Rivalry is really simple
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1
University of Otago, New Zealand
When I started researching binocular rivalry in 1974 there were at least five properties that made it hard to understand with the only extant, neurally plausible theory: that it occurs through reciprocal inhibition of monocular neurons processing the two stimuli. 1. Decreases to the “stimulus strength” of one rival image increase the other image’s dominance durations but leave unchanged that image’s dominance durations (Levelt’s second proposition). 2. Suppression is not spatially selective. For example, with rivalry between 0° and 90° gratings, a 45° grating monocular probe suffers just as much suppression as one at 10°. 3. Monocular rivalry exists: Rivalry can occur between two images that are presented to the same eye. 4. Semantic properties of the stimuli (such as interest and attention) affect rivalry and it can be controlled voluntarily. 5. Aftereffects from one rival stimulus accrue as if the stimulus were continuously visible. Now all of these problems are resolved, both by new data, and by the theory that rivalry involves reciprocal inhibition of neurons at different levels of the visual system, along with feedback connections to make dynamic networks of neurons engaging in rivalry. This makes rivalry easy to understand: 1. Levelt’s second proposition is true only for a limited range of stimulus strengths. More generally, when one image has higher stimulus strength than the other, its dominance duration increases. This is consistent with models incorporating reciprocal inhibition. 2. There are exceptions to rivalry suppression’s acting equally on most probes presented to an eye: Color-rivalry suppression is ineffective for contoured probes, and contour-rivalry suppression is ineffective for probes with high temporal frequencies. In the case of susceptible probes, non-selectivity is consistent with feedback connections’ establishing networks of rivaling neurons that effectively receive input only from one or the other eye. 3. Not only does monocular rivalry exist, but so do other forms of rivalry that also do not depend on dichoptic presentation, such as swap rivalry and motion-induced blindness. These are all consistent with rivalry’s existing between neurons at higher levels of the visual system from which eye-of-origin information has been discarded. 4. The effects of semantic properties and of voluntary control are consistent with feedback from higher levels of the visual system. 5. Aftereffects from one rival stimulus are reduced by suppression as long as the adapting contrast is not high enough to saturate the aftereffect. The new theory and data of rivalry are consistent with visual consciousness being mediated at different levels of the visual system.
Conference:
10th International Conference on Cognitive Neuroscience, Bodrum, Türkiye, 1 Sep - 5 Sep, 2008.
Presentation Type:
Oral Presentation
Topic:
Symposium 11: Visual consciousness at different levels of the brain
Citation:
O’Shea
R
(2008). Rivalry is really simple.
Conference Abstract:
10th International Conference on Cognitive Neuroscience.
doi: 10.3389/conf.neuro.09.2009.01.051
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Received:
27 Nov 2008;
Published Online:
27 Nov 2008.
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Correspondence:
R.P O’Shea, University of Otago, Dunedin, New Zealand, r_oshea@otago.ac.nz