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PubMed1992

Brain connections: interhemispheric fiber systems and anatomical brain asymmetries in humans.

The present review summarizes some results of a research program oriented to determine the anatomical substrates of interhemispheric communication in humans, as seen in postmortem material. One main finding is a sensible pattern of histological differentiation along the corpus callosum, indicating specific properties of interhemispheric conduction for axonal fibers involved in different brain functions. Callosal regions that connect primary and secondary sensory and motor areas are characterized by a large proportion of fast-conducting, large-diameter fibers, while regions connecting the so-called association areas and prefrontal areas bear a high density of slow-conducting, lightly myelinated and thin fibers. These findings are interpreted in a functional context, suggesting that the fast-conducting fibers connecting sensory and motor areas contribute to fuse the two hemirepresentations in each hemisphere. It has also been determined that an increased callosal area indicates an increased number of callosal fibers, a finding that validates previous morphometric studies done in several laboratories. No sex differences in callosal size, shape, or in callosal fiber composition were found. Finally, an inverse relation was found between the anatomical asymmetries in the size of the Sylvian fissure and the size and number of fibers in specific segments of the corpus callosum. There were sex differences in terms of the particular callosal regions showing a significant correlation with asymmetries, and in terms of the fiber types that were correlated with asymmetries.

Animals↗
PubMed1992

Functional classes of cortical projection neurons develop dendritic distinctions by class-specific sculpting of an early common pattern.

We demonstrate in rat neocortex that the distinct laminar arrangements of the apical dendrites of two classes of layer 5 projection neurons, callosal and corticotectal, do not arise de novo, but are generated later in development from a common tall pyramidal morphology. Neurons of each class initially elaborate an apical dendrite in layer 1. Layer 5 callosal neurons later lose the segments of their apical dendrite superficial to layer 4, generating their characteristic short pyramidal morphology. The apical dendrite of layer 5 callosal neurons later lose the segments of their apical dendrite superficial to layer 4, generating their characteristic short pyramidal morphology. The apical dendrite of layer 5 callosal neurons is actively eliminated, rather than passively displaced, as superficial cortical layers expand. Corticotectal neurons and callosal neurons superficial to layer 5 maintain their apical dendrite to layer 1. Therefore, this selective dendritic loss occurs in a neuron class-specific manner and, within the callosal population, in a lamina-specific manner. Based on our additional observations and other studies, this phenomenon can be extended to other types of cortical projection neurons. These findings show that selective dendritic elimination plays a major role in shaping the functional architecture characteristic of the adult cortex.

Animals↗
PubMed1990

Axon overproduction and elimination in the corpus callosum of the developing rhesus monkey.

We have studied the cytological and quantitative aspects of axon addition and elimination in the corpus callosum of the developing rhesus monkey. Electron microscopic analysis reveals that during fetal development the number of callosal axons increases from 4 million at embryonic day 65 (E65) to 188 million at birth (E 165). Thus, the number of callosal axons in newborn monkeys exceeds the number present in the adult (an average of 56 million; LaMantia and Rakic, 1990a) by at least 3.5 times. Although there is some variability among the 11 fetal and newborn monkeys examined, there appears to be a progressive increase in the total number of callosal axons from midgestation through birth. The presence and numbers of growth cones from E65 through birth suggests that axon addition occurs exclusively during this period. There is no ultrastructural or quantitative indication of postnatal axon addition. After birth, about 70% of the axons in the callosum are eliminated in 2 phases. During the first phase, which includes the first 3 postnatal weeks, approximately 80 million axons are lost at an estimated rate of 4.4 million/d or 50/sec. During the second phase, which continues for the following 3 months, an additional 50 million axons are eliminated at a rate of 0.5 million/d or 5/sec until the adult value is reached. A discontinuous distribution of different classes of axons along the anterior-posterior axis of the tract reminiscent of the pattern seen in the adult is detectable before the onset of the first phase of axon elimination. Since the basic topography and terminal field patterns of callosal projections are well established before birth in all regions of the monkey cortex examined so far (Goldman-Rakic et al., 1983; Killackey and Chalupa, 1986; Dehay et al., 1988; Schwartz and Goldman-Rakic, 1990), we conclude that the massive postnatal elimination of callosal axons described here is unlikely to play a significant role in the development of discretely patterned callosal projection zones or their columnar terminations. The coincidence of axon elimination and the increase in synaptic density throughout the primate cerebral cortex during the first 6 postnatal months (Rakic et al., 1986), however, suggests that supernumerary axons may be lost during a process that results in the local proliferation of synapses from a subset of initial interhemispheric projections.

Aging↗
PubMedDate not supplied

Trauma to the corpus callosum: MR features.

The frequency, distribution, and appearance of corpus callosum injuries were evaluated with MR and CT in a prospective study of 78 patients with acute (n = 63) and chronic (n = 15) head injuries. Traumatic lesions of the corpus callosum were detected in 47% of patients. MR was significantly (p less than .001) more sensitive than CT in the detection of callosal injuries. MR and CT visualized 100% and 27%, respectively, of the traumatic callosal lesions that were detected in the study population. The majority of lesions were located in the splenium but a few were also found in the body and genu. Patients with callosal injuries had a significantly higher incidence of primary brainstem injury (p less than .02) as well as a greater number of subcortical gray-matter (p less than .05) and diffuse axonal "shear" (p less than .001) lesions. In addition, patients with callosal injuries had a significantly higher incidence of traumatic lesions of the septum pellucidum (p less than .007) and fornix (p less than .001). Intraventricular hemorrhage occurred significantly more often (p less than .002) in patients with callosal injuries, especially if traumatic lesions of the fornix or septum pellucidum were also present. Patients with callosal injuries had significantly lower initial Glasgow Coma Scale scores (mean, 6.6) than those without injuries (mean, 10.7) (p less than .001). Injury to the corpus callosum occurs much more often with nonfatal head injuries than had been believed previously.

Adolescent↗
PubMed1985

Comparison of the distributions of ipsilaterally and contralaterally projecting corticocortical neurons in cat visual cortex using two fluorescent tracers.

Using the retrograde fluorescent tracers Fast Blue and Diamidino Yellow we have studied the callosal and ipsilateral corticocortical connections between the cat's area 17/18 border region and the posteromedial lateral suprasylvian visual area (PMLS), as well as the callosal connections of each of these regions with its contralateral homologue. The main goal was to determine whether single cortical neurons project with branching axons to more than one cortical target. In addition, the double-labeling technique enabled us to examine, within a single section of cortical tissue, the relative distributions of neurons with different cortical targets. Most corticocortical neurons labeled in the area 17/18 border region and in area PMLS projected to only one of the cortical injection sites tested. When two callosal neuron types were labeled in the same area, no double-labeled neurons were found. When ipsilateral corticocortical and callosal neurons were labeled in combination, a few double-labeled neurons were found in both cortical regions examined. The most common type of double-labeled neuron was located in area PMLS and projected bilaterally to the area 17/18 border region. Our findings regarding the laminar distributions of ipsi- and contralaterally projecting neurons are in agreement with previous studies. In addition, we have found that, for callosal neurons within the upper layers of areas 17 and 18, neurons projecting to the contralateral area 17/18 border are located in the lower half of layer II/III and in upper layer IV, whereas neurons projecting to contralateral area PMLS are restricted to the lower portion of layer II/III. In addition, for callosal neurons within the deep layers of area PMLS, neurons projecting to contralateral area PMLS are located throughout layers V and VI, whereas neurons projecting to the contralateral area 17/18 border are restricted to layer VI. There are numerous other possible targets for axon collaterals not examined in this paper. However, the scarcity of neurons with multiple projections demonstrated in this study reflects the high degree of specificity of cortical connectivity. This anatomical organization may be the basis for a precise channeling of differential information at the single neuron level.

Amidines↗
PubMed1996

Atrophy of the corpus callosum associated with cognitive impairment and widespread cortical hypometabolism in carotid artery occlusive disease.

OBJECTIVE: To investigate whether atrophy of the corpus callosum is associated with cognitive impairment and widespread cerebral cortical hypometabolism in carotid artery occlusive disease. PATIENTS: Twelve patients with unilateral internal carotid artery occlusive disease (1 with severe stenosis and 11 with occlusion) and no cortical infarction in the chronic stage (mean +/- SD age, 64 +/- 5 years). MAIN OUTCOME MEASURES: Midsagittal corpus callosum area-skull area ratio (on T1-weighted magnetic resonance images), the sum of the scaled scores of the 6 subtests on the Wechsler Adult Intelligence Scale-Revised (Digit Span, Arithmetic, Picture Arrangement, Object Assembly, Block Design, and Digit Symbol), and cerebral metabolic rate of oxygen (measured with position emission tomography by using the oxygen 15 steady-state technique). RESULTS: The degree of cognitive impairment varied but was strongly correlated with the severity of callosal atrophy (r = 0.92, P < .001). Patients with callosal atrophy and cognitive decline also showed decreased oxygen consumption in the bilateral cerebral cortices. Stepwise regression analysis revealed that the severity of white matter lesions, especially in the centrum semiovale, and that of cortical atrophy in the hemisphere with arterial disease were 2 important factors for callosal atrophy. CONCLUSIONS: Callosal atrophy is associated with cognitive impairment and widespread cerebral cortical hypometabolism in carotid artery occlusive disease without cortical infarction. Callosal atrophy might reflect the severity of the disconnection between cortical regions, and this may be an important factor in the development of cognitive impairment with widespread cortical hypometabolism in carotid artery occlusive disease without large cortical lesions.

Aged↗
PubMed1996

Comparative morphology of three types of projection-identified pyramidal neurons in the superficial layers of cat visual cortex.

The morphology and dendritic organization of corticocortical neurons in the superficial layers of area 18 that project to area 17 were studied by intracellular injection of lucifer yellow in the fixed-slice preparation. This corticocortical population contains primarily standard pyramidal cells, but occasional nonpyramidal, modified, fusiform, star, and inverted pyramidal cells were also seen. All cell types were present throughout layer 2 and in the upper and middle parts of layer 3. Standard pyramidal cells were found exclusively in lower layer 3. The mean somatic area of the area 17 projecting neurons was 251 microns 2. The width of basal dendritic fields was correlated to cell size for standard pyramidal cells but not for the other cell types. Next, the morphology and dendritic organization of the area 17 projecting neurons were compared to the pyramidal cells of the local horizontal patch networks and of the callosal system. The depth profile of the area 17 projecting and callosal pyramidal groups was virtually identical, peaking at 400 microns from the pial surface, whereas the local patch pyramidal group peaked at 281 microns. The local patch, area 17 projecting, and callosal pyramidal cells displayed increasingly larger mean somatic areas and basilar dendritic field width measurements. The number of basal dendritic branch points was greatest for callosal cells, and it was indistinguishable between local patch and area 17 projecting neurons. In the tangential plane, circular dendritic fields were observed on all callosal cells, but they were found on only approximately half of the local patch and area 17 projecting neurons. The remaining local patch and area 17 projecting neurons displayed mediolaterally and anteroposteriorly elongated basal dendritic fields, respectively.

Animals↗
PubMed1987

No sex-related differences in human corpus callosum based on magnetic resonance imagery.

Recent studies have reported sex-related differences in the morphology of the human corpus callosum in cadaver brains. To further investigate these reports, sagittal magnetic resonance image scans from 40 male and 40 female subjects were used to compare callosal morphology. Relative callosal measurements were calculated by morphometric analysis. Significant sex-related differences were not found for callosal areas, maximal callosal width, or callosal curvature. These results indicate the need for further study before claims of sex-related differences can be accepted.

Corpus Callosum↗
PubMed1977

Anatomy of interhemispheric connections in the visual system of Boston Siamese and ordinary cats.

In Siamese cats, previous studies have shown that a genetic mutation causes retinogeniculate fibers in each eye which arise from the temporal retina representing the 20 degrees of ipsilateral visual field adjacent to the vertical meridian to cross aberrantly in the optic chiasm, thereby terminating in the wrong lateral geniculate nucleus. The abnormality is expressed subsequently at the level of the visual cortex. This paper presents anatomical evidence that the pattern of commissural visual connections in the "Boston" variety of Siamese cat also is highly abnormal in comparison to that of ordinary cats. The topographical distribution of neurons supplying visual fibers to the splenium of the corpus callosum was studied in Boston Siamese and ordinary cats using the method of retrograde transport of horseradish peroxidase (HRP) following localized cortical injections made through a recording micropipette. In ordinary cats, after an HRP injection at the border between cortical areas 17 and 18, which represents the vertical meridian of the visual field, HRP-labeled cells in areas 17 and 18 of the opposite hemisphere were found only immediately adjacent to the 17-18 border, thus confirming the results of previous investigations. In Boston Siamese cats, the border represents a region in the ipsilateral visual field roughly 20 degrees away from the vertical meridian, and the vertical meridian representation is displaced to sites within areas 17 and 18 proper. When HRP was injected at the 17-18 border, labeled cells in the opposite hemisphere were located well within area 17 near the suprasplenial sulcus, and also well within area 18; few labeled cells were found at the 17-18 border. When an HRP injection was placed at the vertical meridian representation, again few HRP-labeled cells were found at the opposite 17-18 border, but instead most were found in area 17 slightly medial to the border, and in area 18 slightly lateral to it. Thee findings were complemented in an autoradiographic study in which orthograde transport of tritiated proline after a localized cortical injection was used to demonstrate the distribution of callosal terminals. Thus the pattern of callosal connections revealed in Boston Siamese cats, although anatomically different from that of ordinary cats, was nevertheless consistent with the proposal that cortical sites representing similar visual field coordinates in each hemisphere are appropriately interconnected via the corpus callosum. The laminar distribution of callosal connections was examined briefly. Layer III pyramidal cells of areas 17 and 18 supplied the majority of terminals to the opposite 17-18 border. Pyramidal cells of Layers II and VI, and Layer IVa in area 18, made a smaller contribution. In areas 17 and 18, the same cortical layers (II, III, and VI; and IVa in 18) were again the major sites of callosal termination. A clear projection to the base of layer I was also noted. The laminar distribution of callosal connections in ordinary and Boston Siamese cats were not substantially different.

Agenesis of Corpus Callosum↗
PubMed1981

The distribution of commissural terminations in somatosensory areas I and II of the grey squirrel.

The topographic distribution of somesthetic interhemispheric projections was studied in grey squirrels using the Fink-Heimer technique following large aspiration lesions of the corpus callosum. On the day of perfusion, receptive fields were determined for microelectrode recording sites in the first, S I, and second, S II, somatosensory areas of cortex, and small electrolytic lesions were made in order to identify some of these sites in prepared brain sections. The cortex was then separated from the rest of the brain, flattened, and cut parallel, so that with the aid of the reference lesions, the total pattern of degeneration could be related to a surface view of the brain and to previous electrophysiological maps of S I (Sur et al., '78) and S II (Nelson et al., '79). The results show that callosal terminations are unevenly distributed in S I and S II, and suggested that there are several categories of callosal inputs to S I. A major region of terminations is in the architectonically distinct "unresponsive zone" within SI, and perhaps in other similar, but narrower, specialized zones within and bordering S I, as previously described in rats (Ryugo and Killackey, '75; Wise and Jones, '76, '78; Akers and Killackey, '78). Other callosal projections terminate within the responsive regions of S I. These regions include at least some of the representation of the body midline, most clearly the midline of the representations of the upper and lower face, as well as regions unrelated to the midline of the body. Most of all of the S I cortex responsive to stimuli away from the midline on the upper and lower lips, the mystacial vibrissae, and the glabrous forepaw was almost free of direct callosal terminations. Except for a central core region, most of S II appears to receive a moderate distribution of callosal inputs.

Animals↗
PubMed1982

Axonal guidance during development of the great cerebral commissures: descriptive and experimental studies, in vivo, on the role of preformed glial pathways.

Do structures exist within the embryonic central nervous system that guide axons across the midline during development of the great cerebral commissures (corpus callosum, anterior commissure)? With the use of serial section and reconstructive computer graphic techniques we have found that during normal ontogeny of the mouse forebrain and before the arrival of the pioneer fibers of the corpus callosum at the midline, a population of primitive glial cells migrates medially (through the fused walls of the dorsal septum) from the ependymal zones of each hemisphere. At the midline, and well rostral to the lamina terminalis, these cells unite to form a bridgelike structure or "sling" suspended below the longitudinal cerebral fissure. The first callosal axons grow along the surface of this cellular bridge as they travel toward the contralateral side of the brain. The "sling" disappears neonatally. The fibers of the anterior commissure grow within the lamina terminalis along a different type of preformed glial structure. Movement of these axons occurs through an aligned system of glial processes separated by wide extracellular spaces. Do these transient glial tissues actually provide guidance cues to the commissural axons? Analyses of three situations in which the glial "sling" is genetically or surgically impaired or nonexistent indicate that this structure does, indeed, play an essential role in the development of the corpus callosum. We have analyzed (1) the embryonic stages of a congenitally acallosal mouse mutant (strain BALB/cCF), (2) several pouch stages of a primitive acallosal marsupial, Didelphys virginiana (opossum), and (3) animals in which the "sling" had been lesioned surgically through the uterine wall in the normal embryo (strain C57BL/6J). In the acallosal mouse mutant fusion of the septal midline is delayed by about 72 hours and the "sling" does not form. Although the would-be callosal axons approach the midline on schedule, they do not cross. Instead, the callosal fibers whirl into a pair of large neuromas adjacent to the longitudinal fissure. Similarly, in the opossum, fusion of the medial septal walls and formation of the glial "sling" are also lacking. However, in this species, instead of traveling dorsally, the "callosal" axons turn ventrally and pass contralaterally by way of the anterior commissure pathway. Surgical disunion of the glial "sling" also resulted in acallosal individuals. The callosal pathology in these affected animals mimicked exactly that of the genetically lesioned mutant. Our observations suggest that many different types of oriented glial tissues exist within the embryonic neural anlage. We propose that such tissues have the ability to influence the directionality of axonal movements and, thereby, play a crucial role in establishing orderly fiber projections within the developing central nervous system.

Agenesis of Corpus Callosum↗
PubMed1991

Patterns of synaptic input on corticocortical and corticothalamic cells in the cat visual cortex. I. The cell body.

Immunocytochemical and electron microscopic methods were used to examine the ultrastructure and synaptology of callosal and corticothalamic pyramidal cell somata in the cat visual cortex (area 17). Callosal and corticothalamic cells were labeled after injection of horseradish peroxidase (HRP) in the contralateral visual cortex or in the ipsilateral lateral geniculate nucleus. The synaptic relationship between each of the two populations of pyramidal cells and cells containing the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) was examined at the light and electron microscope level using the combined techniques of retrograde transport of HRP and GABA immunocytochemistry. We found that callosal and corticothalamic cell somata have an ultrastructure and synaptology that distinguishes them from each other. Reconstructions from electron micrographs of serial sections revealed that the vast majority of synapses (89-96%) on the cell body of pyramidal cells were formed by GABAergic axon terminals, and that within each population of pyramidal cells there was variability in the number and density of axosomatic synapses. Callosal pyramidal cells received a greater number and higher density of axosomatic synapses than corticothalamic cells. These data suggest that callosal cells receive more inhibition than corticothalamic cells at the level of their somata.

Animals↗
PubMed2006

Focal Wallerian degeneration of the corpus callosum in large middle cerebral artery stroke: serial diffusion tensor imaging.

PURPOSE: To detect lesion-related focal Wallerian degeneration (WD) changes in different segments of the corpus callosum (CC) in patients with large middle cerebral arterial (MCA) territory stroke using diffusion tensor imaging (DTI). MATERIALS AND METHODS: Eight patients underwent DTI scans at three different time points: six to eight weeks, 10-12 weeks, and beyond six months of stroke onset. Eight healthy age-matched controls were also scanned using the same protocol at three different time points. Region-of-interest (ROI) analysis was performed on seven segments of the CC to determine the fractional anisotropy (FA), mean diffusivity (MD), and corresponding callosal cross-sectional areas. RESULTS: On repeated-measures analysis of variance (ANOVA), a significant reduction in the FA values was observed from the first to the third study compared to controls, reflecting temporal degeneration in the rostrum, genu, rostral body, anterior midbody, and splenium of the CC. However, a significant temporal elevation in MD values was observed in only the rostral body and anterior midbody of the CC. This was associated with a significant region-specific reduction in the cross-sectional areas at time points beyond six months, and appears to be consistent with the loss of callosal structural components due to interruption of the cortico-callosal fibers secondary to WD. CONCLUSION: These results indicate that cortico-callosal topographical changes exhibit a significant temporal decline in observed FA values that is suggestive of cortico-callosal WD in patients with large MCA territory stroke.

Adult↗
PubMed1986

Motor responses mediated by orthodromic and antidromic activation of the rostral portion of the cat corpus callosum.

The effects of microstimulation of the rostral portion of the corpus callosum (CC) were examined in seven chronic cats submitted to either unilateral motor cortex ablation (5 preparations) or transection of the rostral two thirds of the CC (2 preparations) in order to identify the routes (ortho- or antidromic) followed by callosal impulses to provoke the motor effects. As in intact animals, motor responses in lesioned preparations consisted of very localized contractions of shoulder, whisker, or eyelid muscles, according to the stimulated sites. Unlike intact animals in which motor responses upon CC microstimulation were bilateral and symmetrical (Spidalieri and Guandalini 1983), in lesioned preparations they appeared contralaterally to the emitting hemisphere, i.e., they were contralateral to the stimulated callosal stump (split-brain preparations) and ipsilateral to the side of the cortical lesion (preparations with unilateral motor cortex ablation), regardless of the current intensity applied (up to a maximum of 50 microA). The unilateral motor responses occurred by the first day after lesion and persisted for the duration of the experiments which lasted to a month or more. Since orthograde degeneration of callosal fibres deprived of their somata has been shown by previous anatomical studies to be complete within 11 days after lesion, these results indicate that selective antidromic activation of callosal fibres is capable of eliciting motor responses. Thresholds for the motor effects in lesioned preparations proved to be from 1.3 to 3.9 (mean, = 2.4 +/- 0.7 SD) times higher than those found before motor cortex ablation. By 18 days after lesion a decrease of threshold currents for the motor responses was observed ranging from 6 to 37% (mean, = 24.2 +/- 13.6 SD), depending on the stimulated sites, relative to values previously found. The shortest train duration and the lowest frequency for minimum threshold were longer (40 vs. 30 ms) and higher (400 vs. 300 Hz), respectively in lesioned preparations than in intact controls. Moreover, a decrease in train duration or frequency provoked larger threshold increases in lesioned preparations than those observed in intact animals. As a whole, these results suggest that in intact animals the motor effects are also mediated by orthodromic callosal volleys.

Animals↗
PubMed2002

Myosin, microtubules, and microfilaments: co-operation between cytoskeletal components during cambial cell division and secondary vascular differentiation in trees.

The immunolocalisation of unconventional myosin VIII ('myosin') in the cells of the secondary vascular tissues of angiosperm (Populus tremula L. x P. tremuloides Michx. and Aesculus hippocastanum L.) and gymnosperm (Pinus pinea L.) trees is described for the first time and related to other cytoskeletal elements, as well as to callose. Both myosin and callose are located at the cell plate in dividing cambial cells, whereas actin microfilaments are found alongside the cell plate; actin and tubulin are both associated with the phragmoplast. Myosin and callose also localise to the plasmodesmata-rich pit fields in the walls of living cells, which are particularly abundant within the common walls between ray cells and between ray cells and axial parenchyma cells in the phloem and xylem. In those xylem ray cells that contact developing vessel elements and tracheids, myosin, tubulin, actin and callose are localised at the periphery of developing contact and cross-field pits; the respective antibodies also highlight the bordered pits between vessels and between tracheids. The aperture of the bordered pits, whose diameter diminishes as the over-arching border of these pits develops, also houses myosin, actin and tubulin. Myosin, actin and callose are also found together around the sieve pores of sieve elements and sieve cells. We suggest that an acto-myosin contractile system (a 'plant muscle') is present at the cell plate, the sieve pores, the plasmodesmata within the walls of long-lived parenchyma cells, and at the apertures of bordered pits during their development.

Actin Cytoskeleton↗
PubMed1989

Corpus callosum dimensions measured by magnetic resonance imaging in bipolar affective disorder and schizophrenia.

Magnetic resonance imaging (MRI) brain scans were performed on 24 schizophrenic patients, 22 bipolar affective patients, and 25 normal control subjects without medical or psychiatric illness using a Picker Vista 0.5 tesla scanner. Specific callosal regions and the cerebral area on the midsagittal slice were measured utilizing the technique described by Nasrallah et al. (1986). No significant differences were found among diagnostic groups in anterior, mid, or posterior callosal width, callosal area, cerebral area, callosal to cerebral area ratio, or the genu (first quartile) to splenium (fourth quartile) ratio. However, male subjects had a significantly greater callosal and cerebral area than female subjects. Gender differences were shown in the genu to splenium ratio in the control groups, but not the affective or schizophrenic groups. The implications of these gender differences are discussed in relation to other studies.

Adult↗
PubMed1991

Brain dysfunction during motor activation and corpus callosum alterations in schizophrenia measured by cerebral blood flow and magnetic resonance imaging.

Sixteen unmedicated (14 never-medicated, 2 with washout periods of 1-2 weeks) schizophrenic patients displaying positive symptoms (e.g., formal thought disorder, hallucinations, delusions) without negative symptoms (e.g., flattening of affect, loss of energy, anhedonia--type I patients), 15 unmedicated (with washout periods from 1 week to 2 years) patients with marked negative symptomatology [type II patients; criterion score below 15/above 35 on the Munich version of the Scale of Assessment of Negative Symptoms (SANS), respectively], and 31 matched normal controls were investigated using regional cerebral blood flow [rCBF; dynamic single-photon emission computerized tomography (SPECT) with Xenon-133 as tracer] and magnetic resonance imaging (MRI; spin-echo technique, T1 weighted, midsagittal cuts). rCBF measurements were performed during both resting conditions and simple motor activation. Separately, on the same day, we performed a planimetric evaluation of the callosal-brain ratio in all subjects using MRI. In accordance with previous results on a smaller sample, we found signs of diffuse bilateral rCBF hyperactivation in type I patients, as compared with signs of nonreactivity in type II schizophrenics. Both activation patterns were different from a strictly contralateral sensorimotor rCBF activation seen in normal persons (only 8 studied with SPECT). The planimetry of relative callosal area did not reveal differences compared to normal persons, when type I/II patients were taken together. However, the threefold increased variance as compared with that found in normal persons suggested biological heterogeneity in patients. We found an increase of relative callosal size in type I as compared with type II patients. In the light of some recent findings linking lack of laterality of several brain functions to increased callosal size, we propose lack of laterality/diffuse hyperactivation and increased callosal size to be connected with positive symptomatology/good prognosis schizophrenia, and vice versa.

Activities of Daily Living↗
PubMed1991

The relationship of hand preference to anatomy of the corpus callosum in men.

Area of the midsagittal section of the corpus callosum, particularly in the region of the isthmus, was found previously to be greater in non-consistent-right-handed than consistent-right-handed men in a sample of 15 postmortem cases. Seven cases were obtained subsequent to this analysis. The new cases showed the same association previously observed between hand preference and area of the corpus callosum and its isthmus. In addition, a high negative correlation was found between isthmal area and a quantitative score of the direction and magnitude of hand preference. In the new cases, handedness was predicted better than chance using statistical functions of callosal anatomy derived from the previous group of 15 cases. These results support a relationship between variation in callosal anatomy and handedness in men and the hypothesis of a relationship between callosal morphology and functional asymmetry. The lack of such a relationship among women suggests that the developmental mechanisms leading to callosal anatomical variation in relation to lateralization are influenced by sex hormones. Methodological issues in the use of magnetic resonance imaging for the quantitative study of callosal anatomy are discussed.

Autopsy↗