Chen R, Tam A, Bütefisch C, Corwell B, Ziemann U, Rothwell J C, Cohen L G
Human Cortical Physiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20982-1430, USA.
J Neurophysiol. 1998 Dec;80(6):2870-81. doi: 10.1152/jn.1998.80.6.2870.
Intracortical inhibition and facilitation in different representations of the human motor cortex. J. Neurophysiol. 80: 2870-2881, 1998. Intracortical inhibition (ICI) and intracortical facilitation (ICF) of the human motor cortex can be studied with paired transcranial magnetic stimulation (TMS). Plastic changes and some neurological disorders in humans are associated with changes in ICI and ICF. Although well characterized in the hand representation, it is not known if ICI and ICF vary across different body part representations. Therefore we studied ICI and ICF in different motor representations of the human motor cortex. The target muscles were rectus abdominus (RA), biceps brachii (BB), abductor pollicis brevis (APB), quadriceps femoris (QF), and abductor hallucis (AH). For each muscle, we measured the rest and active motor thresholds (MTs), the motor-evoked potential (MEP) stimulus-response curve (MEP recruitment), ICI, and ICF. The effects of different interstimulus intervals (ISIs) were studied with a conditioning stimulus (CS) intensity of 80% active MT. The effects of different CS intensities were studied at ISI of 2 ms for ICI and ISI of 15 ms for ICF. MT was lowest for APB, followed by BB, AH, and QF, and was highest for RA. Except for BB, MEP recruitment was generally steeper for muscles with lower MT. ICI and ICF were present in all the motor representations tested. The stimulus intensity necessary to elicit ICI was consistently lower than that required to elicit ICF, suggesting that they are mediated by separate mechanisms. Despite wide differences in MT and MEP recruitment, the absolute CS intensities (expressed as percentage of the stimulator's output) required to elicit ICI and ICF appear unrelated to MT and MEP recruitment in the different muscles tested. These findings suggest that the intracortical mechanisms for inhibition and facilitation in different motor representations are not related to the strength of corticospinal projections.
人类运动皮层不同表征中的皮质内抑制和易化作用。《神经生理学杂志》80: 2870 - 2881, 1998年。人类运动皮层的皮质内抑制（ICI）和皮质内易化（ICF）可通过配对经颅磁刺激（TMS）进行研究。人类的可塑性变化和一些神经系统疾病与ICI和ICF的变化有关。尽管在手部表征中已得到充分表征，但尚不清楚ICI和ICF在不同身体部位表征中是否存在差异。因此，我们研究了人类运动皮层不同运动表征中的ICI和ICF。目标肌肉为腹直肌（RA）、肱二头肌（BB）、拇短展肌（APB）、股四头肌（QF）和拇展肌（AH）。对于每块肌肉，我们测量了静息和主动运动阈值（MTs）、运动诱发电位（MEP）刺激 - 反应曲线（MEP募集）、ICI和ICF。使用80%主动MT的条件刺激（CS）强度研究了不同刺激间隔（ISIs）的影响。在ICI的ISI为2 ms和ICF的ISI为15 ms时研究了不同CS强度的影响。APB的MT最低，其次是BB、AH和QF，RA的MT最高。除BB外，MT较低的肌肉的MEP募集通常更陡峭。在所有测试的运动表征中均存在ICI和ICF。引发ICI所需的刺激强度始终低于引发ICF所需的强度，这表明它们由不同的机制介导。尽管MT和MEP募集存在很大差异，但在不同测试肌肉中引发ICI和ICF所需的绝对CS强度（以刺激器输出的百分比表示）似乎与MT和MEP募集无关。这些发现表明，不同运动表征中的皮质内抑制和易化机制与皮质脊髓投射的强度无关。
