EFFECTS OF DIFFERENTIAL INTERFERENCE WITH POSTNATAL CEREBELLAR NEUROGENESIS ON MOTOR-PERFORMANCE, ACTIVITY LEVEL, AND MAZE-LEARNING OF RATS - DEVELOPMENTAL-STUDY

In 7 experiments the cerebellum was irradiated in infant Long-Evans hooded rats with selected exposure schedules designed to produce Ss in which the cerebellar cortex was (a) normal except for agenesis of late forming granule cells with axons situated in the uppermost molecular layer (12-25X); (b) lacking in stellate cells, with a severe reduction in granule cells with axons in the upper molecular layer (8-25X); (c) morphologically disorganized but had intermediate cell agenesis (4-5X); or (d) disorganized and devoid of practically all postnatally forming interneurons (4-25X). In the 1st 2 experiments young adult Ss had to traverse rotating rods that differed in texture and types of obstacles. The 8-25X Ss showed no deficits on any rod. The 3rd study dealt with spontaneous motor performance in the open field. The 4-5X and 4-25X Ss were hypoactive as infants and young adults; this is attributed to motor deficits. The 8-25X and 12-25X Ss were hyperactive in the open field as young adults. Exp IV examined intra- and/or intersession habituation but found no group differences. In Exp V, using activity wheels, 4-25X Ss were hypoactive, and 8-25X and 12-25X Ss were hyperactive as young adults. In Exp VI, young adults were tested in a multiple-unit water maze. The 4-25X group was deficient on single alternation, the 4-5X and 12-25X groups on double alternation. Exp VII showed that only the 4-25X group failed to alternate spontaneously in a nonaversive situation. Results suggest that cerebellar cortex is hierarchically organized. (40 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1979 American Psychological Association.