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Biomedical subjects

B Kolb

Publications and source records attributed to B Kolb.

At least 73 records · Page 4Linked to original sources
PubMed1993

Proximal and distal impairments in rat forelimb use in reaching follow unilateral pyramidal tract lesions.

Although it was once thought that the corticospinal (pyramidal) tract was the main substrate of voluntary movement, the extent to which it is involved in the control of proximal vs. distal musculature, independent finger movements, and movements characteristic of different species of animals now is unclear. The objective of this study was to examine the effects of pyramidal tract lesions on skilled forelimb use in rats. In addition, cell morphology in motor cortex following lesions was examined. Naive and trained rats received unilateral pyramidal sections just rostral to the pyramidal decussation. Performance was assessed and filmed on two reaching tasks. Measures of reaching consisted of success in obtaining food, kinematic analysis of limb trajectory and velocity, and qualitative evaluation of 10 movement components comprising a reach. Pyramidal tract lesions only impaired reaching for single food pellets. Almost all movements comprising a reach, except digit opening, were impaired, including lifting, aiming, pronating and supinating the limb, and releasing food. Although success in limb use was unchanged over the 180 day observation period, there were significant improvements in the qualitative features of limb use. Histologically, the morphology of pyramidal cells in the forelimb area ipsilateral to the lesion seemed normal. Rats with additional damage to adjacent structures, such as the medial lemniscus and olivary complex, were much more severely impaired on the reaching tasks, and displayed similar impairments as judged by qualitative and kinematic measures. The results demonstrate that a number of movements involved in independent limb use are chronically impaired by pyramidal tract lesions in the rat. Nevertheless, significant use of the limb is possible, due perhaps to both the contribution of extrapyramidal motor systems and the influence of the remaining pyramidal system through its extrapyramidal connections. The results not only show that the rat pyramidal tract supports functions very similar to those of primates and thus might provide a good model for some aspects of pyramidal tract dysfunctions, but also they argue that the pyramidal tract is involved in both proximal and distal limb movements.

Animals↗
PubMed1993

Possible anatomical basis of recovery of function after neonatal frontal lesions in rats.

Rats given medial frontal lesions on Postnatal Day 1 or Day 10 were trained on the Morris water task on Days 19-21 or Days 56-58. The operated groups were equally impaired at the water task on Days 19-21, but the Day 10 rats had recovered by 56 days. Dendritic arborization and spine density were analyzed in parietal layer II-III pyramidal cells. At Day 60, but not at Day 22, the Day 10 animals had more dendritic spines per unit dendritic length than did the controls or Day 1 rats. Thus, there was functional recovery rather than sparing after frontal lesions at 10 days, and the recovery was correlated with an increase in dendritic spines.

Age Factors↗
PubMed1993

Endotoxin primes perfused rabbit lungs for enhanced vasoconstrictor response to staphylococcal alpha-toxin.

The major pore-forming exotoxin of Staphylococcus aureus, staphylococcal alpha-toxin, causes thromboxane-mediated pulmonary hypertension and prostanoid-independent protracted vascular leakage in perfused rabbit lungs. We asked whether lung responsiveness to the staphylococcal agent would be altered by a preceding period of endotoxin priming. Isolated rabbit lungs were perfused with Krebs-Henseleit buffer in the presence or absence of 100 ng/ml Salmonella abortus equii endotoxin for up to 5 h. The lipopolysaccharide exposure evoked the release of large quantities of tumor necrosis factor into the vascular and alveolar spaces but did not significantly alter pulmonary artery pressure, organ weight, or the repeatedly assessed capillary filtration coefficient (Kfc). Two and 4 h after endotoxin administration, alpha-toxin (10 to 30 ng/ml) was bolus-injected into the pulmonary artery. Toxin-evoked prostanoid generation (TxB2, 6-keto-PGF1 alpha) and pressor responses were markedly accelerated and enhanced in endotoxin-primed lungs, both for the 2 h and the 4 h priming period. No significant influence of endotoxin was noted when applied simultaneously with alpha-toxin. Cyclooxygenase inhibition suppressed the alpha-toxin-evoked pressure rise in both endotoxin-primed and nonprimed lungs. Endotoxin priming did not influence the alpha-toxin-induced protracted increase in Kfc values, assessed in the presence of cyclooxygenase inhibition. We conclude that endotoxin primes rabbit lungs for enhanced prostanoid generation and pulmonary hypertension in response to S. aureus alpha-toxin. Such cooperativity of endotoxin priming and exotoxin triggering may be relevant in critically ill patients suffering from both endotoxemia and gram-positive sepsis.

6-Ketoprostaglandin F1 alpha↗
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↗