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Krystel R. Huxlin, Jennifer Williams, Brian Sullivan, Mary Hayhoe; Training-induced improvements of visual motion perception after V1 cortical damage in humans. Journal of Vision 2005;5(8):708. doi: 10.1167/5.8.708.
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© ARVO (1962-2015); The Authors (2016-present)
Damage to the adult primary visual cortex (V1) causes largely permanent visual impairment. Visual motion perception is one of the main visual perceptual abilities affected by V1 lesions, yet it is critical for navigation and multiple other levels of interaction with our dynamic environment. Recent pilot studies on cats with damage to early visual cortex suggest that intensive visual discrimination training in the blind field can induce a localized recovery of motion thresholds. To assess whether improvements in visual motion perception can be elicited in adult humans with V1 damage, three patients were recruited one year after a stroke that induced homonymous visual field defects. They were taught to self-administer a two-alternative, forced-choice, global direction discrimination task within their blind fields. On a daily basis, they performed 300 trials of this task using random-dot stimuli that are optimally processed in higher-level visual areas such as the MT+ complex, which was intact in these patients. Slow but significant recovery of global motion sensitivity was observed that was highly specific to the visual field location(s) retrained. With discrimination retraining, all patients progressed from no conscious perception of the random dot stimulus and severely abnormal discrimination thresholds to conscious perception and near-normal thresholds at the retrained location(s). Patients also demonstrated enlargements of the usable field of vision using Humphrey perimetry and improved ability to detect and track moving objects in a realistic virtual environment. Thus, intensive direction discrimination retraining with dynamic random dot stimuli in portions of the blind field improves visual motion perception after V1 damage in adult humans. Whether this recovery is mediated by spared primary visual cortex, extra-geniculostriate pathways or training-induced re-organization of intact, higher level visual cortical areas remains to be determined.
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