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PubMed1990

A left to right hemisphere callosal transfer deficit of nonlinguistic information in alexithymia.

Schalling-Sifneos and MMPI Alexithymia Scales were used to screen 730 Japanese subjects. The 27 subjects scoring highest and the 26 scoring lowest on both scales were designated high and low alexithymic respectively. The two groups were tested by tachistoscopically presenting them with a lateralized visual matching task, which incorporated both linguistic and nonlinguistic stimuli. Differences in ipsilateral and contralateral hand reaction times were used as an indicator of callosal transfer speed. The results indicated that the two groups did not differ in the callosal transfer of linguistic information. They differed significantly, however, in the right to left hemisphere transfer of nonlinguistic information. This result is suggestive of a physiological basis in alexithymia.

Adult↗
PubMed1993

Callosal atrophy with reduced cortical oxygen metabolism in carotid artery disease.

BACKGROUND AND PURPOSE: In cerebrovascular disease, brain atrophy may be a reflection of ischemic changes. Minor changes that are not detectable as infarction on computed tomography may result in atrophy with metabolic depression. We evaluated the relation between size of the corpus callosum and cerebral cortical oxygen metabolism in carotid artery disease. METHODS: We used magnetic resonance imaging and positron emission tomography to evaluate 13 right-handed male patients with transient ischemic attacks or minor strokes and unilateral internal carotid artery occlusive disease, two with stenosis and 11 with occlusion. Computed tomography showed only minor subcortical abnormalities in the affected hemisphere. Midsagittal corpus callosum areas on T1-weighted magnetic resonance images, white matter lesions on T2-weighted images, and the cerebral metabolic rate of oxygen measured by the oxygen-15 steady-state technique were analyzed. RESULTS: Compared with 13 age- and sex-matched control subjects showing the same degree of white matter areas of high intensity, the patients had significantly decreased callosal areas. The degree of corpus callosum atrophy was significantly correlated with the mean cortical oxygen metabolic rate. The same tendency was also found in five patients without infarcts on computed tomography. However, neither the callosal area nor the hemispheric metabolic rate was correlated with the extent of white matter lesions. CONCLUSIONS: These findings indicate that atrophy of the corpus callosum occurs in association with a decrease in cortical oxygen metabolism. Corpus callosum atrophy may be a useful morphological index that reflects the cerebral cortical metabolic state in carotid artery occlusive disease.

Aged↗
PubMed2002

Callosal anomalies in patients with spinal dysraphism: correlation of clinical and neuroimaging features with hemispheric abnormalities.

Dysgenesis of the corpus callosum can occur in association with spinal dysraphic lesions. Clinical and neuroimaging features were reviewed in 23 patients (12 male, 11 female; mean age 11.3 years) with caudal spinal dysraphism (myeloschisis in eight, meningomyelocele in 10, and lumbosacral lipoma in five) to characterize types and degrees of callosal and other cerebral anomalies. T1- and T2-weighted magnetic resonance images were obtained, and the total midsagittal cross-sectional area of the corpus callosum was determined. The corpus callosum appeared normal in nine patients and was abnormal in 14. In five patients the corpus callosum was narrow, with all regions present; the cerebral hemispheres were hypoplastic. Two patients with dysgenesis of frontal, parietal, and occipital lobes had a small, partly agenetic corpus callosum. In the remaining seven patients the posterior third of the corpus callosum was absent or hypoplastic; six of them had ventriculomegaly that selectively affected the occipital horns (colpocephaly). All callosal anomalies were accompanied by hemispheric ones. This supports a disordered developmental relationship between the corpus callosum and the hemispheres as a cause. Spinal dysraphism can no longer be considered a single developmental abnormality, given the frequent association of other defects.

Adolescent↗
PubMed2005

Occipital-callosal pathways in children: Validation and atlas development.

Diffusion tensor imaging and fiber tracking were used to measure fiber bundles connecting the two occipital lobes in 53 children of 7-12 years of age. Independent fiber bundle estimates originating from the two hemispheres converge onto the lower half of the splenium. This observation validates the basic methodology and suggests that most occipital-callosal fibers connect the two occipital lobes. Within the splenium, fiber bundles are organized in a regular pattern with respect to their cortical projection zones. Visual cortex dorsal to calcarine projects through a large band that fills much of the inferior half of the splenium, while cortex ventral to calcarine sends projections through a band at the anterior inferior edge of the splenium. Pathways projecting to the occipital pole and lateral-occipital regions overlap the dorsal and ventral groups slightly anterior to the center of the splenium. To visualize these pathways in a typical brain, we combined the data into an atlas. The estimated occipital-callosal fiber paths from the atlas form the walls of the occipital horn of the lateral ventricle, with dorsal paths forming the medial wall and the ventral paths bifurcating into a medial tract to form the inferior-medial wall and a superior tract that joins the lateral-occipital paths to form the superior wall of the ventricle. The properties of these fiber bundles match those of the hypothetical pathways described in the neurological literature on alexia.

Anatomy, Artistic↗
PubMed1987

Callosal apraxia.

A 39-year-old right-handed woman suffered a ruptured pericallosal aneurysm. Serial MRI studies showed damage to the genu and most of the body of the corpus callosum but not the splenium. Both supplementary motor areas (SMA) appeared intact. We studied the patient's praxis performance at intervals over a 4-month period with a standardized battery. The study suggests that apraxia seen in patients with callosal lesions is probably due to the callosal damage, not to the usually associated SMA lesion. Our findings support Liepmann's idea that the left hemisphere is dominant for praxis in both hands. We propose, however, that the dominance effect is related to the type of test given and varies among individuals. As regards the latter, in some individuals the left hemisphere is strongly dominant for motor tasks, while in others it is less so. As regards the type of test, the most enduring left-hand apraxia is seen in verbal, not visuomotor tests.

Adolescent↗
PubMed1987

Cerebral dominance, sex, and callosal size in MRI.

We measured the MRI area of corpus callosum in 104 normal adults, 51 men, 53 women, 52 right- and 52 left-handers. There were no significant sex or handedness differences. Callosal areas did not correlate with brain size nor with measures of lateralization for hand performance, dichotic listening, or visual field preference. The results are contrary to the notion of increased callosal connectivity in left-handers, women, or individuals with less-lateralized function.

Adolescent↗
PubMed1989

Human callosal function: MRI-verified neuropsychological functions.

A commissurotomy patient, with MRI-revealed sparing of some rostral and splenial fibers of the corpus callosum, judged whether pairs of words rhymed. We presented one word in each pair to her left visual field and the other to her right visual field. The 2 words in each pair either sounded and looked alike (R + L +), sounded alike but looked different (R + L -), sounded different but looked alike (R - L +), or both sounded and looked different (R - L -). Although in previous studies the patient has demonstrated little or no ability to transfer information between her brain hemispheres, she was able to perform the rhyming judgment significantly better than chance when the words both looked and sounded alike. However, her accuracy did not differ from chance in the other 3 conditions, or when she was asked to indicate if 2 letters presented to her opposing visual fields were the same or different. A second commissurotomy patient, with an MRI-verified full callosal section, performed at chance in all conditions, and normal control subjects were significantly better than chance in all conditions but R + L -. We discuss the results in terms of the specificity of the information carried by groups of callosal fibers.

Adult↗
PubMed2001

Callosal agenesis with cyst: a better understanding and new classification.

OBJECTIVE: To analyze imaging studies of 25 cases of agenesis of the corpus callosum with interhemispheric cyst to assess this malformation itself and associated anomalies. METHODS: CT (6 patients) and MRI (19 patients) were retrospectively reviewed. The patients were categorized according to morphologic and clinical characteristics. RESULTS: Based on morphology, the patients were separated into two major types, each with subtypes. Type 1 cysts appear to be an extension or diverticulation of the third or lateral ventricles, whereas Type 2 are loculated and do not communicate with the ventricular system. Type 1a were associated with presumed communicating hydrocephalus but no other cerebral malformations. Type 1b were associated with hydrocephalus secondary to diencephalic malformations prohibiting egress of CSF from the third ventricle into the aqueduct of Sylvius. Type 1c were associated with small head size and apparent cerebral hemispheric dysplasia or hypoplasia. Type 2a (multiloculated cysts) were associated with no abnormalities other than callosal agenesis/hypogenesis. Type 2b were associated with deficiencies of the falx cerebri, subependymal heterotopia, and polymicrogyria (and were almost all in patients diagnosed with Aicardi syndrome). Type 2c were associated with subcortical heterotopia. Type 2d consists of interhemispheric arachnoid cysts. Other than those with Type 2b cysts, gender predominance was overwhelmingly male. CONCLUSION: Agenesis of the corpus callosum with interhemispheric cyst appears to consist of a heterogeneous group of disorders that have in common callosal agenesis and extraparenchymal cysts, both of which are among the commonest CNS malformations. This article proposes a classification system, based primarily on morphology, by which this complex group of disorders might begin to be better understood.

Agenesis of Corpus Callosum↗
PubMed2001

Mapping callosal morphology and cognitive correlates: effects of heavy prenatal alcohol exposure.

BACKGROUND: Abnormalities of the corpus callosum (CC) have been documented in fetal alcohol syndrome (FAS), ranging from subtle decrements in its size to partial and even complete agenesis. Prenatal exposure to alcohol is also known to result in neurocognitive deficits. OBJECTIVE: To 1) investigate abnormalities in size, shape, and location of the CC within the brain in individuals with FAS and in those exposed to high amounts of alcohol prenatally but without FAS (PEA group); and 2) determine if there is a relationship between callosal dysmorphology and cognitive test performance. METHODS: MRI and novel surface-based image analytic methods were used. Twenty alcohol-exposed subjects (8 to 22 years) along with 21 normal controls (8 to 25 years) were studied with high-resolution MRI and measures of verbal learning and visuospatial abilities. RESULTS: In addition to callosal area reductions, most severe in the splenium, the CC is significantly displaced in patients exposed to alcohol prenatally. In the alcohol-exposed group, this structure lies more anterior and inferior in posterior regions with relatively normal localization of anterior regions. These findings are significant in the FAS group, and a similar but less severe pattern is observed in the PEA patients. The authors show that the amount of CC displacement is correlated with impairment in verbal learning ability and that CC displacement is a better predictor of verbal learning than regional CC area. The brain-behavior relationship is only significant within the alcohol-exposed group, and the effect is not solely mediated by overall impaired verbal intellectual functioning. CONCLUSIONS: These results further emphasize the vulnerability of midline brain structures to prenatal alcohol exposure.

Adolescent↗
PubMed1984

Pollen-pistil interactions in interspecific crosses of Populus (sections Aigeiros and Leuce): pollen adhesion, hydration and callose responses.

Intersectional crosses between species of sections Aigeiros (Populus deltoides, P. X euramericana or P. nigra) and Leuce (P. alba or P. tremuloides) are known to be reciprocally incompatible. The site of pollen tube arrest is on the stigma surface in pollinations between pistils of section Leuce and pollen of section Aigeiros; tubes failed to penetrate the stigma surface. In reciprocal matings, pollen of section Leuce germinated and tubes penetrated the stigma and style, where arrest occurred. Rejection may be accompanied by swelling of the tube tips, and callose plug formation. In the cross between P. deltoides and P. alba a callose response was detected in the cell walls of the transmitting tissue, adjacent to the rejected pollen tubes.

Microscopy, Electron, Scanning↗
PubMed1985

New evidence on the callosal system.

In the present paper experimental data on the principles of functional organization of the animal callosal system and the roles of symmetry and asymmetry in interhemispheric interaction are considered. A conclusion has been made that the cerebral hemispheres function not according to homotopicity principle but according to the principle of heterotopicity. A utilization of both homotopical callosal projections and intracortical pathways takes place. In interhemispheric relations the major role is played by the principle of the common pathway. Of great importance in asymmetry organization is the physiological dominant, which is formed and reinforced by excitation spreading through the corpus callosum and along intracortical pathways. Transcallosal excitation, interacting with thalamocortical and extracallosal ones, contributes to the creation and modulation of functional interhemispheric 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↗
PubMed1986

Chlorantine fast green BLL as a stain for callose in oak phloem.

Sections of oak bark were stained with chlorantine fast green BLL, used as a 0.25% aqueous solution. All tissues were unstained, except for local deposits of material associated with phloem cell walls, which stained deep green. This green-staining material also stained specifically with resorcinol blue and with the aniline blue fluorescence technique, the usual histochemical tests for callose. The chlorantine fast green-staining material was removed from sections by treatment with a beta-1,3-glucan hydrolase. It is concluded that chlorantine fast green BLL stains callose in plant sections and is a useful additional stain for the histochemical detection of this polymer.

Azo Compounds↗
PubMed2002

Effects of callosal lesions in a model of letter perception.

During cognitive tasks, the cerebral hemispheres cooperate, compete, and in general, interact via the corpus callosum. Although behavioral studies in normal and split-brain subjects have revealed a great deal about the transcallosal exchange of information, a fundamental question remains unanswered and controversial: Are transcallosal interhemispheric influences primarily excitatory or inhibitory? In this context, we examined the effects of simulating sectioning of the corpus callosum in a computational model of visual letter recognition. Differences were found, following simulated callosal sectioning, in the performance of each individual hemisphere, in the mean activation levels of hemispheres, and in the specific patterns of activity, depending on the nature of the callosal influences. Together with other recent computational modeling results, the findings are most consistent with the hypothesis that transcallosal influences are predominantly excitatory, and they suggest measures that could be examined in future experimental studies to help resolve this issue.

Brain Injuries↗
PubMed2002

The role of the anterior commissure in callosal agenesis.

Two individuals with callosal agenesis (J.P. and M.M.) and 10 neurologically normal participants were tested on tasks requiring interhemispheric visual integration. M.M., whose anterior commissure was within normal limits, was much worse at matching colors and letters between visual fields than within visual fields, whereas J.P., whose anterior commissure was greatly enlarged, showed no evidence of interhemispheric disconnection. This suggests that in some cases of callosal agenesis, probably a minority, an enlarged anterior commissure may compensate for the lack of the corpus callosum. Neither acallosal participant showed interhemispheric disconnection on tasks requiring integration of location and orientation, however, suggesting that the anterior commissure plays no role in such tasks. These tasks may depend on subcortical commissures, such as the intertectal commissure.

Adult↗
PubMed2004

Diffusion tensor MR imaging visualizes the altered hemispheric fiber connection in callosal dysgenesis.

We report three cases of callosal dysgenesis that were evaluated by diffusion tensor imaging and fiber tractography. In partial agenesis of corpus callosum, fiber tracts from all regions of brain converged to a partially developed small genu portion and connected to the contralateral side. In complete callosal agenesis, fibers from the hemispheres failed to cross the midline and formed thick bundles running anteroposteriorly (eg, Probst bundle). The thickness of the anterior commissure was enlarged or smaller than normal brain, and other white matter tracts were not markedly different from normal brain tissue.

Abnormalities, Multiple↗
PubMed1989

[Interhemispheric visual information transfer in callosal agenesis].

It has been well established that acquired lesions of the corpus callosum such as surgical section bring about disturbances of interhemispheric transfer of visual information. In contrast, patients with callosal agenesis do not display these specific deficits. The mechanisms of this compensation have been postulated as follows; (1) bilateral development of language function, (2) exploitation of extracallosal commissure fibers such as the anterior commissure. Several studies have reported, however, minor disturbances of interhemispheric visual transfer in callosal agenesis, such as less efficient interhemispheric transfer of complex visual stimuli (Gott & Saul, 1978), slower reaction time in interhemispheric comparison of visual stimuli (Sauerwein & Lassonde, 1983), or deficits in spatial localization in the right hemi-field (Martin, 1985). In order to settle these issues, we have administered four kinds of tachistoscopic visual recognition tests on 4 patients with complete agenesis of the corpus callosum confirmed by magnetic resonance imaging (MRI). This technique enabled us to see the mid-sagittal plane of the corpus callosum and diagnose its total absence with much higher certainty and precision than previous studies employing computed tomography (CT) or pneumoencephalography. Case 1: A 41-year-old right-handed man visited us because of recurrent numbness in the four extremities. Neurological examination revealed no abnormalities. MRI has confirmed that the corpus callosum was totally lacking, and that the anterior commissure was normally visualized. Case 2: A 31-year-old right-handed man was referred to us for the treatment of partial complex seizure. Total agenesis and lipoma of the corpus callosum was diagnosed by MRI and reconstructed sagittal view of CT scan.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

MRI of corpus callosal syndromes.

Six patients, 6 to 13 years old, with corpus callosal abnormalities diagnosed by electroencephalography or CT were studied with a 0.15 T MR imager to determine the effectiveness of MRI in evaluating midline anomalies. Spin-echo images in the coronal, axial, and sagittal planes were obtained in two patients with Aicardi's syndrome and partial agenesis of the corpus callosum, in one patient with Dandy-Walker syndrome, and in two patients with septooptic dysplasia. Inversion recovery and spin-echo images were obtained in one patient with lipoma of the corpus callosum. Partial agenesis of the corpus callosum was seen in septooptic dysplasia, an association that has not been reported previously in the radiologic literature. Direct sagittal and coronal MRI provided better anatomic visualization of the brain and ventricles than did reformatted CT. T1-weighted images are sufficient to diagnose and delineate the extent of midline cerebral abnormalities. The unique capability of direct sagittal imaging makes MRI the best procedure for evaluating corpus callosal and other midline abnormalities.

Abnormalities, Multiple↗