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Hemispheric asymmetry in visuospatial attention assessed with transcranial magnetic stimulation

Müri, R. ; Bühler, R. ; Heinemann, D. ; Mosimann, U. ; Felblinger, J. ; Schlaepfer, T. ; Hess, C.

In: Experimental Brain Research, 2002, vol. 143, no. 4, p. 426-430

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    Title
    • Hemispheric asymmetry in visuospatial attention assessed with transcranial magnetic stimulation
    Author
    • Müri, R.. Department of Neurology, University of Bern, Inselspital, 3010, Bern, Switzerland
    • Bühler, R.. Eye Movement Research Laboratory, Department of Neurology, Department of Psychology, and Psychiatric Neuroimaging Group, Inselspital, University of Bern, Bern, Switzerland
    • Heinemann, D.. Eye Movement Research Laboratory, Department of Neurology, Department of Psychology, and Psychiatric Neuroimaging Group, Inselspital, University of Bern, Bern, Switzerland
    • Mosimann, U.. Eye Movement Research Laboratory, Department of Neurology, Department of Psychology, and Psychiatric Neuroimaging Group, Inselspital, University of Bern, Bern, Switzerland
    • Felblinger, J.. Eye Movement Research Laboratory, Department of Neurology, Department of Psychology, and Psychiatric Neuroimaging Group, Inselspital, University of Bern, Bern, Switzerland
    • Schlaepfer, T.. Eye Movement Research Laboratory, Department of Neurology, Department of Psychology, and Psychiatric Neuroimaging Group, Inselspital, University of Bern, Bern, Switzerland
    • Hess, C.. Eye Movement Research Laboratory, Department of Neurology, Department of Psychology, and Psychiatric Neuroimaging Group, Inselspital, University of Bern, Bern, Switzerland
    Document Type
    • Postprint
    OAI-PMH Identifier
    • oai:doc.rero.ch:316540
    Summary
    Transcranial magnetic stimulation (TMS) was used to study visuospatial attention processing in ten healthy volunteers. In a forced choice recognition task the subjects were confronted with two symbols simultaneously presented during 120ms at random positions, one in the left and the other in the right visual field. The subject had to identify the presented pattern out of four possible combinations and to press the corresponding response key within 2 s. Double-pulse TMS (dTMS) with a 100-ms interstimulus interval (ISI) and an intensity of 80% of the stimulator output (corresponding to 110-120% of the motor threshold) was applied by a nonfocal coil over the right or left posterior parietal cortex (PPC, corresponding to P3/P4 of the international 10-20 system) at different time intervals after onset of the visual stimulus (starting at 120ms, 270ms and 520ms). Double-pulse TMS over the right PPC starting at 270ms led to a significant increase in percentage of errors in the contralateral, left visual field (median: 23% with TMS vs 13% without TMS, P=0.0025). TMS applied earlier or later showed no effect. Furthermore, no significant increase in contra- or ipsilateral percentage of errors was found when the left parietal cortex was stimulated with the same timing. These data indicate that: (1) parietal influence on visuospatial attention is mainly controlled by the right lobe since the same stimulation over the left parietal cortex had no significant effect, and (2) there is a vulnerable time window to disturb this cortical process, since dTMS had a significant effect on the percentage of errors in the contralateral visual hemifield only when applied 270ms after visual stimulus presentation