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| Research article summary (published 30 Dec 2001): |
Shading and texture: separate information channels with a common adaptation mechanism?
Full Abstract
We outline a scheme for the way in which early vision may handle information about shading (luminance modulation, LM) and texture (contrast modulation, CM). Previous work on the detection of gratings has found no sub-threshold summation, and no cross-adaptation, between LM and CM patterns. This strongly implied separate channels for the detection of LM and CM structure. However, we now report experiments in which adapting to LM (or CM) gratings creates tilt aftereffects of similar magnitude on both LM and CM test gratings, and reduces the perceived strength (modulation depth) of LM and CM gratings to a similar extent. This transfer of aftereffects between LM and CM might suggest a second stage of processing at which LM and CM information is integrated. The nature of this integration, however, is unclear and several simple predictions are not fulfilled. Firstly, one might expect the integration stage to lose identity information about whether the pattern was LM or CM. We show instead that the identity of barely detectable LM and CM patterns is not lost. Secondly, when LM and CM gratings are combined in-phase or out-of-phase we find no evidence for cancellation, nor for 'phase-blindness'. These results suggest that information about LM and CM is not pooled or merged--shading is not confused with texture variation. We suggest that LM and CM signals are carried by separate channels, but they share a common adaptation mechanism that accounts for the almost complete transfer of perceptual aftereffects.
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Author information
Author/s: Georgeson, Mark A (MA); Schofield, Andrew J (AJ);
Affiliation: School of Psychology, University of Birmingham, Birmingham B15 2TT, UK. m.a.georgeson(-atsign-)aston.ac.uk
Journal and publication information
Publication Type: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't
Journal: Spatial vision (Spat Vis), published in Netherlands. (Language: eng)
Reference: 2002-; vol 16 (issue 1) : pp 59-76
Dates: Created 2003/03/14; Completed 2003/04/22; Revised 2006/11/15;
PMID: 12636225, status: MEDLINE (last retrieval date: 11/6/2008)
Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.
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