Size Of Callosum Research Articles

Corpus Callosum Size in Tourette’s Syndrome

The size of the corpus callosum (CC) in Tourette’s syndrome (TS) and ADHD was determined by analysis of MRI data in 77 children and adolescents, aged 6 to 16 years, including 27 controls, at the Kennedy Krieger Institute, Johns Hopkins University School of Medicine, Baltimore, MD.

Lack of activational influence of ovarian hormones on the size of the female rat's corpus callosum

The sex difference in the midsagittal area of the adult rat corpus callosum (CC) has been shown to be mediated, in part, by gonadal steroids in early development, with the sensitive period of hormone action in the female extending at least up to postnatal day 25. Given this prolonged sensitivity, the current study attempted to delineate organizational vs. activational influences of gonadal hormones on the female rat CC. In Experiment 1, callosal size was examined across the estrous cycle at 52 and 90 days of age. In Experiment 2, females were ovariectomized at 78 days and CC parameters assessed at 110 days. Last, in Experiment 3, females were ovariectomized at 78 days and sacrificed at 110 days; in addition, sham females were sacrificed during proestrus or estrus. Neither stage of estrous cycle nor adult ovariectomy affected midsagittal CC size. These results provide evidence for organizational effects of ovarian steroids on the female callosum, with the sensitive period of hormone action ending sometime between days 25 and 78.

Size of the Corpus Callosum in Cerebral Palsy

It has been suggested that the size of the corpus callosum may have diagnostic significance in cerebral palsy, although this relationship is incompletely defined. Ninety-one patients with cerebral palsy had been studied by magnetic resonance imaging in the 5-year period from 1990 to 1994. Fifty-seven of these 91 patients had a technically appropriate midsagittal magnetic resonance image for quantitative morphometric analysis. The ratio of the area of the corpus callosum to the area of the supratentorial brain was compared to published age- and gender-specific norms. Imaging findings were correlated with clinical history and cause of cerebral palsy. The corpus callosum was of normal size in 43 patients and more than 2 standard deviations below the mean in 14 patients. The causes for cerebral palsy included hypoxic ischemic encephalopathy (32), cerebral dysgenesis (8), and porencephalic strokes (6); the etiology could not be established in 11 patients. The size of the corpus callosum was highly correlated with the cause of cerebral palsy, such that all patients with cerebral dysgenesis had hypoplasia of the corpus callosum (one-sided z test, p < 0.0001). Conversely, the callosum was of normal size in 32 of 38 patients with hypoxic ischemic encephalopathy and porencephalic strokes. The presence of a hypoplastic corpus callosum is highly associated with cerebral dysgenesis as a cause for cerebral palsy.

Interhemispheric transfer time differences related to aging and gender

The difference in simple reaction times to unstructured stimuli contralateral to the hand used for response (‘crossed’ responses) and those stimuli ipsilateral to the hand used for response (‘uncrossed’ responses)—or crossed-uncrossed difference (CUD) is assumed to be a reliable index of interhemispheric transfer time (IHTT). Studies using the CUD paradigm with acallosal patients as well as a variety of populations with known variations in callosal size or functioning have demonstrated that such callosal differences are reflected in differences in recorded CUD times. Recent studies have suggested that elderly individuals show a reduction in size of the corpus callosum, particularly in the anterior region. In order to assess any potential change in callosal transfer efficiency with aging, CUDs were obtained from elderly (60+ years) and younger subjects (18–30 years). The elderly subjects showed a significantly elongated CUD compared to younger subjects, with elderly females contributing the greatest increase. No significant gender differences were found for younger subjects. In addition, an unexpected trend for an overall right field reaction time advantage was found for all subgroups, accompanied by a larger calculated CUD for right hand responses than for left hand responses.

A computerized approach for morphological analysis of the corpus callosum.

A new technique for analyzing the morphology of the corpus callosum is presented, and it is applied to a group of elderly subjects. The proposed approach normalizes subject data into the Talairach space using an elastic deformation transformation. The properties of this transformation are used as a quantitative description of the callosal shape with respect to the Talairach atlas, which is treated as a standard. In particular, a deformation function measures the enlargement/shrinkage associated with this elastic deformation. Intersubject comparisons are made by comparing deformation functions. This technique was applied to eight male and eight female subjects. Based on the average deformation functions of each group, the posterior region of the female corpus callosum was found to be larger than its corresponding region in the males. The average callosal shape of each group was also found, demonstrating visually the callosal shape differences between the two groups in this sample. The proposed methodology utilizes the full resolution of the data, rather than relying on global descriptions such as area measurements. The application of this methodology to an elderly group indicated sex-related differences in the callosal shape and size.

Progression of atrophy of the corpus callosum with deterioration of cerebral cortical oxygen metabolism after carotid artery occlusion: a follow up study with MRI and PET.

In cerebrovascular disease, progression of brain atrophy may reflect an increase in ischaemic changes. The purpose of this study was to determine whether atrophy of the corpus callosum progresses in association with a deterioration in cerebral cortical oxygen metabolism after occlusion of the carotid artery. Magnetic resonance imaging and PET were used to serially evaluate six patients with occlusion of the unilateral internal carotid artery at intervals ranging from 12 to 50 months. One patient had no symptoms, one had a transient ischaemic attack, and four had a minor stroke. All patients had presented at most only subcortical lesions at the first evaluation. During follow up, no patient showed extension of subcortical lesions or recurrent stroke. The initial total callosal area:skull area ratio for the patients was significantly less than that for 14 age matched normal control subjects. The yearly decrease of callosal size in the patients, which differed significantly from zero and exceeded that in the controls, was significantly correlated with the deterioration in mean cerebral cortical oxygen metabolism. Three of the four patients who showed significant progression of callosal atrophy presented deterioration in haemodynamic states as well. It is concluded that in some patients atrophy of the corpus callosum progresses after occlusion of the carotid artery even in the absence of any overt episode of stroke, and that this atrophy is associated with deterioration in cerebral cortical oxygen metabolism. An increase in cerebral morphological changes with deterioration in cerebral metabolism related to ischaemia may occur after occlusion of the carotid artery, even in the absence of symptoms.

Increased corpus callosum size in musicians

Using in-vivo magnetic resonance morphometry it was investigated whether the midsagittal area of the corpus callosum (CC) would differ between 30 professional musicians and 30 age-, sex- and handedness-matched controls. Our analyses revealed that the anterior half of the CC was significantly larger in musicians. This difference was due to the larger anterior CC in the subgroup of musicians who had begun musical training before the age of 7. Since anatomic studies have provided evidence for a positive correlation between midsagittal callosal size and the number of fibers crossing through the CC, these data indicate a difference in interhemispheric communication and possibly in hemispheric (a)symmetry of sensorimotor areas. Our results are also compatible with plastic changes of components of the CC during a maturation period within the first decade of human life, similar to those observed in animal studies.

Aetiology of Schizophrenia

For most of this century the causes of schizophrenia have been largely unknown. However, the application of new techniques in genetics, neuroimaging, psychopharmacology and epidemiology are beginning to disclose the aetiology of the disorder. It is hoped that elucidation of the causes of schizophrenia will lead to new and more effective treatments. Family and twin studies indicate that genetic factors are important, although single major genes for susceptibility have not yet been identified. If the genes are determined, gene therapy may become a viable option for the treatment of schizophrenia. Environmental factors are also important and may explain the seasonal variation in births of individuals with schizophrenia and regional variations in the incidence of the disorder. The contributions of obstetric complications and maternal influenza virus infection to schizophrenia are currently being evaluated. There are observed differences in the presentation of schizophrenia between males and females, and these need to be accounted for by aetiological theories. Several observations support the theory that schizophrenia results from processes occurring during neurodevelopment. These processes may be responsible for structural and functional abnormalities that have been detected in the brains of patients with schizophrenia. Abnormalities in the temporal lobe have been related to hallucinations, delusions and thought disorder, while abnormalities in the frontal lobe have been associated with negative symptoms. Observed differences between schizophrenic patients and healthy individuals in the size of the corpus callosum and subcortical structures may also have neurodevelopmental origins. At the neurochemical level, dysfunction of central dopamine systems may mediate symptoms of schizophrenia. Traditional antipsychotics are antagonists of dopamine D2-receptors, but some of the new atypical antipsychotics appear to have a different action and drugs that interact with newly discovered receptor subtypes are under investigation. Schizophrenia has significant psychosocial consequences for the patient, and psychosocial factors such as adverse life events and high expressed emotion in the family have been observed to increase the likelihood of relapses of the disorder.

Magnetic resonance imaging of the corpus callosum: predictors of size in normal adults.

Eighty normal adults were studied with MRI to investigate the relationship between regional morphology of the corpus callosum and characteristics such as age, gender, education, and cranial size. The variability coefficient was 20% in total callosal area and from 19% to 40% in regional callosal area. Increasing age and smaller cranial area were both associated with smaller total and regional callosal areas; there were no effects of gender and education. The relative effects of age and cranial size varied across regions and were most prominent for anterior subdivisions. However, age and cranial size together explained less than half the variance in regional callosal size. Further study is needed to identify additional correlates of regional callosal anatomy.

Interhemispheric transfer time and corpus callosum size.

We examined the relationship between the size of five mid-sagittal corpus callosum subareas (measured with in vivo magnetic resonance morphometry) and hand reaction times at dichotic consonant-vowel monitoring in fifty healthy young adults. Based on the reaction times, interhemispheric transfer times between auditory and motor brain areas were calculated and related to anterior and posterior corpus callosum subarea measurements. We found no relationship between the size of callosal subareas and auditory or motor interhemispheric transfer times. We did, however, find a significant correlation between mean reaction time and total corpus callosum size. Our results suggest that normal variation in callosal size or shape is not related to individual differences in auditory lateralization. Instead, callosal size may be associated with speed of information processing.

The relationship of age, gender, handedness, and sidedness to the size of the corpus callosum

We correlated the area and size of the corpus callosum, as measured by MR imaging, with the individual's handedness, sidedness, age, and gender. A total of 117 patients (59 male, 58 female) aged 15-75 years were selected for this study. This included 12 persons who were either left-handed or ambidextrous. Each patient was tested extensively to determine handedness and sidedness. Callosal areas and thickness were measured and correlated with brain size. The body of the corpus callosum decreases in size with age and is larger in right-handed persons. The cross-sectional areas of the genu, splenium, and corpus callosum, overall, do not vary significantly with respect to age, gender, sidedness, or handedness. The size of the corpus callosum consistently decreases with age. Otherwise, few statistical differences in callosal size relate to gender, sidedness, or handedness.

Callosal size in children with learning disabilities

The corpus callosum (CC), the main structure subserving hemispheric collaboration, that is necessary for efficient cognitive functioning, undergoes developmental processes such as axonal retraction and myelination. Callosal growth therefore is vulnerable for adverse events such as perinatal asphyxia, but there are also genetic and epigenetic factors that determine form and thickness. MRI scans of 110 children, either with specific learning disabilities (LD), i.e. dysphasia/dyslexia, or with several degrees of general LD, showed callosa that were highly variable in size. The callosal size corrected for brain size did not vary significantly according to the severity of the LD, although it tended to be smaller in severe LD, i.e. mental retardation. Callosal size varied however, due to the likely presence of genetic influences or of adverse perinatal events. Children with familial dysphasia/dyslexia, had a thicker CC, possibly reflecting a poorly understood neurodevelopmental mechanism that inhibits the establishment of cerebral dominance. LD children (all subgroups together) with perinatal adverse events had a smaller CC than the familial cases, suggesting CC damage. Despite a multitude of developmental factors influencing the final size, this study suggests that total callosal size, supposedly linked to interhemispheric function, may contribute to the pathophysiological mechanisms that give rise to LD.

Analysis of cross-sectional area measurements of the corpus callosum adjusted for brain size in male and female subjects from childhood to adulthood.

Interest in anatomic evaluation of the corpus callosum is based upon the expectation that its function will be influenced by its structure. Using MR images, the size of the corpus callosum was determined by measuring its area in the midsagittal plane. A callosal index was calculated for each subject by dividing the callosal size by cerebral size, also measured from the MR image. This callosal index was designed to allow comparison of callosal size between different groups, despite differences in brain size that existed between the groups. The validity of this index was supported by the statistically significant, positive correlation between measured callosal area and cerebral size. Using MR images and the callosal index, adult males were shown to have a larger corpus callosum and larger cerebrum, compared to adult females. However, the callosal index was identical for male and female subjects. This demonstrated there relative size of the callosum was the same for males and females. Childhood development of the corpus callosum was documented through the first two decades of life by a progressive increase in the callosal index. In adults, cerebral atrophy caused a decline in callosal size, but no decline due to simple advancing age was found in normal adult subjects. This use of cerebral size to calculate a callosal index appeared to be useful in comparing callosal size between subjects and may be useful in future study of other disease states of the corpus callosum.

Anatomical-behavioral relationships: Corpus callosum morphometry and hemispheric specialization

We obtained midsagittal measures of the corpus callosum in 60 healthy young adults (right-handed and left-handed males and females), and examined whether individual differences in anatomical measures of callosal connectivity are related to behavioral laterality measures in the same subjects. In an attempt to tap functionally-distinct callosal “channels”, four behavioral laterality tasks were used that differed in sensory modality (visual, auditory, tactile) and/or level of cognitive processing (sensory versus semantic). In addition, the tasks had both intrahemispheric and interhemispheric conditions. Sex differences were found for measures of the posterior body (i.e. isthmus) of the corpus callosum, which, in turn, interacted with handedness. In contrast, only handedness effects were found for the behavioral laterality measures. Anatomical-behavioral correlations did not disclose relationships between callosal size and performance on task conditions requiring sensory interhemispheric integration or transfer. Instead, the correlational findings are consistent with the view that the corpus callosum participates in such higher order “control” functions as the support of bilateral representation of language, functional interhemispheric inhibition, and the maintenance of hemispheric differences in arousal. This is consistent with the finding that regional callosal size is related to the number of small diameter fibers, which are presumed to interconnect homologous association cortices in the two hemispheres.

Anatomical characteristics of the corpus callosum and clinical correlates in schizophrenia.

Nineteen DSM-III-R schizophrenic patients and 15 normal subjects, matched for sex and age, were evaluated according to their clinical and corpus callosum structural characteristics. They were evaluated on their size of callosum by means of Magnetic Resonance Imaging. Neither diagnosis nor sex significantly affects corpus callosum indices. Statistical analysis evidentiates a relationship between DSM-III-R axis-V scores and corpus callosum length in schizophrenics, and between age at onset of the illness and corpus callosum length in schizophrenics.

Corpus Callosum Size in Delphinid Cetaceans

The midsagittal surface area of the corpus callosum was determined by computer-assisted morphometry in juvenile and adult members of 13 species of the cetacean family Delphinidae. In 57 brains, absolute callosal areas ranged from 104 to 829 mm2. When compared to other mammal groups possessing a corpus callosum, callosal area in dolphins was smaller in relation to brain mass with a ratio range (mm2/g) of 0.08-0.31. The corpus callosum was decreased relative to brain mass in the larger-brained odontocetes, suggesting that increases in brain size were not necessarily allied with needs for equivalent increases in callosal linkage. One delphinid species, Tursiops truncatus, for which the largest single-species sample was available, was examined for sex differences in callosal size relative to brain mass. Among 10 males and 5 females the averaged ratio was not distinguishable between sexes.

Size of the corpus callosum and auditory comprehension in schizophrenics and normal controls

19 schizophrenic patients and 15 normal controls, matched for sex and age, were evaluated by magnetic resonance imaging for corpus callosal size and had neuropsychological functioning assessed using an auditory comprehension test. Although the MRI data did not reveal any significant differences between groups, the degree of laterality to the left versus right ear response was significantly correlated with the size of the posterior part of the corpus callosum in male schizophrenics.

Corpus callosotomy: a quantitative study of the extent of resection, seizure control, and neuropsychological outcome.

Corpus callosotomy is valuable for controlling medically intractable generalized seizures in appropriate patients, but postoperative development of language disorders, neuropsychological impairment, and motor dysfunction have all been noted. The extent of callosum resection has been implicated as a possible determinant of outcome, but this hypothesis has not been formally tested. Analysis of the records of all patients who underwent corpus callosotomy at the University of California, San Francisco, from 1986 to 1991 showed that, of 15 patients who underwent anterior or complete callosotomy, seven were entirely or nearly seizure-free, four had at least a 50% reduction in seizure frequency, and four had no change. To determine callosal size and extent of callosotomy, preoperative and postoperative magnetic resonance images were measured with computer-based planimetry. Seizure outcome was not significantly associated with preoperative callosal size or extent of callosotomy. Intelligence quotient scores did not change significantly after callosotomy. No severe neuropsychological deficits developed after anterior or complete callosotomy, even in patients with mixed cerebral dominance or bilateral language representation. These results indicate that division of the anterior one-half to two-thirds of the corpus callosum is nearly as effective as more extensive anterior sectioning or complete callosotomy in reducing drop-attack and generalized tonic-clonic seizures in appropriate patients, and that the extent of callosotomy is not an important factor on outcome when at least 50% to 65% of the callosum is divided. Mixed cerebral dominance and other unusual patterns of language and memory organization do not appear to increase the postoperative risk for neuropsychological deficits, regardless of the extent of anterior section.

Multiple dimensions of handedness and the human corpus callosurn

Consistency of right-hand preference correlates with callosal isthmus size. Anterior corpus callosum (CC) regions vary as a function of sex and right- versus left-hand preference. We analyzed regional CC anatomy in a sample of right- and left-handed men and women on the basis of both degree ("Consistency") and direction ("Hand") of hand preference scores. Significant Hand x Consistency effects indicated that both are important factors in CC organization. These data also suggested that a single continuum of hand preference and regional CC size may not be applicable across all subjects.

Corpus callosum morphometry and dichotic listening performace: Individual differences in functional interhemispheric inhibition?

We examined the relationship between midsagittal corpus callosum area, as seen by magnetic resonance imaging, and behavioral laterality effects from a dichotic listening task requiring cross-callosal relay of an auditory signal, in 60 healthy young adults. Four patients with complete forebrain commissurotomy were also given the dichotic listening task, confirming that in this task, the report of left ear items is dependent on callosal pathways. Contrary to our predictions, callosum measures were unrelated to either a laterality measure or to inferior (typically left) ear performance. Surprisingly, superior (typically right) ear accuracies, which do not depend on cross-callosal sensory transfer, were significantly and negatively correlated with callosum size. These findings show that normal variations in callosum size do not appear to contribute significantly to individual differences in hemispheric specialization. Callosum size may, instead, be associated with degree of functional interhemispheric inhibition.