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Raymond van Ee; Visual awareness and voluntary control. Journal of Vision 2005;5(8):707. doi: 10.1167/5.8.707.
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© ARVO (1962-2015); The Authors (2016-present)
Visual awareness and voluntary control seem to be related: when we are confronted with ambiguous images we are in some cases and to some extent able to voluntarily select a percept. This provides the ideal opportunity to study neural underpinnings of voluntary control in relation to the percepts rather than to the stimulus. However, to date voluntary control has not been used in neurophysiological studies on the correlates of visual awareness, presumably because 1) the perceptual durations of rivaling ambiguous percepts were generally too short, and 2) the role of voluntary control was insignificant. We have recently developed a bi-stable slant rivalry paradigm that exhibits 1) long percept durations, 2) beneficial metrical (quantitative) aspects, and 3) perceptual durations that are under considerable voluntary control of the observer. We have examined the role of voluntary control for the perceptual reversals of slant rivalry and we compared these with orthogonal grating rivalry, house-face rivalry, and Necker cube rivalry. Here we report that we found qualitative similarities for the role of voluntary control, consistent with a shared underlying mechanism. But we also found quantitative differences that are inconsistent with one single underlying mechanism. Further, we found that perceptual flips were neither necessarily correlated with eye movements, nor with blinks. We found significant functional magnetic resonance imaging activation correlating with the instigation of awareness of stereopsis, and activation that increased metrically with increasing perceptual reversals.
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