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Interhemispheric Effect of Parietal TMS on Somatosensory Response Confirmed Directly with Concurrent TMS-fMRI

Blankenburg, F; Ruff, CC; Bestmann, S; Bjoertomt, O; Eshel, N; Josephs, O; ... Driver, J; + view all (2008) Interhemispheric Effect of Parietal TMS on Somatosensory Response Confirmed Directly with Concurrent TMS-fMRI. J NEUROSCI , 28 (49) 13202 - 13208. 10.1523/JNEUROSCI.3043-08.2008. Gold open access

Abstract

Transcranial magnetic stimulation (TMS) has been used to document some apparent interhemispheric influences behaviorally, with TMS over the right parietal cortex reported to enhance processing of touch for the ipsilateral right hand (Seyal et al., 1995). However, the neural bases of such apparent interhemispheric influences from TMS remain unknown. Here, we studied this directly by combining TMS with concurrent functional magnetic resonance imaging (fMRI). We applied bursts of 10 Hz TMS over right parietal cortex, at a high or low intensity, during two sensory contexts: either without any other stimulation, or while participants received median nerve stimulation to the right wrist, which projects to left primary somatosensory cortex ( SI). TMS to right parietal cortex affected the blood oxygenation level-dependent signal in left SI, with high-versus low-intensity TMS increasing the left SI signal during right-wrist somatosensory input, but decreasing this in the absence of somatosensory input. This state-dependent modulation of SI by parietal TMS over the other hemisphere was accompanied by a related pattern of TMS-induced influences in the thalamus, as revealed by region-of-interest analyses. A behavioral experiment confirmed that the same right parietal TMS protocol of 10 Hz bursts led to enhanced detection of perithreshold electrical stimulation of the right median nerve, which is initially processed in left SI. Our results confirm directly that TMS over right parietal cortex can affect processing in left SI of the other hemisphere, with rivalrous effects ( possibly transcallosal) arising in the absence of somatosensory input, but facilitatory effects ( possibly involving thalamic circuitry) in the presence of driving somatosensory input.

Type:Article
Title:Interhemispheric Effect of Parietal TMS on Somatosensory Response Confirmed Directly with Concurrent TMS-fMRI
Open access status:An open access publication
DOI:10.1523/JNEUROSCI.3043-08.2008
Publisher version:http://ukpmc.ac.uk/abstract/MED/19052211
Keywords:TMS, fMRI, interhemispheric, rivalry, somatosensory, SI, TRANSCRANIAL MAGNETIC STIMULATION, CALLOSAL CONNECTIONS, CORTICAL ACTIVATIONS, SENSORIMOTOR CORTEX, TACTILE EXTINCTION, CUTANEOUS STIMULI, RETICULAR NUCLEUS, CAUSAL INFLUENCES, VISUAL-CORTEX, MOTOR CORTEX
UCL classification:UCL > School of Life and Medical Sciences > Faculty of Brain Sciences > Psychology and Language Sciences (Division of) > Institute of Cognitive Neuroscience
UCL > School of Life and Medical Sciences > Faculty of Brain Sciences > Institute of Neurology > Imaging Neuroscience
UCL > School of Life and Medical Sciences > Faculty of Brain Sciences > Institute of Neurology > Motor Neuroscience and Movement Disorders
UCL > School of Life and Medical Sciences > Faculty of Life Sciences

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