Cortical excitability changes induced by deafferentation of the contralateral hemisphere.
Cortical excitability changes induced by deafferentation of the contralateral hemisphere.
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DOI：
10.1093/brain/awf140
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发表时间：
2002-06
期刊：
影响因子：
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通讯作者：
K. Werhahn;Jennifer Mortensen;A. Kaelin-Lang;B. Boroojerdi;L. Cohen
中科院分区：
文献类型：
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作者：
K. Werhahn;Jennifer Mortensen;A. Kaelin-Lang;B. Boroojerdi;L. Cohen
缺血神经阻滞(INB)短期剥夺感觉输入会导致去传入运动皮质的功能重组。在这里，我们表明，INB也引起了去传入皮层对侧同位区域的功能变化。检测右手INB前、中、后小手和肱二头肌经颅磁刺激(TMS)诱发电位(MEP)波幅。INB增加了(I)完整的手和(Ii)去传入的手(上臂)近端的身体部分的皮质代表的兴奋性，而其他身体部分的代表如胸肌或腿部肌肉的兴奋性没有变化。这种影响在整个去传入过程中持续存在，并在之后恢复到基线水平。在INB期间，对脑干电刺激的运动反应保持不变，表明这种影响可能来自皮质。GABA(A)受体激动剂劳拉西潘阻断了这种兴奋性的增加。在INB期间，手部肌肉之间的半球间抑制减少。截肢者慢性去传入后，小手肌的MEP波幅和运动输出曲线较老年对照组降低，运动阈值升高。这些结果表明，急性手部去传入可以引起去传入皮层对侧手部运动表征兴奋性的局灶性增加，这种兴奋性受跨痂相互作用和GABA能传递的影响，并且在慢性去传入的情况下是平衡的。
Short-term deprivation of sensory input by ischaemic nerve block (INB) leads to functional reorganization in the deafferented motor cortex. Here, we show that INB also elicits functional changes in homotopic regions of the cortex contralateral to the deafferented one. We measured motor evoked potential (MEP) amplitudes elicited by transcranial magnetic stimulation (TMS) in small hand and biceps brachii muscles before, during and after INB of the right hand. INB increased excitability of the cortical representation of (i) the intact hand and (ii) body parts proximal to the deafferented hand (upper arm), in the absence of excitability changes in other body part representations such as thorax or leg muscles. This effect persisted throughout the entire period of deafferentation and returned to baseline values afterward. Motor responses to brainstem electrical stimulation remained unchanged during INB, indicating that the effect is probably of cortical origin. Lorazepam, a GABA(A) receptor agonist, blocked this increased excitability. Interhemispheric inhibition between hand muscles decreased during INB. After chronic deafferentation in amputees, MEP amplitudes and motor output curves in small hand muscles were depressed and motor thresholds were elevated compared with aged-matched controls. These results indicate that acute hand deafferentation can elicit a focal increase in excitability in the hand motor representation contralateral to the deafferented cortex that is influenced by transcallosal interactions and GABAergic transmission, and is balanced in the setting of chronic deafferentation.