Functional consequences of transplantation of frontal neocortex vary with age of donor tissue and behavioral task

The spatial learning of rats with medial prefrontal lesions was compared to that of animals with cortical transplants of frontal tissue from donors of embryonic age 17, 19, 21, or 23 days. The age of the donor tissue significantly affected the extent that the transplanted tissue developed as the E17 and E19 grafts were markedly larger than those from E21 or E23 animals. Nonetheless, transplants were viable at all ages. Rats with E19 grafts, but not rats with grafts at other ages, showed significant reduction of the expected deficit on the Morris water task. In contrast, only rats with E21 grafts showed enhanced performance on a T-maze alternation task. The contrasting effects of the grafts of different aged tissue suggests that there may be some specific contributions of cortical grafts of different ages that leads to partial restoration of function.