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Biomedical subjects

B Kolb

Publications and source records attributed to B Kolb.

150 records · Page 9Linked to original sources
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Recovery from early cortical lesions in rats. III. Neonatal removal of posterior parietal cortex has greater behavioral and anatomical effects than similar removals in adulthood.

The behavioral, anatomical, and electrophysiological effects of posterior parietal cortex lesions (Krieg's area 7) were compared in rats with removals at 1, 5, or 10 days of age or in adulthood. Behaviorally, the animals were administered several tests including grooming, beam walking, swimming, the Morris water task and a radial arm maze. Lesions at 10 days of age permitted behavioral sparing on most behavioral tasks, whereas lesions at 1 or 5 days of age allowed little sparing and even produced larger deficits than observed in adult operates on some tasks. Anatomical measures showed a direct relationship between cortical thickness and age of lesion: the earlier the lesion, the thinner the cortex. An analysis of postsurgical changes in cortical thickness showed only a small reduction in cortical thickness shortly after the lesions, with the major reduction occurring during adolescence. Electrophysiological recordings of cortical activity showed that rats with 1-day lesions had abnormal neocortical atropine-resistant activity and had an increased incidence of seizures. The results suggest that the neocortex of the rat may be particularly sensitive to perinatal injury.

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Environmental enrichment and cortical injury: behavioral and anatomical consequences of frontal cortex lesions.

Rats with large unilateral or bilateral frontal cortical lesions were placed in either isolated or enriched housing conditions for 90 d and then were compared behaviorally and neuroanatomically to control rats. The frontal lesions reduced chronic body weight, produced impairments in claw cutting, food hoarding, tongue extension, and spatial navigation in the Morris water task, and increased running wheel activity. Enriched rearing attenuated many of the behavioral changes, but with the exception of tongue extension and spatial navigation, it had similar effects in both normal and brain-injured animals. Analysis of the brains showed that enrichment increased brain weight and dendritic branching in visual cortex similarly in normal and brain-injured rats. In contrast, however, enrichment affected parietal neurons in normal but not in brain-damaged animals. Instead, the frontal operates showed an increase in parietal branching irrespective of the rearing condition, which implies that the lesion itself may have led to some form of reactive synaptogenesis that subsequently precluded environmental effects.

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Dissociation of the medial prefrontal, posterior parietal, and posterior temporal cortex for spatial navigation and recognition memory in the rat.

Rats with lesions of the medial prefrontal, posterior parietal, or posterior temporal cortex were tested in five spatial navigation tasks, which varied in egocentric or allocentric demands, a visual discrimination task, and two delayed nonmatching-to-sample tasks. Rats with prefrontal lesions were impaired at every spatial navigation task, whereas rats with posterior parietal lesions had selective spatial navigation impairments. Rats with prefrontal lesions were also impaired at a visual delayed nonmatching-to-sample task, as they were unable to learn the task, even with no delay. The results are consistent with the idea that the basic plan of mammalian cortex includes prefrontal, posterior parietal, and posterior temporal regions, each of which have generally similar functions across mammalian taxa. There are, however, species-typical differences that reflect specific ecological pressures on the development of the different regions.

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Sex differences in cortical plasticity and behavior following anterior cortical kindling in rats.

This experiment examined the effect of electrical kindling on the morphology of frontal (Fr1) neocortical layer III pyramidal cell dendrites in both male and female rats. Repeated elicitation of afterdischarge resulted in an increase in the severity of the behavioural seizures and an increase in afterdischarge duration, frequency and amplitude in all rats. The late component of the transcallosal evoked responses also increased following both 7 and 25 kindling sessions in male rats and following 25 kindling sessions in female rats. Analysis of the Golgi-Cox impregnated pyramidal cell dendrites indicated a significant decrease in the amount of apical and basilar dendritic spine density, length and branching in female rats following 7 days, but not 25 days, of kindling. Male rats had significantly lower apical and basilar dendritic spine density and branching measures following 25 days, but not 7 days, of kindling, as well as significantly lower apical and basilar dendritic length following 7 days of kindling. The differential gender effect suggests that males and females recruit similar plastic mechanisms although at different times in response to electrical kindling.

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PubMedDate not supplied

An observer's view of locomotor asymmetry in the rat.

Motor asymmetries in locomotion were studied in rats with unilateral neocortical removals in order to illustrate the utility of direct observation of behavior. Rats with unilateral cortical removals showed different postural asymmetries on simple tests that appear superficially similar and the observed motor asymmetries were differentially affected by postoperative recovery time as well as age at surgery. It is recognized that automated recording devices may be useful for measuring some brain-behavior relations but it is argued that automated recording cannot replace direct observation.

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