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Abstract:
To understand conscious vision, scientists must elucidate how
the brain selects specific visual signals for awareness. In
binocular rivalry, discrepant monocular patterns compete for
consciousness. Controversy surrounds whether rivalry reflects
neural competition among pattern representations (Leopold &
Logothetis, 1996) or monocular channels (Blake, 1989). Here we show
that rivalry arises from interocular competition by monitoring fMRI
activity in a monocular region of primary visual cortex (V1)
corresponding to the blind spot. This region receives input solely
from the ipsilateral eye and not from the blind-spot eye. Subjects
reported their dominant percept while viewing rivalrous orthogonal
gratings in the visual location corresponding to the blind spot and
its surround. As predicted by interocular rivalry, the monocular V1
blind-spot representation was strongly activated when the
ipsilateral grating became perceptually dominant and sharply
suppressed when the blind-spot grating became dominant. These
awareness-related responses were as large as those observed during
actual alternations between the ipsilateral and blind-spot grating,
suggesting that rivalry is fully resolved in monocular visual
cortex. Our findings provide the first physiological evidence that
interocular competition mediates binocular rivalry. Furthermore,
they suggest that V1 plays an important role in the selection and
expression of conscious visual information. Supported by a
McDonnell-Pew grant to FT and a NIH grant to SAE.
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