Document Detail

The unseen color aftereffect of an unseen stimulus: insight from blindsight into mechanisms of color afterimages.
MedLine Citation:
PMID:  10500229     Owner:  NLM     Status:  MEDLINE    
We show here that, in the absence of a direct geniculostriate input in human subjects, causing loss of sight in the visual half-field contralateral to the damage, the pupil responds selectively to chromatic modulation toward the long-wavelength (red) region of the spectrum locus even when the stimulus is isoluminant for both rods and cones and entirely restricted to the subjects' "blind" hemifields. We also show that other colors are less or wholly ineffective. Nevertheless, red afterimages, generated by chromatic modulation toward the green region of the spectrum locus, also cause constrictions of the pupil even when green stimuli are themselves completely ineffective in the blind hemifield. Moreover, human subjects with damage to or loss of V1 are typically completely unaware of the stimulus that generates the aftereffect or of the aftereffect itself, both of which can be seen clearly in normal vision. The results show that pupillary responses can reveal the processing of color afterimages in the absence of primary visual cortex and in the absence of acknowledged awareness. This phenomenon is therefore a striking example of "blindsight" and makes possible the formulation of a model that predicts well the observed properties of color afterimages.
J L Barbur; L Weiskrantz; J A Harlow
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  96     ISSN:  0027-8424     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  1999 Sep 
Date Detail:
Created Date:  1999-10-21     Completed Date:  1999-10-21     Revised Date:  2013-04-16    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  11637-41     Citation Subset:  IM    
City University, Applied Vision Research Centre, Northampton Square, London EC1V 0HB, England.
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MeSH Terms
Middle Aged
Pupil / physiology*
Vision, Ocular*
Grant Support
//Wellcome Trust

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