Document Detail

Asymmetric spatial frequency tuning of motion mechanisms in human vision revealed by masking.
MedLine Citation:
PMID:  17652766     Owner:  NLM     Status:  MEDLINE    
PURPOSE: To investigate the spatial frequency selectivity of the human motion system by using the technique of visual masking. METHODS: Modulation-depth thresholds for identifying the direction of a sinusoidal test pattern were measured over a range of spatial frequencies (0.25-4 cyc/deg) in the absence and presence of a temporally jittering mask. RESULTS: At the lowest test frequency (0.25 cyc/deg), maximum masking occurred when the test and mask shared the same spatial frequency, decreasing as the difference in spatial frequency between the test and mask increased. However, as test spatial frequency increased, maximum masking began to shift to when the mask was presented at approximately 1 octave below the test spatial frequency. Control experiments demonstrated that the asymmetric masking functions at higher test spatial frequencies was not affected by mask amplitude nor was it an effect of speed. The results confirmed that the peak at 1 octave from the test still occurred when the potential for off-frequency looking was minimized by presenting two masks positioned equidistant in frequency from the test grating. Control experiments revealed, however, that the peak at 1 octave below the test was mediated by image size and/or the number of cycles presented on screen. CONCLUSIONS: These findings provide support for the notion that motion perception is mediated by band-pass, spatial-frequency-selective mechanisms. Moreover, asymmetric tuning of the masking functions may reflect asymmetric spatial frequency selectivity of the mechanisms in the human visual system that encode motion or inhibition between mechanisms tuned to different spatial frequencies.
Claire V Hutchinson; Tim Ledgeway
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Investigative ophthalmology & visual science     Volume:  48     ISSN:  0146-0404     ISO Abbreviation:  Invest. Ophthalmol. Vis. Sci.     Publication Date:  2007 Aug 
Date Detail:
Created Date:  2007-07-26     Completed Date:  2007-09-26     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7703701     Medline TA:  Invest Ophthalmol Vis Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  3897-904     Citation Subset:  IM    
Visual Neuroscience Research Group, School of Psychology, University of Nottingham, Nottingham, United Kingdom.
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MeSH Terms
Motion Perception / physiology*
Neural Inhibition / physiology
Perceptual Masking / physiology*
Photic Stimulation
Sensory Thresholds / physiology

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

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