Cerebral Cortex Advance Access originally published online on September 30, 2004
Cerebral Cortex 2005 15(6):870-876; doi:10.1093/cercor/bhh187
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Cerebral Cortex V 15 N 6 © Oxford University Press 2004; all rights reserved
Hemispheric Asymmetries for Different Components of Global/Local Attention Occur in Distinct Temporo-parietal Loci
Center for Cognitive Neuroscience, Duke University, Durham, NC 27708, USA
Address correspondence to Daniel Weissman, Box 90999, Center for Cognitive Neuroscience, Duke University, Durham, NC 27708, USA. Email: weissman{at}duke.edu.
Data from brain-damaged and neurologically intact populations indicate hemispheric asymmetries in the temporo-parietal cortex for discriminating an object's global form (e.g. the overall shape of a bicycle) versus its local parts (e.g. the spokes in a bicycle tire). However, it is not yet clear whether such asymmetries reflect processes that (i) bias attention toward upcoming global versus local stimuli and/or (ii) attend/identify global versus local stimuli after they are presented. To investigate these possibilities, we asked sixteen healthy participants to perform a cued global/local attention task while their brain activity was recorded using event-related functional magnetic resonance imaging (fMRI). The results indicated a novel double dissociation. Hemispheric asymmetries for deploying attention toward expected global versus local object features were specific to the intraparietal sulcus (iPs). However, hemispheric asymmetries for identifying global versus local features after they were presented were specific to the inferior parietal lobe/superior temporal gyrus (IPL/STG). This double dissociation provides the first direct evidence that hemispheric asymmetries associated with different components of global/local attention occur in distinct temporo-parietal loci. Furthermore, it parallels an analogous dissociation reported in a recent fMRI study of spatial orienting, suggesting that global/local attention and spatial attention might rely on similar cognitive/neural mechanisms.
Key Words: attention fMRI hemispheric asymmetries hierarchical stimuli parieto-temporal cortex
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