Document Detail

Speed-dependent responses in V5: A replication study.
MedLine Citation:
PMID:  10329290     Owner:  NLM     Status:  MEDLINE    
In a previous paper, we used fMRI to examine motion-sensitive responses in human area V5 as a function of stimulus speed. As predicted by electrophysiological findings, we observed optimal responses at intermediate speeds of around 7 to 30 degrees /s. These results revealed a nonlinear (inverted "U") dependency on speed that was also evident in V3a. In this paper we repeated the experiment using an improved stimulus and a larger range of speeds. We replicated our previous findings and extended our characterization of speed-dependent responses: Optimal responses were seen in V5 at speeds of 4 and 8 degrees /s and in V3a at speeds of 4 to 16 degrees /s. We were also able to show an interaction between speed (fast vs slow) and contrast (color > luminance) in V5. This interaction was anticipated on the basis of the different properties of the geniculate and extrageniculate inputs to V5. Finally, we were also able to demonstrate an interaction between motion (moving vs stationary) and contrast (color > luminance) in V4. This suggests that for V4, color-specific responses are augmented in the context of motion; or equivalently, that color contrast enhances any motion-sensitive responses in V4.
D Chawla; C Buechel; R Edwards; A Howseman; O Josephs; J Ashburner; K J Friston
Publication Detail:
Type:  Clinical Trial; Controlled Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  NeuroImage     Volume:  9     ISSN:  1053-8119     ISO Abbreviation:  Neuroimage     Publication Date:  1999 May 
Date Detail:
Created Date:  1999-07-07     Completed Date:  1999-07-07     Revised Date:  2009-09-29    
Medline Journal Info:
Nlm Unique ID:  9215515     Medline TA:  Neuroimage     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  508-15     Citation Subset:  IM    
Copyright Information:
Copyright 1999 Academic Press.
Wellcome Department of Cognitive Neurology, Institute of Neurology, Queen Square, London, WC1N 3BG, United Kingdom.
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MeSH Terms
Contrast Sensitivity
Image Processing, Computer-Assisted
Magnetic Resonance Imaging / methods*
Nonlinear Dynamics
Photic Stimulation
Grant Support
//Wellcome Trust

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