HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 96/6/3016    most recent 00411.2006v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Vesia, M. Articles by Crawford, J. D. Search for Related Content PubMed PubMed Citation Articles by Vesia, M. Articles by Crawford, J. D.

Hemispheric Asymmetry in Memory-Guided Pointing During Single-Pulse Transcranial Magnetic Stimulation of Human Parietal Cortex

¹Canadian Institutes of Health Research Group on Action and Perception, ²Centre for Vision Research and ³Departments of Psychology, ⁴Kinesiology and Health Science, and ⁵Biology, York University, Toronto, Canada

Submitted 18 April 2006; accepted in final form 18 September 2006

Dorsal posterior parietal cortex (PPC) has been implicated through single-unit recordings, neuroimaging data, and studies of brain-damaged humans in the spatial guidance of reaching and pointing movements. The present study examines the causal effect of single-pulse transcranial magnetic stimulation (TMS) over the left and right dorsal posterior parietal cortex during a memory-guided "reach-to-touch" movement task in six human subjects. Stimulation of the left parietal hemisphere significantly increased endpoint variability, independent of visual field, with no horizontal bias. In contrast, right parietal stimulation did not increase variability, but instead produced a significantly systematic leftward directional shift in pointing (contralateral to stimulation site) in both visual fields. Furthermore, the same lateralized pattern persisted with left-hand movement, suggesting that these aspects of parietal control of pointing movements are spatially fixed. To test whether the right parietal TMS shift occurs in visual or motor coordinates, we trained subjects to point correctly to optically reversed peripheral targets, viewed through a left–right Dove reversing prism. After prism adaptation, the horizontal pointing direction for a given visual target reversed, but the direction of shift during right parietal TMS did not reverse. Taken together, these data suggest that induction of a focal current reveals a hemispheric asymmetry in the early stages of the putative spatial processing in PPC. These results also suggest that a brief TMS pulse modifies the output of the right PPC in motor coordinates downstream from the adapted visuomotor reversal, rather than modifying the upstream visual coordinates of the memory representation.

This article has been cited by other articles:

				G. Blohm, G. P. Keith, and J. D. Crawford Decoding the Cortical Transformations for Visually Guided Reaching in 3D Space Cereb Cortex, June 1, 2009; 19(6): 1372 - 1393. [Abstract] [Full Text] [PDF]

				M. Vesia, X. Yan, D. Y. Henriques, L. E. Sergio, and J. D. Crawford Transcranial Magnetic Stimulation Over Human Dorsal-Lateral Posterior Parietal Cortex Disrupts Integration of Hand Position Signals Into the Reach Plan J Neurophysiol, October 1, 2008; 100(4): 2005 - 2014. [Abstract] [Full Text] [PDF]

				S. L. Prime, M. Vesia, and J. D. Crawford Transcranial Magnetic Stimulation over Posterior Parietal Cortex Disrupts Transsaccadic Memory of Multiple Objects J. Neurosci., July 2, 2008; 28(27): 6938 - 6949. [Abstract] [Full Text] [PDF]

				S. W. C. Chang, A. R. Dickinson, and L. H. Snyder Limb-Specific Representation for Reaching in the Posterior Parietal Cortex J. Neurosci., June 11, 2008; 28(24): 6128 - 6140. [Abstract] [Full Text] [PDF]