Document Detail

Lateral modulation of contrast discrimination: flanker orientation effects.
MedLine Citation:
PMID:  12678649     Owner:  NLM     Status:  MEDLINE    
We used a dual-masking paradigm to study how contrast discrimination is influenced by the presence of adjacent stimuli differing in orientation. The task of the observer was to detect a vertical Gabor target superimposed on a vertical Gabor pedestal in the presence of flankers. The Gabor flankers had orientations ranging from 0 degrees (parallel to the target) to 90 degrees (orthogonal). The flankers had two different facilitatory effects: (a) Threshold facilitation. The flankers facilitated target detection at low pedestal contrasts. This facilitation was narrowly tuned to flanker orientation. (b) Pedestal enhancement. The flankers at high contrast enhanced the masking effectiveness of the pedestal. This pedestal enhancement changed little with flanker orientation. We fitted the data with a sensitivity modulation model in which the flanker effects were implemented as multiplicative factors modulating the sensitivity of the target mechanism to both excitatory and inhibitory inputs. The model parameters showed that, (a) pedestal enhancement occurs when flanker facilitation to the pedestal is greater than to the target; (b) while the sensitivity modulation was tuned sharply with flanker orientation, the ratio between the excitatory and the inhibitory factors remained constant. The explanation of the flanker orientation effect requires the both the values of each factor and the ratio between them.
Chien-Chung Chen; Christopher W Tyler
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of vision     Volume:  2     ISSN:  1534-7362     ISO Abbreviation:  J Vis     Publication Date:  2002  
Date Detail:
Created Date:  2003-04-07     Completed Date:  2003-04-23     Revised Date:  2008-04-29    
Medline Journal Info:
Nlm Unique ID:  101147197     Medline TA:  J Vis     Country:  United States    
Other Details:
Languages:  eng     Pagination:  520-30     Citation Subset:  IM    
The Smith-Kettlewell Eye Research Institute, San Francisco, CA, USA.
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MeSH Terms
Contrast Sensitivity / physiology*
Discrimination (Psychology)
Models, Psychological
Perceptual Masking / physiology
Sensory Thresholds / physiology
Grant Support

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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