Objective: To analyze preserved and impaired aspects of feedforward grip forc e control during cyclic arm movements with a hand- held object after cerebellar damage. Methods: We tested eight subjects with unilateral o...Objective: To analyze preserved and impaired aspects of feedforward grip forc e control during cyclic arm movements with a hand- held object after cerebellar damage. Methods: We tested eight subjects with unilateral or bilateral cerebell ar pathologies and eight healthy control subjects. Participants performed cyclic vertical arm movements with a hand held instrumented object at three different speeds. Results: Compared to controls, patients excerted increased grip forces. The minimum force ratio between grip force and load force was constant across al l movement frequencies, suggesting that patients anticipated speed- related cha nges in load magnitudes by adjusting the grip force. Thus the scaling of grip fo rce level to self- generated load magnitudes was preserved. The coupling betwee n grip and load profiles was assessed by cross correlation analysis. Patients ex hibited significantly decreased maximum coefficients of cross correlation implic ating impaired anticipation of inertial load fluctuations. However feedforward c ontrol could be preserved, as obvious from zero time lags of the maximum cross c orrelation coefficient. Conclusions: Our findings suggest that cerebellar lesion s affect the processing of predictive grip force modulation in anticipation of i nertial loads. Our results add further evidence to the theoretical concept that the cerebellum implements internal feedforward models. However, preserved functi ons may indicate compensatory mechanisms or extracerebellar aspects of grip and load force regulation. Significance: The observed dissociation of performance de ficits may have direct clinical implication and may guide the development of ind ividual therapeutic strategies for patients with cerebellar disorders.展开更多
文摘Objective: To analyze preserved and impaired aspects of feedforward grip forc e control during cyclic arm movements with a hand- held object after cerebellar damage. Methods: We tested eight subjects with unilateral or bilateral cerebell ar pathologies and eight healthy control subjects. Participants performed cyclic vertical arm movements with a hand held instrumented object at three different speeds. Results: Compared to controls, patients excerted increased grip forces. The minimum force ratio between grip force and load force was constant across al l movement frequencies, suggesting that patients anticipated speed- related cha nges in load magnitudes by adjusting the grip force. Thus the scaling of grip fo rce level to self- generated load magnitudes was preserved. The coupling betwee n grip and load profiles was assessed by cross correlation analysis. Patients ex hibited significantly decreased maximum coefficients of cross correlation implic ating impaired anticipation of inertial load fluctuations. However feedforward c ontrol could be preserved, as obvious from zero time lags of the maximum cross c orrelation coefficient. Conclusions: Our findings suggest that cerebellar lesion s affect the processing of predictive grip force modulation in anticipation of i nertial loads. Our results add further evidence to the theoretical concept that the cerebellum implements internal feedforward models. However, preserved functi ons may indicate compensatory mechanisms or extracerebellar aspects of grip and load force regulation. Significance: The observed dissociation of performance de ficits may have direct clinical implication and may guide the development of ind ividual therapeutic strategies for patients with cerebellar disorders.
