Movement Analysis of Cerebellar Limb Ataxia

The overall purpose of the project is to study how the central nervous system compensates for cerebellar dysfunction. This question will be investigated in patients with cerebellar upper limb ataxia. The assumption behind the experiment is that one of the cerebellar functions is to perform fast intramovement control by "on-line" integration of the information about the execution of the ongoing movement into the actual motor program. Impairment of this function is assumed to be the cause of the cerebellar limb ataxia. To compensate the lost cerebellar function the CNS may employ alternative sensory information sources about the ongoing movement. In order to investigate this issue, two series of experiments are proposed. The first phase of the project, will test the hypothesis that cerebellar patients (Cps) are more sensitive to external perturbations occurring during a movement. Healthy subjects and patients with cerebellar upper limb ataxia will perform single-joint arm movements to visual targets using a special manipulandum. External force impulses of different timing and magnitude will be applied to the manipulandum during the movement to induce perturbations requiring fast corrective responses. Kinematic, electromyographic and dynamic parameters of the resulting movements and corrective responses of both groups (healthy subjects and Cps) will be analyzed, compared and used for elaboration of a model of cerebellar limb ataxia. The second phase of the project will test the assumption, that preceding visual information about the perturbative impulse can be integrated in the motor program and con improve motor performance of the Cps. Both groups will be tested using a modified experimental protocol where a precuing visual information about the ongoing perturbative impulse will be available to a subject. For the analysis of the data obtained in the second phase the model of cerebellar limb ataxia elaborated in the initial phase of the project will be applied. The proposed project differs from the previous studies on patients with cerebellar limb ataxia by an advanced combined kinematic and neurophysiological analysis and modeling of the cerebellar ataxic movements. Results obtained and experience acquired in this research may be applied in different basic and clinical studies of movement disorders and may lead to a development of new diagnostic and rehabilitative methods.