Varied influence of damage to the motor cortex on precision avoidance and escape reactions in dogs.

The influence of local extirpation of the representation of the forelimb in the motor area of the cortex on the performance of precision elevations of this limb was investigated. Even imprecise avoidance reactions to an acoustic signal did not recover spontaneously. Irregular motoric reactions which were insufficient in amplitude could easily be restored in the course of retraining, but precise movements (both rapid fused, as well as relatively slow stepwise movements) did not recover for at least a half year after the operation. By contrast with this, precise rapid reactions in response to electrical stimulation of a "working" limb (inducing unconditioned reflex flexion) remained essentially preserved, i.e., the capacity to stop the movement in the correct (previously learned) position of the limb was preserved. The capacity to fix the position of the raised limb was not lost, but was persistently impaired. The capacity to overcome the unconditioned reflex flexion during the performance of extensor "slow" escape reaction was reduced sharply and persistently. Limb presentation reactions regulated by vision were essentially spontaneously and nearly completely restored within a month.