Effects of differential interference with postnatal cerebellar neurogenesis on motor performance, activity level, and maze learning of rats: A developmental study.

Abstract

The region of the cerebellum was X-irradiated in infant rats with selected exposure schedules designed to produce animals in which the cerebellar cortex was (a) essentially normal except for agenesis of late forming granule cells with axons situated in the uppermost molecular layer (12-15X), (b) lacking in stellate cells, with a severe reduction in granule cells with axons in the upper molecular layer (8-15X), (c) morphologically disorganized but had only intermediate cell agenesis (4-5X), or (d) disorganized and devoid of practically all postnatally forming interneurons (4-15X). In the first two experiments young adults had to traverse rotating rods that differed in texture and types of obstacles. The 8-15X animals showed no deficits on any of the rods tested. The third study dealt with spontaneous motor performance in the open field at three ages. The 4-5X and 4-15X animals were /lypoactive as infants and young adults; this was attributed to their motor deficits. The 8-15X and 12-15X animals were hyperactive in the open field as young adults. The fourth experiment examined intra-and/or intersession habituation. No group differences were found in habituation patterns. In the fifth experiment, using activity wheels, the 4-15X group was /rypoactive, and the 8-15X and 12-15X groups were hyperactive as young adults. In the sixth experiment young adults were tested for learning performance in a multiple-unit water maze. The 4-15X group was deficient on single alternation; the 4-5X and 12-15X groups on double alternation. The seventh experiment shed some light on the single alternation deficit of the 4-15X group; only these animals failed to alternate spontaneously in a nonaversive situation. In conclusion, these behavioral results, combined with those of recent morphological investigations, suggest that the cerebellar cortex is hierarchically organized: The basal domain of Purkinje cells and the lower molecular layer are implicated in the coordination of movements; the apical domain of Purkinje cells and the upper molecular layer, in the coordination of actions.The cerebellar cortex has an unusually not only of neurons of the cerebellar cortex precise geometric organization (Eccles, Ito, (Altman, 1969; 1972a , 1972b , 1972c) but of & Szentagothai, 1967. This is paralleled by the Purkinje cells and neurons of the cerethe precise chronology of the time of origin bellar deep nuclei (Altman & Bayer, 1978a)

The paleocerebellum and the integration of behavioral function

“…These are precisely the class of deficits that characterize decompositions and failures of associated movements. The present results suggest that, in addition to the motor coordination aspects of cerebellar function, one must also consider what Pellegrino and Altman (1979) have termed its "action coordination functions"-functions that relate to the integration of patterns of behavior.…”

“…Spontaneous alternation between opposing responses (such as turning left vs. turning right) is highly characteristic of the normal exploratory behavior of animals (Dember & Fowler, 1958). Pellegrino and Altman (1979), however, report that animals with cerebellar agenesis fail to show this normal pattern of response alternation. Moreover, while these animals can acquire numerous complex maze habits as readily as normal animals, they are greatly impaired when the maze is configured so as to require the serial alternation between right and left turns.…”

Quantitative studies on regional differences in purkinje cell dendritic spines and parallel fiber synaptic density

“…Pellegrino and Altman (1979) suggested that in the apical domain of Purkinje cells, coordination of action takes place. High synaptic density of parallel fiber synapses, tagether with thick and numerous spiny branchlets and spines with extremely thin stalks, would explain the very large logical capacities of Purkinje cells in lobule VIa (Shepherd 1974).…”

Developmental and oncogenic radiation effects on neural stem cells and their differentiating progeny in mouse cerebellum

“…Irradiation of the cerebellum has multiple effects on its development, including reduction of the overall size, foliar/ lobular malformations [11,12], and functional deficiencies such as tremor, ataxia, hypoactivity, and cognitive deficits [13][14][15][16][17]. Populations of NSCs orchestrate the specification and patterning of the cerebellum.…”