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Liu Liu, Christopher Pack; Training alters the causal contribution of area MT to visual motion perception. Journal of Vision 2016;16(12):1133. doi: 10.1167/16.12.1133.
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© 2017 Association for Research in Vision and Ophthalmology.
Visual stimuli elicit neural activation in a large number of distinct cortical areas. In principle, visual perception could arise from a distributed process that combines information across these areas, or it could rely exclusively on the areas that are most specialized for each stimulus. We have examined these possibilities, using a motion discrimination task and reversible inactivation of the middle temporal (MT) area of the visual cortex. Area MT is highly specialized for processing visual motion. Monkeys were trained to report the direction of motion of a moving grating, which has been shown to be represented in many different visual cortical areas. Following this training, reversible inactivation of MT, using muscimol injections, had surprisingly little effect on behavioral performance (22% increase in psychophysical thresholds). This suggests that the brain uses a distributed representation to make perceptual decisions. The same monkeys were then trained to report the motion direction of random dots embedded in noise. This stimulus elicits far stronger direction selectivity in MT than elsewhere, suggesting that it is a specialized probe of MT; as in previous studies, we found that MT inactivation devastated behavioral performance for this stimulus. Surprisingly, following training on the dots task, we found that muscimol injections had a much more powerful effect on the perception of motion for gratings as well (500% increase in psychophysical threshold). This suggests that the readout of sensory information depends strongly on perceptual experience, and that specialized training on one stimulus can have detrimental effects on the perception of other stimuli.
Meeting abstract presented at VSS 2016
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