Rost Katrin, Nowak Dennis A, Timmann Dagmar, Hermsdörfer Joachim
Clinical Neuropsychology Research Group, Department of Neuropsychology, München-Bogenhausen Hospital, Technical University of Munich, Dachauer Strasse 164, D-80992 Munich, Germany.
Clin Neurophysiol. 2005 Jun;116(6):1405-14. doi: 10.1016/j.clinph.2005.02.015. Epub 2005 Apr 7.
To analyze preserved and impaired aspects of feedforward grip force control during cyclic arm movements with a hand-held object after cerebellar damage.
We tested eight subjects with unilateral or bilateral cerebellar pathologies and eight healthy control subjects. Participants performed cyclic vertical arm movements with a hand held instrumented object at three different speeds.
Compared to controls, patients excerted increased grip forces. The minimum force ratio between grip force and load force was constant across all movement frequencies, suggesting that patients anticipated speed-related changes in load magnitudes by adjusting the grip force. Thus the scaling of grip force level to self-generated load magnitudes was preserved. The coupling between grip and load profiles was assessed by cross correlation analysis. Patients exhibited significantly decreased maximum coefficients of cross correlation implicating impaired anticipation of inertial load fluctuations. However feedforward control could be preserved, as obvious from zero time lags of the maximum cross correlation coefficient.
Our findings suggest that cerebellar lesions affect the processing of predictive grip force modulation in anticipation of inertial loads. Our results add further evidence to the theoretical concept that the cerebellum implements internal feedforward models. However, preserved functions may indicate compensatory mechanisms or extra-cerebellar aspects of grip and load force regulation.
The observed dissociation of performance deficits may have direct clinical implication and may guide the development of individual therapeutic strategies for patients with cerebellar disorders.
分析小脑损伤后手持物体进行周期性手臂运动时前馈握力控制的保留和受损方面。
我们测试了8名单侧或双侧小脑病变患者以及8名健康对照者。参与者手持装有仪器的物体以三种不同速度进行周期性垂直手臂运动。
与对照组相比，患者施加的握力增加。在所有运动频率下，握力与负载力之间的最小力比是恒定的，这表明患者通过调整握力来预测与速度相关的负载大小变化。因此，握力水平与自身产生的负载大小之间的比例关系得以保留。通过互相关分析评估握力与负载曲线之间的耦合。患者表现出互相关的最大系数显著降低，这意味着对惯性负载波动的预测受损。然而，从前馈控制来看，最大互相关系数的零时间滞后表明前馈控制可以保留。
我们的研究结果表明，小脑病变会影响在预测惯性负载时对握力调制的处理。我们的结果为小脑实现内部前馈模型这一理论概念提供了进一步的证据。然而，保留的功能可能表明存在补偿机制或握力与负载力调节的小脑外因素。
观察到的性能缺陷分离可能具有直接的临床意义，并可能指导小脑疾病患者个体化治疗策略的制定。
