Evidence for perceptual learning with repeated stimulation after partial and total cortical blindness |
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Authors: | Trevethan Ceri T Urquhart James Ward Richard Gentleman Douglas Sahraie Arash |
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Institution: | 1Vision and Attention Laboratories, School of Psychology, University
of Aberdeen, UK;2Richard Ward Opticians, Odiham, Hampshire, UK;3Centre for Brain Injury Rehabilitation, Royal Victoria Hospital,
Dundee, UK |
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Abstract: | Lesions of occipital cortex result in loss of sight in the corresponding regions of visual fields. The traditional view that, apart from some spontaneous recovery in the acute phase, field defects remain permanently and irreversibly blind, has been challenged. In patients with partial field loss, a range of residual visual abilities in the absence of conscious perception (blindsight) has been demonstrated (Weiskrantz, 1986). Recent findings (Sahraie et al., 2006, 2010) have also demonstrated increased visual sensitivity in the field defect following repeated stimulation. We aimed to extend these findings by systematically exploring whether repeated stimulation can also lead to increased visual sensitivity in two cases with total (bilateral) cortical blindness. In addition, for a case of partial blindness, we examined the extent of the recovery as a function of stimulated region of the visual field, over extended periods of visual training. Positive auditory feedback was provided during the training task for correct detection of a spatial grating pattern presented at specific retinotopic locations using a temporal two alternative forced-choice paradigm (Neuro-Eye Therapy). All three cases showed improved visual sensitivity with repeated stimulation. The findings indicate that perceptual learning can occur through systematic visual field stimulation even in cases of bilateral cortical blindness. |
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Keywords: | blindsight visual field training Neuro-Eye Therapy spatial frequency feedback perceptual learning |
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