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Cerebral Cortex Advance Access published online on October 31, 2006
Cerebral Cortex, doi:10.1093/cercor/bhl093
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© The Author 2006. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org

Article

Attentional Modulation of Receptive Field Structure in Area 7a of the Behaving Monkey

Salma Quraishi 1, Barbara Heider 2, and Ralph M. Siegel 2 *

1 Center for Molecular and Behavioral Neuroscience, Rutgers University, 197 University Avenue, Newark, NJ 07102, USA; Current address: Neurological Sciences Institute, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, OR 97006, USA
2 Center for Molecular and Behavioral Neuroscience, Rutgers University, 197 University Avenue, Newark, NJ 07102, USA

* To whom correspondence should be addressed.
Ralph M. Siegel, E-mail: axon{at}cortex.rutgers.edu


  Abstract

Spatial attention modulates the activity of inferior parietal neurons. A statistically rigorous approach to classical retinotopic mapping was used to quantify the receptive fields of area 7a neurons under 2 attentional conditions. Measurements were made with retinal stimulation held constant and the locus of attention manipulated covertly. Both tasks required central fixation but differed in the locus of covert attention (either on the center fixation point or on a peripheral square target in one of 25 locations). The neuron's identity over the recording session was confirmed using chaos theory to characterize unique temporal patterns. Sixty-six percent of the neurons changed prestimulus activity based on task state. Retinotopic mapping showed no evidence for foveal sparing. Attentional factors influenced visual responses for ~30% of the neurons. Two types of modulation were equally observed. One group of cells had a multiplicative scaling of response, with equal instances of enhancement and suppression. A second group of cells had a complex interaction of visual and attentional signals, such that spatial tuning was subject to a nonlinear modulation across the visual field based on attentional constraints. These 2 cell groups may have different roles in the shift of attention preceding motor behaviors and may underlie shifts in parietal retinotopic maps observed with intrinsic optical imaging.

Keywords: attention; chaos theory; cortex; retinotopic map; spatial representation.
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