The cortical motor threshold reflects microstructural properties of cerebral white matter

被引:83
作者
Kloeppel, Stefan [1 ,2 ]
Baeumer, Tobias [3 ]
Kroeger, Johan [3 ]
Koch, Martin A. [4 ]
Buechel, Christian [4 ]
Muenchau, Alexander [3 ]
Siebner, Hartwig R. [5 ]
机构
[1] Univ Clin Freiburg, Dept Neurol, Neurozentrum, Freiburg, Germany
[2] UCL, Wellcome Trust Ctr Neuroimaging, London WC1E 6BT, England
[3] Univ Med Ctr Hamburg Eppendorf, Dept Neurol, Hamburg, Germany
[4] Univ Med Ctr Hamburg Eppendorf, Dept Syst Neurosci, Hamburg, Germany
[5] Univ Kiel, Dept Neurol, D-2300 Kiel, Germany
关键词
cortical excitability; diffusion tensor imaging; fractional anisotropy; handedness; internal capsule; motor threshold; transcranial magnetic stimulation; white matter tract;
D O I
10.1016/j.neuroimage.2008.01.019
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
Transcranial magnetic stimulation (TMS) can be used to probe distinct aspects of excitability of the primary motor hand area (M1(Hand)). The motor threshold (MT) reflects the trans-synaptic excitability of corticospinal output neurons. The MT corresponds to the minimal intensity at which TMS evokes a contralateral motor response. Here, we employed diffusion weighted imaging (DWI) to examine whether inter-individual differences in MT of the left and right M1(Hand), an index of cortical excitability, are associated with variations in fractional anisotropy (FA), an index of white matter microstructure. Resting and active MT showed an inverse linear relationship with regional FA values in large bihemispheric clusters, including the white matter underlying primary motor, premotor and posterior prefrontal cortices, as well as the genu of the internal capsule, cerebral peduncles and corpus callosum. The linear increase in FA with cortical excitability as indexed by the MT remained significant after controlling for differences in handedness or coil-cortex distance. The posterior limb of the internal capsule, where fast-conducting corticospinal fibres from M1(Hand) pass through, showed only a weak linear relationship between FA and MT. The FA measurements show that a high level of corticospinal excitability is associated with a higher fibre coherence in large parts of cerebral white matter. The higher FA values in the white matter beneath premotor and motor cortices may reflect a structural property of cortico-cortical connections that renders M1(Hand) more susceptible to TMS-induced trans-synaptic excitation of the corticospinal fibres and may account for the inverse linear relationship between MT and FA. (C) 2008 Elsevier Inc. All rights reserved.
引用
收藏
页码:1782 / 1791
页数:10
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