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Biomedical subjects

B Kolb

Publications and source records attributed to B Kolb.

At least 19 recordsLinked to original sources
PubMed1992

Cortical and striatal structure and connectivity are altered by neonatal hemidecortication in rats.

The cortical cytoarchitecture, cortical thickness, corticostriatal connections, cortical dendritic arborization, and striatal patch-matrix compartmentalization were compared in rats with neonatal (1 day of age) or adult hemidecortication. Neonatal hemidecortication produced few changes in cytoarchitecture of the remaining hemisphere and did not preclude the development of a patch-matrix compartmentalization in either striatum. There was a significant modification of contralateral cortical-striatal connections, however, as there were extensive crossed connections from layer II/III of the prefrontal cortex in the neonatal hemidecorticates, which contrasts with connections from layer V in the normal brain. Adult hemidecorticates had no crossed corticostriatal connections. Neonatal hemidecortication also led to an increase in cortical thickness relative to adult operates or controls and the neonatal hemidecorticates, and led to an increase in dendritic arborization in layer II/III pyramidal cells of the somatosensory and motor cortex but not in the visual or temporal cortex. The results suggest that the behavioral sparing of sensorimotor and some prefrontal functions after neonatal hemidecortication could be supported, in part, by the anatomical changes in the prefrontal and sensorimotor connectivity and dendritic arborization.

Animals↗
PubMed1992

Developmental changes in the recognition and comprehension of facial expression: implications for frontal lobe function.

Children aged 6-15 years old and adults (over 18) were given three tests designed to test perception and comprehension of facial expression. In the first test subjects were given two composite symmetrical faces made from the left or right half of a normal face, the subjects' task being to indicate which composite more closely resembled the original face. In the second test the subjects matched a series of photographs from Life magazine with key photographs of one of six distinct emotions (sad, fear, happy, anger, disgust, surprise). In the third test the subjects chose a key photograph that was appropriate for the face of a faceless character in a cartoon. On the composite faces test the subjects in all groups exhibited a preference for the left visual field composite, implying that all age groups were processing the faces in a similar manner. The results of the other two tests showed that there was an improvement in the perception of facial expression between the ages of 6 and 8 years, little change until about 13 years, and then a second improvement to adult performance at about 14 years. The performance of the 8- to 13-year-old children was similar to that of adult patients with frontal lobe injuries, which could be taken as evidence that the regions of the frontal lobe involved in the performance of these tasks may not be mature until about 14 years of age.

Adult↗
PubMed1992

Ventrolateral prefrontal cortex lesions in rats impair the acquisition and retention of a tactile-olfactory configural task.

Rats with aspirative lesions of the ventrolateral frontal cortex were tested on acquisition and postsurgical retention of an associative learning task that required that they learn a tactile-olfactory configural discrimination. The task required that they pull up a string to obtain attached food and that they identify the correct string using a compound of string size and odor. The rats were not impaired in initial learning or reversal of the olfactory elements of the discrimination. They were impaired in acquisition and retention of the compound, and their deficit was proportional to lesion size. The results confirm that the ventrolateral frontal cortex is involved in processing of olfactory information and imply that the prefrontal cortex is involved in at least certain types of cross-modal configural associative learning.

Animals↗
PubMed1992

Noradrenaline depletion blocks behavioral sparing and alters cortical morphogenesis after neonatal frontal cortex damage in rats.

The possibility that cortical noradrenaline (NA) is necessary for sparing of function that occurs after neonatal frontal cortex damage was examined. Spatial localization by rats with frontal cortex damage on postnatal day 7 (P7) was better than that by rats with similar damage sustained as adults. The sparing was abolished in rats depleted of cortical NA by means of neonatal 6-hydroxydopamine (6HDA) administration. The blockade of sparing in the P7 frontal operates was associated with a smaller brain, thinner cortex, and reduced cortical dendritic branching relative to saline-treated P7 frontal operates. NA depletion alone in unoperated rats did not affect spatial learning but did reduce brain size and dendritic branching. Rats with frontal lesions on P4 did not show sparing of spatial localization, and 6HDA administration had no additional behavioral effect. Overall, these data are consistent with the notion that NA has some general function in maintaining some forms of plasticity in posterior cortex.

Animals↗
PubMed1991

Sparing of function after neonatal frontal lesions correlates with increased cortical dendritic branching: a possible mechanism for the Kennard effect.

This study examined the possibility that the presence or absence of behavioral sparing following neonatal frontal lesions might be correlated with changes in the complexity of dendritic branching. Rats were given bilateral frontal lesions in either adulthood, the day of birth, or on day 10. Ninety days later the animals were trained in a spatial navigation task. The animals' brains were then processed for Golgi-Cox staining and the dendritic branching of the pyramidal cells in the parietal cortex was analyzed. Frontal cortical lesions in newborn rats produced a severe behavioral deficit in the water task whereas frontal removal at 10 days of age allowed sparing of function relative to adult operates (that is, the Kennard effect). Analysis of dendritic arbor in sensorimotor cortex revealed that the day-10 animals exhibited a dramatic proliferation of dendritic arbor relative to control rats. In contrast, the day-1 animals had slightly less dendritic branching than control animals. Rats with frontal lesions in adulthood showed a small, but significant, increase in dendritic branching. The correlation between behavioral sparing and the increase in dendritic arborization following neonatal lesions may be illustrative of a general mechanism underlying the Kennard effect.

Animals↗
PubMed1991

Sparing of two types of hippocampal rhythmical slow activity (RSA, theta) in adult rats decorticated neonatally.

The electroencephalographic (EEG) activity of the hippocampus was examined in adult freely moving rats that had had all of the neocortex, including the cingulate cortex and cingulum, removed at birth. Both the cholinergic and serotonergic forms of rhythmical slow activity (RSA or theta) were present in the dorsal hippocampus and retained their normal relation to behavior. The results show that following decortication, inputs to and connections within the hippocampus apparently retain the ability to produce normal EEG. Since adult decortications abolish serotonergic RSA, the results also suggest that following neonatal injury there is reorganization within remaining serotonergic projections to the hippocampus that spare this form of RSA.

Animals↗
PubMed1990

Recovery from occipital stroke: a self-report and an inquiry into visual processes.

This report summarizes the behavioural effects of a right occipital stroke in the author. An upper left quandrantanopia resolved over the first 50 poststroke days to leave a scotoma that included the left upper quadrant of the fovea and extended upwards about 6 degrees and lateral about 15 degrees. There was no further reduction in size over the next 4 years. In the early stages of recovery there was an inability to detect consciously either the presence of objects or their motion, except upon reflection once an object entered the intact visual field. This has been referred to previously as blindsight. On about the fourth day poststroke, part of the scotoma became visually active, producing a scintillating aura, which remains. Shortly thereafter colour perception returned in the scotoma, as did motion detection. Although there was little additional change in the field defect after 2 months, the author's visual abilities have continued to improve, in large part because of a shift in fixation such that information at the centre of the visual field now falls about 1.5 degrees into the lower right portion of the fovea. The implications of the visual and behavioural changes are discussed in the context of multiple visual systems and with respect to recovery of function.

Adult↗
PubMed1989

Tongue protrusion mediated by spared anterior ventrolateral neocortex in neonatally decorticate rats: behavioral support for the neurogenetic hypothesis.

Many changes in anatomical organization and behavior follow circumscribed, neonatal cortical ablations. These include functional sparing and compensatory anatomical changes. An objective of this study was to examine the generality of such changes by reversing the usual experimental procedure, removing all cortex but a circumscribed area and examining whether the remnant made new anatomical connections, adopted new functions and whether it continued to subserve the typical functions of that area. All neocortex and cingulate cortex, except a small portion of anterior-lateral neocortex, which is normally involved in tongue and mouth use, was removed from one-day-old or adult rats. Fluorescent labelling and behavioral tests were used to evaluate its function. The results showed: (1) The remnant cortical tissue maintained similar connections in neonatal and adult groups and similar connections to those found in rats that had received no lesions. (2) The rats still displayed behaviors normally supported by this cortex, including tongue protrusion to obtain food and picking up and eating hard food efficiently. (3) Impairments were obtained on tests normally mediated by the ablated cortex, including skilled reaching and grooming. (4) When the cortical remnant was removed, tongue protrusion and efficiency of food consumption were similarly impaired in both neonate and adult groups. An additional serendipitous finding was a dissociation between two types of tongue movement: licking from a ventrally-located surface survived cortical removal but tongue protrusion did not. The results show that bilaterally spared small remnants of neocortex maintain normal functions and do not assume new functions or make new connections despite neonatal decortication. The results provide behavioral support for the neurogenetic hypothesis, which postulates that cortical circuitry is specified during early embryonic development. This suggests that there are constraints on neural remodelling and behavioral recovery following neonatal lesions. The implications of these results are discussed with respect to the documented remodelling and sparing that occur following partial or unilateral lesions within functional systems.

Animals↗
PubMed1989

Brain development, plasticity, and behavior.

Damage to the infant brain is associated with a complex array of behavioral and anatomical effects. Recent research is leading to a new understanding of the nature of, and mechanisms underlying, recovery from brain damage.

Animals↗
PubMed1988

Sparing of skilled forelimb reaching and corticospinal projections after neonatal motor cortex removal or hemidecortication in the rat: support for the Kennard doctrine.

Skilled forelimb use in reaching for food was studied in rats with variously sized and placed unilateral cortical lesions given in adulthood or on the day of birth. Fluorescent retrograde labelling was used to document changes in corticospinal tracts. In free choice tests, preferential use of the limb ipsilateral to damage was induced by adult motor, but not parietal or occipital, cortex damage. Similar preference for the ipsilateral limb was induced by neonatal motor and parietal, but not occipital, cortex damage. In both adult and neonate groups success with the preferred limb decreased in proportion to the increase in lesion size. To force use of the non-preferred limb, a bracelet, which prevented reaching but not other movements, was attached to the forearm of the preferred forelimb. Success with the non-preferred limb was poorer than with the preferred limb and success again decreased in proportion to the increase in lesion size. Adult and neonatal rats were divided into 4 groups according to the extent of motor cortex damage. Across all lesion sizes the neonatal operates were significantly more successful than the adult operates and their reaching movements appeared more normal. Surprisingly, some rats with large adult motor cortex lesions or hemidecortications were able to reach. Slow-motion video analysis of reaching impairments in both adult and neonate groups showed that limb extension and food grasping were less impaired than limb retraction and adduction of the limb to the mouth. The results show that the integrity of a neocortical hemisphere is not essential for contralateral limb use in reaching, but contributes to successful use of the limb. Following neonatal lesions, facilitation may be promoted by the ipsilateral neocortex through an augmented ipsilateral corticofugal pathway.

Animals↗
PubMed1988

Recovery from early cortical damage in rats. IV. Effects of hemidecortication at 1, 5 or 10 days of age on cerebral anatomy and behavior.

Rats with complete removal of the neocortex of one hemisphere in adulthood (hemidecorticate) were compared behaviorally and anatomically with rats with similar removals at 1, 5, or 10 days of age. There was an unexpected relationship between cortical thickness in adulthood and age at surgery: the earlier the lesion the thicker the cortex. At the two extremes rats hemidecorticated in adulthood had a reduction of up to 10% in the contralateral hemisphere, rats with hemidecortications on the day of birth had cortex that was thicker than adult operates. Behaviorally, the animals were administered several tests including a spatial navigation task, tests of beam walking and swimming, tests of turning bias, and a measure of claw cutting. The main finding was that although the hemidecortication at all ages produced a reliable behavioral change on all measures, the neonatal hemidecorticates performed better than the adults. Further, the earlier the lesion, the better the animals performed. These results are contrasted with the effects of bilateral frontal or parietal neocortical removals in infancy where the earliest lesions have the most severe effect on cortical thickness and behavior. This comparison shows that unilaterality of brain damage is an important factor in predicting recovery or sparing of function from early lesions.

Animals↗
PubMed1988

The effects of neonatal gonadectomy and prenatal stress on cortical thickness and asymmetry in rats.

In Study I measures of cortical thickness were taken in 90-day-old male and female Sprague-Dawley, Wistar, and Long-Evans rats that were born to pregnant females shipped to the laboratory in late pregnancy and that were either gonadectomized at birth or left intact. No evidence for hemispheric differences in cortical thickness was found in any of the groups. Gonadectomy resulted in increased cortical thickness in male Sprague-Dawley and Wistar rats and in small increases in thickness of the left hemisphere in Long-Evans rats, especially males. No effects of gonadectomy were found in females of any strain. The lack of the expected right-over-left difference in cortical thickness in intact males may have been due to prenatal stress caused by housing, handling, and shipping. In Study 2 measures of cortical thickness were taken in 90-day-old male and female Sprague-Dawley rats that were bred in our laboratory, but otherwise similarly treated at birth. In this second study, the expected right-over-left hemispheric difference in cortical thickness was found in intact male rats; none was found in gonadectomized males or in either of the female groups. The lack of asymmetry in gonadectomized males appeared to be due to an increase in thickness in the left hemisphere. Taken together these studies provide support for the idea that hormones of testicular origin suppress cortical enlargement in the perinatal period, particularly in the left hemisphere.

Animals↗
PubMed1988

Frontal cortex grafts have opposite effects at different postoperative recovery times.

We studied the effect of different postoperative times on the behavioral recovery following brain implants. Adult male rats received cortical tissue grafts 2 weeks after aspiration of the medial frontal cortex. Either 2 (Immediate Group) or 28 (Delay Group) days after grafting, the performance of these rats on a behavioral battery, comprising the Morris water maze task, forepaw use, and grooming, was compared to that of rats with similar lesions and postoperative recovery times but no grafts. Rats tested immediately after receiving implants performed better on the spatial navigation task than rats with similar lesions but no grafts. This improvement, however, was less than that shown by rats with lesions but no grafts permitted to recover for 28 days before testing. In contrast, in the Delay Group, rats with grafts were more greatly impaired than were their operated controls. Neither lesions nor grafts affected grooming although the Immediate Group with grafts were significantly more impaired in using their forepaws during feeding than were any of the other groups. These results lead us to conclude that differing postoperative recovery times and task requirements may account for some of the inconsistent results of the influence of brain grafts on behavioral recovery reported in the literature. We also conclude that cortical tissue implants can have two effects with different time courses and opposite net behavioral effects.

Animals↗
PubMed1988

Contributions of cingulate cortex to two forms of spatial learning and memory.

The contribution of anterior and posterior cingulate cortical areas to spatial learning and memory was examined in 4 experiments using the place-navigation task. Rats with complete bilateral cingulate cortex aspiration or aspiration of posterior cingulate cortex (area 29) alone could not swim directly to a hidden platform located in a fixed place. When animals with these lesions were tested for 40 d in a place-alternation task in which they received 16 daily trials with the platform placed in a new location each day, they did not show reliable improvement in place navigation. The inability to swim to changing locations or to a single location was not overcome by preoperative training in these tasks. Rats with anterior cingulate cortex aspirations showed a less severe impairment in both tasks and, with more training than is necessary for control rats, they acquired near-normal place-navigation accuracy. Rats with complete cingulate cortex aspiration were almost as accurate as control rats in learning to swim to a visible platform. The results imply that posterior cingulate areas play an essential role in the use of topographical information, probably by transmitting and elaborating information passing between the hippocampal system and neocortical association areas.

Animals↗