THE EFFECTS OF AMPHETAMINE ON RECOVERY OF FUNCTION AFTER CORTICAL DAMAGE IN THE RAT DEPEND ON THE BEHAVIORAL REQUIREMENTS OF THE TASK

The effects of amphetamine on the recovery of function following unila teral lesions of the rat somatic sensorimotor cortex (SMC) were examin ed. Rats with large SMC were tested on two measures of locomotor placi ng: the beam-walking test and the foot-fault test. Amphetamine produce d an immediate and enduring facilitation of recovery on the beam-walki ng test. In contrast, the drug had no effect on the rats' ability to a ccurately place the forelimbs on the rungs of the elevated grid during locomotion on the foot-fault test. These data suggest that amphetamin e may facilitate recovery when the requirements of the task produce a deficit in the initiation of locomotion but not when the animal is req uired to use somatosensory and proprioceptive cues to guide performanc e on the task, A second group of rats with smaller SMC lesions was eva luated with tactile-placing tests and the bilateral-tactile stimulatio n task, The forelimb placing reaction is elicited by unilateral tactil e stimulation of the vibrissae or forelimb, whereas the ipsilateral as ymmetry observed on the bilateral-tactile stimulation test has been in terpreted as an impairment in processing stimuli presented on both sid es of the body. On two measures of forelimb placing amphetamine produc ed a facilitation of recovery, but restoration of function was not obs erved during the period of drug intoxication. In contrast, amphetamine had no effect on recovery of function on the bilateral-tactile stimul ation test, Taken together, these data suggest that the behavioral req uirements of the task are an important factor in determining the facil itatory effects of amphetamine on recovery of function.