Modulation of practice-dependent plasticity in human motor cortex
Modulation of practice-dependent plasticity in human motor cortex
复制标题
DOI：
10.1093/brain/124.6.1171
复制
发表时间：
2001-06-01
期刊：
影响因子：
14.5
通讯作者：
Cohen, LG
中科院分区：
文献类型：
--
作者：
Ziemann, U;Muellbacher, W;Cohen, LG
运动练习可能会导致运动皮层中经过训练的表征扩展，但尚不清楚这种依赖练习的可塑性是否能够被有目的地增强或抑制。主要基于动物实验的证据表明，γ - 氨基丁酸（GABA）相关的皮层抑制活动在控制可塑性可能发生的程度方面很重要。我们测试了GABA在调节人类运动皮层中依赖练习的可塑性方面的作用。通过去传入/去传出造成手部缺血性神经阻滞（INB）来降低GABA相关的皮层抑制，通过给予GABAA受体激动剂劳拉西泮来增加这种抑制。在实验1中，健康受试者进行运动练习（MP），包括在无（单独MP）或有INB（MP + INB）的情况下重复进行肱二头肌的快速收缩。通过经颅磁刺激（TMS）评估肱二头肌运动皮层表征的变化。与单独MP和单独INB条件下的轻微变化或无变化相比，MP + INB导致运动诱发电位（MEP）的大小以及成对脉冲兴奋性显著增加。在实验2中，当受试者预先接受安慰剂处理时，MP + INB诱导的肱二头肌表征的这种显著增加得以重现，但当受试者预先接受劳拉西泮处理时，这种增加被阻止，甚至转变为减少。这些发现表明，GABA相关抑制的降低促进了人类运动皮层中依赖练习的可塑性，而增加则抑制它。在实验3中，还在行为水平上测试了依赖练习的可塑性（如同前两个实验一样通过TMS评估）。MP + INB诱导的肱二头肌MEP大小的显著增加与最快的肘部屈曲运动的峰值加速度增加相平行。同样，单独MP条件下MEP大小缺乏变化与峰值加速度缺乏变化相平行。我们提出，可以利用GABA活性的变化有目的地调节可塑性；例如，在神经疾病患者病变后增强可塑性变化和功能恢复。
Motor practice may lead to expansion of trained representations in the motor cortex, but it is unknown whether this practice-dependent plasticity can be purposefully enhanced or depressed. Evidence, mainly based on animal experiments, indicates that the activity of GABA-related cortical inhibition is important in controlling the extent to which plasticity may occur. We tested the role of GABA in modulating practice-dependent plasticity in the human motor cortex. A decrease in GABA-related cortical inhibition was achieved by ischaemic nerve block (INB) in the hand by deafferentation/deefferentation and an increase was achieved by administration of the GABAA receptor agonist lorazepam, In Experiment 1, healthy subjects performed motor practice (MP), consisting of repeated ballistic contractions of the biceps muscle in the absence (MP alone) or presence of INB (MP+INB), Changes in the biceps motor cortex representation were assessed by transcranial magnetic stimulation (TMS), MP+INB resulted in a dramatic increase in the size of the motor evoked potential (MEP) and in paired-pulse excitability compared with mild or no changes in the MP-alone and INB-alone conditions. In Experiment 2, this dramatic increase in biceps representation induced by MP+INB was replicated when subjects were pretreated with placebo, but this increase was prevented or even switched to a decrease when subjects were pretreated with lorazepam, These findings indicate that a decrease in GABA-related inhibition facilitates practice-dependent plasticity in the human motor cortex, whereas an increase depresses it. In Experiment 3, practice-dependent plasticity (assessed by TMS, as in the first two experiments) was also tested at the behavioural level, The dramatic increase in biceps MEP size induced by MP+INB was paralleled by an increase in peak acceleration of the fastest elbow flexion movements, Similarly, the lack of change in MEP size in the MP-alone condition was paralleled by a lack of change in peak acceleration. We propose that changes in GABA activity may be instrumented to modulate plasticity purposefully; for instance, to enhance plastic change and recovery of function after a lesion in neurological patients.