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Anasuya Das, Duje Tadin, Krystel Huxlin; Going beyond blindsight: properties of recovered vision in cortically blind fields. Journal of Vision 2014;14(10):660. doi: https://doi.org/10.1167/14.10.660.
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© ARVO (1962-2015); The Authors (2016-present)
Damage to the primary visual cortex (V1) or its immediate afferents results in a dense scotoma, termed cortical blindness (CB). CB subjects have some residual visual ability, termed blindsight, which allows them to process and even re-learn to discriminate stimuli with high temporal and low spatial frequency content. The present study asked whether training-induced visual re-learning following V1 damage can be elicited by stimuli outside the spatio-temporal bandwidth of blindsight. Specifically, can coarse orientation discrimination of static, non-flickering gabors be re-learned de novo in CB fields - i.e. without prior or concurrent training with moving or flickering stimuli. Second, can visual re-learning induced by such training transfer to untrained orientation and direction discriminations? Finally, does double training with a motion direction and a static orientation discrimination task provide any advantages in generalization of learning relative to training orientation alone. We found CB subjects are able to relearn static orientation discrimination following single as well as double training. However, a key dissociation emerged in the extent of transfer observed with the double-trained group demonstrating recovery of complex motion discrimination thresholds, including range and motion coherence thresholds, at the orientation-trained locations. The single-trained (static orientation only) group, on the other hand, could only discriminate simple motion stimuli. Both groups of subjects had roughly equivalent, though incomplete recovery of fine orientation and direction discrimination, as well as contrast sensitivity. In conclusion, CB subjects are able to relearn static orientation discrimination in their blind field, but those who train only on orientation discrimination generalize less to untrained motion stimuli. These findings suggest that although complex visual motion may be superior as a training stimulus, the cortically blind visual system is able to relearn to process a much wider range of stimuli than predicted by blindsight alone.
Meeting abstract presented at VSS 2014
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