Chu Way Tong Virginia, Sanger Terence D
Department of Bioengineering, Stanford University, California, USA.
Mov Disord. 2009 Jul 15;24(9):1299-305. doi: 10.1002/mds.22573.
Children with secondary dystonia due to cerebral palsy (CP) often exhibit excess variability in their movements. To investigate the relationship between excess variability and single-joint control in these children, we compared their force variations during single-joint isometric tasks to age-matched controls. Subjects performed isometric biceps contractions at six target force levels scaled to their maximum voluntary contraction. Similar studies in healthy adults have shown that movement variability exhibits characteristics of signal-dependent noise (SDN). We look for the first time at whether variability in single-joint force contractions in healthy children and children with CP exhibit similar characteristics of SDN. Results showed that compared to controls, patients exhibited increased variability (standard deviation about the mean), increased force error bias (difference between the mean and target), and increased dependence of force error bias on target force level. Signal-dependence of the noise was significant only in healthy subjects due to the higher overall variability in the patients. A control experiment using filtered visual feedback confirmed that overcorrection for perceived error was not the cause of the observed variability. These results contribute to a better understanding of movement variability in childhood dystonia and have potential use in therapeutic interventions designed to increase force production reliability.
患有因脑瘫（CP）导致的继发性肌张力障碍的儿童，其运动往往表现出过度的变异性。为了研究这些儿童过度变异性与单关节控制之间的关系，我们将他们在单关节等长任务中的力变化与年龄匹配的对照组进行了比较。受试者在六个根据其最大自主收缩进行缩放的目标力水平下进行等长二头肌收缩。在健康成年人中进行的类似研究表明，运动变异性表现出信号依赖噪声（SDN）的特征。我们首次研究了健康儿童和患有CP的儿童在单关节力收缩中的变异性是否表现出类似的SDN特征。结果表明，与对照组相比，患者表现出更大的变异性（均值周围的标准差）、更大的力误差偏差（均值与目标之间的差异）以及力误差偏差对目标力水平的依赖性增加。由于患者总体变异性较高，噪声的信号依赖性仅在健康受试者中显著。一项使用滤波视觉反馈的对照实验证实，对感知误差的过度校正不是观察到的变异性的原因。这些结果有助于更好地理解儿童肌张力障碍中的运动变异性，并在旨在提高力产生可靠性的治疗干预中具有潜在用途。
