Prodoehl J, Corcos D M, Vaillancourt D E
Department of Movement Sciences (M/C 994), College of Applied Health Sciences, University of Illinois at Chicago, 808 South Wood Street, 690 CME, Chicago, Illinois 60612, USA.
J Neurol Neurosurg Psychiatry. 2006 Aug;77(8):909-14. doi: 10.1136/jnnp.2006.091363. Epub 2006 May 11.
A fundamental feature underlying many movement disorders is increased variability in the motor response. Despite abnormalities of grip force control in people with dystonia, it is not clear whether dystonia is also associated with increased variability in force output and whether force variability in dystonia is affected by the presence or absence of visual feedback.
To examine force variability in 16 patients with writer's cramp and 16 matched controls.
The variability of force output at the wrist under conditions of both vision and no vision was examined. The underlying frequency structure of the force signal was also compared across groups. Participants produced isometric wrist flexion to targets at 25% and 50% of their maximum voluntary contraction strength under conditions of both vision and no vision.
Similar levels of force variability were observed in patients with dystonia and controls at the lower force levels, but patients with dystonia were less variable in their force output than controls at the higher force level. This reduction in variability in people with dystonia at 50% maximum voluntary contraction was not affected by vision. Although a similar dominant frequency in force output was observed in people with dystonia and controls, a reduced variability in the group with dystonia at the higher force level was due to reduced power in the 0-4-Hz frequency bin.
The first evidence of a movement disorder with reduced variability is provided. The findings are compatible with a model of dystonia, which includes reduced cortical activation in response to sensory input from the periphery and reduced flexibility in motor output.
许多运动障碍的一个基本特征是运动反应的变异性增加。尽管肌张力障碍患者存在握力控制异常，但尚不清楚肌张力障碍是否也与力输出的变异性增加有关，以及肌张力障碍中的力变异性是否受视觉反馈的有无影响。
研究16例书写痉挛患者和16例匹配对照者的力变异性。
检测了视觉条件和无视觉条件下腕部力输出的变异性。还比较了各组之间力信号的潜在频率结构。参与者在视觉条件和无视觉条件下，以最大自主收缩强度的25%和50%对目标进行等长腕部屈曲。
在较低力水平下，肌张力障碍患者和对照者的力变异性水平相似，但在较高力水平下，肌张力障碍患者的力输出变异性低于对照者。肌张力障碍患者在最大自主收缩50%时变异性的降低不受视觉的影响。尽管肌张力障碍患者和对照者在力输出方面观察到相似的主导频率，但肌张力障碍组在较高力水平下变异性的降低是由于0-4赫兹频段的功率降低。
提供了首个变异性降低的运动障碍的证据。这些发现与肌张力障碍模型相符，该模型包括对来自外周的感觉输入的皮质激活减少以及运动输出的灵活性降低。
