Reduction of excitability ("inhibition") in the ipsilateral primary motor cortex is mirrored by fMRI signal decreases |
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Authors: | Hamzei Farsin Dettmers Christian Rzanny Reinhard Liepert Joachim Büchel Christian Weiller Cornelius |
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Institution: | Neurologisches Universit?tsklinikum, Hamburg-Eppendorf Martinistrasse 52, 20246 Hamburg, Germany. |
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Abstract: | Functional magnetic resonance imaging (fMRI) was used to investigate how focal cortical inhibition affects the blood oxygen level-dependent (BOLD) signal. Phasic low force pinch grip reduces excitability of the ipsilateral primary motor cortex. This task was used to study BOLD signal changes during inhibition. Six right-handed normal volunteers participated in the study. They were asked to perform a right-handed pinch grip repetitively at 1 Hz and 5% of their individual maximal voluntary contraction (MVC). Data were acquired with a 1.5 Tesla Magnetom and continuous multislice T2*-weighted images. The contralateral primary motor cortex (M1) revealed an activation in the knob-shaped hand representation of the central sulcus area. More importantly, a decreased (often referred to as "negative") BOLD signal in the ipsilateral M1 was observed. We suggest phasic low force pinch grip as a reproducible, easy model of focal inhibition. Decreased cortical excitability presents as decreased BOLD signal using fMRI. |
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