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Ceri T. Trevethan, Arash Sahraie, Larry Weiskrantz; Blindsight superior to ‘sighted-sight’?. Journal of Vision 2004;4(8):204. doi: 10.1167/4.8.204.
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© ARVO (1962-2015); The Authors (2016-present)
Background: DB, the first blindsight case to be tested extensively, has demonstrated the ability to detect and discriminate certain stimuli presented within his perimetrically blind field defect. DB is able to detect and discriminate visual stimuli that are considerably ‘less detectable’ than the optimal stimulus parameters often required to elicit blindsight (Sahraie et al 2003). Purpose: To test DB's ability to carry out 3 psychophysical visual tasks in his visual field defect compared to his sighted field. Methods: Using a 2AFC paradigm we investigated DB's ability to detect low contrast Gabor patches (diameter limited to 2, 4.6 c/ with temporal Gaussian on/off set) and to discriminate between the outline of a square and a rectangle (0.6 aspect ratio, 5% luminance contrast). Using a Forced Response paradigm, DB was tested on his ability to make a ‘same/difference’ discrimination between the presentation of two rectangles compared to a square and a rectangle (0.6 aspect ratio, 8% luminance contrast, 3 separation between stimuli). DB's performance in his sighted field and within his field defect are compared. Results: In his field defect, DB detected the presence of the 8% contrast stimulus, compared to a sighted field threshold of 15% (p < .001, binomial). DB also demonstrated significantly superior performance on both the ‘square vs. rectangle’ and ‘same/difference’ task within the field defect compared to the sighted field (p < .001, binomial). Conclusions: Superior detection and discrimination ability has been demonstrated within DB's cortically blind field defect compared to his sighted field. Monocular testing suggests differences between each eye cannot account for these results. Results will be discussed in relation to control experiments on participants with normal vision and to the implications for rehabilitation regimes.
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