Document Detail

Stereopsis from contrast envelopes.
MedLine Citation:
PMID:  10367053     Owner:  NLM     Status:  MEDLINE    
We report two experiments concerning the site of the principal nonlinearity in second-order stereopsis. The first exploits the asymmetry in perceiving transparency with second-order stimuli found by Langley et al. (1998) (Proceedings of the Royal Society of London B, 265, 1837-1845) i.e. the product of a positive-valued contrast envelope and a mean-zero carrier grating can be seen transparently only when the disparities are consistent with the envelope appearing in front of the carrier. We measured the energy at the envelope frequencies that must be added in order to negate this asymmetry. We report that this amplitude can be predicted from the envelope sidebands and not from the magnitude of compressive pre-cortical nonlinearities measured by other researchers. In the second experiment, contrast threshold elevations were measured for the discrimination of envelope disparities following adaptation to sinusoidal gratings. It is reported that perception of the envelope's depth was affected most when the adapting grating was similar (in orientation and frequency) to the carrier, rather than to the contrast envelope. These results suggest that the principal nonlinearity in second-order stereopsis is cortical, occurring after orientation- and frequency-selective linear filtering.
K Langley; D J Fleet; P B Hibbard
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Vision research     Volume:  39     ISSN:  0042-6989     ISO Abbreviation:  Vision Res.     Publication Date:  1999 Jul 
Date Detail:
Created Date:  1999-06-28     Completed Date:  1999-06-28     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0417402     Medline TA:  Vision Res     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  2313-24     Citation Subset:  IM; S    
Department of Psychology, University College London, UK.
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MeSH Terms
Adaptation, Ocular
Contrast Sensitivity / physiology*
Depth Perception / physiology*
Models, Neurological
Pattern Recognition, Visual / physiology
Sensory Thresholds / physiology
Vision Disparity / physiology

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