Manto M U, Bosse P
Fonds National de la Recherche Scientifique, Université Libre de Bruxelles, Hôpital Erasme Neurologie, 808, Route de Lennik, 1070 Bruxelles, Belgium.
Neurol Res. 2003 Jul;25(5):434-44. doi: 10.1179/016164103101201715.
The role of the cerebellum in the spatial tuning of goal-directed multi-joint movements in human is unknown. We analyzed the directional tuning of phasic EMG activities associated with upper limb reaching movements (12 targets) in the vertical plane in healthy subjects and in patients exhibiting cerebellar ataxia. Tuning of phasic EMG activities was investigated in seven muscles (brachioradialis, biceps, medial and long head of triceps, anterior and posterior deltoid, latissimus dorsi). We digitally compressed the EMG activities corresponding to slow reaches to the same targets into the time frame of the fast EMG traces. Estimates of gravity-related components were subtracted. Peaks of EMG activities in the resulting phasic traces were identified for each muscle and each target. Aberrant privileged directions of M Peak EMG (directions associated with the maximal peak of EMG amongst the 12 peaks of EMG activity in the sagittal plane) were found in all ataxic patients. Directional dominance, defined as the ratio of the M Peak EMG divided by the peak EMG in the opposite direction, was significantly higher in controls than in ataxic patients for one distal muscle (brachioradialis) and one proximal muscle (anterior deltoid). The spreading of EMG activities assessed by the global areas of the polar plots of phasic traces was broader in patients for the biceps and medial head of triceps. The distribution of densities of EMG activities (DDEMG) amongst the four quarters of the vertical plane, an index of the contrast in the intensities between quarters in polar plots, revealed increased values in control subjects for the brachioradialis, the biceps and the anterior deltoid as compared to ataxic patients. Representation of Net Vectors obtained from polar plots of peaks of EMG activities demonstrated an abnormal directional tuning in ataxic patients. In the majority of the cases, the Net Vector was outside the normal range for the following muscles: brachioradialis, biceps, anterior deltoid, posterior deltoid. This study reveals that cerebellar ataxia is associated with defective spatial properties of EMG activity during multiple joint movements. Privileged directions associated with M Peak EMG and Net Vectors are erroneous. We demonstrate that the cerebellum plays a determinant and unsuspected role in the spatial modulation of activation during speed-related action for reaching.
小脑在人类目标导向的多关节运动空间调整中的作用尚不清楚。我们分析了健康受试者和患有小脑共济失调的患者在垂直平面内与上肢伸展运动（12个目标）相关的相位肌电图（EMG）活动的方向调整。在七块肌肉（肱桡肌、肱二头肌、肱三头肌内侧头和长头、三角肌前束和后束、背阔肌）中研究了相位EMG活动的调整。我们将对应于缓慢到达相同目标的EMG活动数字压缩到快速EMG轨迹的时间框架内。减去重力相关分量的估计值。确定了每条肌肉和每个目标在所得相位轨迹中EMG活动峰值。在所有共济失调患者中均发现了M峰EMG的异常优势方向（矢状面中12个EMG活动峰值中与EMG最大峰值相关的方向）。对于一块远端肌肉（肱桡肌）和一块近端肌肉（三角肌前束），方向优势（定义为M峰EMG除以相反方向的EMG峰值的比率）在对照组中显著高于共济失调患者。对于肱二头肌和肱三头肌内侧头，患者中通过相位轨迹极坐标图的总面积评估的EMG活动分布更宽。垂直平面四个象限内EMG活动密度分布（DDEMG），即极坐标图中各象限强度对比度的指标，显示与共济失调患者相比，对照组中肱桡肌、肱二头肌和三角肌前束的值增加。从EMG活动峰值极坐标图获得的净向量表示表明共济失调患者存在异常的方向调整。在大多数情况下，净向量超出了以下肌肉的正常范围：肱桡肌、肱二头肌、三角肌前束、三角肌后束。这项研究表明，小脑共济失调与多关节运动期间EMG活动的空间特性缺陷有关。与M峰EMG和净向量相关的优势方向是错误的。我们证明小脑在与速度相关的伸手动作激活的空间调制中起决定性且未被怀疑的作用。
