Brouwer B, Sale M V, Nordstrom M A
School of Rehabilitation Therapy, Queen's University, Kingston, ON, Canada.
Exp Brain Res. 2001 Jun;138(4):467-76. doi: 10.1007/s002210100730.
Transcranial magnetic stimulation (TMS) was used to assess the relative contribution of the corticospinal (CS) pathway in activating the first dorsal interosseous (FDI) muscle in each hand of 16 right- (RH) and 16 left-handed (LH) subjects with varied degrees of hand preference. It was hypothesised that asymmetry in corticospinal activation of the two hands may be related to hand preference and interlimb differences in manual performance. Subjects performed isometric index finger abduction at force levels of 0.5 N, 1 N and 2 N while TMS was applied at resting threshold intensity (T), 0.9T, or 0.8T. The amount of contraction-induced facilitation of the muscle evoked potential (MEP) was used as an estimate of corticospinal involvement in the task. Patterns of MEP facilitation in each hand were compared with measures of manual performance (finger tapping speed, Purdue pegboard, maximal FDI strength). Threshold TMS intensities for an MEP in FDI at rest were similar in LH and RH subjects, and did not vary between hands. Facilitation of the MEP with voluntary activation was larger overall on the left side (P<0.05), but the asymmetry was dependent on the degree of lateralisation of hand preference. For subjects with consistent hand preference (either LH or RH), MEP facilitation in active FDI was larger for the left hand. For non-consistent RH subjects, contraction-induced MEP facilitation was larger in the right FDI muscle than the left. Asymmetry of MEP facilitation was not correlated with differences between hands in finger tapping speed or performance in the pegboard task, but was associated with relative differences in FDI strength. MEP facilitation tended to be larger in the stronger FDI muscle of the pair. We conclude that corticospinal involvement in the command for index finger abduction is generally greater when the left hand is used, although in RH subjects the asymmetry is influenced by the degree of lateralisation of hand preference. The corticospinal asymmetry is not related to speed or dexterity of finger movements, but the association with muscle strength suggests that it may be influenced in part by preferential use of one hand for tasks which strengthen the FDI muscle.
经颅磁刺激（TMS）被用于评估皮质脊髓（CS）通路在激活16名右利手（RH）和16名左利手（LH）受试者每只手的第一背侧骨间肌（FDI）时的相对贡献，这些受试者具有不同程度的手偏好。研究假设两只手皮质脊髓激活的不对称性可能与手偏好以及手部运动表现的肢体间差异有关。受试者在0.5N、1N和2N的力水平下进行等长示指外展，同时在静息阈值强度（T）、0.9T或0.8T施加TMS。肌肉诱发电位（MEP）收缩诱导的易化量被用作皮质脊髓参与该任务的估计值。将每只手的MEP易化模式与手部运动表现的测量值（手指敲击速度、普渡木钉板测试、FDI最大力量）进行比较。静息时FDI中MEP的阈值TMS强度在LH和RH受试者中相似，且两只手之间无差异。主动激活时MEP的易化总体上在左侧更大（P<0.05），但这种不对称性取决于手偏好的偏侧化程度。对于手偏好一致的受试者（无论是LH还是RH），主动FDI中MEP的易化在左手更大。对于手偏好不一致的RH受试者，收缩诱导的MEP易化在右侧FDI肌肉中比左侧更大。MEP易化的不对称性与手指敲击速度或木钉板任务表现的双手差异无关，但与FDI力量的相对差异有关。MEP易化在一对中较强的FDI肌肉中往往更大。我们得出结论，当使用左手时，皮质脊髓参与示指外展指令的程度通常更大，尽管在RH受试者中，这种不对称性受手偏好偏侧化程度的影响。皮质脊髓不对称性与手指运动的速度或灵活性无关，但与肌肉力量的关联表明，它可能部分受到在加强FDI肌肉的任务中优先使用一只手的影响。
