Document Detail

Attentional load and sensory competition in human vision: modulation of fMRI responses by load at fixation during task-irrelevant stimulation in the peripheral visual field.
MedLine Citation:
PMID:  15459076     Owner:  NLM     Status:  MEDLINE    
Perceptual suppression of distractors may depend on both endogenous and exogenous factors, such as attentional load of the current task and sensory competition among simultaneous stimuli, respectively. We used functional magnetic resonance imaging (fMRI) to compare these two types of attentional effects and examine how they may interact in the human brain. We varied the attentional load of a visual monitoring task performed on a rapid stream at central fixation without altering the central stimuli themselves, while measuring the impact on fMRI responses to task-irrelevant peripheral checkerboards presented either unilaterally or bilaterally. Activations in visual cortex for irrelevant peripheral stimulation decreased with increasing attentional load at fixation. This relative decrease was present even in V1, but became larger for successive visual areas through to V4. Decreases in activation for contralateral peripheral checkerboards due to higher central load were more pronounced within retinotopic cortex corresponding to 'inner' peripheral locations relatively near the central targets than for more eccentric 'outer' locations, demonstrating a predominant suppression of nearby surround rather than strict 'tunnel vision' during higher task load at central fixation. Contralateral activations for peripheral stimulation in one hemifield were reduced by competition with concurrent stimulation in the other hemifield only in inferior parietal cortex, not in retinotopic areas of occipital visual cortex. In addition, central attentional load interacted with competition due to bilateral versus unilateral peripheral stimuli specifically in posterior parietal and fusiform regions. These results reveal that task-dependent attentional load, and interhemifield stimulus-competition, can produce distinct influences on the neural responses to peripheral visual stimuli within the human visual system. These distinct mechanisms in selective visual processing may be integrated within posterior parietal areas, rather than earlier occipital cortex.
Sophie Schwartz; Patrik Vuilleumier; Chloe Hutton; Angelo Maravita; Raymond J Dolan; Jon Driver
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2004-09-30
Journal Detail:
Title:  Cerebral cortex (New York, N.Y. : 1991)     Volume:  15     ISSN:  1047-3211     ISO Abbreviation:  Cereb. Cortex     Publication Date:  2005 Jun 
Date Detail:
Created Date:  2005-05-11     Completed Date:  2005-06-22     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9110718     Medline TA:  Cereb Cortex     Country:  United States    
Other Details:
Languages:  eng     Pagination:  770-86     Citation Subset:  IM    
Laboratory for Neurology and Imaging of Cognition, Department of Neurosciences, University of Geneva, Switzerland.
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MeSH Terms
Attention / physiology*
Brain Mapping
Fixation, Ocular / physiology*
Functional Laterality / physiology
Magnetic Resonance Imaging*
Parietal Lobe / physiology
Photic Stimulation
Visual Cortex / physiology
Visual Fields / physiology*
Visual Perception / physiology*

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

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