Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CALLOSITIES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources
PubMed2001

Callosal commissural neurons of Dab1 deficient mutant mouse, yotari.

The yotari mouse is an autosomal recessive mutant mouse, caused by mutation of disabled homolog 1 (Dab1) gene. The mutant mouse is recognized by unstable gait and tremor and by early deaths around at the time of weaning. The cytoarchitectures of cerebeller and cerebral cortices and hippocampal formation of the yotari mouse are abnormal. These malformations strikingly resemble those of reeler mouse. In the present study we examined the callosal commissural (CC) neurons of yotari, reeler and normal mice with the injection of recombinant adenovirus into the frontal area 1 (Fr1) to find some possible phenotypes specific for the yotari mouse. The distribution pattern of CC neurons of the yotari was similar to that of the reeler: retrogradely labeled CC neurons were seen throughout all depths of the contralateral Fr1. However, the present statistical analysis revealed that the difference of the mean intracortical position of the CC neurons between the yotari and the reeler is significantly different (Student's t-test), suggesting that the phenotype of the yotari is clearly different from that of the reeler.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Abnormal distributions of callosal commissural and corticothalamic neurons in the cerebral neocortex of Shaking Rat Kawasaki.

Shaking Rat Kawasaki (SRK) is an autosomal recessive mutant rat recognized by unstable gait and tremor and by early death around the time of weaning. We previously reported that corticospinal tract neurons are malpositioned in the motor cortex of the SRK rat [Ikeda and Terashima (1997) J. Comp. Neurol. 383, 370-380]. In the present study, we examined the distribution pattern of callosal commissural (CC) and corticothalamic (CT) neurons of SRK and normal rats with the injection of horseradish peroxidase (HRP) into the contralateral hemisphere or wheat germ agglutinin-conjugated HRP into the ventral lateral thalamic nucleus. The intracortical distribution pattern of retrogradely labeled CC and CT neurons in the motor cortex of SRK rat was abnormal: CC neurons were more deeply situated and CT neurons were more superficially situated in the SRK cortex than the corresponding components in the normal cortex. Most of labeled CC and CT neurons had abnormal dendritic configurations. Statistical analysis revealed that the difference of the mean intracortical position of CC and CT neurons of the SRK was significantly different from the normal counterparts (Student's t-test, P<0.01). Taken together with previous findings, our data demonstrate that the abnormal cytoarchitecture of SRK cortex resembles the reeler cortex.

Agenesis of Corpus Callosum↗
PubMed1997

Effect of callosal bisection on seizure development and interhemispheric transfer effects in feline motor cortical kindling.

Motor cortical (MC) kindling was carried out in 12 adult cats, seven with the corpus callosum (CC) intact and five with the CC bisected, to study interhemispheric transfer effects and the effect of callosal bisection on both seizure development and interhemispheric transfer effects. MC kindling developed from partial motor seizures to partial onset generalized convulsions. Interhemispheric negative transfer effect, but not positive, existed in secondary site kindling and primary site retest of the CC-intact group, as shown by: (i) electroencephalographically lateralized seizure development in the stimulated hemisphere; (ii) delayed generalization of partial onset generalized convulsions; and (iii) a markedly unstable generalized convulsive seizure state. The CC-bisected group showed: (i) significantly delayed seizure development from partial motor seizure stage to generalized convulsive seizure stage in primary and secondary kindling; (ii) facilitated intrahemispheric seizure development; (iii) the diminution of interhemispheric negative transfer effect; (iv) modified generalized convulsions showing extremely asymmetrical generalized convulsions shifting from contralaterally dominant convulsions to ipsilaterally dominant ones (n = 2) or alternate generalized convulsions changing from contralateral hemiconvulsions to ipsilateral ones (n = 3). The results obtained suggest that the CC plays a major role in interhemispheric seizure propagation as well as interhemispheric negative transfer effects in MC kindling and may have suppressive effect on intrahemispheric motor seizure development in MC kindling. However, interhemispheric seizure propagation and interhemispheric negative transfer effects were mediated via other structures, possibly subcortical structures, when the CC was bisected.

Animals↗
PubMed2003

Callosal role in generation of epileptiform discharges: quantitative analysis of EEGs recorded in patients undergoing corpus callosotomy.

OBJECTIVE: Corpus callosotomy tends to decrease seizure frequency and severity rather than transforming the seizure pattern from a generalized form into a lateralized or a partial one. The finding implies that bisection of the corpus callosum (CC) disrupts the epileptogenicity itself. In order to gain further insight into the possible role played by the CC in intractable generalized epilepsy, quantitative analyses of long-term EEGs were performed. METHODS: Analyses were made of epileptiform discharges contained in the pre- and postoperative long-term EEGs in 7 patients who had an anterior callosotomy for intractable epilepsy. The duration, number, and amplitude of all epileptiform burst activities were measured and statistically analyzed. RESULTS: After callosotomy, the total number of epileptiform burst activities, mean duration, and the total number of spike discharges decreased significantly. The two hemispheres could be divided into dominant and non-dominant ones as to the quantity of the residual epileptiform discharges. CONCLUSIONS: Corpus callosotomy unevenly reduced preoperative epileptiform discharges in both hemispheres, suggesting a facilitatory role played by the callosal neurons that enables the asymmetrical epileptogenic susceptible state of the two hemispheres to develop bisynchronous and bisymmetrical epileptiform discharges. SIGNIFICANCE: Corpus callosotomy decreased the quantity of the epileptiform discharges, suggesting the transhemispheric facilitation of seizure mechanisms.

Cerebral Cortex↗
PubMedDate not supplied

Transcallosal circuitry revealed by blocking and disinhibiting callosal input in the cat.

The purpose of this study was to obtain quantitative measures of the influence of callosal input to cells at the area 17/18 border region where transcallosal axons terminate most densely. Single-cell recordings were performed at the area 17/18 border region of the right hemisphere, while gamma-aminobutyric acid (GABA) or its antagonist, bicuculline, were applied to the transcallosal projecting regions of the left hemisphere to either block or overactivate the cells which projected to the neurons at the recording site. The results showed that visually evoked responses of the cells at the area 17/18 border were affected by administration of GABA or bicuculline to the contralateral hemisphere. Blockade of transcallosal input by application of GABA in the left hemisphere diminished the visually evoked responses of 51% of the neurons in the right hemisphere, and led to an increase in response magnitude for 17% of the neurons. Disinhibition of transcallosal input by application of bicuculline increased the evoked activity of 40% of the neurons and diminished the response magnitude of 20% of the neurons in the right hemisphere. GABA and bicuculline failed to show antagonistic effects on some cells. Thirty-two percent of the cells were affected by only one type of drug administration, and 13% of the cells showed either an increase or a decrease in responses after both GABA and then bicuculline administration. This study demonstrated complex interactions between neurons connected by the transcallosal pathway. A model of the transcallosal circuitry was proposed to explain the results.

Animals↗
PubMed1992

Cognition and the corpus callosum: verbal fluency, visuospatial ability, and language lateralization related to midsagittal surface areas of callosal subregions.

Normal volunteers (28 women), 20-45 years old, completed tests of visuospatial ability, verbal fluency, and language lateralization, and the midsagittal surface areas of the splenium, isthmus, midregion, and genu of the corpus callosum were measured from inversion recovery magnetic resonance images. Multivariate statistics were used to analyze patterns of correlations. Verbal fluency correlated positively with the area of the splenium and with the area of a posterior callosal factor defined largely by the splenium. The posterior callosum, particularly the splenium, also correlated negatively with language lateralization. There were no other consistent brain-behavior relationships. These results are relevant to understanding factors involved in the development of cognitive characteristics that show sex differences and to understanding the neural basis of language lateralization and verbal abilities.

Adult↗
PubMed2005

Early visual evoked potentials in callosal agenesis.

Three participants with callosal agenesis and 12 neurologically normal participants were tested on a simple reaction time task, with visual evoked potentials collected using a high-density 128-channel system. Independent-components analyses were performed on the averaged visual evoked potentials to isolate the components of interest. Contrary to previous research with acallosals, evidence of ipsilateral activation was present in all 3 participants. Although ipsilateral visual components were present in all 4 unilateral conditions in the 2 related acallosal participants, in the 3rd, these were present only in the crossed visual field-hand conditions and not in the uncrossed conditions. Suggestions are made as to why these results differ from earlier findings and as to the neural mechanisms facilitating this ipsilateral activation.

Adult↗
PubMed2006

Efficiency of callosal transfer and hemispheric interaction.

The corpus callosum (CC) is essential to hemispheric interaction, but it is unclear how individual callosal properties affect interaction between the cerebral hemispheres. A number of studies have demonstrated some relationship between morphology or structure of the CC and measures of hemispheric interaction. However, to the authors' knowledge, none of these studies has been able to show a clear, direct relationship between a behavioral measure of transfer speed through the CC, interhemispheric transfer time (IHTT), and a behavioral measure of hemispheric interaction. Eighty participants were tested over 6 sessions on 2 tasks assessing IHTT and hemispheric interaction. The Poffenberger paradigm was used to measure IHTT, and a divided split-visual-field letter-matching task was used to assess hemispheric interaction. A significant correlation that could not be accounted for by other factors such as functional lateralization, handedness, age, sex, or attention was found between these 2 measures. These results are discussed in relation to CC morphology and structure and functional and structural hemispheric lateralization.

Adolescent↗
PubMed2001

Impairment of binocular vision in the adult cat induces plastic changes in the callosal cortical map.

In the primary visual cortex of normally reared adult cat, neurons activated through the corpus callosum are almost entirely located at the 17/18 border. They display small receptive fields distributed along the central vertical meridian of the visual field and are orientation selective. Here we demonstrate that a few weeks of monocular deprivation or unilateral convergent strabismus produced in adulthood does not modify the cortical distribution of these neurons, but leads to an increase of their receptive field size mainly toward the ipsilateral hemifield and to a loss of their orientation selectivity. We conclude that manipulation of binocular vision in the adult modifies neither the location of the primary callosal cortical map nor its retinotopy. In contrast, it induces functional plastic changes in this map which lead to a significant widening of the area of visual space signalled through the corpus callosum. These plastic changes are interpreted as the result of the strengthening of normally hidden subthreshold synaptic inputs.

Animals↗
PubMed1998

A cytokinesis-defective mutant of Arabidopsis (cyt1) characterized by embryonic lethality, incomplete cell walls, and excessive callose accumulation.

The genetic control of cell division in eukaryotes has been addressed in part through the analysis of cytokinesis-defective mutants. Two allelic mutants of Arabidopsis (cyt1-1 and cyt1-2) altered in cytokinesis and cell-wall architecture during embryogenesis are described in this report. Mutant embryos appear slightly abnormal at the heart stage and then expand to form a somewhat disorganized mass of enlarged cells with occasional incomplete walls. In contrast to the keule and knolle mutants of Arabidopsis and the cyd mutant of pea, which also exhibit defects in cytokinesis during embryogenesis, cyt1 embryos cannot be rescued in culture, are desiccation-intolerant at maturity, and produce cell walls with excessive callose as revealed through staining with the aniline blue fluorochrome, Sirofluor. Some cyt1 defects can be partially phenocopied by treatment with the herbicide dichlobenil, which is thought to interfere with cellulose biosynthesis. The distribution of unesterified pectins in cyt1 cell walls is also disrupted as revealed through immunocytochemical localization of JIM 5 antibodies. These features indicate that CYT1 plays an essential and unique role in plant growth and development and the establishment of normal cell-wall architecture.

Alleles↗
PubMed2002

Is a cortical spike discharge "transferred" to the contralateral cortex via the corpus callosum?: An intraoperative observation of electrocorticogram and callosal compound action potentials.

PURPOSE: By means of the intraoperative electrophysiologic observation, we reevaluated the "transfer" theory that a transcallosal volley invoked by a cortical spike discharge in one hemisphere directly causes its contralateral counterpart via the corpus callosum (CC). METHODS: Twenty-six patients who underwent corpus callosotomy were the subjects of this study. Intraoperatively, electrocorticograms from both hemispheres were simultaneously monitored with callosal compound action potentials (CCAPs) from the CC. Analysis was conducted on (a) the interhemispheric delay of bilaterally synchronous spike-and-wave discharges (BSSWs), and (b) the chronological relation between BSSWs and CCAPs. RESULTS: The side of prior spike discharges was never fixed but was occasionally reversed. Interhemispheric delays between the BSSWs were not constant, regardless of direction, and fluctuated in all patients. Most of the interhemispheric delays were distributed within 20 ms with a mode of 0 ms. The waveform of the CCAP was characterized by slow-rising negative potential change that attained its peak after a cortical spike discharge. These findings were identical in all the patients regardless of whether the BSSWs were changed or unchanged after callosotomy. CONCLUSIONS: If the "transfer" role of the CC is true, interhemispheric delays between BSSWs must be longer than interhemispheric axonal conduction time (about 20 ms), and a preceding cortical spike discharge must produce a CCAP and then a contralateral one in order of time. However, this hypothesis was not confirmed in the present study. We propose the interhemispheric recruitment of the epileptogenic state as a different role of the CC on epileptogenesis.

Adolescent↗
PubMed2000

Reorganisation of the visual cortex in callosal agenesis and colpocephaly.

Structural defects involving eloquent regions of the cerebral cortex may be accompanied by abnormal localisation of function. Using functional magnetic resonance imaging (fMRI), we studied the organisation of the visual cortex in a patient with callosal agenesis and colpocephaly, whose visual acuity and binocular visual fields were normal. The stimulus used was a moving grating confined to one hemifield, on a background of moving dots. In addition to activation patterns elicited by stimulation of each hemifield in the patient, the activation pattern was compared to that seen in six normal volunteers. fMRI demonstrated large scale reorganisation of visual cortical areas in the left hemisphere, and fewer activation foci were observed in both occipital lobes when compared with normal subjects.

Adolescent↗
PubMed1992

The antidepressant effect of carbamazepine in callosal agenesis: a case report.

A dramatic resolution of severe depressive symptoms following carbamazepine administration in a patient with callosal agenesis is reported. Maintenance treatment with carbamazepine resulted in the alleviation of concomitant organic symptoms and in a marked improvement in quality of vital functions.

Agenesis of Corpus Callosum↗
PubMed2000

The relationship of callosal anatomy to paw preference in dogs.

Previous studies have described the paw preference and asymmetry in dog brains, based on experimental studies. The purpose of the present study is to investigate a possible association between callosal anatomy and paw preference in dogs. The midsagittal area of the dog corpus callosum was measured in its entirety and in six subdivisions in a sample of 21 brains obtained from 9 male and 12 female mongrel dogs which had paw preference testing. The present study showed significant paw differences in dog corpus callosum. A posterior segment of the callosum, the isthmus, was significantly larger in the right pawedness than the left.

Animals↗
PubMed2002

A new sign of callosal disconnection syndrome: agonistic dyspraxia. A case study.

We report a patient with callosal haemorrhage and no extracallosal involvement who developed a unique form of intermanual conflict. In the acute phase the patient showed a mild speech disturbance and right hemiparesis, and in her right hand, a grasp reflex and compulsive manipulation of tools, all attributable to transient frontal involvement. In the chronic phase there was intermanual conflict occasionally associated with the sensation of a second left hand. The patient also presented a sign consisting of compulsive, automatic execution of orders by one hand (the left or the right) when the patient was specifically asked to perform the movement with the other hand (the right or the left, respectively). There was no left-right confusion in this patient. We call this condition agonistic dyspraxia. In contrast with diagonistic dyspraxia, this consists of the agonistic behaviour of the other hand under conditions in which the hand that has been instructed to respond cannot execute the request.

Adult↗
PubMed1984

Pseudoneglect in a patient with partial callosal disconnection.

Each hemisphere may not only be responsible for processing stimuli from the contralateral sensory systems and for programming movements of the contralateral hand, but may also be important for mediating attention-intention within the contralateral hemispace. If each hemisphere mediates attention-intention within contralateral hemispace, both hemispheres must work in concert especially when an arm is crossed and used in opposite hemispace. If both hemispheres did not work together, the directional bias of each hemisphere would become manifest and induce the contralateral extremity to err toward its own hemispace, inducing pseudoneglect . To test this hypothesis, we examined a patient who had a partial callosal disconnection. In trying visually and somaesthetically to bisect lines with her left hand in right hemispace, the patient made systematic errors to the left; in bisecting lines in left hemispace with her right hand, she made systematic errors to the right. The patient also made less dramatic systematic errors even when a hand was used in its own hemispace, which suggests that each hemisphere mediates attention-intention within and towards the contralateral hemispace.

Adolescent↗
PubMed1987

Posterior callosal infarction. Clinicopathological correlations.

Clinicoanatomical observations on a patient with partial interhemispheric disconnection associated with complete ischaemic destruction of the splenium and of the posterior part of the body of the corpus callosum are presented. Neuropathological examination of the areas containing degenerated white matter indicated that the lesions affected the transcallosal fibres that link the cortex of the occipital lobes and the superior parietal lobules (SPL). The white matter situated in the temporal lobes was intact. This suggests that in man, and contrary to what has been described in the monkey, the callosal pathway followed by the temporal fibres is rostral to the one followed by the parietal or at least by the SPL fibres. The most prominent disconnection syndrome elements were left tactile anomia (in spite of a rather good tactile-motor integration between the hemispheres), left visual anomia, agraphia of the left hand and 'diagnostic' apraxia. The fact that the anterior part of the corpus callosum was intact accounts for the preservation of interhemispheric transfer of somatic sensory information and for the absence of left extinction during the dichotic listening test. An attempt is made to give a more detailed explanation of the results obtained during the different tests.

Aged↗
PubMed1990

Hemispatial neglect in a patient with callosal infarction.

Left hemispatial neglect, confined to right-hand and verbal responses, was exhibited by a 56-yr-old right-handed male patient with callosal lesions due to cerebral infarction. Various disconnection signs were also present. His CT and MRI scans disclosed major lesions situated in the posterior half of the genu and the whole trunk of the corpus callosum, as well as in the left medial frontal and temporo-occipital lobes. Left hemispatial neglect was invariably demonstrated in right-hand performance such as copying drawings, line bisection, matching identical figures and copying multiple digit numbers, and in verbal performance such as confrontation naming and reading aloud multiple digit numbers. In contrast, little or no right hemispatial neglect was demonstrated in tasks performed with the left hand. These findings support the hypothesis that the left hemisphere is only concerned with attending to the contralateral hemispace and that the right hemisphere is specialized for attending to both sides of space although the preponderant tendency is for attending to the contralateral hemispace. The neglect symptoms observed in our patient may be a disconnection sign which was attributable to a combination of lesions in the corpus callosum and in the left medial frontal lobe.

Attention↗