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J Neurophysiol. 2010 Dec;104(6):3644-56. doi: 10.1152/jn.00303.2010. Epub 2010 Sep 15.

Spatially distributed encoding of covert attentional shifts in human thalamus.

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  • 1Department of Vision Science, UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK.

Abstract

Spatial attention modulates signal processing within visual nuclei of the thalamus--but do other nuclei govern the locus of attention in top-down mode? We examined functional MRI (fMRI) data from three subjects performing a task requiring covert attention to 1 of 16 positions in a circular array. Target position was cued after stimulus offset, requiring subjects to perform target detection from iconic visual memory. We found positionally specific responses at multiple thalamic sites, with individual voxels activating at more than one direction of attentional shift. Voxel clusters at anatomically equivalent sites across subjects revealed a broad range of directional tuning at each site, with little sign of contralateral bias. By reference to a thalamic atlas, we identified the nuclear correspondence of the four most reliably activated sites across subjects: mediodorsal/central-intralaminar (oculomotor thalamus), caudal intralaminar/parafascicular, suprageniculate/limitans, and medial pulvinar/lateral posterior. Hence, the cortical network generating a top-down control signal for relocating attention acts in concert with a spatially selective thalamic apparatus-the set of active nuclei mirroring the thalamic territory of cortical "eye-field" areas, thus supporting theories which propose the visuomotor origins of covert attentional selection.

PMID:
20844113
PMCID:
PMC3007633
DOI:
10.1152/jn.00303.2010
[PubMed - indexed for MEDLINE]
Free PMC Article
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