Document Detail


A feature-tracking model simulates the motion direction bias induced by phase congruency.
MedLine Citation:
PMID:  16643089     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Here we report a new motion illusion where the prevailing motion direction is strongly influenced by the relative phase of the harmonic components of the stimulus. The basic stimulus is the sum of three sinusoidal contrast-reversing gratings: the first, the third, and the fifth harmonic of two square wave gratings that drift in opposite direction. The phase of one of the fifth components was kept constant at 180 deg, whereas the phase of the other fifth harmonic was varied over the range 0-150 deg. For each phase value of the fifth harmonic, the motion was strongly biased toward its direction, corresponding to the direction with stronger phase congruency between the three harmonics. The strength of the prevailing motion was assessed by measuring motion direction discrimination thresholds, by varying the contrast of the third and the fifth harmonics plaid pattern. Results show that the contrast of high harmonics had to be increased by more than a factor of 10, to achieve a balance of motion for phase differences greater than 60 deg between the 2 fifth harmonics. We also measured the dependence on the absolute phase of harmonic components and found that it is not an important parameter, excluding the possibility that local luminance cues could be mediating the effect. A feature-tracking model based on previous work is proposed to simulate the data. The model computes local energy function from a pair of space-time separable front stage filters and applies a battery of directional second stage mechanisms. It is able to simulate quantitatively the phase congruency dependence illusion and the insensitivity to overall phase. Other energy models based on directional filters fail to simulate the phase congruency dependency effect.
Authors:
M Michela Del Viva; M Concetta Morrone
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2006-03-01
Journal Detail:
Title:  Journal of vision     Volume:  6     ISSN:  1534-7362     ISO Abbreviation:  J Vis     Publication Date:  2006  
Date Detail:
Created Date:  2006-04-28     Completed Date:  2006-05-16     Revised Date:  2008-04-29    
Medline Journal Info:
Nlm Unique ID:  101147197     Medline TA:  J Vis     Country:  United States    
Other Details:
Languages:  eng     Pagination:  179-95     Citation Subset:  IM    
Affiliation:
Dipartimento di Psicologia, Università di Firenze, Firenze, Italy. michela@in.cnr.it
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MeSH Terms
Descriptor/Qualifier:
Cues
Humans
Illusions / etiology*
Lighting
Models, Psychological*
Motion Perception*
Orientation*
Photic Stimulation / methods*

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


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