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Science 27 November 1992:
Vol. 258. no. 5087, pp. 1489 - 1491
DOI: 10.1126/science.1439839
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Articles

Science, Vol 258, Issue 5087, 1489-1491
Copyright © 1992 by American Association for the Advancement of Science

articles

Residual vision in a scotoma: implications for blindsight

R Fendrich, CM Wessinger, and MS Gazzaniga

Center for Neuroscience, University of California, Davis 95616.

Blindsight, the ability of some blind patients to describe attributes of stimuli they have no conscious awareness of seeing, has been attributed to a secondary (retinotectal) visual pathway. However, it has also been proposed that blindsight could be due to residual function within the primary (geniculostriate) visual pathway. Data have now been obtained that support the second alternative. With an image stabilizer ensuring the accurate retinal placement of stimuli, dense visual field mapping was carried out with a hemianopic patient. This perimetry revealed, embedded in the patient's scotoma, an isolated 1-degree island of residual vision that was not disclosed by conventional perimetric methods. Stimuli presented to this island could be detected and discriminated, although the subject reported he did not see them. The existence of this island of vision implies a corresponding island of functioning cortex within the patient's lesion. Other instances of blindsight may be mediated by similar islands of functioning cortex.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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Striate Cortical Lesions Affect Deliberate Decision and Control of Saccade: Implication for Blindsight.
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Neural Substrates of Blindsight After Hemispherectomy.
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Neuroscientist 13, 506-518
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Unconscious processing of orientation and color without primary visual cortex.
J. L. Boyer, S. Harrison, and T. Ro (2005)
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Extrageniculate mediation of unconscious vision in transcranial magnetic stimulation-induced blindsight.
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Psychoanatomical substrates of Balint's syndrome.
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Visual Responses of Neurons in the Middle Temporal Area of New World Monkeys after Lesions of Striate Cortex.
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Intact verbal description of letters with diminished awareness of their forms.
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Sources of blindsight.
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Science 261, 493-494
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Unraveling the dark paradox of 'blindsight'.
M Barinaga (1992)
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