third of the dominant or suppressed
gratings. Contralateral-ipsilateral difference waves were strongly
modulated by dominance (50-100 at midline, 70-220 at sites 2-4 cm
laterally). The electrical and optical findings converge in
demonstrating that early visual cortical activity reflects
perceptual variations in the face of unchanging physical
stimulation.
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