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Anasuya Das, Krystel R. Huxlin; Beyond blindsight: perceptual re-learning of visual motion discrimination in cortical blindness improves static orientation discrimination. Journal of Vision 2012;12(14):14. doi: 10.1167/12.14.14.
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© ARVO (1962-2015); The Authors (2016-present)
Cortical blindness is a dense unilateral scotoma that follows primary visual cortex damage. Interestingly CB subjects retain the ability to detect stimuli that have high temporal and low spatial frequency content — termed blindsight, as detection is not always accompanies by awareness. Recent work has shown the effectiveness of repeated perceptual stimulation in shifting the blind field border by using stimuli that are optimized for eliciting blindsight. Previous work from our lab has shown that global direction discrimination can be relearned in the blindfield and this learning generalized to other motion stimuli, which still fell within the spatio-temporal channels of blindsight. The question that still remains is whether visual motion relearning is specific to motion stimuli or whether it transfers to non-motion stimuli that traditionally do not elicit blindsight. CB subjects were trained on a global direction discrimination task in their blindfield and then transfer of learning was tested using static gabors. We measured contrast sensitivity and orientation discrimination at the retrained location pre- and post-training. Contrast sensitivity for static gabors improved post-training especially for spatial frequencies less that 5cpd, however contrast thresholds were not equivalent to intact field thresholds. A subset of our patients then underwent contrast learning, which further improved contrast thresholds to comparable intact field levels. Orientation difference thresholds also improved significantly for low spatial frequency static gabors. These results suggest that perceptual learning in cortically blind fields generalizes to a broader range of stimuli than predicted by blindsight alone.
Meeting abstract presented at OSA Fall Vision 2012
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