Effect of corpus callosum damage on ipsilateral motor activation in patients with multiple sclerosis: a functional and anatomical study

Functional MRI (fMRI) studies have shown increased activation of ipsilateral motor areas during hand movement in patients with multiple sclerosis (MS). We hypothesized that these changes could be due to disruption of transcallosal inhibitory pathways. We studied 18 patients with relapsing-remitting MS. Conventional T1- and T2-weighted images were acquired and lesion load (LL) measured. Diffusion tensor imaging (DTI) was performed to estimate fractional anisotropy (FA) and mean diffusivity (MD) in the body of the corpus callosum (CC). fMRI was obtained during a right-hand motor task. Patients were studied to evaluate transcallosal inhibition (TCI, latency and duration) and central conduction time (CCT). Eighteen normal subjects were studied with the same techniques. Patients showed increased MD (P < 0.0005) and reduced FA (P < 0.0005) in the body of the CC. Mean latency and duration of TCI were altered in 12 patients and absent in the others. Between-group analysis showed greater activation in patients in bilateral premotor, primary motor (M1), and middle cingulate cortices and in the ipsilateral supplementary motor area, insula, and thalamus. A multivariate analysis between activation patterns, structural MRI, and neurophysiological findings demonstrated positive correlations between T1-LL, MD in the body of CC, and activation of the ipsilateral motor cortex (iM1) in patients. Duration of TCI was negatively correlated with activation in the iM1. Our data suggest that functional changes in iM1 in patients with MS during a motor task partially represents a consequence of loss of transcallosal inhibitory fibers.     

Meta-analysis of magnetic resonance imaging studies of the corpus callosum in bipolar disorder

Objective: The corpus callosum (CC) plays a pivotal role in inter‐hemispheric transfer and integration of information and is a relatively understudied structure in bipolar disorder (BD). Magnetic resonance imaging (MRI) studies have reported callosal abnormalities in this condition but findings have been inconsistent. Structural changes affecting the CC may underlie functional abnormalities in BD and could contribute to, or explain the pathophysiology of, the condition. Method: A systematic review was carried out to identify, appraise and summarize MRI studies which compared callosal areas in BD with an unrelated control group. The findings were then synthesized using random effects meta‐analysis. Consideration was given to a number of variables to explain heterogeneity. Results: Five case–control studies were identified. Bipolar patients showed reduced callosal areas in comparison with healthy volunteers with no evidence of heterogeneity or publication bias. Conclusion: Findings from this study indicate that callosal areas are reduced in BD and suggest that a failure to integrate information across the hemispheres may contribute to the pathophysiology of the disorder. Further research is necessary to clarify the underlying cellular changes leading to these morphometric differences.     

Detecting abnormalities of corpus callosum connectivity in autism using magnetic resonance imaging and diffusion tensor tractography

The corpus callosum (CC) has emerged as one of the primary targets of autism research. To detect aberrant CC interhemispheric connectivity in autism, we performed T1-weighted magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI)-based tractography in 18 children with high functioning autism (HFA) and 16 well-matched typically developing (TD) children. We compared global and regional T1 measures (CC volume, and CC density), and the DTI measures [fractional anisotropy (FA), apparent diffusion coefficient (ADC), average fiber length (AFL), and fiber number (FN)] of transcallosal fibers, between the two groups. We also evaluated the relationships between scores on the Childhood Autism Rating Scale (CARS) and CC T1 or DTI measurements. Significantly less white matter density in the anterior third of the CC, and higher ADC and lower FN values of the anterior third transcallosal fiber tracts were found in HFA patients compared to TD children. These results suggested that the anterior third CC density and transcallosal fiber connectivity were affected in HFA children.     

A study of the septum pellucidum and corpus callosum in schizophrenia with MR imaging

Surface areas of the septum pellucidum, corpus callosum and the brain were measured from mid-saggital slices obtained with magnetic resonance imaging in 18 patients with schizophrenia and an equal number of normal volunteers. The patients showed larger septa and septo-brain ratios. These indices correlated with age in both patients and controls. In the patients, septal area also correlated with duration of illness. Changes in the septum pellucidum were unrelated to the intensity of positive and negative symptoms of schizophrenia. The patients had significantly longer corpora callosa, but the two groups did not differ on its size or the ratio between the latter and the mid-saggital slice area. Dimensions of the corpus callosum did not correlate with age, duration of the illness or positive and negative symptoms of schizophrenia. The anteroposterior elongation of the structure seemed to accompany enlargement of the septum pellucidum.     

Diffusion tensor imaging metrics of the corpus callosum in relation to bimanual coordination: Effect of task complexity and sensory feedback

When manipulating objects with both hands, the corpus callosum (CC) is of paramount importance for interhemispheric information exchange. Hence, CC damage results in impaired bimanual performance. Here, healthy young adults performed a complex bimanual dial rotation task with or without augmented visual feedback and according to five interhand frequency ratios (1:1, 1:3, 2:3, 3:1, 3:2). The relation between bimanual task performance and microstructural properties of seven CC subregions (i.e., prefrontal, premotor/supplementary motor, primary motor, primary sensory, occipital, parietal, and temporal) was studied by means of diffusion tensor imaging (DTI). Findings revealed that bimanual coordination deteriorated in the absence as compared to the presence of augmented visual feedback. Simple frequency ratios (1:1) were performed better than the multifrequency ratios (non 1:1). Moreover, performance was more accurate when the preferred hand (1:3–2:3) as compared to the nonpreferred hand (3:1–3:2) moved faster and during noninteger (2:3–3:2) as compared to integer frequency ratios (1:3–3:1). DTI findings demonstrated that bimanual task performance in the absence of augmented visual feedback was significantly related to the microstructural properties of the primary motor and occipital region of the CC, suggesting that white matter microstructure is associated with the ability to perform bimanual coordination patterns in young adults. Hum Brain Mapp, 2013. © 2011 Wiley Periodicals, Inc.     

The corpus callosum during postnatal undernourishment and recovery: A morphometric analysis of myelin and axon relationships

This study was designed to compare morphometric relationships between myelin lamellae and axons in undernourished and well nourished developing rats, and in rats nutritionally rehabilitated for two weeks. Although sampling techniques employed in this study were not specifically designed to compare numbers of myelinated fibers in test and control populations, we did observe a trend indicating a reduction in the numbers of myelinated fibers. The mean numbers of myelin lamellae, from an average of all myelinated axons, were not different in control and test population. However, regression analysis of axon sizes by numbers of myelin lamellae revealed significant differences from the normal in 21-day-old undernourished rats. For callosal axons of any size, there were too few myelin lamellae in the undernourished rats. A partial recovery was observed in relatively small fibers by 35 days of age, but no recovery was observed in larger sized fibers. Comparison of the frequency distribution of axon circumferences of myelinated fibers revealed an increase in average axonal caliber. Computation shows that although mean numbers of lamellae were not altered by undernourishment, the axons themselves are increased in size by about 10%. This unexpected result indicates that the relationship normally governing the numbers of myelin lamellae is altered by postnatal nutritional deprivation, and that the relatively larger axon calibers do not produce in the ensheating oligodendroglia any compensatory increase in the layers of myelin.     

Meta-analysis of magnetic resonance imaging studies of the corpus callosum in schizophrenia

OBJECTIVES: The corpus callosum plays a pivotal role in inter-hemispheric transfer and integration of information. Magnetic resonance studies have reported callosal abnormalities in schizophrenia but findings have been inconsistent. Uncertainty has persisted despite a meta-analytic evaluation of this structure several years ago. We set out to perform a further meta-analysis with the addition of the numerous reports published on the subject to test the hypothesis that the corpus callosum is abnormal in schizophrenia. METHOD: A systematic search was carried out to identify suitable magnetic resonance studies which reported callosal areas in schizophrenia compared to controls. Results from the retrieved studies were compared in a meta-analysis whilst the influence of biological and clinical variables on effect size was ascertained with meta-regression analysis. RESULTS: Twenty-eight studies were identified. Corpus callosum area was reduced in schizophrenia in comparison to healthy volunteers. This effect was larger in first episode patients. Similarly, heterogeneity detected among the studies was associated with course of illness indicating that chronic subjects with schizophrenia showed larger callosal areas. There was no evidence of publication bias. CONCLUSIONS: This study confirms the presence of reduced callosal areas in schizophrenia. The effect is of a larger magnitude at first presentation and less so in subjects with a chronic course generally medicated with antipsychotics.     

精神分裂症患者胼胝体的磁共振成像研究

目的　了解精神分裂症患者脑部胼胝体的改变及其与临床症状的关系。方法　选取符合中国精神障碍分类与诊断标准第3版精神分裂症诊断标准的住院患者95例(患者组),正常人20名(对照组),按规定序列作头颅核磁共振扫描,测定胼胝体长度、胼胝体宽度(膝部、体部、压部)。于入院当天及住院第4周后评价阳性和阴性症状量表(PANSS)。进行患者组与对照组、短病程组(≤5年, 30例)与长病程组( >5年, 65例)、家族性组(37例)与散发性组(58例)的胼胝体长度、宽度等比较。结果　(1)患者组胼胝体长度[ ( 6 8±0 4 )mm]明显短于对照组[ ( 8 0±0 4 )mm];t=3 24,P<0 05; (2)短病程组与长病程组胼胝体各测量值的差异无统计学意义; (3)家族性组胼胝体压部宽度[ (0 98±0 15)mm]小于散发性组[ (1 07±0 13)mm];t=-2 85,P<0 05; (4)PANSS阳性因子分与胼胝体长度呈正相关(r=0 21,P=0 04 ),反应缺乏减分率与胼胝体长度呈负相关(r=-0 21,P=0 04); (5)胼胝体长度、胼胝体体部宽度与起病年龄有密切关系(P=0 049,P=0 045)。结论　精神分裂症患者胼胝体缩小,尤以家族史阳性者为著,胼胝体异常有可能是精神分裂症症状的病理学基础之一。     

Role of the corpus callosum in the somatosensory activation of the ipsilateral cerebral cortex: an fMRI study of callosotomized patients

To verify whether the activation of the posterior parietal and parietal opercular cortices to tactile stimulation of the ipsilateral hand is mediated by the corpus callosum, a functional magnetic resonance imaging (fMRI, 1.0 tesla) study was performed in 12 control and 12 callosotomized subjects (three with total and nine with partial resection). Eleven patients were also submitted to the tactile naming test. In all subjects, unilateral tactile stimulation provoked a signal increase temporally correlated with the stimulus in three cortical regions of the contralateral hemisphere. One corresponded to the first somatosensory area, the second was in the posterior parietal cortex, and the third in the parietal opercular cortex. In controls, activation was also observed in the ipsilateral posterior parietal and parietal opercular cortices, in regions anatomically corresponding to those activated contralaterally. In callosotomized subjects, activation in the ipsilateral hemisphere was observed only in two patients with splenium and posterior body intact. These two patients and another four with the entire splenium and variable portions of the posterior body unsectioned named objects explored with the right and left hand without errors. This ability was impaired in the other patients. The present physiological and anatomical data indicate that in humans activation of the posterior parietal and parietal opercular cortices in the hemisphere ipsilateral to the stimulated hand is mediated by the corpus callosum, and that the commissural fibres involved probably cross the midline in the posterior third of its body.     

White matter abnormalities observed in bipolar disorder: a diffusion tensor imaging study

OBJECTIVES: An increased incidence in white matter abnormalities is among the most frequently reported brain change in patients with bipolar disorder. The objective of the present study was to examine white matter tract integrity, using diffusion tensor imaging (DTI), in bipolar patients and healthy comparison subjects. METHODS: Eleven DSM-IV bipolar I patients and 10 healthy age- and sex-matched controls were studied. DTI data were acquired on a 1.5 Tesla scanner. Fractional anisotropy (FA) and diffusivity (trace) were determined from axial images using region of interest (ROI) analyses. The ROIs were manually placed in the midline and forward projecting arms of the genu (anterior) and the midline of the splenium (posterior) of the corpus callosum. RESULTS: Bipolar patients had significantly higher FA in the midline of the genu compared with healthy controls. Regional white matter differences were also observed, with significantly lower FA in the genu than forward projecting regions in both groups and lower FA in the genu than the splenium in controls. CONCLUSIONS: Diffusion tensor imaging revealed significant microstructural differences in the genu, as measured by elevated FA in bipolar patients compared with healthy controls. These preliminary findings further support the hypothesis that anomalous frontal brain mechanisms may be associated with bipolar disorder.     

A histological study of the corpus callosum in chronic schizophrenia

As a followup to a post-mortem study of the brains of schizophrenic and control subjects where the corpus callosum was found to be significantly thicker anteriorly in early onset compared to late onset schizophrenia, histological sections of 18 schizophrenic, 7 manic-depressive, and 11 medical/surgical control subjects were prepared using a stain for glia and a stain for callosal fibers. A quantitative study of the concentration of glial cells and interhemispheric callosal fibers revealed no difference between groups. A neuropathologist unaware of the tissue origin rated the histological sections for gliosis. There was significantly more severe gliosis in the callosi of the late onset schizophrenics compared to early onset schizophrenics as well as the control group. These preliminary findings suggesting callosal pathology are discussed, and the need for further studies is stressed.     

Sex differences in associations between spatial ability and corpus callosum morphology

Rotating mental representations of objects is accompanied by widespread bilateral brain activations. Thus, interhemispheric communication channels may play a relevant part when engaging in mental rotation tasks. Indeed, links between mental rotation and dimensions of the corpus callosum—the brain's main commissure system—have been reported. However, existing findings are sparse and inconsistent across studies. Here we set out to further characterize the nature of any such links, including their exact location across the corpus callosum. For this purpose, we applied an advanced image analysis approach assessing callosal thickness at 100 equidistant points in a sample of 38 healthy adults (19 men, 19 women), aged between 22 and 45 years. We detected a sex interaction, with significant structure–performance relationships in women, but not in men. Specifically, better mental rotation performance was linked to a thicker female corpus callosum within regions of the callosal splenium, posterior midbody, and anterior third. These findings may suggest sex differences in problem solving strategies where in women, more than in men, stronger interhemispheric connectivity—especially between occipitoparietal, frontal, and prefrontal regions—is associated with improved task performance. © 2018 Wiley Periodicals, Inc.     

Focal lesions in the splenium of the corpus callosum in patients with epilepsy

Purpose:   A focal lesion in the splenium of the corpus callosum is a rare finding in patients with epilepsy. Intoxication with antiepileptic drugs, edema after generalized seizures, or a rapid change of antiepileptic drug levels have been proposed as possible mechanisms. The aim of the present study was to analyze the relationship between this lesion and possible etiologic factors.
Patients and methods:   We analyzed the magnetic resonance imaging (MRI) scans of 1,050 patients undergoing prolonged video-EEG (electroencephalography) monitoring and identified 24 patients with a focal lesion in the splenium of the corpus callosum. Twenty-four age- and gender-matched temporal lobe epilepsy patients without such a lesion served as a control group. We evaluated the following parameters for their possible etiologic significance: epilepsy syndrome, seizure types in medical history, seizure frequency during the past year prior to admission for prolonged video-EEG monitoring, localization of interictal spikes and ictal EEG patterns in patients with focal epilepsies as documented during prolonged video-EEG-monitoring, seizure types and seizure frequency during prolonged video-EEG monitoring, past as well as current antiepileptic medication, withdrawal of antiepileptic drugs during monitoring including duration of medication withdrawal, and finally drug levels above the therapeutic range.
Results :  The parameters analyzed showed no significant difference between the group of patients with focal lesions in the splenium of the corpus callosum and the control group.
Conclusion:   We could not identify a single etiologic factor responsible for the lesion in the splenium of the corpus callosum.     

Predicting visual working memory with multimodal magnetic resonance imaging

The indispensability of visual working memory (VWM) in human daily life suggests its importance in higher cognitive functions and neurological diseases. However, despite the extensive research efforts, most findings on the neural basis of VWM are limited to a unimodal context (either structure or function) and have low generalization. To address the above issues, this study proposed the usage of multimodal neuroimaging in combination with machine learning to reveal the neural mechanism of VWM across a large cohort (N = 547). Specifically, multimodal magnetic resonance imaging features extracted from voxel‐wise amplitude of low‐frequency fluctuations, gray matter volume, and fractional anisotropy were used to build an individual VWM capacity prediction model through a machine learning pipeline, including the steps of feature selection, relevance vector regression, cross‐validation, and model fusion. The resulting model exhibited promising predictive performance on VWM (r = .402, p < .001), and identified features within the subcortical‐cerebellum network, default mode network, motor network, corpus callosum, anterior corona radiata, and external capsule as significant predictors. The main results were then compared with those obtained on emotional regulation and fluid intelligence using the same pipeline, confirming the specificity of our findings. Moreover, the main results maintained well under different cross‐validation regimes and preprocess strategies. These findings, while providing richer evidence for the importance of multimodality in understanding cognitive functions, offer a solid and general foundation for comprehensively understanding the VWM process from the top down.     

胼胝体发育不良临床、磁共振成像分析（附116例）

目的探讨胼胝体发育不良（AgCC）的临床和MRI表现。方法将患者分为3组：（1）原发性单纯性AgCC组;（2）原发性AgCC合并其他脑发育畸形组;（3）继发性AgCC组,分析其临床及MRI表现。结果胼胝体变薄是最常见的畸形,原发性AgCC合并其他脑发育畸形组更易有胼胝体完全缺如、脑室扩大、生长发育迟缓、智力低下。结论原发性AgCC合并其他脑发育畸形组的临床表现较原发性单纯性AgCC组重。     

White matter magnetic resonance imaging hyperintensity in Alzheimer's disease: correlations with corpus callosum atrophy

We have previously demonstrated with MRI that as well as marked white matter involvement in late-onset Alzheimer's disease (AD), atrophy of the corpus callosum may also be present. This finding prompted us to study possible correlations between atrophy of the corpus callosum and white matter hyperintensity (WMH) and between white matter lesions and the severity of the disease. We compared the corpus callosum and white matter lesions on MRI from 15 AD patients and 15 controls. The white matter lesions were scored according to the Scheltens' rating scale. We found a significant reduction of the area of the corpus callosum and more severe white matter lesions in AD patients than in controls. Both atrophy of the corpus callosum and the severity of lesions depended mainly on the diagnosis of senile dementia of the Alzheimer type and on age but not on the diagnosis of presenile AD. We demonstrated a negative correlation between white matter lesions scores and areas of corpus callosum in AD patients and no correlation between the white matter lesions and the severity of the disease. We demonstrated that white matter lesions including WMH and atrophy of the corpus callosum are more frequent in AD than in controls. The predominance of white matter lesions in senile AD may be explained by the combination of aging and disease processes.     

Probabilistic topography of human corpus callosum using cytoarchitectural parcellation and high angular resolution diffusion imaging tractography

The function of the corpus callosum (CC) is to distribute perceptual, motor, cognitive, learned, and voluntary information between the two hemispheres of the brain. Accurate parcellation of the CC according to fiber composition and fiber connection is of upmost important. In this work, population‐based probabilistic connection topographies of the CC, in the standard Montreal Neurological Institute (MNI) space, are estimated by incorporating anatomical cytoarchitectural parcellation with high angular resolution diffusion imaging (HARDI) tractography. First, callosal fibers are extracted using multiple fiber assignment by continuous tracking algorithm based on q‐ball imaging (QBI), on 12 healthy and young subjects. Then, the fiber tracts are aligned in the standard MNI coordinate system based on a tract‐based transformation scheme. Next, twenty‐eight Brodmann's areas on the surface of cortical cortex are registered to the MNI space to parcellate the aligned callosal fibers. Finally, the population‐based topological subdivisions of the midsagittal CC to each cortical target are then mapped. And the resulting subdivisions of the CC that connect to the frontal and somatosensory associated cortex are also showed. To our knowledge, it is the first topographic subdivisions of the CC done using HARDI tractography and cytoarchitectonic information. In conclusion, this sophisticated topography of the CC may serve as a landmark to further understand the correlations between the CC, brain intercommunication, and functional cytoarchitectures. Hum Brain Mapp 2009. © 2009 Wiley‐Liss, Inc.     

高功能孤独症患儿胼胝体及额叶体积的磁共振研究

目的探讨高功能孤独症(high functioning autism,HFA)患儿的胼胝体以及额叶体积是否异常。方法对17例6~14岁的HFA患儿(智商≥70)以及16名年龄、性别、智商等与患者组相匹配的健康学龄儿童进行T1加权三维容积磁共振成像。根据改良的Witelson范式将胼胝体划分为五个亚区,采用自编软件计算和比较两组被试胼胝体区及各个亚区的体积,应用个体脑结构地图集(Individual brain atlases using SPM,IBASPM)工具箱计算额叶体积。结果 HFA组与正常对照组相比额叶总体积及左侧额叶体积增大[(193.91±23.23)cm3vs(177.86±18.2)cm3,P=0.04;(96.08±11.89)cm3vs(87.52±9.14)cm3,P=0.03],而右侧额叶、胼胝体总体积及各亚区的体积差异均无统计学意义(P>0.05);HFA组胼胝体前三分之一部的体积与额叶总体积、右侧额叶体积呈正相关(r=0.51,P=0.04;r=0.50,P=0.04);未见HFA组中儿童孤独症评定量表评分与胼胝体及额叶的体积存在相关(P>0.05)。结论 HFA患儿的额叶体积增...     

A study of the corpus callosum in epilepsy using magnetic resonance imaging

The corpus callosum of a group of epileptic patients (N = 48) was compared to that of normal healthy volunteers (N = 14) using magnetic resonance imaging (MRI). The mid-callosal thickness was significantly greater in the sub-group of epileptic patients with generalized seizures. This provides some support for the concept of the corpus callosum playing a role in seizure propagation.