PubMed Health⌕ Search

Biomedical subjects

G F Sherman

Publications and source records attributed to G F Sherman.

At least 55 records · Page 3Linked to original sources
PubMed1990

The midsagittal area of the corpus callosum and total neocortical volume differ in three inbred strains of mice.

Differences in the midsagittal area of the corpus callosum have been reported between human males and females, between handled and nonhandled rats, and both within and between various strains of mice. This measure has, in addition, been related to handedness in humans and "pawedness" in certain strains of mice. The present study investigated the between- and within-strain differences in three inbred strains of mice, two with autoimmune disorders and spontaneously occurring developmental neuropathology, in the midsagittal area of the corpus callosum, the total neocortical volume, and the asymmetry of the neocortex. These morphometric measures were obtained from coronally sectioned celloidin-embedded material from New Zealand Black (NZB/BINJ), BXSB/MpJ, and DBA/2J mouse strains. NZB mice had a total neocortical volume larger than that of either the BXSB or DBA strains, whereas the BSXB mice had a midsagittal area of the corpus callosum larger than that of either of the other two strains. In addition, there was a positive correlation between these two measures. There was no correlation between total neocortical asymmetry and midsagittal area of the corpus callosum in any of the three strains. Finally, there were no differences in any morphometric measure between animals with or without developmental neuropathology in any given strain.

Analysis of Variance↗
PubMed1990

Individual variability in cortical organization: its relationship to brain laterality and implications to function.

The human brain and the brains of most mammals studied for this purpose demonstrate hemispheric asymmetry of gross anatomical landmarks and/or architectonic cortical subdivisions. The magnitude as well as the direction of these cortical asymmetries vary among individuals, and in some species there exist significant population directional biases. The magnitude, if not the direction, of cortical asymmetry is found to predict for relative numbers of neurons comprising a given pair of hemispheric architectonic homologues such that the more asymmetric the region is, the smaller the number of neurons. Similarly, the more asymmetric a region is, the smaller the density of interhemispheric connections and (probably) the greater the density of intrahemispheric connections. Developmentally, the decrease in the number of neurons characterizing the more asymmetrical regions appears to reflect mainly increased unilateral ontogenetic cell loss, and diminished callosal connectivity might signify increased developmental axonal pruning. These relationships between cell numbers, callosal connections, and presumed intrahemispheric relationships can be entertained to explain variability in anatomo-clinical correlations for language function and aphasia between left- and right-handers and men and women.

Animals↗
PubMed1989

Interhemispheric connections differ between symmetrical and asymmetrical brain regions.

Coronal sections from the brains of male Wistar rats that underwent corpus-callosectomy in adulthood were stained with Cresyl Violet for Nissl substance or by the Fink-Heimer method for terminal axonal degeneration. Measurements of volumetric asymmetry of neocortical region SM-I were made, and the per cent of terminal degeneration computed. As in previous studies, there was a negative correlation between asymmetry coefficient and total (right plus left) architectonic volume, indicating that symmetrical brain regions are larger than the average of the corresponding regions in asymmetrical brains. It was also found that as volumetric asymmetry increased, the per cent of axonal termination decreased, partly as a result of a decrease in the number of patches of callosal axonal termination. These results are interpreted in the light of what is known about the ontogenesis of callosal connectivity, and mechanisms for the development of architectonic asymmetry in the cerebral cortex are postulated.

Animals↗
PubMed1989

The effect of developmental neuropathology on neocortical asymmetry in New Zealand black mice.

Cerebral asymmetry can be considered along two continua-one based on direction (i.e., left or right) and another based on magnitude (i.e., symmetrical or asymmetrical). The possibility exists that these continua operate independently (Collins, 1981). To examine this possibility, the brains of 21 New Zealand Black (NZB) mice with molecular layer neuronal ectopias and 19 NZB mice without ectopias were studied. In NZB mice without ectopias, the magnitude of cerebral cortical asymmetry was negatively correlated to total cerebral cortical volume, a finding previously reported in both humans (Galaburda, Corsiglia, Rosen and Sherman, 1987) and rats (Galaburda, Aboitiz, Rosen and Sherman, 1986). NZB mice with ectopias showed no such relationship. However, both groups of mice had a consistent rightward bias in the direction of neocortical asymmetry, replicating previous results in rodents (Diamond, Johnson and Ingham, 1975; Diamond, Dowling and Johnson, 1981; Kolb, Sutherland, Nonneman and Whishaw, 1982; Ward and Collins, 1985). This suggests that the mechanisms underlying the magnitude of cerebral cortical asymmetry differ from those underlying the direction of this asymmetry.

Animals↗
PubMed1989

Cerebrocortical microdysgenesis with anomalous callosal connections: a case study in the rat.

A spontaneously occurring area of cerebrocortical microdysgenesis, resembling microgyria, and having its origin during development was noted in the left auditory cortex of a rat which had received a callosal section in adult life. Adjoining sections were prepared with cresyl violet for visualization of cell bodies, and by the Fink-Heimer method for degenerating axonal terminals. The microdysgenetic region was characterized by fused molecular layers containing ectopic neurons and by abnormal cortical lamination. The architecture of terminal degeneration of callosal axons within this region was abnormal with a notable absence of the usual lamination pattern and the presence instead of dense terminations in what would normally be layers I-IV and in connecting bridges running across layer V. Abnormal developmental processes that might account for the anomalous projection patterns in cortical malformations are discussed in the light of knowledge about normal corticogenesis. The behavioral implications for some childhood learning disorders are also considered.

Agenesis of Corpus Callosum↗
PubMed1987

Neuroanatomical anomalies in autoimmune mice.

The cerebral cortex was examined for signs of pathology in the NZB, BXSB, and MRL autoimmune strains of mice, crosses among these strains, and control mice. Previously, we reported that 20% of NZB mice had ectopic collections of neurons in layer I of the cortex. In this study we replicated this finding in the NZB, and extended it to the BXSB strain, and BXSB/NZB and MRL/NZB hybrids. The MRL strain, however, did not have a large number of individuals with brain anomalies. Thus, a number of autoimmune mice strains and hybrids develop brain anomalies, although at least one autoimmune strain does not. We suggest that in certain autoimmune strains maternal autoantibodies cross the placenta and damage the developing fetal brain, and that these strains may be useful experimental models for studying the development of brain anomalies seen in the dyslexic human.

Animals↗
PubMed1986

Histological asymmetry in the primary visual cortex of the rat: implications for mechanisms of cerebral asymmetry.

The present study was designed to specify the contributions of various histological parameters to hemispheric asymmetry of architectonic areas. It was found that the primary visual cortex of the rat is asymmetrical in volume, and that the asymmetry reflects side differences in the number of neurons. The implications of this finding for the understanding of mechanisms involved in the production of brain asymmetries are discussed.

Animals↗
PubMed1985

Developmental dyslexia: four consecutive patients with cortical anomalies.

We report the neuroanatomical findings in 4 consecutively studied brains of men with developmental dyslexia. The patients, who ranged in age between 14 and 32 years, were diagnosed as dyslexic during life. Nonrighthandedness and several autoimmune and atopic illnesses were present in the personal and family histories. All brains showed developmental anomalies of the cerebral cortex. These consisted of neuronal ectopias and architectonic dysplasias located mainly in perisylvian regions and affecting predominantly the left hemisphere. Furthermore, all brains showed a deviation from the standard pattern of cerebral asymmetry characterized by symmetry of the planum temporale. The neuroanatomical findings in these 4 patients are discussed with reference to developmental cortical anomalies, cerebral asymmetries, reorganization of the brain after early lesions, and the association between learning disorders, left handedness, and diseases of the immune system.

Adolescent↗
PubMed1985

Cortical anomalies in brains of New Zealand mice: a neuropathologic model of dyslexia?

Cortical anomalies have been reported in the brains of dyslexic individuals. In addition, dyslexic and left-handed individuals have a higher than expected rate of some immune-related diseases. The possible association between immune and cerebrocortical pathology was investigated in the immune-defective New Zealand Black mouse and its hybrid with the New Zealand White mouse. Structural anomalies similar to those present in the dyslexic brain were seen in the brains of these mice.

Animals↗
PubMed1984

Neocortical asymmetry and open-field behavior in the rat.

The total volume of the neocortex in each cerebral hemisphere was measured in male and female rats that had been exposed to one of two early experience treatments and subsequently tested behaviorally. Rats were either handled in infancy and raised in enriched environments or not handled in infancy and raised in standard lab cages. In adulthood they were tested in the open field for activity, for initial direction of movement out of the start box, and for laterality of wall-hugging behavior. Early experience did not have an effect on neocortical asymmetry, but a gender difference was disclosed. The right neocortex of males was larger than the left by a mean of 1.5%. Females rats did not show a significant asymmetry, although when asymmetry was present it was in favor of the left side. Cortical asymmetry correlated with open-field behavior. The degree of activity decreased with increasing neocortical asymmetry, and an interesting gender effect was present. Also, there was a positive correlation between neocortical asymmetry and direction of wall-hugging behavior, but only in animals with volume differences of less than 1%. These findings represent the first documentation of behavioral correlations with anatomic brain asymmetries in nonhuman species.

Animals↗
PubMed1983

Lateralization of spatial preference in the female rat.

Female rat pups were either left undisturbed in infancy and raised in lab cages or were handled in infancy and raised in enriched environments. In adulthood, animals underwent brain surgery consisting of: 1) a right neocortical ablation, 2) a left neocortical ablation, 3) a sham operation, or 4) no surgery. After recovering, they were tested for the initial direction of movement (left or right) in the open field. Nonhandled intact females were biased to move leftward indicating an asymmetrical brain organization. The intact handled-enriched group was unbiased. The right and left lesions caused the animals to move ipsilateral to the lesion, but there was no difference in the magnitude or response in either early experience group. Thus, early experience in the female rat has a different effect then in the male, and the nature of the brain organization in the two sexes is markedly different.

Animals↗
PubMed1983

Handling in infancy, brain laterality and muricide in rats.

Rats were handled for the first 20 days of life or were not disturbed. Between 21 and 50 days approximately half of each group was reared in enriched environments while the remainder was group reared in laboratory cages. When adult, four males from each litter received a right neocortical ablation, a left ablation, a sham operation, or no surgery. They were tested for mouse killing between 9-12 months of age. Intact non-handled controls without enrichment experience had a 96% incidence of muricide. Handling and enrichment treatments independently and additively reduced the rate of mouse killing in animals with intact brains. There was no evidence of brain laterality for animals which received no extra stimulation in early life. In contrast, the brains of handled animals were lateralized, with the left lesion group having a higher killing response than the right. Non-lesioned handled rats had approximately the same level of muricide as those with a right hemisphere lesion, leading to the inference that in the intact brain the left hemisphere inhibits the killing response of the right.

Aggression↗
PubMed1981

Stimulation in infancy facilitates interhemispheric communication in the rabbit.

Experimental rabbits were stimulated in infancy by being handled, while controls were undisturbed. After reaching adulthood, the animals were tested for activity in an open field with: (i) the right eye occluded; (ii) the left eye occluded; and (iii) neither eye occluded. For rabbits not stimulated in infancy, the correlation between activity scores for the left eye and right eye occlusion conditions was not significant (r = 0.115). In contrast, the correlation was highly significant for handled animals (r = 0.829). The results of the nonhandled group are consistent with other research which has failed to find interocular transfer of visual information, while the significant interhemispheric correlations within the handled group are consistent with prior findings obtained with rats. The results suggest that stimulation in infancy may act to facilitate the functional competence of the corpus callosum.

Animals↗
PubMed1980

Handling in infancy, taste aversion, and brain laterality in rats.

Rats were handled for the first 20 days of life or were not disturbed. When adults, they were trained to approach and drink from a bottle containing sweetened milk and were then given an injection of lithium chloride to induce a taste aversion conditioned emotional response. Others were injected with physiological saline. Rats within each of the treatment groups were then randomly assigned to 4 surgical procedures: removal of the right or left neocortex; sham surgery; or no surgery. Postoperatively, they were tested for retention of taste aversion by presenting the sweetened milk and recording the amount consumed. The initial consummatory behavior was very low (showing retention of the aversion) and increased over time. There were no differences in the reacquisition curves of the non-handled groups which had received lithium chloride. The curves of the handled groups did differ: thos with an intact right hemisphere (left neocortical lesion) had the lowest asymptote, followed by the group with an intact left brain, while those with intact whole brains consumed the greatest amount of milk. In the groups given an injection of physiological saline, those with a left hemisphere lesion consumed less milk than the other groups, regardless of their early handling experience. The data show: (1) that the rat's brain is lateralized, with the right hemisphere being preferentially involved in conditioned emotional behavior; and (2) that handling in infancy makes the left hemisphere less suceptible to conditioned fear.

Animals↗
PubMed1980

Brain and behavioral asymmetries for spatial preference in rats.

Rats were handled daily for 3 min between birth and weaning, or were nonhandled controls. When adult, 4 males from each litter received a right neocortical ablation, a left ablation, a sham operation, or no surgery. A month later all animals were tested in the open field for 4 days, and their initial direction of movement from the starting square (whether right or left) was recorded. Non-handled rats with intact brains (sham-operated and no-surgery groups pooled) had a mean directionality score near zero, thus indicating no right-left spatial preference. However, non-handled animals without a left hemisphere were significantly more biased in going to the ipsilateral side than were their siblings with right-brain ablations. Thus, in non-handled animals behavioral symmetry in making spatial choices is due to balanced brain asymmetry, in which the right hemisphere biases the animal to move leftward while the left hemisphere acts to inhibit this response. In contrast, intact handled rats had a significant preference to go to the left, thus suggesting that in handled animals the right hemisphere controls spatial preference.

Animals↗