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PubMed2005

The transcription factor gene Nfib is essential for both lung maturation and brain development.

The phylogenetically conserved nuclear factor I (NFI) gene family encodes site-specific transcription factors essential for the development of a number of organ systems. We showed previously that Nfia-deficient mice exhibit agenesis of the corpus callosum and other forebrain defects, whereas Nfic-deficient mice have agenesis of molar tooth roots and severe incisor defects. Here we show that Nfib-deficient mice possess unique defects in lung maturation and exhibit callosal agenesis and forebrain defects that are similar to, but more severe than, those seen in Nfia-deficient animals. In addition, loss of Nfib results in defects in basilar pons formation and hippocampus development that are not seen in Nfia-deficient mice. Heterozygous Nfib-deficient animals also exhibit callosal agenesis and delayed lung maturation, indicating haploinsufficiency at the Nfib locus. The similarity in brain defects in Nfia- and Nfib-deficient animals suggests that these two genes may cooperate in late fetal forebrain development, while Nfib is essential for late fetal lung maturation and development of the pons.

Agenesis of Corpus Callosum↗
PubMed2004

Gross morphology and morphometric sequelae in the hippocampus, fornix, and corpus callosum of patients with severe non-missile traumatic brain injury without macroscopically detectable lesions: a T1 weighted MRI study.

OBJECTIVE: The gross morphology and morphometry of the hippocampus, fornix, and corpus callosum in patients with severe non-missile traumatic brain injury (nmTBI) without obvious neuroradiological lesions was examined and the volumes of these structures were correlated with performance on memory tests. In addition, the predictability of the length of coma from the selected anatomical volumes was examined. METHOD: High spatial resolution T1 weighted MRI scans of the brain (1 mm3) and neuropsychological evaluations with standardised tests were performed at least 3 months after trauma in 19 patients. RESULTS: In comparison with control subjects matched in terms of gender and age, volume reduction in the hippocampus, fornix, and corpus callosum of the nmTBI patients was quantitatively significant. The length of coma correlated with the volume reduction in the corpus callosum. Immediate free recall of word lists correlated with the volume of the fornix and the corpus callosum. Delayed recall of word lists and immediate recall of the Rey figure both correlated with the volume of the fornix. Delayed recall of the Rey figure correlated with the volume of the fornix and the right hippocampus. CONCLUSION: These findings demonstrate that in severe nmTBI without obvious neuroradiological lesions there is a clear hippocampal, fornix, and callosal volume reduction. The length of coma predicts the callosal volume reduction, which could be considered a marker of the severity of axonal loss. A few memory test scores correlated with the volumes of the selected anatomical structures. This relationship with memory performance may reflect the diffuse nature of the damage, leading to the disruption of neural circuits at multiple levels and the progressive neural degeneration occurring in TBI.

Adult↗
PubMed1984

Role of corpus callosum in functional organization of cat striate cortex.

The short-term (3-51 days) and long-term (31-42 wk) effects of corpus callosum transection on the receptive-field properties of neurons were assessed at the single-cell, architectural, and topographical levels of organization in the cat striate cortex. Corpus callosum transection decreased the proportion of neurons that could be activated from both eyes. In short-term animals, the reduction in binocularity was restricted to the representation of a vertical strip of visual space extending from the vertical meridian to at least 12 degrees lateral. In the long-term animals, the reduction in binocularity was restricted to the representation of visual space 4 degrees lateral to the vertical meridian. Therefore, the reduction in the representation of 4-12 degrees was only temporary. In both groups, the reduction in binocularity was less in the representation of area centralis than at other retinal locations in the same vertical strip. The region of area 17 affected permanently by the transection receives fibers from the contralateral hemisphere in normal animals. The region affected temporarily by the transection contains callosal cells but does not contain callosal terminals. Binocularity was assessed separately for simple I, simple II, and complex receptive-field types. The reduction in binocularity in the 12 degrees strip in short-term animals and in the 4 degrees strip in long-term animals was accounted for mainly by a reduction in binocularity of simple I and complex cells. As in normal animals, complex cells in callosum-transected cats were always more binocular than the other cell types. An analysis of the effects of corpus callosum transection on different cortical layers showed that a greater proportion of cells in the supragranular layers II and III showed a reduction in binocularity than in the infragranular layers V and VI. The proportion of binocular neurons in layer IV was not significantly different from normal. The major decreases in binocularity occurred in layers II, III, and VI for simple I and simple II cells and in layers II, III, and V for complex cells. The binocularity of simple II cells in layer IV and complex cells in layer VI was not affected. The effects of the transection on the columnar organization of the cortex were assessed by making electrode tracks that passed in the radial or laminar dimensions of the cortex. Reconstructions of the radial tracks showed that cells within one radial column tended to be dominated by the same eye. In adjacent columns, cells tended to be dominated by different eyes.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Efferent neurons and suspected interneurons in second somatosensory cortex of the awake rabbit: receptive fields and axonal properties.

1. Receptive-field properties of antidromically identified efferent neurons within the representation of vibrissae and sinus hairs above the mouth were examined in secondary somatosensory cortex (S-2) of fully awake adult rabbits. Efferent neurons studied included callosal neurons (CC neurons, n = 88), ipsilateral corticocortical neurons (C-IC neurons, n = 51) that project to primary somatosensory cortex (S-1), and corticofugal neurons of layer 5 (CF-5 neurons, n = 63) and layer 6 (CF-6 neurons, n = 42) that project to and/or beyond the thalamus. Appropriate collision tests demonstrated that substantial numbers of corticocortical efferent neurons (21 of 113 tested) project an axon to both the corpus callosum and to ipsilateral S-1. 2. Suspected interneurons (SINs, n = 62) were also studied. These neurons were not activated antidromically from any stimulus site but did respond synaptically to electrical stimulation of the ventrobasal (VB) thalamus with a burst of three or more spikes at frequencies of 600 to greater than 900 Hz. Most of these neurons also responded synaptically to stimulation of S-1 and the corpus callosum. The action potentials of these neurons were much shorter (mean, 0.49 ms) than those of efferent neurons (mean, 1.01 ms). 3. CF-5 neurons differed from CC, C-IC, and CF-6 neurons in their spontaneous firing rates, axonal properties, and receptive-field properties. Whereas CF-5 neurons had a mean spontaneous firing rate of 5.7 spikes/s, CC, C-IC, and CF-6 neurons all had mean values of less than 1/s. Axonal conduction velocities of CF-5 neurons were much higher (mean, 11.90 m/s) than either CC (mean, 2.63 m/s), C-IC (mean, 0.86 m/s), or CF-6 (mean, 1.73 m/s) neurons. A decrease in antidromic latency (the "supernormal" period), which was dependent on prior impulse activity, was seen in most CC, C-IC, and CF-6 neurons but was minimal or absent in CF-5 neurons of comparable conduction velocity. Although all CF-5 neurons responded to peripheral sensory stimulation, many CC (52%), C-IC (49%), and CF-6 (55%) neurons did not. CC and CF-6 neurons that did not respond to sensory stimulation had significantly lower axonal conduction velocities and spontaneous firing rates than those that responded to such stimulation. Whereas no CC, C-IC, or CF-6 neuron responded synaptically to callosal stimulation, 43% of CF-5 neurons (and 78% of SINs) did so respond. Similar differences in synaptic responsivity to stimulation of S-1 were seen in these populations.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed2002

Interhemispheric transmission of visuomotor information in humans: fMRI evidence.

Normal human subjects underwent functional magnetic resonance imaging (fMRI) while performing a simple visual manual reaction-time (RT) task with lateralized brief stimuli, the so-called Poffenberger's paradigm. This paradigm was employed to measure interhemispheric transmission (IT) time by subtracting mean RT for the uncrossed hemifield-hand conditions, that is, those conditions not requiring an IT, from the crossed hemifield-hand conditions, that is, those conditions requiring an IT to relay visual information from the hemisphere of entry to the hemisphere subserving the response. The obtained difference is widely believed to reflect callosal conduction time, but so far there is no direct physiological evidence in humans. The aim of our experiment was twofold: first, to test the hypothesis that IT of visuomotor information requires the corpus callosum and to identify the cortical areas specifically activated during IT. Second, we sought to discover whether IT occurs mainly at premotor or perceptual stages of information processing. We found significant activations in a number of frontal, parietal, and temporal cortical areas and in the genu of the corpus callosum. These activations were present only in the crossed conditions and therefore were specifically related to IT. No selective activation was present in the uncrossed conditions. The location of the activated callosal and cortical areas suggests that IT occurs mainly, but not exclusively, at premotor level. These results provide clear cut evidence in favor of the hypothesis that the crossed-uncrossed difference in the Poffenberger paradigm depends on IT rather than on a differential hemispheric activation.

Adult↗
PubMed2006

Regional pattern of increased water diffusivity in hippocampus and corpus callosum in mild cognitive impairment.

BACKGROUND: Corpus callosum atrophy possibly indicates neuronal degeneration in association cortex in Alzheimer's disease (AD). Water diffusivity allows detecting physiological changes that probably occur earlier than structural shrinkage in cerebral regions during the development of AD. OBJECTIVE: To simultaneously investigate the focal volumetric and early structural changes with apparent diffusion coefficient (ADC) of corpus callosum in mild cognitive impairment (MCI), and to explore the regional pattern of ADC increase in hippocampus and corpus callosum. METHODS: Thirteen subjects with MCI and 13 healthy age-matched control subjects were studied. With three-dimensional volumetric spoiled gradient recalled echo MRI images, we measured the volume of hippocampus and corpus callosum. Using MRI-guided diffusion-weighted imaging analysis, we calculated ADCs from hippocampus and corpus callosum. Within the receiver-operation curve (ROC) statistical framework, areas under ROC curves from hippocampal and callosal ADCs were compared in differentiating between MCI and controls. RESULTS: After normalization to intracranial volume, hippocampal, not callosal, volume was significantly reduced in MCI. ADC values were increased in hippocampus and corpus callosum in MCI. The extent of ADC increase was similar between hippocampus and corpus callosum. CONCLUSION: Alterations in water diffusivity may precede corpus callosum atrophy during the development of MCI. Diffusion changes might occur simultaneously in allocortex and neocortex in MCI.

Aged↗
PubMed2006

Gross anatomy of the corpus callosum in Alzheimer's disease: regions of degeneration and their neuropsychological correlates.

BACKGROUND/AIMS: Differences in the gross shape of the corpus callosum (CC) and its subregional areas were investigated on brain MRI of patients with probable Alzheimer's disease (AD) and age- and gender-matched healthy normal control subjects. The AD patients differed from the normal control subjects in terms of a more convex shape and a reduced area of the CC. METHODS: As for the comparisons of the subregional areas of the CC, we adapted a splitting method which takes into account the modification of the global shape of the CC, and we implemented it by normalizing the CC, to avoid the bias introduced by the observed callosal shape variability. RESULTS: The application of this method unveiled that the regional CC reductions were located in the anterior and posterior third of the CC, i.e. where small myelinated fibers are more frequent. None of the neuropsychological scores collected at the time of the MRI investigation of AD could predict a regional and/or overall callosal area reduction. The only measure that correlated with area of the isthmus of the CC was the MMSE that was administered to all participants. CONCLUSIONS: This latter result may be used as an in vivo indicator of the progress of neocortical disintegration in AD.

Aged↗
PubMed1985

Surgery for epilepsy. Selective partial microsurgical callosotomy for intractable multiform seizures: criteria for clinical selection and results.

A series of 35 patients have been submitted to microsurgical callosotomy since February 1978, their age ranging from 6 to 42 years. The surgical procedure consisted either of a frontal parasagittal trephination or a larger frontoparietal rectangular craniotomy to allow the investigation of the surgical areas of the hemispheres with electrocorticography under local anesthesia. This allowed us to better follow the electrographic abnormalities and plan the extent of the callosal section suited to each case, in particular rostral and genual section, section of the trunk only or subtotal section sparing the splenium. In 2 cases, cortical resection was associated with the split. The callosal fibers which were divided by careful section under the resected portion provided a critical postoperative control of the extent of the lesion. Results and selection criteria will also be analyzed.

Adolescent↗
PubMed1983

Depth electrode recording in patients undergoing corpus callosotomy for intractable epilepsy.

6 patients undergoing anterior corpus callosotomy for intractable epilepsy have been studied with depth electroencephalography (EEG). Recording before, during and after surgery has confirmed the ability of depth EEG to demonstrate and identify lateralized, focal and often multifocal disturbances. Callosal section has an immediate and lasting effect on clinical seizures and is accompanied by EEG changes with loss of generalization and synchrony following commissurotomy. Depth electrodes within the corpus callosal radiations variably reflect preoperative epileptiform activity recorded from the temporal and frontal regions and postoperatively confirm loss of a potential route of propagation through the commissure.

Adolescent↗
PubMed1980

Effects of early undernutrition on dendritic spines of cortical pyramidal cells in the rat.

Restricted food intake in male rats between birth and 20 days of age reduced the density of spines of layer V pyramidal cells in the frontal, parietal and occipital cortices. The loss of dendritic spines was more marked in pyramidal cell areas receiving projections from nonspecific multisynaptic systems than in cell areas associated with specific afferent systems or in areas receiving callosal projections. It was suggested that the differential effect of undernutrition in nonspecific, specific and callosal afferent projection areas of the pyramidal cortex might be related to the impairment of brain integrative functions reported to follow perinatal undernourishment.

Animals↗
PubMed1996

A morphological study of neurons expressing NADPH diaphorase activity in the visual cortex of the golden hamster.

The distribution of the enzyme nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase, which is identical to nitric oxide synthase (NOS), was examined in cortical area 17 and the 17/18a border region in the brain of the golden hamster. The activity of the enzyme was present as a network of processes and in special populations of neurons in the visual cortex. The dense enzyme-positive network exhibited numerous varicosities distributed throughout the cortex. The prominent orientation of the processes in layer I and the white matter are parallel to the surface of the brain, but those in layers II-IV are perpendicular to the surface of the brain. However, the processes in layers V and VI seem to run randomly. The NADPH diaphorase-positive cells could be divided into two classes: heavily stained neurons and lightly stained neurons. For the lightly stained NADPH diaphorase-positive neurons, only the cell bodies could be observed, whereas for the heavily stained neurons, the cell bodies and their varicosity-carrying dendrites and, occasionally, the smooth, thin and weakly stained axons were visible. The heavily stained neurons were morphologically diverse, but no pyramidal or spiny neurons were found. Multipolar and bipolar neurons were located throughout the depth of the cortex, including the white matter, more frequently in layers V and VI. Occasionally, monopolar neurons were found in layer VI. Callosal projecting neurons in the visual cortex were labeled retrogradely with the use of FluoSpheres applied at the opposite visual cortex, but these neurons did not co-localize with the NADPH diaphorase-positive neurons, suggesting that the callosal projecting neurons and NADPH diaphorase-positive neurons belong to two populations of cells in the visual cortex.

Animals↗
PubMed1988

The corpus callosum in nonhuman primates. Determinants of size.

The relationships between brain weight, sex and various callosal parameters including cross-sectional surface area and maximum splenial width in nonhuman primates are delineated. Overall, brain weight is a good predictor of quantitative aspects of the corpus callosum. However, both pongids and strepsirhines evince sex differences on certain callosal measures. No sex differences were found for either the ceboids or cercopithecoids. We speculate that one aspect of primate brain evolution has involved the modulation of interhemispheric connectivity along the lines of sex.

Animals↗
PubMed1998

Computational studies of lateralization of phoneme sequence generation.

The mechanisms underlying cerebral lateralization of language are poorly understood. Asymmetries in the size of hemispheric regions and other factors have been suggested as possible underlying causal factors, and the corpus callosum (interhemispheric connections) has also been postulated to play a role. To examine these issues, we created a neural model consisting of paired cerebral hemispheric regions interacting via the corpus callosum. The model was trained to generate the correct sequence of phonemes for 50 monosyllabic words (simulated reading aloud) under a variety of assumptions about hemispheric asymmetries and callosal effects. After training, the ability of the full model and each hemisphere acting alone to perform this task was measured. Lateralization occurred readily toward the side having larger size, higher excitability, or higher-learning-rate parameter. Lateralization appeared most readily and intensely with strongly inhibitory callosal connections, supporting past arguments that the effective functionality of the corpus callosum is inhibitory. Many of the results are interpretable as the outcome of a "race to learn" between the model's two hemispheric regions, leading to the concept that asymmetric hemispheric plasticity is a critical common causative factor in lateralization. To our knowledge, this is the first computational model to demonstrate spontaneous lateralization of function, and it suggests that such models can be useful for understanding the mechanisms of cerebral lateralization.

Algorithms↗
PubMed2005

Corpus callosum atrophy in Wernicke's encephalopathy.

BACKGROUND AND PURPOSE: Neuropathologic changes in Wernicke's encephalopathy (WE) involve variable brain structures. Corpus callosum involvement in WE, however, is largely unknown. The authors investigated the degree and the pattern of corpus callosum changes in WE according to the etiologies. METHODS: Nineteen patients with WE (between 34 and 81 years) and 19 age- and sex-matched control participants were included. The total cross-sectional callosal area and 5 callosal subregions (C1-C5) were measured by tracing outer margins in the midsagittal sections. Subregions were determined by placing radial dividers with 10 rays. The pixel numbers for corpus callosums were calculated, and the values obtained were adjusted for head size variations. RESULTS: The causes of WE were alcoholism (10), intestinal surgery (5), anorexia (3), and hyperemesis gravidarum (1). The mean size of the total corpus callosum was significantly reduced in alcoholic WE (P< .001; 527.8 +/- 70.8 mm2 for alcoholic WE; 664.6 +/- 58.1 mm2 for the corresponding controls), but not in nonalcoholic WE. In subregion analysis, prefrontal callosum (C2) atrophy was the most prominent in alcoholic WE. In contrast, only splenium (C5) was atrophied in nonalcoholic WE. The degree of atrophy did not change throughout the follow-up period (mean 5.3 weeks). CONCLUSION: This study suggests that the extent and location of corpus callosum atrophy differs between alcoholic WE and nonalcoholic WE, implying separate contribution of alcohol neurotoxicity and nutritional deficiency.

Adult↗
PubMedDate not supplied

Correction of clawtoes by the Girdlestone-Taylor flexor-extensor transfer procedure.

Several techniques have been suggested for correction of clawtoe deformities in the lateral toes, ranging from multiple arthrodesis of the interphalangeal joints to phalanx resections, partial or total amputation of the impaired toes. An evaluation of the flexor-extensor transfer procedure is the basis of this study. Between 1977 and 1983, 39 feet were operated on in 31 patients, presenting a wide variation in etiology, degree of deformity, and symptoms. Average age at the time of surgery was 57.5 (16 to 80). All of the patients were available for recall and were able to return for an interview and examination. Average length of follow-up was 38 months (range, 10-80 months). The report includes a general discussion of the deformities, description of the operative technique, and the results obtained in our series. Assessment emphasized a subjective report including patient satisfaction, cosmetic result, relief of pain, and objective examination to evaluate the presence of recurrent callosities, range of movement at the metatarsophalangeal joint, and degree of residual passive mobility of the toes. Reduction of metatarsalgia and callosities with improved shape of the toes was achieved in most cases. Our experience indicates that the treatment can be recommended for use in the elderly, too, in appropriate cases. Radical procedures are rarely accepted for cosmetic as well as for functional reasons.

Adolescent↗
PubMed1994

Calcaneal dome osteotomy: a new procedure for revising triple arthrodesis.

A preliminary report of a new calcaneal osteotomy is presented. Five patients ranging in age from 18 to 35 years underwent a calcaneal dome osteotomy. They all had painful and significant foot deformity, recurrent tenosynovitis, callosities, and shoe wear problems. The osteotomy was developed to correct the deformity present in patients that had a previous triple arthrodesis. The crescentic shape of the osteotomy allowed for the correction of various degrees and patterns of deformity with accuracy and provided a broad area of contact resulting in osteotomy union. The results achieved by this new technique showed that deformity was corrected, callosities had disappeared, and all the osteotomies were healed. All patients were satisfied by the procedure.

Adolescent↗
PubMed2003

Callosum and movement control: case reports.

This article explores the role of directionality of callosal traffic (codified as handedness), based on personal clinical observations and a critical review of the literature. Based on this evidence, a technical definition of handedness is offered as opposed to the behavioral method in use until now. In the vast majority of right-handers neural and behavioral handedness match. The situation is the opposite in left-handers where two thirds of them are wired to be right-handers, causing the well-known heterogeneity seen in left-handed cohorts. The callosum-length proximity of the dominant side of the body to the command center in the major hemisphere is the source of its neurophysiological superiority compared to the nondominant side. Clinical syndromes in which the new scheme are manifested are reviewed, indicating the existence of an excitatory influence by the neuronal aggregate devoted to voluntary actions, housed in the major hemisphere, on their counterparts in the minor hemisphere. The latter is exclusively devoted to volitional movements occurring on the nondominant side. Thus, it is the directionality of callosal traffic that is responsible for cerebral asymmetries seen in the motor realm.

Adult↗
PubMed2006

Laterality of seizure onset and the simple reaction time: revamping the Poffenberger's paradigm for seizure surgery.

BACKGROUND: Crossed-uncrossed differentials (CUDs) are viewed as surrogates for interhemispheric transfer time (IHTT). Not uncommonly CUDs assume statistically significant negative values (inverted CUDs). This raises doubts of the accepted interpretation of CUDs, i.e. intra- and inter-hemispheric routings of signals in uncrossed and crossed responses, respectively. METHOD: Based on the evidence supporting directionality in callosal traffic, data are provided indicating that callosal transfers exclusively involve non-dominant responses and such transfers are modality non-specific. The evidence also indicates that neural handedness corresponds to behavioral only in a statistical manner and the former remains unchanged regardless of the subject's life experience. RESULTS: The neurally dominant side is the side that is directly connected to the major hemisphere (command center). The connection of the non-dominant side to the command center is via the corpus callosum; therefore, a delay occurs in the reaction time of all non-dominant effectors, corresponding to IHTT. Accordingly, negative CUDs indicate a mismatch of neural and behavioral (avowed) handedness of the subject. This group comprises a minority of 15-20% of the population. CONCLUSION: Comparing the response time of symmetrically located effector is a robust way of lateralizing a person's major hemisphere. The latter is also the site of initiation of seizures, as the minor hemisphere is bereft of independent motor activity. Sensory signals arising from the nondominant side of the body traverse the callosum before reaching the major hemisphere. Searching for ipsilateral somatosensory evoked potentials provides another approach in lateralizing the non-dominant side of the body (ipsilateral to the major hemisphere). Practical uses of a conceptually revamped Poffenberger paradigm in neurosurgery are briefly reviewed.

Cerebral Cortex↗