EFFECTS OF DELAY AND DURATION OF LIGHT DEPRIVATION ON RECOVERY OF FUNCTION FROM NEGLECT INDUCED BY UNILATERAL MEDIAL AGRANULAR PREFRONTAL CORTEX LESIONS IN RATS

Forty-eight hours of postoperation light deprivation (LD) has been fou nd to produce complete and permanent behavioral recovery of function f rom neglect induced by unilateral lesions of medial agranular cortex ( AGm) in rats. The two experiments in the present study parametrically examined the postoperation delay prior to LD and the duration of LD ne cessary to produce recovery from severe neglect. Subjects in both expe riments received unilateral AGm lesions and were tested for the degree of neglect of visual, tactile, and auditory stimuli prior to and afte r experiencing LD. The results of the study of delay of LD indicated t hat LD administered 4 h postsurgery produced dramatic immediate recove ry from severe neglect, and the recovery lasted for the duration of be havioral testing (3 weeks) following LD. The longer delay groups (52 a nd 100 h) and the no-manipulation controls did not demonstrate behavio ral recovery. The 28-h delay group demonstrated an intermediate effect following LD. The results of the study of duration of LD indicated th at the therapeutic effect of LD was duration dependent. Forty-eight ho urs of LD produced a significant reduction in the severity of neglect, but shorter durations (4 and 24 h) did not. The results of the presen t study indicate that a critical postoperative period exists in which LD must be initiated in order to produce recovery from severe neglect and that LD has to be administered for a period of at least 24 h to pr oduce any evidence of recovery of function. These findings may have cl inical implications for the treatment of neglect in humans.