Document Detail

Attention mechanisms in visual search -- an fMRI study.
MedLine Citation:
PMID:  11506648     Owner:  NLM     Status:  MEDLINE    
The human visual system is usually confronted with many different objects at a time, with only some of them reaching consciousness. Reaction-time studies have revealed two different strategies by which objects are selected for further processing: an automatic, efficient search process, and a conscious, so-called inefficient search [Treisman, A. (1991). Search, similarity, and integration of features between and within dimensions. Journal of Experimental Psychology: Human Perception and Performance, 17, 652--676; Treisman, A., & Gelade, G. (1980). A feature integration theory of attention. Cognitive Psychology, 12, 97--136; Wolfe, J. M. (1996). Visual search. In H. Pashler (Ed.), Attention. London: University College London Press]. Two different theories have been proposed to account for these search processes. Parallel theories presume that both types of search are treated by a single mechanism that is modulated by attentional and computational demands. Serial theories, in contrast, propose that parallel processing may underlie efficient search, but inefficient searching requires an additional serial mechanism, an attentional "spotlight" (Treisman, A., 1991) that successively shifts attention to different locations in the visual field. Using functional magnetic resonance imaging (fMRI), we show that the cerebral networks involved in efficient and inefficient search overlap almost completely. Only the superior frontal region, known to be involved in working memory [Courtney, S. M., Petit, L., Maisog, J. M., Ungerleider, L. G., & Haxby, J. V. (1998). An area specialized for spatial working memory in human frontal cortex. Science, 279, 1347--1351], and distinct from the frontal eye fields, that control spatial shifts of attention, was specifically involved in inefficient search. Activity modulations correlated with subjects' behavior best in the extrastriate cortical areas, where the amount of activity depended on the number of distracting elements in the display. Such a correlation was not observed in the parietal and frontal regions, usually assumed as being involved in spatial attention processing. These results can be interpreted in two ways: the most likely is that visual search does not require serial processing, otherwise we must assume the existence of a serial searchlight that operates in the extrastriate cortex but differs from the visuospatial shifts of attention involving the parietal and frontal regions.
U Leonards; S Sunaert; P Van Hecke; G A Orban
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of cognitive neuroscience     Volume:  12 Suppl 2     ISSN:  0898-929X     ISO Abbreviation:  J Cogn Neurosci     Publication Date:  2000  
Date Detail:
Created Date:  2001-08-16     Completed Date:  2001-09-06     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8910747     Medline TA:  J Cogn Neurosci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  61-75     Citation Subset:  IM    
K.U. Leuven, Belgium.
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MeSH Terms
Attention / physiology*
Brain Mapping / methods*
Cerebral Cortex / physiology*
Frontal Lobe / physiology
Magnetic Resonance Imaging / methods
Occipital Lobe / physiology
Parietal Lobe / physiology
Pattern Recognition, Visual / physiology*
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