ADAPTIVE BEHAVIORAL REACTIONS OF REACHING IN RATS FOLLOWING DISCRETE SOMATOSENSORIMOTOR CORTEX LESIONS

To test the effects of lesions of forelimb somatosensorimotor subareas on the reaching behavior, the rats were trained to reach for food pel lets in a horizontal tube and through a grid. Reaching attempts were m onitored by continual movement recording using magnetic induction and reaching success was quantitatively evaluated. In rats with bilateral lesions centered over the forelimb motor subarea (FMCL), reaches with the preferred forepaw were accompanied by reaching attempts with the n onpreferred forelimb. The latter declined over the recording period bu t larger residual movements were still observed at the end. Relative t o control group, the performance of rats with FMCL was significantly d ecreased in both reaching tasks, however the reaching success into tub e was significantly lower than through a grid. Rats with lesions cente red over forelimb cutaneous representation (FCRL) showed signs of tact ile deficit. Chosen reaching tactic represented an attempt to compensa te for the tactile deficit. No reaches with the nonpreferred forepaw w ere observed. Relative to controls, the reaching success in rats with FCRL was decreased by the same amount in both reaching tasks. When rea ching into the tube, the rats with FCRL performed significantly better than rats with FMCL over the whole recording period; when reaching th rough the grid no statistical difference in performance was observed b etween groups though the rats with FMCL performed better than the rats with FCRL. The discrete somatosensorimotor cortex lesions did not onl y result in different direct reaching deficits and performance, but al so resulted in different behavioral reactions.