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Chiari I malformation associated with callosal dysgenesis and ectopic neurohypophysis.

In patients with Chiari I malformation there usually is no anomaly of the supratentorial structures. In this communication we report a patient with Chiari I malformation, callosal dysgenesis, and an ectopic neurohypophysis. Both the splenium and the rostrum of the corpus callosum were hypoplastic, suggesting an intrinsic error which operated around 20 weeks of gestation. This may provide a clue for the time of onset of Chiari I malformation.

Agenesis of Corpus Callosum↗
PubMed1991

Frontal and callosal neuropsychological performances in schizophrenia. Further evidence of possible attention and mnesic dysfunctions.

Some level of frontal and callosal dysfunction has been reported in patients with schizophrenia. In the present study 68 normal controls and 117 schizophrenic patients were administered the Wisconsin Card Sorting Test (WCST), which involves the function of the frontal areas, and the Auditory Comprehension Test (ACT) which involves the corpus callosum and to a lesser degree attention and mnesic mechanisms. WCST correctly discriminated 69.8% of schizophrenics and 74.2% of controls, ACT 86.7% of schizophrenics and 90.2% of controls. Moreover, schizophrenics correctly classified by the WCST performed more poorly than schizophrenics incorrectly classified by the WCST on the related ACT indices for the attention and mnesic mechanisms. There were no differences in present age, age at onset, duration of the illness, diagnostic subtype and course of the disease between correctly and incorrectly classified schizophrenics by the WCST and the ACT. These data indicate a prevalent malfunctioning of attention and mnesic mechanisms in schizophrenia. Finally there seems to be no relationship between these neurofunctional abnormalities and demographic and clinical characteristics of the disease.

Adult↗
PubMed2005

Paralinguistic processing in children with callosal agenesis: emergence of neurolinguistic deficits.

Recent research revealed impaired processing of both nonliteral meaning and affective prosody in adults with agenesis of the corpus callosum (ACC) and normal intelligence. Since normal children have incomplete myelination of the corpus callosum, it was hypothesized that paralanguage deficits in children with ACC would be less apparent relative to their peers. The Familiar and Novel Language Comprehension Test (FANL-C) and Prosody Test were given to 18 children with ACC and normal intelligence and 17 controls matched for age (7-13 years), education, and IQ (83-122). When controlling for age, children with ACC were significantly poorer in comprehension of the precise meaning of both literal and nonliteral items on the FANL-C. Adults with ACC had previously been shown to have difficulty only on nonliteral items. The effect size for nonliteral comprehension in children with ACC was smaller than that seen in adults. There was only a trend for the child ACC group to perform worse on the recognition of affective prosody. Thus, while deficits in paralinguistic processing were apparent, children with ACC were not as clearly different from age peers as adults, and were equally deficient at comprehending literal and nonliteral expressions. The differences in results between adults and children with ACC are thought to reflect incomplete callosal development in normal children, and the importance of the corpus callosum in the early stages of the development of the ability to process literal language.

Adolescent↗
PubMed2004

Effects of callosal agenesis on rotational side preference of BALB/cCF mice in the free swimming test.

In order to test the hypothesis that the ontogenetic development of the corpus callosum is related to the establishment of behavioral laterality, the rotatory behavior in the free swimming test was studied in male mice of the BALB/cCF strain, in which approximately 20% of the animals present total or partial callosal agenesis. All animals were submitted to three sessions of the free-swimming rotatory test in three different sessions (diameter of the recipient = 21 cm; session duration = 5 min; inter-test interval = 48 h). The number and direction of the 30 and 360 degrees turns were recorded. Animals were classified as side-consistent turners (to the right or to the left) when they did not change their preferred side of rotation in all three sessions and in both turning units. In general our results suggested that acallosal animals present more pronounced laterality than normal ones. In the acallosal group, the percentage of consistent turners was significantly higher than that of non-consistent turners. The percentage of animals that presented strong turning preferences in the acallosal group was higher than in the normal group. In first session, the acallosal group presented a higher average number of turns to preferred side than the normal group. Taken together, our results constitute an endorsement to the hypothesis that the normal development of the corpus callosum is related to the establishment of cerebral laterality.

Agenesis of Corpus Callosum↗
PubMed2005

Arthrogryposis multiplex congenita with callosal agenesis and dentato-olivary dysplasia.

We report the autopsy case of a boy with arthrogryposis multiplex congenita, associated with callosal agenesis and dentato-olivary dysplasia. The patient manifested with dysmorphic facial features and suffered from intractable epilepsy during the neonatal period. These sets of complications suggest that a common molecular mechanism may be involved in the development of corpus callosum and the folding of the dentate and inferior olivary nuclei. Deep brain structures, including the brainstem and the cerebellum, may be involved in the pathophysiology of symptomatic generalized epilepsy. The differential diagnoses for the clinical and pathological characteristics of this patient are discussed.

Agenesis of Corpus Callosum↗
PubMed2005

Sound lateralization in subjects with callosotomy, callosal agenesis, or hemispherectomy.

The question of whether there is a right-hemisphere dominance in the processing of auditory spatial information in human cortex as well as the role of the corpus callosum in spatial hearing functions is still a matter of debate. Here, we approached this issue by investigating two late-callosotomized subjects and one subject with agenesis of the corpus callosum, using a task of sound lateralization with variable interaural time differences. For comparison, three subjects with left or right hemispherectomy were also tested by employing identical methods. Besides a significant reduction in their acuity, subjects with total or partial section of the corpus callosum exhibited a considerable leftward bias of sound lateralization compared to normal controls. No such bias was found in the subject with callosal agenesis, but merely a marginal reduction of general acuity. Also, one subject with complete resection of the left cerebral cortex showed virtually normal performance, whereas another subject with left hemispherectomy and one subject with right hemispherectomy exhibited severe deficits, with almost total loss of sound-lateralization ability. The results obtained in subjects with callosotomy indicate that the integrity of the corpus callosum is not indispensable for preservation of sound-lateralization ability. On the other hand, transcallosal interhemispheric transfer of auditory information obviously plays a significant role in spatial hearing functions that depend on binaural cues. Moreover, these data are compatible with the general view of a dominance of the right cortical hemisphere in auditory space perception.

Acoustic Stimulation↗
PubMed2006

Minicolumnar structure in Heschl's gyrus and planum temporale: Asymmetries in relation to sex and callosal fiber number.

AIM: To investigate the cytoarchitectural basis of asymmetries in human auditory cortex. Minicolumn spacing and number, and regional cortical volume and surface area were measured in the primary auditory region (Heschl's gyrus, HG) and posterior auditory association region (planum temporale, PT) in 17 neurologically normal adults (10 female, seven male). PT surface area, minicolumn spacing and minicolumn number were greater in the left hemisphere. HG surface area was larger in the left hemisphere. Asymmetries of minicolumn number in primary and association auditory regions correlated with axonal fiber numbers in the subregions of the corpus callosum through which they project. PT minicolumn number was more asymmetrical in men than women but total number was similar in the two sexes. We conclude that asymmetry of the surface area of the PT is a function of minicolumn spacing. Fewer callosal projections between the plana are found when the minicolumn spacing is more asymmetrical.

Aged↗
PubMed1992

Symmetric synapses formed by callosal afferents in rat visual cortex.

Following an electron microscopic examination of 437 degenerating terminals of callosally projecting axons in layer II/III at the 17/18a border, it has been found that some of these terminals form symmetric synapses with dendritic shafts (1.83%), pyramidal cell bodies (1.37%) and dendritic spines (0.46%). The remainder of the axon terminals (96.33%) form asymmetric synapses, mainly with dendritic spines although a few form synapses with dendrites. These results suggest that in the rat visual cortex the corpus callosum is a source of both inhibitory and excitatory input to the contralateral hemisphere.

Afferent Pathways↗
PubMed1997

Bilateral coupling in learned blinking: effects of lesion aimed at callosal disconnection of the cat motor cortex.

The effects of selective transection of the rostralmost portion of the corpus callosum, which contains fibers interconnecting the motor cortices of the two hemispheres, on interocular temporal coupling in the initiation of learned symmetrical blinking were examined in 5 cats trained to blink in response to a 500-ms tone paired with 100-ms airpuffs randomly delivered to either eye (alternate airpuff; 3 animals) or simultaneously directed to both eyes (bilateral airpuff; 2 animals) 400 ms after tone onset. Lesioning had no effect on ability to respond, but did cause a significant increase in the mean conditioned response (CR) latencies of both eyes in all subjects. In the intact cats, a statistically significant difference between the mean CR latencies of the two eyes (hereafter called side superiority) was found in three animals, two of which exhibited superiority of the left eye. After lesioning, it was found that the right eye proved superior to the left eye in four subjects. Both before and after lesioning, side superiority was not due to the ability of one eye to give CRs consistently shorter than those of the other eye, but it crucially depended on the higher proportion of trials in which the superior eye led. A linear correlation between CR latencies of the right and left eye was found in all animals both before and after lesioning. It is suggested that subsequent to lesioning aimed at callosal disconnection of the motor cortex, the effects on initiation of learned symmetrical blinking are the consequences of withdrawal of both bilaterally balanced modulatory influences to both eyes and lateralized modulatory influences to the left eye.

Animals↗
PubMed1991

Limitations of interhemispheric extracallosal transfer of visual information in callosal agenesis.

A 57-year-old patient with callosal but not anterior commissure agenesis was investigated with a visual interfield comparison and a naming task. Stimuli were presented tachistoscopically either bilateral-simultaneously or unilaterally in the LVF and/or RVF. The stimuli presented bilaterally differed with respect to their degree of similarity. Whereas the patient was able to detect gross differences between stimuli presented in the left and right half-field, he was impaired at discriminating similar and identical stimuli across the half-fields. Identification by naming was correct on unilateral presentation of a stimulus, while with bilateral presentation of two stimuli, errors increased considerably with the stimulus named second. The data are thought to indicate a limited capacity of the extracallosal commissures, probably the anterior, for the transfer of visual information.

Agenesis of Corpus Callosum↗
PubMed1983

Elaboration of representations in a left-handed subject with callosal damage.

Four experiments were carried out in a familial left-handed patient who, following a vascular accident, underwent a callosal lesion and had a right hemianopia. Previous observations by Poncet et al. (1978) demonstrated that both hemispheres controlled expressive language. In the first experiment haptic unimanual exploration showed that each system (right hand/left hemisphere; left hand/right hemisphere) elaborated very different mental representations of the stimulus and gave different types of verbal report of it (naming and talking about). In the second experiment, manual exploration of a maze in the search of a target was performed randomly with the right hand and following a competent spatial strategy with the left hand. The third experiment investigated the ability of the right hemisphere to discriminate the phonetic features of the names of objects that were identified but not named. In the fourth experiment, recognition memory of objects was shown to be better when information was processed by the left hand - right hemisphere system than by the right hand - left hemisphere system. Findings are discussed in terms of verbal vs. non-verbal processes and of perceptual awareness.

Adolescent↗
PubMed1985

Anatomical and behavioral study of a case of asymptomatic callosal agenesis.

This paper presents radiological and behavioral observations of a case of asymptomatic congenital agenesis of the corpus callosum. CT scan data indicated that a small portion of the corpus callosum might have been preserved, although this is difficult to demonstrate with the usual criteria. Nuclear magnetic resonance showed the small preserved portion on the sagittal plane. The results of the behavioral studies agree well with already published data: the agenesis of the callosum does not induce a split-brain syndrome but does cause slight motor disturbances, an improvement of the ipsilateral paths of control, and the development of extra-callosal interhemispheric pathways.

Adolescent↗
PubMed1988

Interhemispheric transfer of spatial tactile information in callosal agenesis and partial commissurotomy.

The De Renzi Rod Test was used to investigate the transfer of spatial tactile information between hands in acallosals and partial commissurotomy patients. The right-handed performance of young acallosals was impaired, confirming the results of an earlier study by Meerwaldt (1983). The adult acallosals, with one exception, showed no difference between right and left hand performances. Two partial callosotomy patients with sparing of the most caudal parts of the body of the callosum showed no difference between the hands. A third callosotomy patient with little, if any, sparing of the most caudal part of the body of the callosum showed a marked impairment when performing the tactile task with the right hand. The unimpaired performances of the adult acallosals are attributed to the use of ipsilateral pathways and the development of behavioural strategies. The callosotomy patients' results are consistent with the mapping by Pandya and Seltzer (1986) of the interhemispheric callosal pathways between the cortical parietal areas in non-human primates.

Adult↗
PubMed1996

Callosal transfer of finger localization information in phonologically dyslexic adults.

Dyslexia, particularly phonological dyslexia, has been hypothesized to be associated with deficits in interhemispheric interactions mediated by the corpus callosum. Twenty-one dyslexic subjects were compared to 21 controls on the Finger Localization Test in order to observe patterns of tactile-motor integration and interhemispheric collaboration. When compared to control subjects, dyslexics showed consistent deficits in finger localization, particularly when more complex trials had to be completed. When subjects were re-grouped according to phonological processing ability (regardless of diagnostic group membership), subjects with lower phonological processing scores were found to perform poorly on complex trials of finger localization, particularly on those trials which reflect callosal transfer of finger localization information from one hemisphere (hand) to the other. These results suggest that interhemispheric transfer of information is critical to efficient phonological processing.

Adolescent↗
PubMed1999

Callosal disconnection syndrome in a left-handed patient due to infarction of the total length of the corpus callosum.

We report on a left-handed patient with an ischemic infarction affecting exclusively the total length of the corpus callosum. This lesion clinically correlated with an almost complete callosal disconnection syndrome as described in callosotomy subjects, including unilateral verbal anosmia, hemialexia, unilateral ideomotor apraxia, unilateral agraphia, unilateral tactile anomia, unilateral constructional apraxia, lack of somesthetic transfer and dissociative phenomena. Despite the patient's left-handedness, his pattern of deficits was similar to the disconnection syndrome found in right-handers. Our report focusses on motor dominance and praxis. We followed-up the improvement in left apraxia and investigated the ability to initiate and learn a new visuo-motor skill. The results permit two tentative assumptions: (1) that the improvement in left apraxia was due to a compensatory increase in ipsilateral proximal muscle control, and (2) that motor dominance, i.e. the competence to initiate and learn a new movement pattern, was hemispherically dissociable from manual dominance in the sense of praxis control.

Apraxias↗
PubMed1999

Bilateral field advantage and evoked potential interhemispheric transmission in commissurotomy and callosal agenesis.

The role of the corpus callosum versus other cerebral commissures in the interhemispheric integration of visual information was studied in four individuals with complete agenesis of the corpus callosum, two individuals with partial agenesis, one total commissurotomy patient, and normal individuals. Evoked potential (EP) indices of interhemispheric transmission of visual sensory responses were observed during matching of unilateral and bilateral visual field letters and patterns. Neither the commissurotomy nor any of the acallosal patients had ipsilateral hemisphere visual EPs (P1 and N1), demonstrating that the posterior callosum is necessary for interhemispheric transmission of these components of visual evoked potentials. While the commissurotomy patient could not compare bilaterally presented letters, the anterior commissure of the acallosal patients appeared to be sufficient for interhemispheric comparison of single letters. However, bilateral comparison of more complex visual patterns resulted in considerable difficulty for complete agenesis patients, while comparison of patterns was more nearly normal when anterior callosal fibers were present (partial agenesis).

Adolescent↗
PubMed2004

Some effects of cortical and callosal damage on conscious and unconscious processing of visual information and other sensory inputs.

Although new methods of investigation from the molecular level to cognition are promoting major advances in the study of the functions of the human brain, the analysis of behavioral and psychological deficits following brain damage is still a major tool for the understanding of cerebral organization. The present paper reviews some aspects of work on functional losses and residual abilities following cortical damage that have allowed to distinguish conscious and unconscious levels of visual input processing. Attention is given to the possible contribution of residual conscious vision of color to unconscious form analysis in visual agnosia. The paper also reviews findings on temporary and permanent deficits that occur after selective lesions of a prominent input-output system of the cerebral cortex, the corpus callosum, with the aim of assessing the possibility of establishing a functional callosal topography.

Animals↗
PubMed2004

Facilitation of motor skill learning by callosal denervation or forced forelimb use in adult rats.

Unilateral forelimb sensorimotor cortex lesions in adult rats produce a compensatory hyper-reliance on the forelimb ipsilateral to the lesion and temporally related glial and neural plasticity in the contralateral homotopic cortex. Recently, we found that these lesions enhance acquisition of a motor skills task with the ipsilateral, non-impaired, forelimb in comparison to shams. This effect might be related to a denervation-induced facilitation of neuroplastic changes in the motor cortex opposite the lesion and/or to the lesion-induced hyper-reliance on the non-impaired forelimb. The present study assessed whether increased forelimb use, denervation of motor cortical callosal afferents, or a combination of the two influences acquisition of a skilled reaching task. Adult rats with partial corpus callosum transections or sham procedures were either forced to rely on one forelimb or permitted normal forelimb use for 8 days. Rats were then trained for 14 days with their previously non-preferred forelimb (and the forced-use limb) on a unilateral pellet retrieval task. Compared to shams, transections produced a greater acquisition rate and asymptotic performance level on the task. Forced-use improved reaching performance relative to controls, but this effect was less enduring than the improvements produced by transections alone. The addition of forced-use to transections did not further enhance performance. These findings suggest that denervation-induced changes are likely to be a major contributor to the enhanced learning observed after unilateral sensorimotor cortex lesions.

Animals↗