Document Detail

Detection of first- and second-order coherent motion in blindsight.
MedLine Citation:
PMID:  21842409     Owner:  NLM     Status:  MEDLINE    
Blindsight patients can detect fast moving stimuli presented within their blind field even when they deny any phenomenal visual experience. Although mounting evidence suggests the presence of different mechanisms and separate neural substrates underlying the processing of first-order (luminance-defined) and second-order (contrast-defined) motion, the perception of second-order motion in blindsight has scarcely been explored. In the present study, we investigated whether two blindsighted patients (GY and MS) can detect a variety of first- and second-order moving stimuli, and by using repetitive transcranial magnetic stimulation (rTMS), we assessed the role of V5/MT(+) and V3(+) in coherent motion processing. The hemianopes and four control subjects performed a two-interval forced-choice task in which they judged whether a pattern of coherently moving first-order or second-order textured squares moved in the first or second interval. They were not asked to report the direction of motion because neither of them could do so better than expected by chance. The results showed that MS, who has extensive destruction of the ventral cortical visual pathway as well as his V1 lesion, could not process second-order motion at all, whereas GY could perform second-order tasks but only at high-contrast modulation. This may have introduced first-order components in second-order moving stimuli and provided artifactual cues to motion. Moreover, rTMS delivered over area V5/MT(+) impaired detection of both first- and second-order motion in undamaged control subjects, whereas rTMS over V3(+) did not impair their performance in any of the stimuli employed. On the other hand, rTMS over V3(+) did impair GY's detection of first-order motion and high-contrast second-order moving textured squares that are likely to contain artifactual luminance cues. rTMS over V5/MT(+) impaired first-order motion detection in MS. Overall, the results suggest that neither of the blindsight patients can detect artifact-free second-order motion.
Andrea Pavan; Iona Alexander; Gianluca Campana; Alan Cowey
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2011-08-14
Journal Detail:
Title:  Experimental brain research     Volume:  214     ISSN:  1432-1106     ISO Abbreviation:  Exp Brain Res     Publication Date:  2011 Oct 
Date Detail:
Created Date:  2011-09-16     Completed Date:  2012-06-26     Revised Date:  2014-02-20    
Medline Journal Info:
Nlm Unique ID:  0043312     Medline TA:  Exp Brain Res     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  261-71     Citation Subset:  IM    
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MeSH Terms
Blindness / physiopathology*
Middle Aged
Motion Perception / physiology*
Photic Stimulation / methods*
Transcranial Magnetic Stimulation / methods
Young Adult
Grant Support
G0601975//Medical Research Council; //Medical Research Council

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