Document Detail

Neural adjustments to chromatic blur.
MedLine Citation:
PMID:  16862835     Owner:  NLM     Status:  MEDLINE    
The perception of blur in images can be strongly affected by prior adaptation to blurry images or by spatial induction from blurred surrounds. These contextual effects may play a role in calibrating visual responses for the spatial structure of luminance variations in images. We asked whether similar adjustments might also calibrate the visual system for spatial variations in color. Observers adjusted the amplitude spectra of luminance or chromatic images until they appeared correctly focused, and repeated these measurements either before or after adaptation to blurred or sharpened images or in the presence of blurred or sharpened surrounds. Prior adaptation induced large and distinct changes in perceived focus for both luminance and chromatic patterns, suggesting that luminance and chromatic mechanisms are both able to adjust to changes in the level of blur. However, judgments of focus were more variable for color, and unlike luminance there was little effect of surrounding spatial context on perceived blur. In additional measurements we explored the effects of adaptation on threshold contrast sensitivity for luminance and color. Adaptation to filtered noise with a 1/f spectrum characteristic of natural images strongly and selectively elevated thresholds at low spatial frequencies for both luminance and color, thus transforming the chromatic contrast sensitivity function from lowpass to nearly bandpass. These threshold changes were found to reflect interactions between different spatial scales that bias sensitivity against the lowest spatial grain in the image, and may reflect adaptation to different stimulus attributes than the attributes underlying judgments of image focus. Our results suggest that spatial sensitivity for variations in color can be strongly shaped by adaptation to the spatial structure of the stimulus, but point to dissociations in these visual adjustments both between luminance and color and different measures of spatial sensitivity.
Michael A Webster; Yoko Mizokami; Leedjia A Svec; Sarah L Elliott
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, N.I.H., Extramural    
Journal Detail:
Title:  Spatial vision     Volume:  19     ISSN:  0169-1015     ISO Abbreviation:  Spat Vis     Publication Date:  2006  
Date Detail:
Created Date:  2006-07-25     Completed Date:  2006-08-10     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  8602662     Medline TA:  Spat Vis     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  111-32     Citation Subset:  IM    
Department of Psychology, University of Nevada, Reno, Nevada 89557, USA.
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MeSH Terms
Adaptation, Ocular / physiology*
Color Perception / physiology*
Contrast Sensitivity / physiology*
Pattern Recognition, Visual*
Photic Stimulation
Visual Pathways / physiology*
Grant Support

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