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Biomedical subjects

B Kolb

Publications and source records attributed to B Kolb.

At least 109 records · Page 6Linked to original sources
PubMed1985

Neonatal frontal lesions in hamsters impair species-typical behaviors and reduce brain weight and neocortical thickness.

Syrian golden hamsters with removals of the medial or ventral subfields of the frontal cortex at 4 days of age were compared behaviorally and neuroanatomically with hamsters with similar removals in adulthood. The behavioral results showed that hamsters with neonatal lesions show little sparing of species-typical behaviors such as hoarding and nest building. Study of the development of animals with early lesions showed that although as young juveniles the operated hamsters did not appear to be different from their littermate controls, as they developed they failed to improve in their performance as their littermates did. As adults these early operates were thus severely impaired relative to their littermates. Nonetheless, under certain environmental conditions it was possible to show that the animals were capable of performing the behaviors nearly as proficiently as normal animals. Thus, in order to thoroughly assess the extent of behavioral sparing following early neonatal lesions, it is necessary to test animals under widely varying stimulus conditions. Finally, when the brains of neonatally operated hamsters were compared with those of animals operated on in adulthood, there were striking differences; although the area of cavity appeared smaller in the neonatal operates, their brains weighed less and the remaining neocortex was thinner.

Animals↗
PubMed1984

Functions of the frontal cortex of the rat: a comparative review.

This review summarizes the anatomical and functional organization of the frontal cortex of the rat in comparison to primates. Lesions of the primary motor or of the prefrontal cortex of both primates and rodents produce a consistent constellation of symptoms that are strikingly similar across species as diverse as rats and humans. Thus, in spite of the tremendous difference in the relative volume of the frontal cortex of mammals, as well as the obvious diversity of behavioral repertoires across mammalian phylogeny, there appears to be a remarkable unity in frontal cortex function across the class mammalia. Hence, motor and prefrontal lesions produce analogous alterations in motor control in rodents and primates even though humans walk upright and have fine control of digit movement and rats walk on all fours and have less dextrous control of distal movements. Similarly, there are analogous changes in behaviors that can be labeled response inhibition, temporal ordering, spatial orientation, social or affective behavior, behavioral spontaneity, olfaction and habituation following prefrontal cortex lesions in both primates and rodents. Finally, it is proposed that the principal function of the prefrontal cortex of mammals is the temporal organization of behavior.

Animals↗
PubMed1984

Decortication abolishes place but not cue learning in rats.

The experiments examined whether decorticate rats are able to acquire a place learning strategy, as compared with a cue learning strategy, to successfully navigate from one place to another and whether the hippocampus, in the absence of the neocortex, contributes to successful performance. Decorticate rats, with or without hippocampectomy, were unable to locate an "invisible" platform submerged at a fixed place in a tank of cool water (made opaque by milk), rather they scrabbled at the edges of the tank and failed even to initiate search strategies. They were able to learn to swim directly to the platform if it was visible. Their ability to find the hidden platform was not enhanced by presurgical experience or two-stage ablations with training before and after ablations. When pretrained on the cue task and tested on the place task, they learned to inhibit scrabbling at the tank edges and "search" in a haphazard fashion for the hidden platform, but they never learned to swim directly toward it. When decorticate rats, trained on the cue task, received superior colliculus or basal ganglia removal in a second operation, cue learning was abolished. Hippocampal removal after decortication left performance on the cue task unaffected. The results demonstrate: (1) the integrity of the neocortex is essential for place learning; (2) the brainstem, including superior colliculus and basal ganglia, is sufficient for cue learning; and (3) in the absence of the neocortex the hippocampus plays no role in guiding either type of navigation. It is concluded that sensorimotor subsystems of the forebrain play a special role as detector-response systems for guiding behaviour in response to constellations of distal stimuli, whereas subcortical structures are sufficient for navigation to a single stimulus.

Animals↗
PubMed1984

Postsurgical enrichment aids adult hemidecorticate rats on a spatial navigation task.

The effect of environmental enrichment on normal rats, rats that received hemidecortication at birth, and rats that received hemidecortication when adult was studied in the Morris water task, which is a spatial navigation task requiring the use of distal cues for successful performance. Enrichment was achieved by housing the rats for 90 days in a large outdoor compound that was designed to model a natural environment. Adult hemidecorticated lab-raised rats were severely impaired in the acquisition of the task but neonatally hemidecorticated rats, although also impaired, showed significant sparing. Postsurgical, but not presurgical, enrichment of adult hemidecorticated rats significantly enhanced their recovery. Enrichment had little effect on neonatally decorticated rats or on normal rats. Although there were no gross anatomical changes associated with enrichment, the paradigm provides both a robust phenomena and a cortically dependent task that is ideal for investigating the processes in the remaining intact hemisphere that must support recovery.

Animals↗
PubMed1984

Evidence for anatomical but not functional asymmetry in the hemidecorticate rat.

Rats with unilateral ablation of the left or right cerebral neocortex or left or right hippocampus were studied in a battery of tests of spatial orientation, motor coordination, and social behavior, including Morris water task, radial arm maze, feeding, narrow beam traversing, puzzle latches, hoarding, grooming, nest building, running wheel activity, male--male interaction, and shock-induced aggression. Comparison of the brains of operated and control rats confirmed previous suggestions that the right hemisphere of the rat is bigger and may have different connections than the left hemisphere. Despite the morphological asymmetries, comparison of the behavior of rats with right hemidecortication with that of rats with left hemidecortication, and of rats with right and of those with left hippocampal lesions, failed to show a single instance of functional asymmetry in the rat brain. These behavioral results stand in marked contrast to previous reports of functional asymmetry in the control of activity, orientation, and rotation.

Afferent Pathways↗
PubMed1983

Abnormalities in cortical and subcortical morphology after neonatal neocortical lesions in rats.

The brain weight, cortical thickness, cross-sectional areas of subcortical structures, and various retrograde changes were compared in rats with neonatal or adult ablation of all or part of the neocortex. Neonatal lesions produced a widespread reduction in brain size accompanied by a variety of major structural changes including modification of the thickness of the residual cortex, necrosis and calcification of subcortical structures, and gross distortion of the structure of the hippocampus. The modification of the cortical thickness, but not the other changes, depended on the site and extent of cortical removal: neonatal frontal cortex ablation reduced the thickness of the remaining neocortex, neonatal posterior cortex ablation had no significant effect upon the thickness of the remaining neocortex, and neonatal hemidecortication increased the thickness of the remaining neocortex.

Animals↗
PubMed1983

"Stick out your tongue": tongue protrusion in neocortex and hypothalamic damaged rats.

Easily administered tests, analogues to the human neurological "stick out your tongue" tests, were devised to assess tongue use in normal, lateral hypothalamic (LH) and decorticate rats. LH and decorticate rats showed loss of tongue protrusion and licking immediately after surgery. Even though LH rats did not recover spontaneous eating dry food and drinking water, they showed extensive recovery of tongue protrusion and use. Decorticate rats regained the ability to eat dry food and drink water, but they showed minimal recovery of tongue protrusion and use. Comparisons of rats with variously located circumscribed neocortical lesions showed maximal tongue protrusion deficits followed orbital frontal cortex ablations. The results show: (1) that the tests developed and described are useful for routine examination of rats that have feeding abnormalities; (2) the feeding abnormalities of decorticate and LH rats can be dissociated; and (3) the orbital frontal cortex and corticofugal pathways passing through or adjacent to the LH may play a special role in the control of tongue and mouth use.

Animals↗
PubMed1983

A behavioural analysis of spatial localization following electrolytic, kainate- or colchicine-induced damage to the hippocampal formation in the rat.

This experiment examines the notion that in the rat the hippocampal formation is an essential structure in the neurological representation of spatial abilities. Spatial localization by rats with different types of hippocampal damage, including bilateral electrolytic lesions, unilateral and bilateral kainic acid-induced CA3-CA4 lesions, and unilateral and bilateral colchicine-induced dentate gyrus lesions, was compared with vehicle-injected and normal control groups in the Morris water task. The task required the rats to escape from cold water by finding a submerged and hidden platform located at a fixed place within the room. The start point was varied randomly from trial to trial and there were no local cues available to indicate the position of the hidden platform. After training, the platform was moved. Escape latencies and the initial swimming headings revealed that all lesion groups, except the unilateral CA3-damaged group, were impaired at finding the platform: the dentate-damaged rats exhibited the greatest deficit. When the platform was moved the control rats swam mainly in the part of the pool that had previously contained the platform and, on finding it in the new location, they showed a marked dishabituation of rearing. None of the bilateral lesion groups showed these effects.

Animals↗
PubMed1983

A comparison of the contributions of the frontal and parietal association cortex to spatial localization in rats.

Rats with lesions of the medial frontal, orbital frontal, or parietal cortex were compared behaviorally with rats with complete removal of the neocortex and normal control rats on three spatial tasks: Morris water task, radial arm maze, and spatial reversals in a Grice box. Decortication produced severe impairments in the acquisition of all three tasks, thus providing a measure against which to compare the severity of the impairments observed following more restricted removals. Rats with parietal cortex lesions were relatively unimpaired at any of the tasks, although they had a significant deficit on the spatial reversal task and had a short-term memory impairment on the radial arm maze. In contrast, rats with medial frontal lesions had a significant, but relatively mild, impairment on the radial arm maze and were very poor at learning the water task. Rats with orbital frontal lesions were nearly as impaired on the radial arm maze and water task as decorticate rats. The results suggest that the frontal and parietal cortex of rats play different roles in the control of spatial orientation but do not support the view that egocentric and allocentric spatial orientation are related to frontal and parietal mechanisms, respectively. In addition, the results suggest that the frontal cortex plays a larger role in the control of spatially guided behavior than has been previously recognized and that both the medial frontal and the orbital (sulcal) frontal cortex play a dissociable role in the control of spatial orientation.

Animals↗
PubMed1983

Neonatal hemidecortication or frontal cortex ablation produces similar behavioral sparing but opposite effects on morphogenesis of remaining cortex.

Rats with complete removal of the neocortex of one hemisphere (hemidecorticate) or of the cortex anterior to bregma in both hemispheres (frontal cortex) in adulthood were compared behaviorally and neuroanatomically with rats with similar removals at 7 days of age. Neonatal ablation of the frontal cortex produced partial sparing of performance on the Morris water task and reduced the thickness of the remaining neocortex. Neonatal hemidecortication produced similar sparing of function on the water task but increased the thickness of the contralateral neocortex. These results imply that behavioral sparing following neonatal cortical lesions is independent of the gross morphogenesis of the remaining neocortex.

Age Factors↗
PubMed1983

Can male decorticate rats copulate?

Sexually experienced or naive male rats, subjected to neocortex removal or neocortex plus hippocampus removal, were paired with female rats for up to 180 days and compared with control rats with respect to success and latency to impregnate the female. All of the control rats and half of the brain-damaged rats successfully impregnated female rats at least once. Success was not correlated with lesion type or presurgical experience. The brain-damaged rats took longer to impregnate the females than control rats. Since the ablations were extensive, more than 95% of the neocortex in many rats, the study shows that decorticate rats can copulate. Presumably the intact subcortical structures are sufficient for male copulation, but cortical structures in some way facilitate rapid female impregnation.

Animals↗
PubMed1983

Cortical control of claw cutting in the rat.

Claw cutting emerges as a behavior between Postnatal Day 30 and 50, and by Day 100 at least 80% of rats have cut their claws. Complete frontal ablation or total decortication at any age abolished claw cutting, but complete posterior neocortex removal did not. In adult rats, motor cortex ablations or hemidecortications abolished claw cutting, whereas the same lesions given to infant rats spared claw cutting. Neonatal telencephalic noradrenaline depletion had no effect on the development or incident of claw cutting. Loss of claw cutting appears to be due to loss of efficient biting and chewing rather than to an inability to orient or to groom. The sparing after infant ablations may be due to functional reorganization of tissue within, or adjacent to, the developing motor cortex. The study demonstrates that careful examination of features of the laboratory rat's appearance can provide useful clues about its behavioral competencies. Furthermore, abnormalities such as loss of claw cutting can serve as a useful diagnostic indication of specific kinds of brain damage.

Animals↗
PubMed1983

Neonatal motor cortex lesions in the rat: absence of sparing of motor behaviors and impaired spatial learning concurrent with abnormal cerebral morphogenesis.

Rats with removal of the motor cortex in adulthood were compared behaviorally and neuroanatomically with rats with similar removals at 4 days of age. The results suggest that neonatal ablation of the motor cortex of rats is more debilitating behaviorally than similar injury in adulthood and produces abnormal morphogenesis of the posterior neocortex. Neonatal lesions of the motor cortex produced more chronic abnormalities in movements of the distal effectors that accompany adult lesions (tongue, snout, and digit use) and, in addition, produced abnormalities in limb placement on a narrow beam and a significant impairment in spatial learning, neither of which is associated with adult lesions. When the brains of neonatally operated rats were compared with those of control rats or rats operated on in adulthood, there were striking differences. Although the area of cavity appeared smaller in the neonatal operates, their brains weighed less, the neocortex was thinner, and the cross-sectional area of the remaining cortex was reduced, when compared with those of the adult-operated group. It is suggested that studies of the acquisition of various neuropsychological learning tasks may have greatly overestimated the degree of sparing following anterior neocortical lesions in rats.

Animals↗
PubMed1983

Performance of schizophrenic patients on tests sensitive to left or right frontal, temporal, or parietal function in neurological patients.

The performances of schizophrenic patients and normal control subjects were compared on an extensive battery of psychological tests that have been found at the Montreal Neurological Hospital to be differentially sensitive to atrophic lesions of the left or right frontal, temporal, or parietal cortex. Schizophrenic patients were significantly impaired at all tests that are disrupted by left or right frontal or temporal lobe lesions but performed within normal limits on all tests that are sensitive to parietal lobe damage. These results imply that schizophrenia results, at least in part, from a bilateral dysfunction of the frontal and temporal lobes.

Adult↗