Is there an optimal age for recovery from motor cortex lesions? I. Behavioral and anatomical sequelae of bilateral motor cortex lesions in rats on postnatal days 1, 10, and in adulthood.
ABSTRACT Rats were given bilateral lesions of the motor cortex on the day of birth (P1), tenth day of life (P10), or in adulthood. They were trained on several motor tasks (skilled forelimb reaching, beam traversing, tongue extension), general motor activity, and a test of spatial learning (Morris water task). Although all lesion groups were impaired at skilled reaching, the P10 group was less impaired than either of the other two lesion groups. Furthermore, on the other motor tests the P10 group did not differ from controls whereas both P1 and adult groups were impaired. Only the P1 lesion group was impaired at the acquisition of the Morris water task. Anatomical analyses revealed that the P1 and P10 rats had smaller brains than the other two groups as well as having a generalized decrease in cortical thickness. Dendritic analysis of layer III pyramidal cells in the parietal cortex revealed a decrease in apical arbor in the lesion groups and an increase in the basilar arbor of the P1 and adult lesion animals. The P1 and adult operated groups showed an increase in spine density in the basilar dendrites of layer V pyramidal cells. Finally, analysis of the pattern of corticospinal projections revealed that the P1 animals had a markedly wider field of corticospinal projection neurons than any of the other groups. The widespread anatomical changes in all lesion groups versus the relatively better behavioral recovery after P10 lesions suggests that day 10 represents an optimal period for adapting to brain damage and subsequent brain reorganization.
- Progress in Neurobiology 02/1989; 32(4):235-76. · 9.04 Impact Factor
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ABSTRACT: Rats with complete removal of the cortex anterior to bregma in adulthood (frontal cortex) were compared behaviorally and neuroanatomically to rats with similar removals at 1, 5, or 10 days of age. The age at which animals received the cortical excision made a significant difference with respect to the development of the thalamus and the remaining cortex as well as the behavioral outcome in adulthood. There was a direct relationship between cortical thickness in adulthood and the age at surgery: the earlier the lesion the thinner the cortex. Part of this anatomical effect was acute, and could be observed within 24 h of surgery, but the major reduction in thickness was not observed until adolescence. Behaviorally, the animals were administered several tests including tongue extension, grooming, beam walking, swimming, and a spatial navigation task. Like the cortical measurements, the behavioral measurements showed a clear relationship between age at surgery and behavioral outcome: the earlier the lesion in infancy, the greater the behavioral impairments. Thus, whereas rats with lesions at 10 days of age showed behavioral sparing, relative to adult operates, on every measure, rats with lesions at 5 days of age performed at about the level of adult operates on most tests and rats with lesions at 1 day had more extensive behavioral impairments than all other groups. These results imply that the effects of cortical injury in infancy are tightly correlated with the precise level of neural maturation at the time of lesion.Behavioural Brain Research 10/1987; 25(3):205-20. · 3.33 Impact Factor
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ABSTRACT: This study examined the behavioural and anatomical effects of intraventricular injections of nerve growth factor in rats with unilateral damage that included Zilles' areas Frl, FL, HL, ParI and the anterior portion of Oc2. Nerve growth factor-treated lesion rats showed attenuation of behavioural symptoms in measures of forelimb function (Whishaw reaching task) and hindlimb function (beam traversing task) as well as a measure of spatial navigation (Morris water task). Analysis of dendritic arborization using a modified Golgi. Cox procedure also showed a complete reversal of lesion-induced atrophy of dendritic fields in pyramidal neurons in motor (Zilles' Fr2) and cingulate (Zilles' Cgl) cortex. In addition, there was a reversal of a lesion-induced reduction in spine density. These results demonstrate that nerve growth factor treatment can facilitate functional recovery from cortical injury. This recovery may be mediated by a reorganization of intrinsic cortical circuitry that is reflected in changes in dendritic arborization and spine density of pyramidal neurons.Neuroscience 03/1997; 76(4):1139-51. · 3.12 Impact Factor