Temporal factors in recovery of function after brain damage

Abstract

Although many experiments have shown that serial lesions of the CNS often result in behavioral sparing, there have also been reports of failure to obtain recovery with the seriatum technique. One factor which might account for the succes or failure of sequential lesion experiments could be the duration of the interoperative interval. Thus, a minimum period may be required between operations in order to initiate the recovery process, and it was the purpose of the present experiment to explore this possibility. We have found that rats given sequential (two-stage) frontal aspiration lesions with either a 30 or 20 day interoperative interval were not disrupted on acquistion of a spatial alternation task when compared with sham-operated controls; animals with two-stage lesions spaced 10 days apart were impaired when contrasted to the latter groups although they performed significantly better than rats given simultaneous, bilateral operations. Because of this finding two groups of rats receiving either two-stage sham operations or two saline injections were also tested as controls for surgical stress. No differences in performance between these two groups of rats were observed. Thus, the severity of the deficit and subsequent behavioral recovery may be related to the interval of time between successive operations. Since all subjects had at least 5 weeks of postoperative recovery prior to training in spatial alternation, it is unlikely that postoperative factors would play as as important a role in functional recovery as the interval between successive lesions.