The impairments in reaching and the movements of compensation in rats with motor cortex lesions: an endpoint, videorecording, and movement notation analysis.

Reaching for food by rats, with the limb contralateral to limb area motor cortex damage, was analyzed using end-point scores, videoanalysis, and Eshkol-Wachmann Movement Notation (EWMN). End point results from groups of rats with small, medium, and large lesions showed reaching success and amount of food grasped per reach decreased with increases in lesion size. Videoanalysis and EWMN showed that the impairments were attributable to: (1) an inability to pronate the paw over the food by abduction of the upper arm, and (2) an inability to supinate the paw at the wrist to orient the food to the mouth. There were no obvious impairments in locating food using olfaction, in positioning the body in order to initiate a reach, or in clasping the digits to grasp food. There were only mild impairments in lifting, aiming, and advancing the limb. In rats with medium and large lesions, loss of pronation and supination were compensated for by a variety of whole body movements. These findings are discussed in reference to neural and behavioral mechanisms underlying recovery of function and the contribution of the motor cortex to skilled movements in the rat and other species.