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1

Measuring Fractional Anisotropy of the Corpus Callosum Using Diffusion Tensor Imaging: MidSagittal versus Axial Imaging Planes  

Microsoft Academic Search

Objective: Many diffusion tensor imaging (DTI) studies of the corpus callosum (CC) have been performed with a relatively thick slice thickness in the axial plane, which may result in underestimating the fractional anisotropy (FA) of the CC due to a partial volume effect. We hypothesized that the FA of the CC can be more accurately measured by using mid-sagittal DTI.

Eung Yeop Kim; Hae-Jeong Park; Dong-Hyun Kim; Seung-Koo Lee; Jinna Kim

2008-01-01

2

Reduced Fractional Anisotropy of Corpus Callosum Modulates Inter-Hemispheric Resting State Functional Connectivity in Migraine Patients without Aura  

PubMed Central

Background Diffusion tensor imaging (DTI) study revealed reduced fractional anisotropy (FA) values in the corpus callosum (CC) in migraine patients without aura. Abnormalities in white matter integrity, particularly in the CC, may affect inter-hemispheric resting state functional connectivity (RSFC). Unfortunately, relatively little is known about the alterations in functional interactions between the cerebral hemispheres during resting state in migraine patients without aura, and even less about how the inter-hemispheric RSFC are affected by the abnormalities of the CC. Methods and findings Twenty-one migraine patients without aura and 21 healthy controls participated in this study, age-, sex-, and education-matched. Tract-based spatial statistics (TBSS) was employed to investigate the white matter alterations of the CC. Meanwhile, voxel-mirrored homotopic connectivity (VMHC) was used to compare the inter-hemispheric RSFC differences between the patients and controls. TBSS analysis revealed reduced FA values in the genu and the splenium of CC in patient group. VMHC analysis showed decreased inter-hemispheric RSFC of anterior cingulate cortex (ACC) in migraine patients without aura relative to that of the controls. Furthermore, in migraine patients without aura, the reduced FA values of the genu of CC correlated with the decreased inter-hemispheric RSFC of the ACC. Conclusions Our findings demonstrated that the migraine patients without aura showed reduced FA values of the genu of CC and decreased inter-hemispheric RSFC of the ACC. The correlation between the above structural and functional changes suggested that the reduced fractional anisotropy (FA) of CC modulates inter-hemispheric VMHC in migraine patients without aura. Our results demonstrated that the VMHC alterations of ACC can reflect the FA changes of the genu of CC in migraine patients without aura.

Yuan, Kai; Qin, Wei; Liu, Peng; Zhao, Ling; Yu, Dahua; Zhao, Limei; Dong, Minghao; Liu, Jixin; Yang, Xuejuan; von Deneen, Karen M.; Liang, Fanrong; Tian, Jie

2012-01-01

3

Corpus Callosum Diffusion Anisotropy Correlates with Neuropsychological Outcomes in Twins Disconcordant for Traumatic Brain Injury  

PubMed Central

SUMMARY Conventional and diffusion tensor MR imaging studies in twins sustaining severe pediatric traumatic brain injury identified reduction in fractional anisotropy (FA) in all regions of the corpus callosum, particularly the posterior body, rostral body, and genu, relative to healthy cotwins. FA from the rostrum, genu, anterior body, posterior body, and isthmus were correlated with measures of reading speed and comprehension; verbal working memory and math fact retrieval scores were correlated only with the rostral body FA.

Ewing-Cobbs, L.; Hasan, K.M.; Prasad, M.R.; Kramer, L.; Bachevalier, J.

2007-01-01

4

Progressive decline in fractional anisotropy on serial DTI examinations of the corpus callosum: a putative marker of disease activity and progression in SPMS  

Microsoft Academic Search

Introduction  Clinical trials of secondary progressive multiple sclerosis (SPMS) is lacking reliable biomarkers or outcome measures that\\u000a reflect tissue injury incurred within a 1- to 2-year observation period. Diffusion tensor imaging (DTI) is sensitive in detecting\\u000a acute brain tissue damage. We monitored SPMS patients over 12 months for diffusion changes within the corpus callosum (CC).\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Bimonthly MRI examinations over a 1-year period

Wei Tian; Tong Zhu; Jianhui Zhong; Xiang Liu; Praveen Rao; Benjamin M. Segal; Sven Ekholm

5

Altered Fractional Anisotropy in Early Huntington's Disease  

PubMed Central

Huntington's disease (HD) is a dominantly inherited neurodegenerative disease best known for chorea. The disorder includes numerous other clinical features including mood disorder, eye movement abnormalities, cognitive disturbance, pendular knee reflexes, motor impersistence, and postural instability. We describe a mild case of HD early in the disease course with depression and subtle neurological manifestations. In addition, we review MRI and diffusion tensor imaging features in this patient. The bicaudate ratio, a measure of caudate atrophy, was increased. Fractional anisotropy values of the bilateral caudate and putamen were increased, signifying neurodegeneration of these structures in HD.

Singh, Silky; Mehta, Hasit; Fekete, Robert

2013-01-01

6

Effects of interpolation methods in spatial normalization of diffusion tensor imaging data on group comparison of fractional anisotropy  

Microsoft Academic Search

This study investigated the effects on the measurement of fractional anisotropy (FA) during interpolation of diffusion tensor images in spatial normalization, which is required for voxel-based statistics. Diffusion tensor imaging data were obtained from nine male patients with attention deficit\\/hyperactivity disorder and nine age-matched control subjects. Regions of interest were selected from the genu of corpus callosum (GCC) and the

Tzu-Cheng Chao; Ming-Chung Chou; Pinchen Yang; Hsiao-Wen Chung; Ming-Ting Wu

2009-01-01

7

White Matter Integrity Measured by Fractional Anisotropy Correlates Poorly with Actual Individual Fiber Anisotropy  

Microsoft Academic Search

Fractional anisotropy (FA), a very widely used measure of fiber integrity based on diffusion tensor imaging (DTI), is a problematic concept as it is influenced by several quantities including the number of dominant fiber directions within each voxel, each fiber's anisotropy, and partial volume effects from neighboring gray matter. High-angular resolution diffusion imaging (HARDI) can resolve more complex diffusion geometries

Alex D. Leow; Liang Zhan; Siwei Zhu; Nathan S. Hageman; Ming-Chang Chiang; Marina Barysheva; Arthur W. Toga; Katie McMahon; Greig I. de Zubicaray; Margaret J. Wright; Paul M. Thompson

2009-01-01

8

Diffusion tensor imaging and tractwise fractional anisotropy statistics: quantitative analysis in white matter pathology  

PubMed Central

Background Information on anatomical connectivity in the brain by measurements of the diffusion of water in white matter tracts lead to quantification of local tract directionality and integrity. Methods The combination of connectivity mapping (fibre tracking, FT) with quantitative diffusion fractional anisotropy (FA) mapping resulted in the approach of results based on group-averaged data, named tractwise FA statistics (TFAS). The task of this study was to apply these methods to group-averaged data from different subjects to quantify differences between normal subjects and subjects with defined alterations of the corpus callosum (CC). Results TFAS exhibited a significant FA reduction especially in the CC, in agreement with region of interest (ROI)-based analyses. Conclusion In summary, the applicability of the TFAS approach to diffusion tensor imaging studies of normal and pathologically altered brains was demonstrated.

Mueller, Hans-Peter; Unrath, Alexander; Sperfeld, Anne D; Ludolph, Albert C; Riecker, Axel; Kassubek, Jan

2007-01-01

9

[Comparison of diffusion tensor imaging-derived fractional anisotropy in multiple centers for identical human subjects].  

PubMed

The fractional anisotropy (FA) is calculated by using diffusion tensor imaging (DTI) with multiple motion probing gradients (MPG). While FA has become a widely used tool to detect moderate changes in water diffusion in brain tissue, the measured value is sensitive to scan parameters (e.g. MPG-direction, signal to noise ratio, etc.). Therefore, it is paramount to address the reproducibility of DTI measurements among multiple centers. The purpose of this study was to assess the inter-center variability of FA. We studied five healthy volunteers who underwent DTI brain scanning three times at three different centers (I-III), each with a 1.5 T scanner having a different MPG-schema. Then, we compared the FA and eigenvalue from the three centers measured in seven brain regions: splenium of corpus callosum (CCs), genu of corpus callosum (CCg), putamen, posterior limb of internal capsule, cerebral peduncle, optic radiation, and middle cerebellar peduncle. At the CCs and CCg, there was a statistical difference (p<0.05) between center Iand center IIfor the same MPG-directions. Furthermore, at CCs and CCg, there was a statistical difference (p<0.05) between center II and center III for different MPG-directions. Conversely, no statistical differences were found between center I and center III for the different MPG-directions for all regions. These results indicate that the FA value was affected by the MPG-schema as well as by the MPG-directions. PMID:23001272

Saotome, Kousaku; Ishimori, Yoshiyuki; Isobe, Tomonori; Satou, Eisuke; Shinoda, Kazuya; Ookubo, Jun; Hirano, Yuuji; Oosuka, Satoru; Matsushita, Akira; Miyamoto, Katsumi; Sankai, Yoshiyuki

2012-01-01

10

Cosmic ray anisotropy in fractional differential models of anomalous diffusion  

NASA Astrophysics Data System (ADS)

The problem of galactic cosmic ray anisotropy is considered in two versions of the fractional differential model for anomalous diffusion. The simplest problem of cosmic ray propagation from a point instantaneous source in an unbounded medium is used as an example to show that the transition from the standard diffusion model to the Lagutin-Uchaikin fractional differential model (with characteristic exponent ? = 3/5 and a finite velocity of free particle motion), which gives rise to a knee in the energy spectrum at 106 GeV, increases the anisotropy coefficient only by 20%, while the anisotropy coefficient in the Lagutin-Tyumentsev model (with exponents ? = 0.3 and ? = 0.8, a long stay of particles in traps, and an infinite velocity of their jumps) is close to one. This is because the parameters of the Lagutin-Tyumentsev model have been chosen improperly.

Uchaikin, V. V.

2013-06-01

11

Acute nicotine administration effects on fractional anisotropy of cerebral white matter and associated attention performance.  

PubMed

Introduction: Nicotinic acetylcholine receptors are present in the cerebral white matter (WM). We hypothesized that WM response to nicotine can be detected by diffusion tensor imaging (DTI); and that such responses may be associated with nicotine-led cognitive enhancement in sustained attention. Methods: A randomized, nicotine-placebo patch, crossover, double-blind clinical trial in two non-overlapping cohorts of smokers was used to test the hypothesis. The discovery cohort consisted of 39 subjects (N = 20/19 controls/schizophrenic patients, age = 36.8 ± 10.1 years) and the replication cohorts consisted of 38 healthy smokers (31.7 ± 10.5 years). WM integrity was measured by fractional anisotropy (FA) values for the whole brain and nine preselected WM tracts using tract-based-spatial-statistics. Results: Nicotine significantly enhanced FA values for the genu of corpus callosum compared with placebo (?FAgenu) (p = 0.01) in smokers with low recent smoking exposure as measured by low average cotinine level. This finding was replicated in the second cohort (p = 0.02). ?FAgenu values explained 22% of variance in performance of a sustained attention task during the nicotine session (p = 0.006). However, this effect was limited to schizophrenia patients (r = 0.62 and 0.09; p = 0.003 and 0.7 for patients and controls, respectively). Conclusion: Acute pharmacological influence of nicotine patch on WM integrity appeared present, but was dependent on nicotine intake from recent smoking. Change in the WM integrity in the genu of corpus callosum was associated with a significant proportion of variability of nicotine-led changes in sustained attention/working memory of the smokers. Further studies will be necessary to understand biophysical underpinning of the nicotine-related changes in FA. PMID:24065920

Kochunov, Peter; Du, Xiaoming; Moran, Lauren V; Sampath, Hemalatha; Wijtenburg, S Andrea; Yang, Yihong; Rowland, Laura M; Stein, Elliot A; Hong, L Elliot

2013-09-18

12

Acute nicotine administration effects on fractional anisotropy of cerebral white matter and associated attention performance  

PubMed Central

Introduction: Nicotinic acetylcholine receptors are present in the cerebral white matter (WM). We hypothesized that WM response to nicotine can be detected by diffusion tensor imaging (DTI); and that such responses may be associated with nicotine-led cognitive enhancement in sustained attention. Methods: A randomized, nicotine-placebo patch, crossover, double-blind clinical trial in two non-overlapping cohorts of smokers was used to test the hypothesis. The discovery cohort consisted of 39 subjects (N = 20/19 controls/schizophrenic patients, age = 36.8 ± 10.1 years) and the replication cohorts consisted of 38 healthy smokers (31.7 ± 10.5 years). WM integrity was measured by fractional anisotropy (FA) values for the whole brain and nine preselected WM tracts using tract-based-spatial-statistics. Results: Nicotine significantly enhanced FA values for the genu of corpus callosum compared with placebo (?FAgenu) (p = 0.01) in smokers with low recent smoking exposure as measured by low average cotinine level. This finding was replicated in the second cohort (p = 0.02). ?FAgenu values explained 22% of variance in performance of a sustained attention task during the nicotine session (p = 0.006). However, this effect was limited to schizophrenia patients (r = 0.62 and 0.09; p = 0.003 and 0.7 for patients and controls, respectively). Conclusion: Acute pharmacological influence of nicotine patch on WM integrity appeared present, but was dependent on nicotine intake from recent smoking. Change in the WM integrity in the genu of corpus callosum was associated with a significant proportion of variability of nicotine-led changes in sustained attention/working memory of the smokers. Further studies will be necessary to understand biophysical underpinning of the nicotine-related changes in FA.

Kochunov, Peter; Du, Xiaoming; Moran, Lauren V.; Sampath, Hemalatha; Wijtenburg, S. Andrea; Yang, Yihong; Rowland, Laura M.; Stein, Elliot A.; Hong, L. Elliot

2013-01-01

13

Neuropathological abnormalities of the corpus callosum in schizophrenia: a diffusion tensor imaging study  

Microsoft Academic Search

OBJECTIVESDiffusion tensor imaging (DTI), a technique capable of examining water diffusion in different tissues and the organisation of white matter tracts, was used to investigate the neuropathology of the corpus callosum in vivo in patients with schizophrenia.METHODSDiffusion tensor imaging was performed in 20 schizophrenic patients and 25 healthy controls. Two complementary measures, mean diffusivity and fractional anisotropy, which are considered

J Foong; M Maier; C A Clark; G J Barker; D H Miller; M A Ron

2000-01-01

14

A longitudinal study of the corpus callosum in chronic schizophrenia  

PubMed Central

Background Decreased callosal size and anisotropy have been described in schizophrenia patients but their longitudinal progression remains poorly understood. Methods We performed diffusion-tensor and structural magnetic resonance imaging at baseline and at follow-up four years later in 49 chronic schizophrenia patients and 16 healthy comparison subjects. Schizophrenia patients were subdivided into good-outcome (n=23) and poor-outcome (n=26) groups. Baseline-to-follow-up changes in size, shape, position and fractional anisotropy of the corpus callosum, divided into five sagittal sections and five rostro-caudal segments, were assessed. Results At baseline scan and in comparison to healthy subjects, schizophrenia patients displayed 1) smaller callosal size, 2) lower average anisotropy in all sagittal sections except the midline, 3) more dorsal average coordinate position. During the four years after the baseline scan, patients with schizophrenia exhibited a more pronounced decline in absolute size of the corpus callosum than healthy comparison subjects. As compared with the good-outcome group, the corpus callosum in poor-outcome patients at baseline was of smaller size and lower average anisotropy, more elongated and posteriorly positioned. During the follow-up interval, poor-outcome patients displayed a more pronounced decline in size but less pronounced decline in anisotropy of the corpus callosum than patients with good outcomes. Conclusions Differences in callosal size between schizophrenia patients and healthy subjects seen at baseline continue to widen in the chronic phase of the illness, especially in patients with poor functional outcome. Baseline differences in callosal anisotropy among patients with different outcomes, however, diminish over time.

Mitelman, Serge A.; Nikiforova, Yekaterina K.; Canfield, Emily L.; Hazlett, Erin A.; Brickman, Adam M.; Shihabuddin, Lina; Buchsbaum, Monte S.

2009-01-01

15

White Matter Fractional Anisotropy Correlates With Speed of Processing and Motor Speed in Young Childhood Cancer Survivors  

SciTech Connect

Purpose: To determine whether childhood medulloblastoma and acute lymphoblastic leukemia (ALL) survivors have decreased white matter fractional anisotropy (WMFA) and whether WMFA is related to the speed of processing and motor speed. Methods and Materials: For this study, 17 patients (6 medulloblastoma, 5 ALL treated with high-dose methotrexate (MTX) (4 x 5 g/m{sup 2}) and 6 with low-dose MTX (3 x 2 g/m{sup 2})) and 17 age-matched controls participated. On a 3.0-T magnetic resonance imaging (MRI) scanner, diffusion tensor imaging (DTI) was performed, and WMFA values were calculated, including specific regions of interest (ROIs), and correlated with the speed of processing and motor speed. Results: Mean WMFA in the patient group, mean age 14 years (range 8.9 - 16.9), was decreased compared with the control group (p = 0.01), as well as WMFA in the right inferior fronto-occipital fasciliculus (IFO) (p = 0.03) and in the genu of the corpus callosum (gCC) (p = 0.01). Based on neurocognitive results, significant positive correlations were present between processing speed and WMFA in the splenium (sCC) (r = 0.53, p = 0.03) and the body of the corpus callosum (bCC) (r = 0.52, p = 0.03), whereas the right IFO WMFA was related to motor speed (r = 0.49, p < 0.05). Conclusions: White matter tracts, using a 3.0-T MRI scanner, show impairment in childhood cancer survivors, medulloblastoma survivors, and also those treated with high doses of MTX. In particular, white matter tracts in the sCC, bCC and right IFO are positively correlated with speed of processing and motor speed.

Aukema, Eline J. [Pediatric Psychosocial Department, Emma Children's Hospital/Academic Medical Center, Amsterdam (Netherlands)], E-mail: e.j.aukema@amc.uva.nl; Caan, Matthan W.A. [Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam (Netherlands); Delft University of Technology, Delft (Netherlands); Oudhuis, Nienke [Pediatric Psychosocial Department, Emma Children's Hospital/Academic Medical Center, Amsterdam (Netherlands); Majoie, Charles [Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam (Netherlands); Vos, Frans M. [Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam (Netherlands); Delft University of Technology, Delft (Netherlands); Reneman, Liesbeth [Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam (Netherlands); Last, Bob F. [Pediatric Psychosocial Department, Emma Children's Hospital/Academic Medical Center, Amsterdam (Netherlands); Department of Developmental Psychology, Free University of Amsterdam, Amsterdam (Netherlands); Grootenhuis, Martha A. [Pediatric Psychosocial Department, Emma Children's Hospital/Academic Medical Center, Amsterdam (Netherlands); Schouten-van Meeteren, Antoinette Y.N. [Department of Pediatric Oncology, Emma Children's Hospital/Academic Medical Center, Amsterdam (Netherlands)

2009-07-01

16

Increased Regional Fractional Anisotropy in Highly Screened Attention-Deficit Hyperactivity Disorder (ADHD)  

Microsoft Academic Search

Diffusion tensor imaging data were collected at 3.0 Tesla from 16 children with attention-deficit hyperactivity disorder (ADHD) and 16 typically developing controls, ages 9 to 14 years. Fractional anisotropy images were calculated and normalized by linear transformation. Voxel-wise and atlas-based region-of-interest analyses were performed. Using voxel-wise analysis, fractional anisotropy was found to be significantly increased in the attention-deficit hyperactivity disorder

Daniel J. Peterson; Matthew Ryan; Sheryl L. Rimrodt; Laurie E. Cutting; Martha B. Denckla; Walter E. Kaufmann; E. Mark Mahone

2011-01-01

17

Evidence for fractional anisotropy and mean diffusivity white matter abnormalities in the internal capsule and cingulum in patients with obsessive-compulsive disorder  

PubMed Central

Background There is evidence to suggest that obsessive–compulsive disorder (OCD) is associated with structural abnormalities in cortico–striato–thalamic circuits, yet the extent of white matter abnormalities is not well established. In this study, we used diffusion tensor imaging (DTI) to examine white matter integrity in specific regions of interest (ROIs) in patients with OCD. Methods Patients with OCD and sex-, age- and IQ-matched healthy controls underwent DTI. The primary objective was to explore whether patients with OCD had white matter abnormalities in the anterior limb of the internal capsule (ALIC), the uncinate fasciculus, the genu of the corpus callosum and the cingulum. The secondary objective was to evaluate the relation between fractional anisotropy and mean diffusivity in these ROIs and other clinical variables (including age at onset of OCD, OCD severity and levels of depressive and anxiety symptomatology) in patients with OCD. Results There were 15 patients and 17 controls enrolled in our study. Compared with healthy controls, patients with OCD showed increased fractional anisotropy in bilateral regions of the ALIC adjacent to the body of the caudate, as well as decreased fractional anisotropy in the right anterior limb near the head of the caudate. Patients also had decreased mean diffusivity in the body of the right cingulum and the left anterior cingulum compared with controls. Correlational analyses revealed significant associations of fractional anisotropy and mean diffusivity in select circuits with OCD, depression and anxiety severity scores. Limitations Inclusion of patients with OCD receiving pharmacotherapy may have been a limitation. In addition, the patients were heterogeneous in terms of their obsessive–compulsive symptom profiles; we did not distinguish between different obsessive–compulsive symptom dimensions. Conclusion The study results provide further evidence for OCD-related white matter abnormalities in the ALIC and cingulum, consistent with a corticostriatal model of OCD.

Lochner, Christine; Fouche, Jean-Paul; du Plessis, Stefan; Spottiswoode, Bruce; Seedat, Soraya; (Psych), MMed; Fineberg, Naomi; Chamberlain, Samuel R.; Stein, Dan J.

2012-01-01

18

The effect of injury timing on white matter changes in the corpus callosum following unilateral brain injury?  

PubMed Central

Motor impairments following unilateral brain injuries may be related to changes in the corpus callosum. The purpose of this study was to determine if the corpus callosum is impacted differently in pediatric versus adult hemiplegia. Diffusion tensor imaging was completed on 41 participants (11 pediatric hemiplegia, 10 adult hemiplegia, 10 pediatric control and 10 adult control). Fractional anisotropy values and cross-sectional areas for five regions of the corpus callosum were compared between subject groups. Additionally, the amount of involuntary activity in the paretic elbow was quantified during non-paretic elbow flexion tasks for a subset of pediatric hemiplegia participants. Fractional anisotropy values were reduced in pediatric hemiplegia compared to pediatric control subjects in callosal regions corresponding to premotor and supplementary motor areas, primary sensory cortex, and parietal, temporal, and occipital cortices. Differences in fractional anisotropy between adult stroke and adult controls were only found in the region corresponding to parietal, temporal, and occipital cortices. Cross-sectional area was affected in all regions of the corpus callosum in pediatric hemiplegia, but only in the primary sensory region in adult hemiplegia. Additionally, changes in the cross-sectional areas were correlated with involuntary mirror movements in the pediatric hemiplegia group. In conclusion, the corpus callosum is affected to a greater extent in pediatric compared to adult hemiplegia, which may explain why unsuppressed mirror movements and difficulty with bimanual coordination are greater problems in this population.

Hawe, Rachel L.; Sukal-Moulton, Theresa; Dewald, Julius P.A.

2013-01-01

19

The effect of injury timing on white matter changes in the corpus callosum following unilateral brain injury.  

PubMed

Motor impairments following unilateral brain injuries may be related to changes in the corpus callosum. The purpose of this study was to determine if the corpus callosum is impacted differently in pediatric versus adult hemiplegia. Diffusion tensor imaging was completed on 41 participants (11 pediatric hemiplegia, 10 adult hemiplegia, 10 pediatric control and 10 adult control). Fractional anisotropy values and cross-sectional areas for five regions of the corpus callosum were compared between subject groups. Additionally, the amount of involuntary activity in the paretic elbow was quantified during non-paretic elbow flexion tasks for a subset of pediatric hemiplegia participants. Fractional anisotropy values were reduced in pediatric hemiplegia compared to pediatric control subjects in callosal regions corresponding to premotor and supplementary motor areas, primary sensory cortex, and parietal, temporal, and occipital cortices. Differences in fractional anisotropy between adult stroke and adult controls were only found in the region corresponding to parietal, temporal, and occipital cortices. Cross-sectional area was affected in all regions of the corpus callosum in pediatric hemiplegia, but only in the primary sensory region in adult hemiplegia. Additionally, changes in the cross-sectional areas were correlated with involuntary mirror movements in the pediatric hemiplegia group. In conclusion, the corpus callosum is affected to a greater extent in pediatric compared to adult hemiplegia, which may explain why unsuppressed mirror movements and difficulty with bimanual coordination are greater problems in this population. PMID:24179855

Hawe, Rachel L; Sukal-Moulton, Theresa; Dewald, Julius P A

2013-08-08

20

A Novel Measure of Fractional Anisotropy Based on the Tensor Distribution Function  

Microsoft Academic Search

Fractional anisotropy (FA), a very widely used measure of fiber integrity based on diffusion tensor imaging (DTI), is a problematic\\u000a concept as it is influenced by several quantities including the number of dominant fiber directions within each voxel, each\\u000a fiber’s anisotropy, and partial volume effects from neighboring gray matter. With High-angular resolution diffusion imaging\\u000a (HARDI) and the tensor distribution function

Liang Zhan; Alex D. Leow; Siwei Zhu; Marina Barysheva; Arthur W. Toga; Katie L. McMahon; Greig I. De Zubicaray; Margaret J. Wright; Paul M. Thompson

2009-01-01

21

Reduced Interhemispheric Connectivity in Schizophrenia- Tractography Based Segmentation of the Corpus Callosum  

PubMed Central

Background A reduction in interhemispheric connectivity is thought to contribute to the etiology of schizophrenia. Diffusion Tensor Imaging (DTI) measures the diffusion of water and can be used to describe the integrity of the corpus callosum white matter tracts, thereby providing information concerning possible interhemispheric connectivity abnormalities. Previous DTI studies in schizophrenia are inconsistent in reporting decreased Fractional Anisotropy (FA), a measure of anisotropic diffusion, within different portions of the corpus callosum. Moreover, none of these studies has investigated corpus callosum systematically, using anatomical subdivisions. Methods DTI and structural MRI scans were obtained from 32 chronic schizophrenic subjects and 42 controls. Corpus callosum cross sectional area and its probabilistic subdivisions were determined automatically from structural MRI scans using a model based deformable contour segmentation. These subdivisions employ a previously generated probabilistic subdivision atlas, based on fiber tractography and anatomical lobe subdivision. The structural scan was then co-registered with the DTI scan and the anatomical corpus callosum subdivisions were propagated to the associated FA map. Results Results revealed decreased FA within parts of the corpus interconnecting frontal regions in schizophrenia compared with controls, but no significant changes for callosal fibers interconnecting parietal and temporo-occipital brain regions. In addition, integrity of the anterior corpus was statistically significantly correlated with negative as well as positive symptoms, while posterior measures correlated with positive symptoms only. Conclusions This study provides quantitative evidence for a reduction of interhemispheric brain connectivity in schizophrenia, involving corpus callosum, and further points to frontal connections as possibly disrupted in schizophrenia.

Kubicki, M.; Styner, M.; Bouix, S.; Gerig, G.; Markant, D.; Smith, K.; Kikinis, R.; McCarley, R.W.; Shenton, M.E.

2008-01-01

22

Prediction of Motor Function Outcome after Intracerebral Hemorrhage Using Fractional Anisotropy Calculated from Diffusion Tensor Imaging  

Microsoft Academic Search

Background: The efficacy of surgical evacuation in patients with intracerebral hemorrhage (ICH) remains unclear for recovery of motor function. The relationship between improvement of motor function outcome and sequential change of fractional anisotropy (FA) values was investigated in patients with ICH, to explore whether motor function outcome can be predicted in the early phase. Indication of the surgical hematoma evacuation

Yasutaka Kuzu; Takashi Inoue; Yoshiyuki Kanbara; Hideaki Nishimoto; Shunro Fujiwara; Kuniaki Ogasawara; Akira Ogawa

2012-01-01

23

Fractional anisotropy of water diffusion in cerebral white matter across the lifespan  

Microsoft Academic Search

Determining the time of peak of cerebral maturation is vital for our understanding of when cerebral maturation ceases and the cerebral degeneration in healthy aging begins. We carefully mapped changes in fractional anisotropy (FA) of water diffusion for eleven major cerebral white matter tracts in a large group (831) of healthy human subjects aged 11–90. FA is a neuroimaging index

P. Kochunov; D. E. Williamson; J. Lancaster; P. Fox; J. Cornell; J. Blangero; D. C. Glahn

2010-01-01

24

Mean diffusivity and fractional anisotropy as indicators of disease and genetic liability to schizophrenia  

Microsoft Academic Search

The goals of this study were to first determine whether the fractional anisotropy (FA) and mean diffusivity (MD) of major white matter pathways associate with schizophrenia, and secondly to characterize the extent to which differences in these metrics might reflect a genetic predisposition to schizophrenia. Differences in FA and MD were identified using a comprehensive atlas-based tract mapping approach using

Kristi A. Clark; Keith H. Nuechterlein; Robert F. Asarnow; Liberty S. Hamilton; Owen R. Phillips; Nathan S. Hageman; Roger P. Woods; Jeffry R. Alger; Arthur W. Toga; Katherine L. Narr

2011-01-01

25

Band mass anisotropy and the intrinsic metric of fractional quantum Hall systems  

NASA Astrophysics Data System (ADS)

It was recently pointed out that topological liquid phases arising in the fractional quantum Hall effect (FQHE) are not required to be rotationally invariant, as most variational wave functions proposed to date have been. Instead, they possess a geometric degree of freedom corresponding to a shear deformation that acts like an intrinsic metric. We apply this idea to a system with an anisotropic band mass, as is intrinsically the case in many-valley semiconductors such as AlAs and Si or in isotropic systems like GaAs in the presence of a tilted magnetic field, which breaks the rotational invariance. We perform exact diagonalization calculations with periodic boundary conditions (torus geometry) for various filling fractions in the lowest, first, and second Landau levels. In the lowest Landau level, we demonstrate that FQHE states generally survive the breakdown of rotational invariance by moderate values of the band mass anisotropy. At 1/3 filling, we generate a variational family of Laughlin wave functions parametrized by the metric degree of freedom. We show that the intrinsic metric of the Laughlin state adjusts as the band mass anisotropy or the dielectric tensor is varied, while the phase remains robust. In the n=1 Landau level, mass anisotropy drives transitions between incompressible liquids and compressible states with charge density wave ordering. In n?2 Landau levels, mass anisotropy selects and enhances stripe ordering with compatible wave vectors at partial 1/3 and 1/2 fillings.

Yang, Bo; Papi?, Z.; Rezayi, E. H.; Bhatt, R. N.; Haldane, F. D. M.

2012-04-01

26

Longitudinal changes of fractional anisotropy in Alzheimer's disease patients treated with galantamine: a 12-month randomized, placebo-controlled, double-blinded study.  

PubMed

Diffusion tensor imaging (DTI) demonstrates decline of fractional anisotropy (FA) as a marker of fiber tract integrity in Alzheimer's disease (AD). We aimed to assess the longitudinal course of white matter microstructural changes in AD and healthy elderly control (HC) subjects and to evaluate the effects of treatment with the cholinesterase inhibitor galantamine on white matter microstructure in AD patients. We enrolled 28 AD patients and 11 healthy elderly control subjects (HC). AD patients were randomly assigned to 6-month double-blind galantamine treatment or placebo, with a 6-month open-label extension phase. DTI was performed at baseline, as well as at 6 and 12-month follow-up in AD patients. The HC subjects underwent DTI at baseline and 12-month follow-up without treatment. We measured FA in regions of interest covering the posterior cingulate and corpus callosum. At 6-month follow-up, the AD group showed significant FA decline in the left posterior cingulate. FA decline was significantly preserved in the posterior body of the corpus callosum in AD group with treatment compared to placebo. At 12-month follow-up, the AD patients showed no differences in FA decline between initial treatment and placebo groups after the 6-month open-label extension phase. A significant FA decline occurred in the left posterior cingulate across the AD and HC groups without between-group differences. DTI demonstrated FA decline in intracortically projecting fiber tracts in aging and AD over 1 year. Galantamine had limited impact on regional FA decline, which was not preserved after additional 6-month open-label treatment. PMID:21818628

Likitjaroen, Y; Meindl, T; Friese, U; Wagner, M; Buerger, K; Hampel, H; Teipel, S J

2011-08-05

27

Fractional anisotropy and mean diffusivity in the corpus callosum of patients with multiple sclerosis: the effect of physiotherapy  

Microsoft Academic Search

Introduction  Modulation of neurodegeneration by physical activity is an active topic in contemporary research. The purpose of this study\\u000a was to investigate changes in the brain's microstructure in multiple sclerosis (MS) after facilitation physiotherapy.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Eleven patients with MS were examined using motor and neuropsychological testing and multimodal MRI at the beginning of the\\u000a study, with second baseline measurement after 1 month without

Ibrahim Ibrahim; Jaroslav Tintera; Antonin Skoch; Filip Jir?; Petr Hlustik; Patricia Martinkova; Karel Zvara; Kamila Rasova

28

Segmented corpus callosum diffusivity correlates with the Expanded Disability Status Scale score in the early stages of relapsing-remitting multiple sclerosis  

PubMed Central

OBJECTIVE: The aim of this study was to characterize the microscopic damage to the corpus callosum in relapsing-remitting multiple sclerosis (RRMS) with diffusion tensor imaging and to investigate the correlation of this damage with disability. The diffusion tensor imaging parameters of fractional anisotropy and mean diffusivity provide information about the integrity of cell membranes, offering two more specific indices, namely the axial and radial diffusivities, which are useful for discriminating axon loss from demyelination. METHOD: Brain magnetic resonance imaging exams of 30 relapsing-remitting multiple sclerosis patients and 30 age- and sex-matched healthy controls were acquired in a 3T scanner. The axial diffusivities, radial diffusivities, fractional anisotropy, and mean diffusivity of five segments of the corpus callosum, correlated to the Expanded Disability Status Scale score, were obtained. RESULTS: All corpus callosum segments showed increased radial diffusivities and mean diffusivity, as well as decreased fractional anisotropy, in the relapsing-remitting multiple sclerosis group. The axial diffusivity was increased in the posterior midbody and splenium. The Expanded Disability Status Scale scores correlated more strongly with axial diffusivities and mean diffusivity, with an isolated correlation with radial diffusivities in the posterior midbody of the corpus callosum. There was no significant correlation with lesion loads. CONCLUSION: Neurological dysfunction in relapsing-remitting multiple sclerosis can be influenced by commissural disconnection, and the diffusion indices of diffusion tensor imaging are potential biomarkers of disability that can be assessed during follow-up.

de Medeiros Rimkus, Carolina; de Faria Junqueira, Thiago; Callegaro, Dagoberto; Otaduy, Maria Concepcion Garcia; da Costa Leite, Claudia

2013-01-01

29

Apparent Diffusion Coefficient, Fractional Anisotropy and T2 Relaxation Time Measurement  

Microsoft Academic Search

Background:  Quantification of apparent diffusion coefficient (ADC), fractional anisotropy (FA), and T2 relaxation time are increasingly\\u000a important for neuroradiologic applications. A transfer of the values established for 1.5-T to 3-T MRI must be supported by\\u000a a dedicated comparison with special emphasis on possible differences in the spatial distribution.\\u000a \\u000a \\u000a \\u000a Material and Methods:  In the present study, brain scans were carried out in 16

Xiao-Qi Ding; Jürgen Finsterbusch; Oliver Wittkugel; Christian Saager; Einar Goebell; Thies Fitting; Ulrich Grzyska; Hermann Zeumer; Jens Fiehler

2007-01-01

30

Fractional anisotropy in white matter tracts of very-low-birth-weight infants  

Microsoft Academic Search

Background  Advances in neonatal intensive care have not yet reduced the high incidence of neurodevelopmental disability among very-low-birth-weight\\u000a (VLBW) infants. As neurological deficits are related to white-matter injury, early detection is important. Diffusion tensor\\u000a imaging (DTI) could be an excellent tool for assessment of white-matter injury. \\u000a \\u000a \\u000a \\u000a Objective  To provide DTI fractional anisotropy (FA) reference values for white-matter tracts of VLBW infants for

Jeroen Dudink; Maarten Lequin; Carola van Pul; Jan Buijs; Nikk Conneman; Johannes van Goudoever; Paul Govaert

2007-01-01

31

Acquisition parameters for diffusion tensor imaging to emphasize fractional anisotropy: phantom study.  

PubMed

Diffusion tensor imaging (DTI) is a magnetic resonance (MR) imaging technique that has attracted attention in recent years for applications such as nerve fiber tracking, neurography, and tumor detection. In DTI measurements, 2 motion-probing gradient (MPG) pulses are applied to evaluate water diffusion. In DTI for nerve fiber tracking, acquisition parameters, such as strength, duration, and separation of MPGs, influence the MR signal. In this study, we set acquisition parameters in DTI to emphasize fractional anisotropy to clarify the direction of nerve fibers. We performed Monte Carlo simulations of restricted diffusion in a cylinder model and phantom measurements with capillary plates to examine the relationship between the acquisition parameters in DTI and the size of restricted structures, particularly their diameter and length, which we will refer to as "compartment size." We confirmed that normalized signal intensities in DTI measurements depend on diffusion time, which, in turn, depends on the separation and duration of the MPG, and they decrease with increase in compartment size. Furthermore, our simulation and phantom results suggest that use of a longer diffusion time effectively emphasizes fractional anisotropy to clarify the direction of nerve fibers. PMID:21720114

Oida, Takenori; Nagahara, Shizue; Kobayashi, Tetsuo

2011-01-01

32

A Novel Approach to Constrain the Escape Fraction and Dust Content at High Redshift Using the Cosmic Infrared Background Fractional Anisotropy  

NASA Astrophysics Data System (ADS)

The Cosmic Infrared Background (CIB) provides an opportunity to constrain many properties of the high-redshift (z > 6) stellar population as a whole. This background, specifically from 1 to 200 ?m, should contain information about the era of reionization and the stars that are responsible for these ionizing photons. In this paper, we look at the fractional anisotropy (?I/I) of this high-redshift population, where ?I is the ratio of the magnitude of the fluctuations and I is the mean intensity. We show that this can be used to constrain the escape fraction of the population as a whole, because the magnitude of the fluctuations of the CIB depends on the escape fraction, while the mean intensity does not. This results in lower values of the escape fraction producing higher values of the fractional anisotropy. This difference is predicted to be larger at longer wavelength bands (above 10 ?m), albeit it is also much harder to observe in that range. We show that the fractional anisotropy can also be used to separate a dusty from a dust-free population. Finally, we discuss the constraints provided by current observations on the CIB fractional anisotropy.

Fernandez, Elizabeth R.; Dole, Herve; Iliev, Ilian T.

2013-02-01

33

Gene Effects Mapped Using Fractional and Geodesic Anisotropy in Diffusion Tensor Images of 92 Monozygotic and Dizygotic Twins  

Microsoft Academic Search

We used tensor-derived measures to map the extent of genetic effects on brain fiber microstructure, in 23 monozygotic and 23 dizygotic twin pairs. All 92 DTI volumes were fluidly registered to a geometrically-centered template via a high-dimensional mapping of co-registered structural-MRI. After tensor re-orientation, we computed three scalar DTI measures: the fractional anisotropy (FA), geodesic anisotropy (GA), and the hyperbolic

Agatha D. Lee; Natasha Leporé; Marina Barysheva; Yiyu Chou; Caroline Brun; Sarah K. Madsen; Katie McMahon; Greig I. de Zubicaray; Matthew Meredith; Margaret J. Wright; Arthur W. Toga; Paul M. Thompson

34

In vivo and ex vivo diffusion tensor imaging of cuprizone-induced demyelination in the mouse corpus callosum.  

PubMed

Diffusion tensor imaging has been widely used in studying rodent models of white matter diseases. In this study, we examined the differences between in vivo and ex vivo fractional anisotropy and diffusivity measurements in the mouse cuprizone model. In the control mouse corpus callosum, ex vivo diffusivities were significantly lower than in vivo measurements, but ex vivo fractional anisotropy values were not significantly different from in vivo fractional anisotropy values. With cuprizone induced demyelination and accompanying pathology in the corpus callosum, changes in in vivo and ex vivo fractional anisotropy and diffusivity measurements were not always in agreement. Our results suggest that ex vivo ?(?) was a more reliable indicator of white matter demyelination than in vivo ?(?) and in vivo ?(?) was a more reliable indicator of axonal injury than ex vivo ?(?) in this model. When comparing in vivo and ex vivo diffusion tensor imaging results of axon and myelin pathology in the rodent models, potential changes in tissue microstructures associated with perfusion fixation should be considered. PMID:21656567

Zhang, Jiangyang; Jones, Melina V; McMahon, Michael T; Mori, Susumu; Calabresi, Peter A

2011-06-07

35

Diffusion Tensor Measures of the Corpus Callosum in Adolescents With Adolescent Onset Alcohol Use Disorders  

PubMed Central

Background In adults, myelination injury is associated with alcoholism. Maturation of the corpus callosum is prominent during adolescence. We hypothesized that subjects with adolescent-onset alcohol use disorders (AUD; defined as Diagnostic and Statistical Manual of Mental Disorders-IV alcohol dependence or abuse) would have myelination mircostructural differences compared to controls. Methods Adolescent subjects (25 males, 7 females) with an AUD (16.9 ± 1.2 years), who were recruited from substance abuse treatment programs and had co-morbid mental disorders, and 28 sociodemographically similar healthy controls (17 males, 11 females; 15.9 ± 1.1 years) underwent a 3.0 T MRI diffusion tensor imaging scan. Results Measures of rostral body fractional anisotropy (FA) were higher in the AUD group than in the control group. Compared to controls, mean diffusivity (MD) was lower, while FA was higher, in the AUD group in the isthmus region. Anterior corpus callosum mircostructural development differed in adolescents with AUD, as age was positively (not negatively) associated with rostrum MD and age was negatively (not positively) associated with rostrum FA. There were sex by group interactions in that control females had higher posterior midbody FA when com pared to female adolescents with AUD. Conclusions Lower MD and higher FA values in the AUD group suggest pre-morbid vulnerability for accelerated prefrontal and temporo-parietal myelin maturation that may enhance the risk for adolescent AUD. Significant (and opposite to developmentally expected) correlations were seen between anterior corpus callosum MD and FA measures and age in the AUD group, suggesting neurotoxic effects of alcohol on adolescent corpus callosum microstructure. As seen in adults, female adolescents with AUD may be especially vulnerable to corpus callosum mircostructural injury. Further diffusion tensor imaging studies of corpus callosum maturation in children at familial risk for alcoholism, and in those with AUD, need to be done to elucidate these mechanisms.

De Bellis, Michael D.; Van Voorhees, Elizabeth; Hooper, Stephen R.; Gibler, Nicole; Nelson, Lauren; Hege, Steve G.; Payne, Martha E.; MacFall, James

2013-01-01

36

Maturation of Corpus Callosum Anterior Midbody Is Associated with Neonatal Motor Function in Eight Preterm-Born Infants  

PubMed Central

Background. The etiology of motor impairments in preterm infants is multifactorial and incompletely understood. Whether corpus callosum development is related to impaired motor function is unclear. Potential associations between motor-related measures and diffusion tensor imaging (DTI) of the corpus callosum in preterm infants were explored. Methods. Eight very preterm infants (gestational age of 28–32 weeks) underwent the Hammersmith neonatal neurological examination and DTI assessments at gestational age of 42 weeks. The total Hammersmith score and a motor-specific score (sum of Hammersmith motor subcategories) were calculated. Six corpus callosum regions of interest were defined on the mid-sagittal DTI slice—genu, rostral body, anterior midbody, posterior midbody, isthmus, and splenium. The fractional anisotropy (FA) and mean diffusivity (MD) of these regions were computed, and correlations between these and Hammersmith measures were sought. Results. Anterior midbody FA measures correlated positively with total Hammersmith (rho = 0.929, P = 0.001) and motor-specific scores (rho = 0.857, P = 0.007). Total Hammersmith scores also negatively correlated with anterior midbody MD measures (rho = ?0.714, P = 0.047). Discussion. These results suggest the integrity of corpus callosum axons, particularly anterior midbody axons, is important in mediating neurological functions. Greater callosal maturation was associated with greater motor function. Corpus callosum DTI may prove to be a valuable screening or prognostic marker.

Mathew, Preethi; Pannek, Kerstin; D'Acunto, M. Giulia; Guzzetta, Andrea; Rose, Stephen E.; Colditz, Paul B.; Finnigan, Simon

2013-01-01

37

Fractional anisotropy distributions in 2- to 6-year-old children with autism.  

PubMed

Background? Increasing evidence suggests that autism is a disorder of distributed neural networks that may exhibit abnormal developmental trajectories. Characterisation of white matter early in the developmental course of the disorder is critical to understanding these aberrant trajectories. Methods? A cross-sectional study of 2- to 6-year-old children with autism was conducted using diffusion tensor imaging combined with a novel statistical approach employing fractional anisotropy distributions. Fifty-eight children aged 18-79 months were imaged: 33 were diagnosed with autism, 8 with general developmental delay, and 17 were typically developing. Fractional anisotropy values within global white matter, cortical lobes and the cerebellum were measured and transformed to random F distributions for each subject. Each distribution of values for a region was summarised by estimating ?, the estimated mean and standard deviation of the approximating F for each distribution. Results? The estimated ? parameter, , was significantly decreased in individuals with autism compared to the combined control group. This was true in all cortical lobes, as well as in the cerebellum, but differences were most robust in the temporal lobe. Predicted developmental trajectories of across the age range in the sample showed patterns that partially distinguished the groups. Exploratory analyses suggested that the variability, rather than the central tendency, component of was the driving force behind these results. Conclusions? While preliminary, our results suggest white matter in young children with autism may be abnormally homogeneous, which may reflect poorly organised or differentiated pathways, particularly in the temporal lobe, which is important for social and emotional cognition. PMID:22998325

Cascio, C; Gribbin, M; Gouttard, S; Smith, R G; Jomier, M; Field, S; Graves, M; Hazlett, H C; Muller, K; Gerig, G; Piven, J

2012-09-24

38

Diffusion Tensor Imaging, White Matter lesions, the Corpus Callosum and Gait in the Elderly  

PubMed Central

Background and Purpose Gait impairment is common in the elderly, especially those with stroke and white matter hyperintensities (WMH) on conventional brain MRI. Diffusion Tensor Imaging (DTI) is more sensitive to white matter damage than conventional MRI. The relationship between DTI measures and gait has not been previously evaluated. Our purpose was to investigate the relationship between the integrity of white matter in the corpus callosum as determined by DTI and quantitative measures of gait in the elderly. Methods One hundred seventy-three participants of a community-dwelling elderly cohort had neurological and neuropsychological examinations and brain MRI. Gait function was measured by Tinetti gait (0-12), balance (0-16) and total (0-28) scores. DTI assessed Fractional Anisotropy in the genu and splenium of the corpus callosum. Conventional MRI was used to evaluate for brain infarcts and WMH volume. Results Participants with abnormal gait had low fractional anisotropy in the genu of the corpus callosum but not the splenium. Multiple regressions analyses showed an independent association between these genu abnormalities and all three Tinetti scores (p <0.001). This association remained significant after adding MRI infarcts and WMH volume to the analysis. Conclusions The independent association between quantitative measures of gait function and DTI findings shows that white matter integrity in the genu of corpus callosum is an important marker of gait in the elderly. DTI analyses of white matter tracts in brain and spinal cord may improve knowledge about the pathophysiology of gait impairment and help target clinical interventions.

Bhadelia, Refeeque A.; Price, Lori Lyn; Tedesco, Kurtis L.; Scott, Tammy; Qiu, Wei Qiao; Patz, Samuel; Folstein, Marshal; Rosenberg, Irwin; Caplan, Louis R.; Bergethon, Peter

2009-01-01

39

Agenesis of the Corpus Callosum  

MedlinePLUS

... Reader Microsoft Word Viewer NINDS Agenesis of the Corpus Callosum Information Page Table of Contents (click to jump ... Clinical Trials Organizations What is Agenesis of the Corpus Callosum? Agenesis of the corpus callosum (ACC) is a ...

40

Photodetachment anisotropy for mixed s-p states: 8/3 and other fractions.  

PubMed

An approximate model for analytical prediction of photoelectron angular distributions in anion photodetachment from mixed s-p states is presented. Considering the dipole-allowed s, p, and d free-electron partial waves, the model describes photodetachment anisotropy in terms of the fractional p character of the initial orbital and the A and B coefficients describing the relative intensities of the p ? d to p ? s and s ? p to p ? s channels, respectively. The model represents an extension of the central-potential model to an intermediate regime encompassing varying degrees of s and p contributions to the initial bound orbital. This description is applicable to a broad class of hybrid molecular orbitals, particularly those localized predominantly on a single atom. Under the additional assumption of hydrogenic or Slater-type orbitals, the B/A ratio in photodetachment from a mixed 2s-2p state is shown to equal 8/3. Corresponding fractions are derived for other ns-np mixing cases. The predictions of the model are tested on several anion systems, including NH(2)(-) and CCl(2)(-). The quantitative discrepancies in the latter case are attributed to the breakdown of the central-atom approximation and a mechanism for corresponding corrections is indicated. PMID:23406123

Sanov, Andrei; Grumbling, Emily R; Goebbert, Daniel J; Culberson, Lori M

2013-02-01

41

Bilingual corpus callosum variability  

Microsoft Academic Search

Magnetic resonance imaging was used to produce midsagittal images of the corpus callosum of 19 right-handed adult male and female subjects. The preliminary findings of this study indicate that significant adaptation in the anterior midbody of the corpus callosum has occurred to accommodate multiple language capacity in bilingual individuals compared to monolingual individuals. The main interpretation of this finding is

Porter E Coggins III; Teresa J Kennedy; Terry A Armstrong

2004-01-01

42

Bilingual Corpus Callosum Variability  

ERIC Educational Resources Information Center

|Magnetic resonance imaging was used to produce midsagittal images of the corpus callosum of 19 right-handed adult male and female subjects. The preliminary findings of this study indicate that significant adaptation in the anterior midbody of the corpus callosum has occurred to accommodate multiple language capacity in bilingual individuals…

Coggins, Porter E., III.; Kennedy, Teresa J.; Armstrong, Terry A.

2004-01-01

43

Bilingual Corpus Callosum Variability  

ERIC Educational Resources Information Center

Magnetic resonance imaging was used to produce midsagittal images of the corpus callosum of 19 right-handed adult male and female subjects. The preliminary findings of this study indicate that significant adaptation in the anterior midbody of the corpus callosum has occurred to accommodate multiple language capacity in bilingual individuals…

Coggins, Porter E., III.; Kennedy, Teresa J.; Armstrong, Terry A.

2004-01-01

44

Not lesser but Greater fractional anisotropy in adolescents with alcohol use disorders?  

PubMed Central

Objective The objective of this study is to examine white matter microstructure using diffusion tensor imaging (DTI) in a sample of adolescents with alcohol use disorders (AUD) and no psychiatric or substance co-morbidity. Methods Fifty adolescents with AUD and fifty non-alcohol abusing controls matched on gender and age were studied with DTI, neurocognitive testing, and a clinical assessment that included measures of alcohol use and childhood trauma. Maps of fractional anisotropy (FA) and mean diffusivity (MD) were computed, registered to a common template, and voxel-wise statistical analysis used to assess group differences. Associations between regions of altered WM microstructure and clinical or neurocognitive measures were also assessed. Results Compared with controls, adolescent drinkers without co-morbid substance abuse or externalizing disorder, showed 1) no regions of significantly lower FA, 2) increased FA in WM tracts of the limbic system; 3) no MD differences; and 4) within the region of higher FA in AUD, there were no associations between FA and alcohol use, cognition, or trauma. Discussion The most important observation of this study is our failure to observe significantly smaller FA in this relatively large alcohol abuse/dependent adolescent sample. Greater FA in the limbic regions observed in this study may index a risk for adolescent AUD instead of a consequence of drinking. Drinking behavior may be reinforced in those with higher FA and perhaps greater myelination in these brain regions involved in reward and reinforcement.

Cardenas, Valerie A.; Greenstein, David; Fouche, Jean-Paul; Ferrett, Helen; Cuzen, Natalie; Stein, Dan J.; Fein, George

2013-01-01

45

Mean diffusivity and fractional anisotropy as indicators of disease and genetic liability to schizophrenia  

PubMed Central

The goals of this study were to first determine whether the fractional anisotropy (FA) and mean diffusivity (MD) of major white matter pathways associate with schizophrenia, and secondly to characterize the extent to which differences in these metrics might reflect a genetic predisposition to schizophrenia. Differences in FA and MD were identified using a comprehensive atlas-based tract mapping approach using diffusion tensor imaging and high resolution structural data from 35 patients, 28 unaffected first-degree relatives of patients, 29 community controls, and 14 first-degree relatives of controls. Schizophrenia patients had significantly higher MD in the following tracts compared to controls: the right anterior thalamic radiations, the forceps minor, the bilateral inferior fronto-occipital fasciculus (IFO), the temporal component of the left superior longitudinal fasciculus (tSLF), and the bilateral uncinate. FA showed schizophrenia effects and a linear relationship to genetic liability (represented by schizophrenia patients, first-degree relatives, and controls) for the bilateral IFO, the left inferior longitudinal fasciculus (ILF), and the left tSLF. Diffusion tensor imaging studies have previously identified white matter abnormalities in all three of these tracts in schizophrenia; however, this study is the first to identify a significant genetic liability. Thus, FA of these three tracts may serve as biomarkers for studies seeking to identify how genes influence brain structure predisposing to schizophrenia. However, differences in FA and MD in frontal and temporal white matter pathways may be additionally driven by state variables that involve processes associated with the disease.

Clark, Kristi A.; Nuechterlein, Keith H.; Asarnow, Robert F.; Hamilton, Liberty S.; Phillips, Owen R.; Hageman, Nathan S.; Woods, Roger P.; Alger, Jeffry R.; Toga, Arthur W.; Narr, Katherine L.

2011-01-01

46

Use of fractional anisotropy value by diffusion tensor MRI for preoperative diagnosis of astrocytic tumors: case report  

Microsoft Academic Search

The fractional anisotropy (FA) value calculated by diffusion tensor MRI can indicate the degree of directionality of water diffusion in astrocytic tumors. Here, we report a case of anaplastic astrocytoma in which FA proved invaluable for the preoperative differential diagnosis. A 60-year-old man complained of headache, and underwent routine neuroimaging and DTI. The routine images suggested a low-grade glioma in

Toshinari Misaki; Takaaki Beppu; Takashi Inoue; Kuniaki Ogasawara; Akira Ogawa; Hiroyuki Kabasawa

2004-01-01

47

Functional Diffusion Tensor Imaging: Measuring Task-Related Fractional Anisotropy Changes in the Human Brain along White Matter Tracts  

Microsoft Academic Search

BackgroundFunctional neural networks in the human brain can be studied from correlations between activated gray matter regions measured with fMRI. However, while providing important information on gray matter activation, no information is gathered on the co-activity along white matter tracts in neural networks.Methodology\\/Principal FindingsWe report on a functional diffusion tensor imaging (fDTI) method that measures task-related changes in fractional anisotropy

René C. W. Mandl; Hugo G. Schnack; Marcel P. Zwiers; Arjen van der Schaaf; René S. Kahn; Hilleke E. Hulshoff Pol; Eric Warrant

2008-01-01

48

Enlarged Thalamic Volumes and Increased Fractional Anisotropy in the Thalamic Radiations in Veterans with Suicide Behaviors  

PubMed Central

Post-mortem studies have suggested a link between the thalamus, psychiatric disorders, and suicide. We evaluated the thalamus and anterior thalamic radiations (ATR) in a group of Veterans with and without a history of suicidal behavior (SB) to determine if thalamic abnormalities were associated with an increased risk of SB. Forty Veterans with mild traumatic brain injury (TBI) and no SB (TBI-SB), 19 Veterans with mild TBI and a history of SB (TB?+?SB), and 15 healthy controls (HC) underwent magnetic resonance imaging scanning including a structural and diffusion tensor imaging scan. SBs were evaluated utilizing the Columbia Suicide Rating Scale and impulsivity was measured using the Barratt Impulsiveness Scale (BIS). Differences in thalamic volumes and ATR fractional anisotropy (FA) were examined between (1) TBI?+?SB versus HC and (2) TBI?+?SB versus combined HC and TBI-SB and (3) between TBI?+?SB and TBI-SB. Left and right thalamic volumes were significantly increased in those with TBI?+?SB compared to the HC, TBI-SB, and the combined group. Veterans with TBI?+?SB had increased FA bilaterally compared to the HC, HC and TBI-SB group, and the TBI-SB only group. Significant positive associations were found for bilateral ATR and BIS in the TBI?+?SB group. Our findings of thalamic enlargement and increased FA in individuals with TBI?+?SB suggest that this region may be a biomarker for suicide risk. Our findings are consistent with previous evidence indicating that suicide may be associated with behavioral disinhibition and frontal-thalamic-limbic dysfunction and suggest a neurobiologic mechanism that may increase vulnerability to suicide.

Lopez-Larson, Melissa; King, Jace B.; McGlade, Erin; Bueler, Elliott; Stoeckel, Amanda; Epstein, Daniel J.; Yurgelun-Todd, Deborah

2013-01-01

49

Reduced fractional anisotropy in the visual limbic pathway of young adults witnessing domestic violence in childhood.  

PubMed

Witnessing domestic violence (WDV) is a traumatic childhood experience associated with increased risk for depression, posttraumatic stress disorder and reduced IQ scores. Specific affects of WDV on brain development have not been assessed. We sought to ascertain whether WDV was associated with abnormalities in white matter (WM) tract integrity using diffusion tensor imaging (DTI). Twenty subjects who witnessed domestic violence (16F/4M, mean age 22.4 ± 2.48 years) but were not physically or sexually abused were compared to 27 healthy controls (19F/8M, 21.9 ± 1.97 years) without exposure to trauma or Axis I and II disorders. DTI images were acquired with a 3T Siemens Trio scanner. Group differences in fractional anisotropy (FA), covaried by age, gender, parental education, perceived financial sufficiency, IQ and degree of exposure to parental verbal aggression were assessed using tract-based spatial statistics (TBSS), which projects FA values onto an alignment-invariant fiber tract representation. FA values in the inferior longitudinal fasciculus of left lateral occipital lobe were significantly lower (P<0.05 corrected for multiple comparison) in the WDV group. FA values correlated inversely with ratings of depression, anxiety, somatization, 'limbic irritability' and neuropsychological measures of processing speed. Measures of radial but not axial diffusivity were affected suggesting alterations in myelination. Degree of FA reduction was associated with duration of witnessing interparental verbal aggression and with exposure between ages 7 and 13 years. The inferior longitudinal fasciculus connects occipital and temporal cortex and is the main component of the visual-limbic pathway that subserves emotional, learning and memory functions that are modality specific to vision. This finding is consistent with the hypothesis that exposure to childhood maltreatment is associated with alterations in fiber pathways that convey the adverse experience to frontal, temporal or limbic regions. PMID:21985907

Choi, Jeewook; Jeong, Bumseok; Polcari, Ann; Rohan, Michael L; Teicher, Martin H

2011-10-01

50

Correlation of Apparent Diffusion Coefficient and Fractional Anisotropy Values in the Developing Infant Brain  

PubMed Central

OBJECTIVE The purpose of our study was to correlate decrease in apparent diffusion coefficient (ADC) and increase in fractional anisotropy (FA) in various white matter (WM) regions using diffusion tenor imaging (DTI) within the first year of life. MATERIALS AND METHODS We performed DTI on 53 infants and measured FA and ADC within 10 WM regions important in brain development. For each region, we calculated the slope of ADC as a function of FA, the correlation coefficient (r) and correlation of determination (r2). We performed a group analysis of r values and r2 values for six WM regions primarily composed of crossing fibers and four regions primarily having parallel fibers. Upon finding that a strong correlation of FA with age existed, we adjusted for age and calculated partial correlation coefficients. RESULTS Slopes of FA versus ADC ranged from ?1.00711 to ?1.67592 (p < 0.05); r values ranged from ?0.81 to ?0.50 and r2 values from 0.25 to 0.66. The four greatest r2 values were within WM regions having large numbers of crossing fibers and the three lowest r2 values were in regions having predominantly parallel fibers. After adjusting for age, slopes ranged from ?1.08095 to 0.09612 (p < 0.05 in five cases); partial correlation coefficients ranged from ?0.49 to 0.03 and r2 values from 0.31 to 0.79. The highest partial correlation coefficients were then relatively equally distributed between the two types of WM regions. CONCLUSION In various regions, FA and ADC evolved with differing degrees of correlation. We found a strong influence of age on the relationship between FA and ADC.

Provenzale, James M.; Isaacson, Jared; Chen, Steven; Stinnett, Sandra; Liu, Chunlei

2013-01-01

51

Influence of the packing fraction and host matrix on the magnetoelastic anisotropy in Ni nanowire composite arrays  

NASA Astrophysics Data System (ADS)

The influence of the packing fraction on thermally induced magnetoelastic effects has been studied in Ni nanowires embedded in polycarbonate, poly(vinylidene difluoride), and alumina nanoporous membranes of different porosities for temperatures between 77 K and 345 K. For nanowires embedded in polymer membranes, the contrasting shift in the ferromagnetic resonance frequency when the temperature is either above or below ambient temperature is consistent with the occurrence of uniaxial magnetoelastic anisotropy effects due to the large thermal expansion coefficient mismatch between the metal nanowires and the membrane. A model which considers the influence of the nanowires packing fraction and the membrane material on the magnetoelastic effects, arising from the matrix-assisted deformation process, is proposed. The model is able to successfully explain the experimentally observed effects for the Ni nanowire arrays embedded in the different porous membranes and their variation with the packing fraction. The possibility to modulate the magnetic anisotropy of such nanocomposites by an appropriate choice of membrane material, packing fraction, and sample temperature is of considerable importance to achieve magnetically tunable devices.

Piraux, Luc; Hamoir, Gaël; Encinas, Armando; De La Torre Medina, Joaquin; Abreu Araujo, Flavio

2013-09-01

52

Corpus callosum in multiple sclerosis  

Microsoft Academic Search

A neuropathological study of 20 multiple sclerosis brains using celloidin-embedded slices was carried out to assess the extent of changes in the corpus callosum. Severe atrophy of the callosum was found in cases with marked hydrocephalus. Demyelination of the callosum varied in extent from slight involvement (with a few small plaques) to almost total myelin loss. A clinical history of

R. O. Barnard; Margaret Triggs

1974-01-01

53

The relationship between early life stress and microstructural integrity of the corpus callosum in a non-clinical population  

PubMed Central

Background Previous studies have examined the impact of early life stress (ELS) on the gross morphometry of brain regions, including the corpus callosum. However, studies have not examined the relationship between ELS and the microstructural integrity of the brain. Methods In the present study we evaluated this relationship in healthy non-clinical participants using diffusion tensor imaging (DTI) and self-reported history of ELS. Results Regression analyses revealed significant reductions in fractional anisotropy (FA) within the genu of the corpus callosum among those exposed to the greatest number of early life stressors, suggesting reduced microstructural integrity associated with increased ELS. These effects were most pronounced in the genu of the corpus callosum compared to the body and splenium, and were evident for females rather than males despite no differences in total ELS exposure between the sexes. In addition, a further comparison of those participants who were exposed to no ELS vs. three or more ELS events revealed lower FA in the genu of the corpus callosum among the ELS-exposed group, with trends of FA reduction in the body and the whole corpus callosum. By contrast, there were no relationships between ELS and volumetric analysis of the CC regions. The two group did not differ significantly on measures of current depression, stress or anxiety. Conclusion Our results reveal that greater exposure to ELS is associated with microstructural alterations in the white matter in the absence of significant volumetric changes. Importantly, our results indicate that exposure to ELS is associated with abnormalities on DTI despite the absence of clinically significant psychiatric symptoms. Future studies are needed to determine whether specific types of ELS are more likely to impact brain structure and function.

Paul, Robert; Henry, Lorrie; Grieve, Stuart M; Guilmette, Thomas J; Niaura, Raymond; Bryant, Richard; Bruce, Steven; Williams, Leanne M; Richard, Clark C; Cohen, Ronald A; Gordon, Evian

2008-01-01

54

Reduced Fractional Anisotropy and Axial Diffusivity in White Matter in 22q11.2 Deletion Syndrome: A Pilot Study  

PubMed Central

Individuals with 22q11.2 deletion syndrome (22q11.2DS) evince a 30% incidence of schizophrenia. We compared the white matter (WM) of 22q11.2DS patients without schizophrenia to a group matched healthy controls using Tract-Based-Spatial-Statistics (TBSS). We found localized reduction of Fractional Anisotropy (FA) and Axial Diffusivity (AD; measure of axonal integrity) in WM underlying the left parietal lobe. No changes in Radial Diffusivity (RD; measure of myelin integrity) were observed. Of note, studies in chronic schizophrenia patients report reduced FA, no changes in AD, and increases in RD in WM. Our findings suggest different WM microstructure in 22q11.2DS than in patients with schizophrenia.

Kikinis, Z.; Asami, T.; Bouix, S.; Finn, C. T.; Ballinger, T.; Tworog-Dube, E.; Kucherlapati, R.; Kikinis, R.; Shenton, M. E.; Kubicki, M.

2012-01-01

55

Tractography of the Corpus Callosum in Huntington's Disease.  

PubMed

White matter abnormalities have been shown in presymptomatic and symptomatic Huntington's disease (HD) subjects using Magnetic Resonance Imaging (MRI) and Diffusion Tensor Imaging (DTI) methods. The largest white matter tract, the corpus callosum (CC), has been shown to be particularly vulnerable; however, little work has been done to investigate the regional specificity of tract abnormalities in the CC. Thus, this study examined the major callosal tracts by applying DTI-based tractography. Using TrackVis, a previously defined region of interest tractography method parcellating CC into seven major tracts based on target region was applied to 30 direction DTI data collected from 100 subjects: presymptomatic HD (Pre-HD) subjects (n?=?25), HD patients (n?=?25) and healthy control subjects (n?=?50). Tractography results showed decreased fractional anisotropy (FA) and increased radial diffusivity (RD) across broad regions of the CC in Pre-HD subjects. Similar though more severe deficits were seen in HD patients. In Pre-HD and HD, callosal FA and RD were correlated with Disease Burden/CAG repeat length as well as motor (UHDRSI) and cognitive (URDRS2) assessments. These results add evidence that CC pathways are compromised prior to disease onset with possible demyelination occurring early in the disease and suggest that CAG repeat length is a contributing factor to connectivity deficits. Furthermore, disruption of these callosal pathways potentially contributes to the disturbances of motor and cognitive processing that characterize HD. PMID:24019913

Phillips, Owen; Sanchez-Castaneda, Cristina; Elifani, Francesca; Maglione, Vittorio; Di Pardo, Alba; Caltagirone, Carlo; Squitieri, Ferdinando; Sabatini, Umberto; Di Paola, Margherita

2013-09-03

56

Relationship between white matter fractional anisotropy and other indices of cerebral health in normal aging: Tract-based spatial statistics study of aging  

Microsoft Academic Search

White matter (WM) fractional anisotropy (FA) is thought to be related to WM integrity and decline in FA is often used as an index of decreasing WM health. However, the relationship of FA to other structural indices of cerebral health has not been well studied. We hypothesized that the decline in WM health will be associated with changes in several

P. Kochunov; P. M. Thompson; J. L. Lancaster; G. Bartzokis; S. Smith; T. Coyle; D. R. Royall; A. Laird; P. T. Fox

2007-01-01

57

MRI of the Corpus Callosum in Multiple Sclerosis: Association with Disability  

PubMed Central

Background Inflammatory demyelination and axon damage in the corpus callosum are prominent features of multiple sclerosis (MS) and may partially account for impaired performance on complex tasks. Objective To characterize quantitative callosal MRI abnormalities and their association with disability. Methods In 69 participants with MS and 29 healthy volunteers, lesional and extralesional callosal MRI indices were estimated via diffusion tensor tractography. Expanded disability status scale (EDSS) and MS functional composite (MSFC) scores were recorded in 53 of the participants with MS. Results All tested callosal MRI indices were diffusely abnormal in MS. EDSS score was correlated only with age (r=0.51). Scores on the overall MSFC and its paced serial auditory addition test (PASAT) and 9-hole peg test components were correlated with callosal fractional anisotropy (r=0.27, 0.35, 0.31, respectively) and perpendicular diffusivity (r=?0.29, ?0.30, and ?0.31) but not with overall callosal volume or callosal lesion volume; the PASAT score was more weakly correlated with callosal magnetization-transfer ratio (r=0.21). Anterior callosal abnormalities were associated with impaired PASAT performance and posterior abnormalities with slow performance on the 9-hole peg test. Conclusion Abnormalities in the corpus callosum can be assessed with quantitative MRI and are associated with cognitive and complex upper-extremity dysfunction in MS.

Ozturk, A.; Smith, S. A.; Gordon-Lipkin, E. M.; Harrison, D. M.; Shiee, N.; Pham, D. L.; Caffo, B. S.; Calabresi, P. A.; Reich, D. S.

2009-01-01

58

Corpus Callosum Abnormalities and their Association with Psychotic Symptoms in Patients with Schizophrenia  

PubMed Central

Background Whilst the neuroanatomical underpinnings of the functional brain disconnectivity observed in patients with schizophrenia remain elusive, white matter fiber bundles of the brain are a likely candidate given that they represent the infrastructure for long-distance neural communication. Methods This study investigated for diffusion abnormalities in 19 patients with chronic schizophrenia (SZ), relative to 19 matched controls, across tractography-defined segments of the Corpus Callosum. Diffusion-weighted images were acquired with 51 non-collinear gradients on a 3T scanner (1.7mm isotropic voxels). The Corpus Callosum was extracted by means of whole-brain tractography and automated fiber-clustering, and was parcellated into six segments on the basis of fiber trajectories. The diffusion indices of Fractional Anisotropy (FA) and Mode were calculated for each segment. Results Relative to the healthy controls, the SZ patients exhibited Mode increases in the Parietal fibers, suggesting a relative absence of crossing fibers. SZ patients also exhibited FA reductions in the Frontal fibers, which were underpinned by increased in Radial Diffusivity, consistent with myelin abnormalities. Significant correlations were observed between patients' degree of Reality Distortion and their FA and Radial Diffusivity, such that the most severely psychotic patients were the least abnormal in terms of their Frontal fiber diffusivity. Conclusions The SZ patients exhibited a variety of diffusion abnormalities in the Corpus Callosum, which were related to the severity of their psychotic symptoms. To the extent that diffusion abnormalities influence axonal transmission velocities, these results provide support for those theories that emphasize neural timing abnormalities in the etiology of schizophrenia.

Whitford, Thomas J.; Kubicki, Marek; Schneiderman, Jason S.; O'Donnell, Lauren J.; King, Rebecca; Alvarado, Jorge L.; Khan, Usman; Markant, Douglas; Nestor, Paul G.; Niznikiewicz, Margaret; McCarley, Robert W.; Westin, Carl-Fredrik; Shenton, Martha E.

2010-01-01

59

[Some structural and functional features of the dorsolateral prefrontal cortex and the corpus callosum genu and auditory information processing (P300) in healthy subjects and patients with juvenile schizophrenia].  

PubMed

Some structural and functional characteristics of the dorsolateral prefrontal cortex and corpus callosum genu were analyzed in comparison with electrophysiological markers of selective attention in 18 mentally healthy subjects and 22 remitted patients with juvenile schizophrenia. In both topography zones there were no statistically significant intergroup differences in N-acetylaspartate and choline compounds (by proton MR-spectroscopy), whereas fractional anisotropy (by diffusion tensor imaging) in the corpus callosum genu was lower in patients. Absence of significant correlations between the imaging characteristics and psychopathology scores and their weak correlations with P300 suggest a poor involvement of the analyzed structures in the processes which determine cognitive disorders in patients with juvenile schizophrenia. PMID:23227726

Lebedeva, I S; Sidorin, S V; Akhadov, T A; Barkhatova, A N; Kaleda, V G; Semenova, N A

60

Relationships between brain water content and diffusion tensor imaging parameters (apparent diffusion coefficient and fractional anisotropy) in multiple sclerosis.  

PubMed

Fifteen multiple sclerosis patients were examined by diffusion tensor imaging (DTI) to determine fractional anisotropy (FA) and apparent diffusion coefficient (ADC) in a superventricular volume of interest of 8 x 8 x 2 cm(3) containing gray matter (GM) and white matter (WM) tissue. Point resolved spectroscopy 2D-chemical shift imaging of the same volume was performed without water suppression. The water contents and DTI parameters in 64 voxels of 2 cm(3) were compared. The water content was increased in patients compared with controls (GM: 244+/-21 vs. 194+/-10 a.u.; WM: 245+/-32 vs. 190+/-11 a.u.), FA decreased (GM: 0.226+/-0.038 vs. 0.270+/-0.020; WM: 0.337+/-0.044 vs. 0.402+/-0.011) and ADC increased [GM: 1134+/-203 vs. 899+/-28 (x10(-6) mm(2)/s); WM: 901+/-138 vs. 751+/-17 (x10(-6) mm(2)/s)]. Correlations of water content with FA and ADC in WM were strong (r=-0.68, P<0.02; r=0.75; P<0.01, respectively); those in GM were weaker (r=-0.50, P<0.05; r=0.45, P<0.1, respectively). Likewise, FA and ADC were more strongly correlated in WM (r=-0.88; P<0.00001) than in GM (r=-0.69, P<0.01). The demonstrated relationship between DTI parameters and water content in multiple sclerosis patients suggests a potential for therapy monitoring in normal-appearing brain tissue. PMID:16331463

Sijens, Paul E; Irwan, Roy; Potze, Jan Hendrik; Mostert, Jop P; De Keyser, Jacques; Oudkerk, Matthijs

2005-12-06

61

In vivo and ex vivo Diffusion Tensor Imaging of Cuprizone Induced Demyelination in the Mouse Corpus Callosum  

PubMed Central

Diffusion tensor imaging (DTI) has been widely used in studying rodent models of white matter diseases. In this study, we examined the differences between in vivo and ex vivo fractional anisotropy (FA) and diffusivity measurements in the mouse cuprizone model. In the control mouse corpus callosum (CC), ex vivo diffusivities were significantly lower than in vivo measurements, but ex vivo FA values were not significantly different from in vivo FA values. With cuprizone induced demyelination and accompanying pathology in the CC, changes in in vivo and ex vivo FA and diffusivity measurements were not always in agreement. Our results suggest that ex vivo ?? was a more reliable indicator of white matter demyelination than in vivo ?? and in vivo ?? was a more reliable indicator of axonal injury than ex vivo ?? in this model. When comparing in vivo and ex vivo DTI results of axon and myelin pathology in the rodent models, potential changes in tissue microstructures associated with perfusion fixation should be considered.

Zhang, Jiangyang; Jones, Melina V.; McMahon, Michael T.; Mori, Susumu; Calabresi, Peter A.

2011-01-01

62

The Corpus Callosum Wallerian Degeneration in the Unilateral Brain Tumors: Evaluation with Diffusion Tensor Imaging (DTI)  

PubMed Central

Purpose: The purpose of this study was to evaluate whether DTI could demonstrate the water diffusivity changes in the corpus callosum (CC), which were not visible on the morphologic imaging in patients with glioblastoma multiforme (GBM) and brain metastases with no midline CC infiltration. Materials and Methods: Twenty-seven patients with treatment naïve unilateral GBM and eleven patients with a solitary brain metastasis with no midline CC infiltration underwent DTI. Ten controls with normal brain MRI were also included. Based on the tensors, the principal diffusion directions, the anisotropy values, and the prior information about the diffusivity pattern in CC, a similarity measure was proposed. Subsequently, the CC was automatically divided into the Witelson subdivisions. Results: We observed significantly decreased fractional anisotropy values in all the regions of CC in the patients with GBM and metastases as compared to those in the controls. The mean diffusivity values showed a significant increase in all the regions of CC, except the splenium in patients with GBM and the isthmus in the patients with metastases, as compared to that in the controls respectively. Conclusion: In conclusion, DTI is more sensitive than the morphologic MR imaging in the evaluation of changes within the CC, in brain tumours which do not infiltrate the CC. However, these changes of the DTI metrics in the CC are due to a Wallerian degeneration rather than a tumour infiltration, as was shown by our results, as similar changes were seen in the GBM as well as the non-infiltrating metastases patients.

Saksena, Sona; Jain, Rajan; Schultz, Lonni; Jiang, Quan; Soltanian-Zadeh, Hamid; Scarpace, Lisa; Rosenblum, Mark; Mikkelsen, Tom; Nazem-Zadeh, Mohammad-Reza

2013-01-01

63

Fractions!  

NSDL National Science Digital Library

Practice all of the activities to help you learn fractions! Go through all five levels of Fractions Review Activities Practice Naming Fractions Do you remember how to do Fraction Sets? Play these games when you have finished the top three activities: Cross the River Pizza Party Fractions Rescue Island Adding Subtracting Fractions SPLAT Mrs. Anderson's Fraction Games Action Fraction Soccer Shootout Fraction Multiplication Soccer Shootout Fraction Division Dirt Bike Fractions Comparisons ...

Lerdahl, Miss

2011-02-01

64

Shape anisotropy: tensor distance to anisotropy measure  

Microsoft Academic Search

Fractional anisotropy, defined as the distance of a diffusion tensor from its closest isotropic tensor, has been extensively studied as quantitative anisotropy measure for diffusion tensor magnetic resonance images (DT-MRI). It has been used to reveal the white matter profile of brain images, as guiding feature for seeding and stopping in fiber tractography and for the diagnosis and assessment of

Yonas T. Weldeselassie; Saba El-Hilo; M. S. Atkins

2011-01-01

65

Oculomotor-corpus callosum dysplasia.  

PubMed Central

An infant with congenital bilateral ophthalmoplegia with levator and pupillary sparing is presented. The eyes are fixed in a divergent position with no apparent motility. The baby is otherwise clinically normal and is developing in a normal fashion except for delayed growth pattern. Visual attention is present and he fixates with either eye. Computed tomography demonstrates an associated dysplasia of the corpus callosum and an abnormal ventricular system. Neuroendocrine studies performed at one year of age demonstrate subnormal levels of growth hormone. It is postulated that this represents an embryodysgenesis involving the developing mesencephalic tegmentum (oculomotor nuclei) and the diencephalic lamina reuniens (corpus callosum). It is the first reported case of congenital ophthalmoplegia with corpus callosum dysplasia. The "embryodysgenic" relationship with other forebrain-ocular anomalies has been alluded to and remains speculative. Images FIGURE 1 FIGURE 2 A FIGURE 2 B

Acers, T E; Blackwell, C

1982-01-01

66

Early musical training and white-matter plasticity in the corpus callosum: evidence for a sensitive period.  

PubMed

Training during a sensitive period in development may have greater effects on brain structure and behavior than training later in life. Musicians are an excellent model for investigating sensitive periods because training starts early and can be quantified. Previous studies suggested that early training might be related to greater amounts of white matter in the corpus callosum, but did not control for length of training or identify behavioral correlates of structural change. The current study compared white-matter organization using diffusion tensor imaging in early- and late-trained musicians matched for years of training and experience. We found that early-trained musicians had greater connectivity in the posterior midbody/isthmus of the corpus callosum and that fractional anisotropy in this region was related to age of onset of training and sensorimotor synchronization performance. We propose that training before the age of 7 years results in changes in white-matter connectivity that may serve as a scaffold upon which ongoing experience can build. PMID:23325263

Steele, Christopher J; Bailey, Jennifer A; Zatorre, Robert J; Penhune, Virginia B

2013-01-16

67

Microstructural White Matter Changes in the Corpus Callosum of Young People with Bipolar Disorder: A Diffusion Tensor Imaging Study  

PubMed Central

To date, most studies of white matter changes in Bipolar Disorder (BD) have been conducted in older subjects and with well-established disorders. Studies of young people who are closer to their illness onset may help to identify core neurobiological characteristics and separate these from consequences of repeated illness episodes or prolonged treatment. Diffusion tensor imaging (DTI) was used to examine white matter microstructural changes in 58 young patients with BD (mean age 23 years; range 16–30 years) and 40 controls. Whole brain voxelwise measures of fractional anisotropy (FA), parallel diffusivity (?//) and radial diffusivity (??) were calculated for all subjects. White matter microstructure differences (decreased FA corrected p<.05) were found between the patients with BD and controls in the genu, body and splenium of the corpus callosum as well as the superior and anterior corona radiata. In addition, significantly increased radial diffusivity (p<.01) was found in the BD group. Neuroimaging studies of young patients with BD may help to clarify neurodevelopmental aspects of the illness and for identifying biomarkers of disease onset and progression. Our findings provide evidence of microstructural white matter changes early in the course of illness within the corpus callosum and the nature of these changes suggest they are associated with abnormalities in the myelination of axons.

Lagopoulos, Jim; Hermens, Daniel F.; Hatton, Sean N.; Tobias-Webb, Juliette; Griffiths, Kristi; Naismith, Sharon L.; Scott, Elizabeth M.; Hickie, Ian B.

2013-01-01

68

Effect of Icosahedral Quasicrystalline Fraction and Extrusion Ratio on Microstructure, Mechanical Properties, and Anisotropy of Mg-Zn-Gd-Based Alloys  

NASA Astrophysics Data System (ADS)

We have fabricated three types of Mg-Zn-Gd-based alloys containing the icosahedral quasicrystalline phase (I-phase) to investigate how volume fraction of the I-phase and extrusion ratio can have an impact on the microstructure, mechanical properties, and anisotropy of the as-extruded alloys. We find that grains are refined and that the ultimate tensile strength and elongation are improved as either the volume fraction of I-phase or the extrusion ratio is increased, which can be attributed to the secondary phase particle stimulate recrystallization nucleation and restrained grain boundary motion. Moreover, anisotropy is mitigated in all of the alloys as either the I-phase fraction or the extrusion ratio is increased owing to the coeffect of texture weakening and grain refinement as well as to the effect of I-phase on twinning. We also find that with the increase in the amount of the I-phase, the yield strength (YS) is decreased for the alloys extruded at a low ratio owing to the texture weakening, yet it is increased for the alloys extruded at high ratio owing to the strengthening originating from the I-phase and refined grains. The mechanical properties are improved for the alloys extruded at high ratio, which is due to their fine grains and uniform microstructure.

Huang, Hua; Yuan, Guangyin; Wang, Zhongchang; Chen, Chunlin; Ding, Wenjiang

2013-06-01

69

Altered white matter microstructure in the corpus callosum in Huntington's disease: implications for cortical "disconnection".  

PubMed

The corpus callosum (CC) is the major conduit for information transfer between the cerebral hemispheres and plays an integral role in relaying sensory, motor and cognitive information between homologous cortical regions. The majority of fibers that make up the CC arise from large pyramidal neurons in layers III and V, which project contra-laterally. These neurons degenerate in Huntington's disease (HD) in a topographically and temporally selective way. Since any focus of cortical degeneration could be expected to secondarily de-afferent homologous regions of cortex, we hypothesized that regionally selective cortical degeneration would be reflected in regionally selective degeneration of the CC. We used conventional T1-weighted, diffusion tensor imaging (DTI), and a modified corpus callosum segmentation scheme to examine the CC in healthy controls, huntingtin gene-carriers and symptomatic HD subjects. We measured mid-sagittal callosal cross-sectional thickness and several DTI parameters, including fractional anisotropy (FA), which reflects the degree of white matter organization, radial diffusivity, a suggested index of myelin integrity, and axial diffusivity, a suggested index of axonal damage of the CC. We found a topologically selective pattern of alterations in these measures in pre-manifest subjects that were more extensive in early symptomatic HD subjects and that correlated with performance on distinct cognitive measures, suggesting an important role for disrupted inter-hemispheric transfer in the clinical symptoms of HD. Our findings provide evidence for early degeneration of commissural pyramidal neurons in the neocortex, loss of cortico-cortical connectivity, and functional compromise of associative cortical processing. PMID:19850138

Rosas, H Diana; Lee, Stephanie Y; Bender, Alexander C; Zaleta, Alexandra K; Vangel, Mark; Yu, Peng; Fischl, Bruce; Pappu, Vasanth; Onorato, Christina; Cha, Jang-Ho; Salat, David H; Hersch, Steven M

2009-10-19

70

Tract shape modelling provides evidence of topological change in corpus callosum genu during normal ageing.  

PubMed

Understanding how ageing affects brain structure is an important challenge for medical science. By allowing segmentation of fasciculi-of-interest from diffusion magnetic resonance imaging (dMRI) data, tractography provides a promising tool for assessing white matter connectivity in old age. However, the output from tractography algorithms is usually strongly dependent on the subjective location of user-specified seed points, with the result that it can be both difficult and time consuming to identify the same tract reliably in cross-sectional studies. Here we investigate whether a novel method for automatic single seed point placement based on tract shape modelling, termed probabilistic model-based neighbourhood tractography (PNT), can reliably segment the same tract from subject to subject in a non-demented cohort aged over 65 years. For the fasciculi investigated (genu and splenium of corpus callosum, cingulum cingulate gyri, corticospinal tracts and uncinate fasciculi), PNT was able to provide anatomically plausible representations of the tract in question in 70 to 90% of subjects compared with 2.5 to 60% if single seed points were simply transferred directly from standard to native space. In corpus callosum genu there was a significant negative correlation between a PNT-derived measure of tract shape similarity to a young brain reference tract and age, and a trend towards a significant negative correlation between tract-averaged fractional anisotropy and age; results that are consistent with previous dMRI studies of normal ageing. These data show that it is possible automatically to segment comparable tracts in the brains of older subjects using single seed point tractography, if the seed point is carefully chosen. PMID:18687404

Bastin, Mark E; Piatkowski, Jakub P; Storkey, Amos J; Brown, Laura J; Maclullich, Alasdair M J; Clayden, Jonathan D

2008-07-18

71

Performance asymmetries in tool use are associated with corpus callosum integrity in chimpanzees (Pan troglodytes): a diffusion tensor imaging study.  

PubMed

The authors examined the relationship of corpus callosum (CC) morphology and organization to hand preference and performance on a motor skill task in chimpanzees. Handedness was assessed using a complex tool use task that simulated termite fishing. Chimpanzees were initially allowed to perform the task wherein they could choose which hand to use (preference measure), then they were required to complete trials using each hand (performance measure). Two measures were used to assess the CC: midsagittal area obtained from in vivo magnetic resonance images and density of transcallosal connections as determined by fractional anisotropy values obtained from diffusion tensor imaging. The authors hypothesized that chimpanzees would perform better on their preferred hand compared to the nonpreferred hand, and that strength of behavioral lateralization (rather the direction) on this task would be negatively correlated to regions of the CC involved in motor processing. Results indicate that the preferred hand was the most adept hand. Performance asymmetries correlated with fractional anisotropy measures but not area measures of the CC. PMID:23398443

Phillips, Kimberley A; Schaeffer, Jennifer; Barrett, Elizabeth; Hopkins, William D

2013-02-01

72

Corpus callosum alterations in very preterm infants: perinatal correlates and 2 year neurodevelopmental outcomes  

PubMed Central

The aim of this study was to relate altered corpus callosum (CC) integrity in 106 very preterm (VPT) infants (<30 weeks’ gestational age or <1250 g birth weight) at term equivalent to perinatal predictors and neurodevelopmental outcomes at two years. T1 and diffusion magnetic resonance images were obtained. The CC was traced, and divided into six sub-regions for cross-sectional area and shape analyses. Fractional anisotropy, mean, axial and radial diffusivity was sampled within the CC, and probabilistic tractography performed. Perinatal predictors were explored. The Bayley Scales of Infant Development (BSID-II) was administered at two years. Intraventricular hemorrhage was associated with a smaller genu and altered diffusion values within the anterior and posterior CC of VPT infants. White matter injury was associated with widespread alterations to callosal diffusion values, especially posteriorly, and radial diffusivity was particularly elevated, indicating altered myelination. Reduced CC tract volume related to lower gestational age, particularly posteriorly. Reduced posterior callosal skew was associated with postnatal corticosteroid exposure. This more circular CC was associated with delayed cognitive development. Higher diffusivity, particularly in splenium tracts, was associated with impaired motor development. This study elucidates perinatal predictors and adverse neurodevelopmental outcomes associated with altered callosal integrity in VPT infants.

Thompson, Deanne K.; Inder, Terrie E.; Faggian, Nathan; Warfield, Simon K.; Anderson, Peter J.; Doyle, Lex W.; Egan, Gary F.

2011-01-01

73

Microstructural organization of corpus callosum projections to prefrontal cortex predicts bimanual motor learning.  

PubMed

The corpus callosum (CC) is the largest white matter tract in the brain. It enables interhemispheric communication, particularly with respect to bimanual coordination. Here, we use diffusion tensor imaging (DTI) in healthy humans to determine the extent to which structural organization of subregions within the CC would predict how well subjects learn a novel bimanual task. A single DTI scan was taken prior to training. Participants then practiced a bimanual visuomotor task over the course of 2 wk, consisting of multiple coordination patterns. Findings revealed that the predictive power of fractional anisotropy (FA) was a function of CC subregion and practice. That is, FA of the anterior CC, which projects to the prefrontal cortex, predicted bimanual learning rather than the middle CC regions, which connect primary motor cortex. This correlation was specific in that FA correlated significantly with performance of the most difficult frequency ratios tested and not the innately preferred, isochronous frequency ratio. Moreover, the effect was only evident after training and not at initiation of practice. This is the first DTI study in healthy adults which demonstrates that white matter organization of the interhemispheric connections between the prefrontal structures is strongly correlated with motor learning capability. PMID:22837217

Sisti, Helene M; Geurts, Monique; Gooijers, Jolien; Heitger, Marcus H; Caeyenberghs, Karen; Beets, Iseult A M; Serbruyns, Leen; Leemans, Alexander; Swinnen, Stephan P

2012-07-26

74

Watershed-based segmentation of the corpus callosum in diffusion MRI  

NASA Astrophysics Data System (ADS)

The corpus callosum (CC) is one of the most important white matter structures of the brain, interconnecting the two cerebral hemispheres, and is related to several neurodegenerative diseases. Since segmentation is usually the first step for studies in this structure, and manual volumetric segmentation is a very time-consuming task, it is important to have a robust automatic method for CC segmentation. We propose here an approach for fully automatic 3D segmentation of the CC in the magnetic resonance diffusion tensor images. The method uses the watershed transform and is performed on the fractional anisotropy (FA) map weighted by the projection of the principal eigenvector in the left-right direction. The section of the CC in the midsagittal slice is used as seed for the volumetric segmentation. Experiments with real diffusion MRI data showed that the proposed method is able to quickly segment the CC without any user intervention, with great results when compared to manual segmentation. Since it is simple, fast and does not require parameter settings, the proposed method is well suited for clinical applications.

Freitas, Pedro; Rittner, Leticia; Appenzeller, Simone; Lapa, Aline; Lotufo, Roberto

2012-02-01

75

Sexual Dimorphism in the Human Corpus Callosum  

Microsoft Academic Search

Preliminary observations suggest a sex difference in the shape and surface area of the human corpus callosum. The sexual dimorphism is striking in the splenium, the caudal or posterior portion of the corpus callosum. The female splenium is both more bulbous and larger than the male counterpart. Since peristriate, parietal, and superior temporal fibers course through the splenium, this finding

Christine de Lacoste-Utamsing; Ralph L. Holloway

1982-01-01

76

Corpus Callosum Size in Delphinid Cetaceans  

Microsoft Academic Search

The midsagittal surface area of the corpus callosum was determined by computer-assisted morphometry in juvenile and adult members of 13 species of the cetacean family Delphinidae. In 57 brains, absolute callosal areas ranged from 104 to 829 mm2. When compared to other mammal groups possessing a corpus callosum, callosal area in dolphins was smaller in relation to brain mass with

Raymond J. Tarpley; Sam H. Ridgway

1994-01-01

77

Glioma infiltration of the corpus callosum: early signs detected by DTI.  

PubMed

The most frequent primary brain tumors, anaplastic astrocytomas (AA) and glioblastomas (GBM): tend to invasion of the surrounding brain. Histopathological studies found malignant cells in macroscopically unsuspicious brain parenchyma remote from the primary tumor, even affecting the contralateral hemisphere. In early stages, diffuse interneural infiltration with changes of the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) is suspected. The purpose of this study was to investigate the value of DTI as a possible instrument of depicting evidence of tumor invasion into the corpus callosum (CC). Preoperatively, 31 patients with high-grade brain tumors (8 AA and 23 GBM) were examined by MRI at 3 T, applying a high-resolution diffusion tensor imaging (DTI) sequence. ADC- and FA-values were analyzed in the tumor-associated area of the CC as identified by fiber tracking, and were compared to matched healthy controls. In (MR-)morphologically normal appearing CC the ADC values were elevated in the tumor patients (n = 22; 0.978 × 10(-3) mm²/s) compared to matched controls (0.917 × 10(-3) mm²/s, p < 0.05), and the corresponding relative FA was reduced (rFA: 88 %, p < 0.01). The effect was pronounced in case of affection of the CC visible on MRI (n = 9; 0.978 × 10(-3) mm²/s, p < 0.05; rFA: 72 %, p < 0.01). Changes in diffusivity and anisotropy in the CC can be interpreted as an indicator of tumor spread into the contralateral hemisphere not visible on conventional MRI. PMID:23344787

Kallenberg, K; Goldmann, T; Menke, J; Strik, H; Bock, H C; Stockhammer, F; Buhk, J H; Frahm, J; Dechent, P; Knauth, M

2013-01-24

78

Shape anisotropy: tensor distance to anisotropy measure  

NASA Astrophysics Data System (ADS)

Fractional anisotropy, defined as the distance of a diffusion tensor from its closest isotropic tensor, has been extensively studied as quantitative anisotropy measure for diffusion tensor magnetic resonance images (DT-MRI). It has been used to reveal the white matter profile of brain images, as guiding feature for seeding and stopping in fiber tractography and for the diagnosis and assessment of degenerative brain diseases. Despite its extensive use in DT-MRI community, however, not much attention has been given to the mathematical correctness of its derivation from diffusion tensors which is achieved using Euclidean dot product in 9D space. But, recent progress in DT-MRI has shown that the space of diffusion tensors does not form a Euclidean vector space and thus Euclidean dot product is not appropriate for tensors. In this paper, we propose a novel and robust rotationally invariant diffusion anisotropy measure derived using the recently proposed Log-Euclidean and J-divergence tensor distance measures. An interesting finding of our work is that given a diffusion tensor, its closest isotropic tensor is different for different tensor distance metrics used. We demonstrate qualitatively that our new anisotropy measure reveals superior white matter profile of DT-MR brain images and analytically show that it has a higher signal to noise ratio than fractional anisotropy.

Weldeselassie, Yonas T.; El-Hilo, Saba; Atkins, M. S.

2011-03-01

79

Corpus callosum volume and neurocognition in autism  

PubMed Central

The corpus callosum has recently been considered as an index of interhemispheric connectivity. This study applied a novel volumetric method to examine the size of the corpus callosum in 32 individuals with autism and 34 age-, gender- and IQ-matched controls and to investigate the relationship between this structure and cognitive measures linked to interhemispheric functioning. Participants with autism displayed reductions in total corpus callosum volume and in several of its subdivisions. Relationships were also observed between volumetric alterations and performance on several cognitive tests including the Tower of Hanoi test. These findings provide further evidence for volumetric alterations in the corpus callosum in autism, but warrant additional studies examining the relationship of this structure and specific measures of interhemispheric connectivity.

Keary, Christopher J.; Minshew, Nancy J.; Bansal, Rahul; Goradia, Dhruman; Fedorov, Serguei; Keshavan, Matcheri S.; Hardan, Antonio Y.

2011-01-01

80

Diffusion tensor imaging (DTI) and colored fractional anisotropy (FA) mapping of the subthalamic nucleus (STN) and the globus pallidus interna (GPi)  

PubMed Central

Introduction The subthalamic nucleus (STN) and the globus pallidus internus (GPi) are the most common surgical targets for the treatment of Parkinson’s disease. We studied directionally colored fractional anisotropy (FA) and diffusion tensor imaging (DTI) sequences to better target these anatomical regions. Methods Four patients undergoing stereotactic surgery for movement disorders were studied. Stereotactic targets and fiber tractography were determined on MRIs using the Schaltenbrand–Wahren atlas for definition in the iPlan software. In addition, post-operative imaging was fused to preoperative FA sequences for end-result identification. Axial, sagittal, and coronal images of the FA sequence were studied. DTI parameters used ranged from 2 to 4 mm for voxel size in the x/y/z planes, fiber length was kept constant at 15 mm and FA threshold of 0.25. Results Colored FA maps resulted in a key signature in and around the STN and GPi. Regions identified include, but were not limited to: the internal capsule, nigral projections, the thalamic fasciculus, Forel’s fields H1 and H2, zona incerta, suthalamic fasciculus, tegmental tracts, and cerebello-rubro-thalamic tract. Conclusions Colored FA maps allow a potential method to identify the STN and GPi accurately. DTI has proven to be a powerful tool that can be used to augment identification of the STN nucleus and GPi used for stereotactic surgery.

Gorgulho, Alessandra; Bari, Ausaf; Behnke, Eric; Frew, Andrew; Gevorkyan, Inga; Pouratian, Nader; DeSalles, Antonio

2010-01-01

81

Corpus callosum morphology in children who stutter  

PubMed Central

Multiple studies have reported both functional and neuroanatomical differences between adults who stutter and their normally fluent peers. However, the reasons for these differences remain unclear although some developmental data suggest that structural brain differences may be present in school-age children who stutter. In the present study, the corpus callosum of children with persistent stuttering, children who recovered from stuttering and typically developing children between 9 and 12 years of age was compared to test if the presence of aberrant callosal morphology is implicated in this disorder. The total corpus callosum midsagittal area and area of each subsection consisting of the rostrum, anterior midbody, posterior midbody and splenium were measured using MIPAV (Medical Image Processing, Analysis, and Visualization). Voxel-based morphometry (VBM) was also used to compare white matter volume. No differences were detected in the corpus callosum area or white matter volume between children with persistent stuttering, children who recovered from stuttering and typically developing children. These results agree with dichotic listening studies that indicate children who stutter show the typical right ear advantage. Therefore, the neural reorganization across the midline shown in adults who stutter may be the result of long-term adaptations to persistent stuttering. Learning outcomes Educational objectives: After reading this article, the reader will be able to: (1) summarize research findings on corpus callosum development; and (2) discuss the characteristics of corpus callosum anatomy in stuttering.

Choo, Ai Leen; Chang, Soo-Eun; Zengin-Bolatkale, Hatun; Ambrose, Nicoline G.; Loucks, Torrey M.

2012-01-01

82

Centrum Semiovale and Corpus Callosum Integrity in Relation to Information Processing Speed in Patients With Severe Traumatic Brain Injury.  

PubMed

OBJECTIVES:: This study investigated white matter alterations in the corpus callosum (CC) and centrum semiovale (CSO), using diffusion tensor imaging and magnetization transfer imaging, in participants with severe traumatic brain injury (TBI) and related these changes to processing speed measures. PARTICIPANTS AND METHODS:: Fourteen adult participants with severe TBI underwent neuroimaging and assessment, using the Symbol Digit Modalities Test and Trail-Making Test, Part B, at approximately 6 months postinjury. Thirteen demographically similar, neurologically intact adults were imaged for comparison. RESULTS:: The TBI group demonstrated lower fractional anisotropy (FA) for the right CSO and higher apparent diffusion coefficient (ADC) for the CSO bilaterally than the control group. Lower FA and higher ADC were noted in all CC regions. Magnetization transfer imaging revealed smaller magnetization transfer ratios (MTRs) in the right and left CSO and CC genu and splenium. Written Symbol Digit Modalities Test performance was related to right CSO FA, bilateral CSO ADC, CC FA, and right CSO MTR, whereas oral Symbol Digit Modalities Test was related to right CSO FA, ADC, and MTR. Trail-Making Test, Part B, was related to right CSO FA and MTR. CONCLUSIONS:: Advanced neuroimaging modalities such as diffusion tensor imaging and magnetization transfer imaging demonstrate significant alterations in white matter, which are related to processing speed. These techniques may be useful in quantifying the extent of injury even in normal appearing white matter after TBI. PMID:22832369

Kourtidou, Paraskevi; McCauley, Stephen R; Bigler, Erin D; Traipe, Elfrides; Wu, Trevor C; Chu, Zili D; Hunter, Jill V; Li, Xiaoqi; Levin, Harvey S; Wilde, Elisabeth A

2012-07-24

83

Structural organization of the corpus callosum predicts the extent and impact of cortical activity in the nondominant hemisphere.  

PubMed

Diffusion tensor imaging (DTI) and functional magnetic resonance imaging (fMRI) were combined to examine the relationship between callosal organization and cortical activity across hemispheres. Healthy young adults performed an incidental verbal encoding task (semantic judgments on words) while undergoing fMRI. Consistent with previous studies, the verbal encoding task was associated with left-lateralized activity in the inferior prefrontal cortex (LIPFC). When subjects were divided into two groups based on fractional anisotropy (FA) values in the anterior corpus callosum (DTI), individuals with low anterior callosal FA were found to exhibit greater activity in a homologous region within the right inferior prefrontal cortex (RIPFC) relative to those with high anterior callosal FA. Interestingly, whereas the magnitude of RIPFC activity did not negatively impact subsequent verbal memory performance for individuals with low anterior callosal FA, greater RIPFC activity during verbal encoding was associated with poorer subsequent memory performance for individuals with high anterior callosal FA. Together, these findings provide novel evidence that individual differences in callosal organization are related to the extent of nondominant cortical activity during performance during a lateralized task, and further, that this relationship has consequences on behavior. PMID:18337422

Putnam, Mary Colvin; Wig, Gagan S; Grafton, Scott T; Kelley, William M; Gazzaniga, Michael S

2008-03-12

84

Obsessive Patient with Agenesis of the Corpus Callosum  

Microsoft Academic Search

Agenesis of the corpus callosum is an uncommon congenital anomaly. The following is a report of a patient with agenesis of the corpus callosum with cavum septum pellucidum and colpocephaly. This patient has also been diagnosed with anankastic personality disorder.

DWH Tam

2002-01-01

85

Influence of Corpus Callosum Damage on Cognition and Physical Disability in Multiple Sclerosis: A Multimodal Study  

PubMed Central

Background Corpus callosum (CC) is a common target for multiple sclerosis (MS) pathology. We investigated the influence of CC damage on physical disability and cognitive dysfunction using a multimodal approach. Methods Twenty-one relapsing-remitting MS patients and 13 healthy controls underwent structural MRI and diffusion tensor of the CC (fractional anisotropy; mean diffusivity, MD; radial diffusivity, RD; axial diffusivity). Interhemisferic transfer of motor inhibition was assessed by recording the ipsilateral silent period (iSP) to transcranial magnetic stimulation. We evaluated cognitive function using the Brief Repeatable Battery and physical disability using the Expanded Disability Status Scale (EDSS) and the MS Functional Composite (MSFC) z-score. Results The iSP latency correlated with physical disability scores (r ranged from 0.596 to 0.657, P values from 0.004 to 0.001), and with results of visual memory (r?=??0.645, P?=?0.002), processing speed (r?=??0.51, P?=?0.018) and executive cognitive domain tests (r?=??0.452, P?=?0.039). The area of the rostrum correlated with the EDSS (r?=??0.442, P?=?0.045). MD and RD correlated with cognitive performance, mainly with results of visual and verbal memory tests (r ranged from ?0.446 to ?0.546, P values from 0.048 to 0.011). The iSP latency correlated with CC area (r?=??0.345, P?=?0.049), volume (r?=??0.401, P?=?0.002), MD (r?=?0.404, P?=?0.002) and RD (r?=?0.415, P?=?0.016). Conclusions We found evidence for structural and microstructural CC abnormalities associated with impairment of motor callosal inhibitory conduction in MS. CC damage may contribute to cognitive dysfunction and in less extent to physical disability likely through a disconnection mechanism.

Llufriu, Sara; Blanco, Yolanda; Martinez-Heras, Eloy; Casanova-Molla, Jordi; Gabilondo, Inigo; Sepulveda, Maria; Falcon, Carles; Berenguer, Joan; Bargallo, Nuria; Villoslada, Pablo; Graus, Francesc; Valls-Sole, Josep; Saiz, Albert

2012-01-01

86

Meta-analysis of corpus callosum size in schizophrenia  

Microsoft Academic Search

Studies with MRI have shown differences in corpus callosum size between schizophrenic patients and controls. Most have found that the corpus callosum is smaller in schizophrenic patients, but in only a minority was this finding statistically significant, perhaps due to small sample sizes. Therefore a meta-analysis of 11 published studies of corpus callosum morphology in schizophrenia was conducted to ascertain

P. W. R. Woodruff; I. C. Mcmanus; A. S. David

1995-01-01

87

Corpus Callosum Area in Children and Adults with Autism  

ERIC Educational Resources Information Center

|Despite repeated findings of abnormal corpus callosum structure in autism, the developmental trajectories of corpus callosum growth in the disorder have not yet been reported. In this study, we examined corpus callosum size from a developmental perspective across a 30-year age range in a large cross-sectional sample of individuals with autism…

Prigge, Molly B. D.; Lange, Nicholas; Bigler, Erin D.; Merkley, Tricia L.; Neeley, E. Shannon; Abildskov, Tracy J.; Froehlich, Alyson L.; Nielsen, Jared A.; Cooperrider, Jason R.; Cariello, Annahir N.; Ravichandran, Caitlin; Alexander, Andrew L.; Lainhart, Janet E.

2013-01-01

88

Evaluation of normal appearing spinal cord by diffusion tensor imaging, fiber tracking, fractional anisotropy, and apparent diffusion coefficient measurement in 13 dogs  

PubMed Central

Background Functional magnetic resonance (fMR) imaging offers plenty of new opportunities in the diagnosis of central nervous system diseases. Diffusion tensor imaging (DTI) is a technique sensitive to the random motion of water providing information about tissue architecture. We applied DTI to normal appearing spinal cords of 13 dogs of different breeds and body weights in a 3.0 T magnetic resonance (MR) scanner. The aim was to study fiber tracking (FT) patterns by tractography and the variations of the fractional anisotropy (FA) and the apparent diffusion coefficient (ADC) observed in the spinal cords of dogs with different sizes and at different locations (cervical and thoracolumbar). For that reason we added a DTI sequence to the standard clinical MR protocol. The values of FA and ADC were calculated by means of three regions of interest defined on the cervical or the thoracolumbar spinal cord (ROI 1, 2, and 3). Results The shape of the spinal cord fiber tracts was well illustrated following tractography and the exiting nerve roots could be differentiated from the spinal cord fiber tracts. Routine MR scanning times were extended for 8 to 12 min, depending on the size of the field of view (FOV), the slice thickness, and the size of the interslice gaps. In small breed dogs (?25 kg body weight) the traceable fiber length was about 5 vertebral bodies which took 10 to 12 min scanning time. FA and ADC values showed mean values of 0.447 (FA), and 0.560?×?10-3 mm2/s (ADC), respectively without any differences detected with regard to different dog sizes and spinal cord 45 segments examined. Conclusion FT is suitable for the graphical depiction of the canine spinal cord and the exiting nerve roots. The FA and ADC values offer an objective measure for evaluation of the spinal cord fiber integrity in dogs.

2013-01-01

89

Identical, but not the same: intra-site and inter-site reproducibility of fractional anisotropy measures on two 3.0T scanners.  

PubMed

Diffusion Tensor Imaging (DTI) is being increasingly used to assess white matter integrity and it is therefore paramount to address the test-retest reliability of DTI measures. In this study we assessed inter- and intra-site reproducibility of two nominally identical 3T scanners at different sites in nine healthy controls using a DTI protocol representative of typical current "best practice" including cardiac gating, a multichannel head coil, parallel imaging and optimized diffusion gradient parameters. We calculated coefficients of variation (CV) and intraclass correlation coefficients (ICC) of fractional anisotropy (FA) measures for the whole brain, for three regions of interest (ROI) and for three tracts derived from these ROI by probabilistic tracking. We assessed the impact of affine, nonlinear and template based methods for spatially aligning FA maps on the reproducibility. The intra-site CV for FA ranged from 0.8% to 3.0% with ICC from 0.90 to 0.99, while the inter-site CV ranged from 1.0% to 4.1% with ICC of 0.82 to 0.99. Nonlinear image coregistration improved reproducibility compared to affine coregistration. Normalization to template space reduced the between-subject variation, resulting in lower ICC values and indicating a possibly reduced sensitivity. CV from probabilistic tractography were about 50% higher than for the corresponding seed ROI. Reproducibility maps of the whole scan volume showed a low variation of less than 5% in the major white matter tracts but higher variations of 10-15% in gray matter regions. One of the two scanners showed better intra-site reproducibility, while the intra-site CV for both scanners was significantly better than inter-site CV. However, when using nonlinear coregistration of FA maps, the average inter-site CV was below 2%. There was a consistent inter-site bias, FA values on site 2 were 1.0-1.5% lower than on site 1. Correction for this bias with a global scaling factor reduced the inter-site CV to the range of intra-site CV. Our results are encouraging for multi-centre DTI studies in larger populations, but also illustrate the importance of the image processing pipeline for reproducibility. PMID:20338248

Vollmar, Christian; O'Muircheartaigh, Jonathan; Barker, Gareth J; Symms, Mark R; Thompson, Pamela; Kumari, Veena; Duncan, John S; Richardson, Mark P; Koepp, Matthias J

2010-03-23

90

Corpus Callosum Size in Deiphinid Cetaceans.  

National Technical Information Service (NTIS)

The midsagittal surface area of the corpus callosum was determined by computer-assisted morphometry in juvenile and adult members of 13 species of the cetacean family Delphinidae. In 57 brains, absolute callosal areas ranged from 104 to 829 mm2. When comp...

R. J. Tarpley S. H. Ridgway

1994-01-01

91

Increased corpus callosum size in musicians  

Microsoft Academic Search

Using in-vivo magnetic resonance morphometry it was investigated whether the midsagittal area of the corpus callosum (CC) would differ between 30 professional musicians and 30 age-, sex- and handedness-matched controls. Our analyses revealed that the anterior half of the CC was significantly larger in musicians. This difference was due to the larger anterior CC in the subgroup of musicians who

Gottfried Schlaug; Lutz Jäncke; Yanxiong Huang; Jochen F. Staiger; Helmuth Steinmetz

1995-01-01

92

Corpus callosum and simple visuomotor integration  

Microsoft Academic Search

Malcolm Jeeves was the first to demonstrate lengthened interhemispheric transmission times in subjects with agenesis of the corpus callosum by using a simple reaction time paradigm with lateralized unstructured light stimuli and crossed and uncrossed hand responses. Uncrossed responses can be integrated within one hemisphere, whereas crossed responses require a communication between the two hemispheres. In the normal brain this

G. Berlucchi; S. Aglioti; C. A. Marzi; G. Tassinari

1995-01-01

93

Predicting Inter-Hemispheric Transfer Time from the Diffusion Properties of the Corpus Callosum in Healthy Individuals and Schizophrenia Patients: A Combined ERP and DTI Study  

PubMed Central

Background Several theories of schizophrenia have emphasized the role of aberrant neural timing in the etiology of the disease, possibly as a consequence of conduction delays caused by structural damage to the white-matter fasciculi. Consistent with this theory, increased inter-hemispheric transmission times (IHTTs) to unilaterally-presented visual stimuli have been reported in patients with schizophrenia. The present study investigated whether or not these IHTT abnormalities could be underpinned by structural damage to the visual fibers of the corpus callosum. Methods 30 schizophrenia patients and 22 matched controls underwent Event Related Potential (ERP) recording, and a subset of 19 patients and 16 controls also underwent 3T Diffusion-Tensor Imaging (DTI). Unilateral visual stimuli (squares, 2 × 2 degrees) were presented 6 degrees lateral to either side of a central fixation point. IHTTs (ipsilateral minus contralateral latencies) were calculated for the P1 and N1 components at occipital-temporal sites in current source density-transformed ERPs. The visual fibers of the corpus callosum were extracted with streamline tractography and the diffusion metrics of Fractional Anisotropy (FA) and Mode calculated. Results While both subject groups exhibited highly significant IHTTs across a range of posterior electrode pairs, and significantly shorter IHTTs from left-to-right hemisphere than vice versa, no significant groupwise differences in IHTT were observed. However, participants’ IHTTs were linearly related to their FA and Mode, with longer IHTTs being associated with lower FA and more prolate diffusion ellipsoids. Conclusions These results suggest that IHTTs are estimable from DTI measures of white matter integrity. In light of the range of diffusion abnormalities that have been reported in patients with schizophrenia, particularly in frontal fasciculi, these results support the conjecture that schizophrenia is ultimately underpinned by abnormalities in neural timing.

Whitford, Thomas J.; Kubicki, Marek; Ghorashi, Shahab; Schneiderman, Jason S.; Hawley, Kathryn J.; McCarley, Robert W.; Shenton, Martha E.; Spencer, Kevin M.

2010-01-01

94

Mean diffusivity, fractional anisotropy maps, and three-dimensional white-matter tractography by diffusion tensor imaging. Comparison between single-shot fast spin-echo and single-shot echo-planar sequences at 1.5 Tesla  

Microsoft Academic Search

Single-shot fast spin-echo (SSFSE)-based magnetic resonance imaging (MRI) has been introduced as a technique with less distortion\\u000a and fewer artifacts for diffusion tensor imaging (DTI). The purpose of this study was to compare mean diffusivity maps, fractional\\u000a anisotropy (FA) maps, and three-dimensional white-matter tractography using data obtained with SSFSE diffusion-tensor MRI\\u000a technique and the much more common DTI method, echo-planar

Masaaki Hori; Keiichi Ishigame; Nobuyuki Shiraga; Hiroshi Kumagai; Shigeki Aoki; Tsutomu Araki

2008-01-01

95

Goldanskii-Karyagin effect and external magnetic field method as tools to measure anisotropy of the recoilless fraction in amorphous materials  

Microsoft Academic Search

Diffraction of X-rays or neutrons can not be used to obtain details about the atomic vibrational anisotropy in the case of amorphous materials due to the lack of well-defined Bragg reflections. Mössbauer spectroscopy can yield some information in such cases, either via the Goldanskii-Karyagin effect or by applying a magnetic field, preferably along the beam axis. The latter method can

K. Ruebenbauer; B. Sepiol

1985-01-01

96

Assessing Corpus Callosum Changes in Alzheimer's Disease: Comparison between Tract-Based Spatial Statistics and Atlas-Based Tractography  

PubMed Central

Tractography based on Diffusion Tensor Imaging (DTI) represents a valuable tool for investigating brain white matter (WM) microstructure, allowing the computation of damage-related diffusion parameters such as Fractional Anisotropy (FA) in specific WM tracts. This technique appears relevant in the study of pathologies in which brain disconnection plays a major role, such as, for instance, Alzheimer's Disease (AD). Previous DTI studies have reported inconsistent results in defining WM abnormalities in AD and in its prodromal stage (i.e., amnestic Mild Cognitive Impairment; aMCI), especially when investigating the corpus callosum (CC). A reason for these inconsistencies is the use of different processing techniques, which may strongly influence the results. The aim of the current study was to compare a novel atlas-based tractography approach, that sub-divides the CC in eight portions, with Tract-Based Spatial Statistics (TBSS) when used to detect specific patterns of CC FA in AD at different clinical stages. FA data were obtained from 76 subjects (37 with mild AD, 19 with aMCI and 20 elderly healthy controls, HC) and analyzed using both methods. Consistent results were obtained for the two methods, concerning the comparisons AD vs. HC (significantly reduced FA in the whole CC of AD patients) and AD vs. aMCI (significantly reduced FA in the frontal portions of the CC in AD patients), thus identifying a relative preservation of the frontal CC regions in aMCI patients compared to AD. Conversely, the atlas-based method but not the TBSS showed the ability to detect a selective FA change in the CC parietal, left temporal and occipital regions of aMCI patients compared to HC. This finding indicates that an analysis including a higher number of voxels (with no restriction to tract skeletons) may detect characteristic pattern of FA in the CC of patients with preclinical AD, when brain atrophy is still modest.

Preti, Maria Giulia; Baglio, Francesca; Lagana, Maria Marcella; Griffanti, Ludovica; Nemni, Raffaello; Clerici, Mario; Bozzali, Marco; Baselli, Giuseppe

2012-01-01

97

Metabolic Levels in the Corpus Callosum and Their Structural and Behavioral Correlates after Moderate to Severe Pediatric TBI  

PubMed Central

Abstract Diffuse axonal injury (DAI) secondary to traumatic brain injury (TBI) contributes to long-term functional morbidity. The corpus callosum (CC) is particularly vulnerable to this type of injury. Magnetic resonance spectroscopy (MRS) was used to characterize the metabolic status of two CC regions of interest (ROIs) (anterior and posterior), and their structural (diffusion tensor imaging; DTI) and neurobehavioral (neurocognitive functioning, bimanual coordination, and interhemispheric transfer time [IHTT]) correlates. Two groups of moderate/severe TBI patients (ages 12–18 years) were studied: post-acute (5 months post-injury; n?=?10), and chronic (14.7 months post-injury; n?=?8), in addition to 10 age-matched healthy controls. Creatine (energy metabolism) did not differ between groups across both ROIs and time points. In the TBI group, choline (membrane degeneration/inflammation) was elevated for both ROIs at the post-acute but not chronic period. N-acetyl aspartate (NAA) (neuronal/axonal integrity) was reduced initially for both ROIs, with partial normalization at the chronic time point. Posterior, not anterior, NAA was positively correlated with DTI fractional anisotropy (FA) (r?=?0.88), and most domains of neurocognition (r range 0.22–0.65), and negatively correlated with IHTT (r?=??0.89). Inverse corerlations were noted between creatine and posterior FA (r?=??0.76), neurocognition (r range ?0.22 to ?0.71), and IHTT (r?=?0.76). Multimodal studies at distinct time points in specific brain structures are necessary to delineate the course of the degenerative and reparative processes following TBI, which allows for preliminary hypotheses about the nature and course of the neural mechanisms of subsequent functional morbidity. This will help guide the future development of targeted therapeutic agents.

Marion, Sarah DeBoard; Copeland, Sarah; Alger, Jeffry R.; O'Neill, Joseph; Cazalis, Fabienne; Mink, Richard; Giza, Christopher C.; Vu, Jennifer A.; Hilleary, Suzanne M.; Kernan, Claudia L.; Newman, Nina; Asarnow, Robert F.

2010-01-01

98

Maximum principal strain and strain rate associated with concussion diagnosis correlates with changes in corpus callosum white matter indices.  

PubMed

On-field monitoring of head impacts, combined with finite element (FE) biomechanical simulation, allow for predictions of regional strain associated with a diagnosed concussion. However, attempts to correlate these predictions with in vivo measures of brain injury have not been published. This article reports an approach to and preliminary results from the correlation of subject-specific FE model-predicted regions of high strain associated with diagnosed concussion and diffusion tensor imaging to assess changes in white matter integrity in the corpus callosum (CC). Ten football and ice hockey players who wore instrumented helmets to record head impacts sustained during play completed high field magnetic resonance imaging preseason and within 10 days of a diagnosed concussion. The Dartmouth Subject-Specific FE Head model was used to generate regional predictions of strain and strain rate following each impact associated with concussion. Maps of change in fractional anisotropy (FA) and median diffusivity (MD) were generated for the CC of each athlete to correlate strain with change in FA and MD. Mean and maximum strain rate correlated with change in FA (Spearman ? = 0.77, p = 0.01; 0.70, p = 0.031), and there was a similar trend for mean and maximum strain (0.56, p = 0.10; 0.6, p = 0.07), as well as for maximum strain with change in MD (-0.63, p = 0.07). Change in MD correlated with injury-to-imaging interval (? = -0.80, p = 0.006) but change in FA did not (? = 0.18, p = 0.62). These results provide preliminary confirmation that model-predicted strain and strain rate in the CC correlate with changes in indices of white matter integrity. PMID:21994062

McAllister, Thomas W; Ford, James C; Ji, Songbai; Beckwith, Jonathan G; Flashman, Laura A; Paulsen, Keith; Greenwald, Richard M

2011-10-13

99

Working memory and corpus callosum microstructural integrity after pediatric traumatic brain injury: a diffusion tensor tractography study.  

PubMed

Abstract Deficits in working memory (WM) are a common consequence of pediatric traumatic brain injury (TBI) and are believed to contribute to difficulties in a range of cognitive and academic domains. Reduced integrity of the corpus callosum (CC) after TBI may disrupt the connectivity between bilateral frontoparietal neural networks underlying WM. In the present investigation, diffusion tensor imaging (DTI) tractography of eight callosal subregions (CC1-CC8) was examined in relation to measures of verbal and visuospatial WM in 74 children sustaining TBI and 49 typically developing comparison children. Relative to the comparison group, children with TBI demonstrated poorer visuospatial WM, but comparable verbal WM. Microstructure of the CC was significantly compromised in brain-injured children, with lower fractional anisotropy (FA) and higher axial and radial diffusivity metrics in all callosal subregions. In both groups of children, lower FA and/or higher radial diffusivity in callosal subregions connecting anterior and posterior parietal cortical regions predicted poorer verbal WM, whereas higher radial diffusivity in callosal subregions connecting anterior and posterior parietal, as well as temporal, cortical regions predicted poorer visuospatial WM. DTI metrics, especially radial diffusivity, in predictive callosal subregions accounted for significant variance in WM over and above remaining callosal subregions. Reduced microstructural integrity of the CC, particularly in subregions connecting parietal and temporal cortices, may act as a neuropathological mechanism contributing to long-term WM deficits. The future clinical use of neuroanatomical biomarkers may allow for the early identification of children at highest risk for WM deficits and earlier provision of interventions for these children. PMID:23627735

Treble, Amery; Hasan, Khader M; Iftikhar, Amal; Stuebing, Karla K; Kramer, Larry A; Cox, Charles S; Swank, Paul R; Ewing-Cobbs, Linda

2013-08-24

100

Diffusion tensor imaging of the corpus callosum in Autism  

Microsoft Academic Search

The corpus callosum is the largest commissural white matter pathway that connects the hemispheres of the human brain. In this study, diffusion tensor imaging (DTI) was performed on subject groups with high-functioning autism and controls matched for age, handedness, IQ, and head size. DTI and volumetric measurements of the total corpus callosum and subregions (genu, body and splenium) were made

Andrew L. Alexander; Jee Eun Lee; Mariana Lazar; Rebecca Boudos; Molly B. DuBray; Terrence R. Oakes; Judith N. Miller; Jeffrey Lu; Eun-Kee Jeong; William M. McMahon; Erin D. Bigler; Janet E. Lainhart

2007-01-01

101

Agenesis and lipoma of corpus callosum. Case report.  

PubMed

The agenesis and lipoma of the corpus callosum is a very rare association. We report the case of a 18-years old woman with rare epileptic seizures since the age of 6 years, normal neurological examination, as well as normal electroencephalogram. The brain computed tomography scanning and the magnetic resonance showed the lipoma and the agenesis of the corpus callosum. PMID:8585829

Silva, D F; Lima, M M; Oliveira, C O; Oliveira, W N; Anghinah, R; Lima, J G

1995-09-01

102

Educational Implications for Agenesis of the Corpus Callosum.  

ERIC Educational Resources Information Center

This case study evaluates the case of a 20-year-old young Australian adult born with agenesis of the corpus callosum, the area of the brain uniting the hemispheres. Deficits commonly associated with agenesis of the corpus callosum are mental retardation, motor involvement, seizure activity, and lateral transfer difficulties. The report: (1)…

Ritter, Shirley A.

103

Corpus Callosum Morphometrics in Young Children with Autism Spectrum Disorder  

ERIC Educational Resources Information Center

This study assessed digital corpus callosum cross sectional areas in 3-4 year olds with autism spectrum disorder (ASD) compared to typically developing (TD) and developmentally delayed (DD) children. Though not different in absolute size compared to TD, ASD callosums were disproportionately small adjusted for increased ASD cerebral volume. ASD…

Boger-Megiddo, Inbal; Shaw, Dennis W. W.; Friedman, Seth D.; Sparks, Bobbi F.; Artru, Alan A.; Giedd, Jay N.; Dawson, Geraldine; Dager, Stephen R.

2006-01-01

104

Corpus Callosum Morphometrics in Young Children with Autism Spectrum Disorder  

ERIC Educational Resources Information Center

|This study assessed digital corpus callosum cross sectional areas in 3-4 year olds with autism spectrum disorder (ASD) compared to typically developing (TD) and developmentally delayed (DD) children. Though not different in absolute size compared to TD, ASD callosums were disproportionately small adjusted for increased ASD cerebral volume. ASD…

Boger-Megiddo, Inbal; Shaw, Dennis W. W.; Friedman, Seth D.; Sparks, Bobbi F.; Artru, Alan A.; Giedd, Jay N.; Dawson, Geraldine; Dager, Stephen R.

2006-01-01

105

Reduced area of the corpus callosum in posttraumatic stress disorder  

Microsoft Academic Search

Magnetic resonance imaging (MRI) studies have revealed decreases in the mid-sagittal area of the corpus callosum (CC) in pediatric posttraumatic stress disorder (PTSD), but at present no data are available in adult PTSD patients. We have previously reported decreased whole-brain white matter (WM) volume in adults with PTSD and now report corpus callosum area from the same sample. MRI was

Gerardo Villarreal; Derek A. Hamilton; David P. Graham; Ira Driscoll; Clifford Qualls; Helen Petropoulos; William M. Brooks

2004-01-01

106

Spontaneous periodic hypothermia with lipoma of the corpus callosum  

PubMed Central

A patient with spontaneous periodic hypothermia who had both a lipoma and agenesis of the corpus callosum is described. Spontaneous periodic hypothermia associated with corpus callosum abnormalities is a distinct entity and although the mechanism underlying the hypothermic episodes is unexplained, the term “diencephalic autonomic epilepsy” does not seem appropriate. Images

Summers, GD; Young, AC; Little, RA; Stoner, HB; Forbes, WSTC; Jones, Rac

1981-01-01

107

Clinical and Diagnostic Profile of Agenesis of the Corpus Callosum  

Microsoft Academic Search

This study reports the clinical profile, etiologies identified, and outcomes for a consecutive series of children with partial or complete agenesis of the corpus callosum. Children with agenesis of the corpus callosum were identified in a comprehensive computerized database of all patients seen in a single pediatric neurology practice over an 11-year interval. Medical records were then systematically reviewed. Twenty-four

Michael I. Shevell

2002-01-01

108

Agenesis of Corpus Callosum: Clinical Description and Etiology  

Microsoft Academic Search

In 135 children (aged 3 months to 15 years) with structural defects of the central nervous system found on magnetic resonance imaging, agenesis of the corpus callosum was evident in 7. The etiology of agenesis of the corpus callosum has been established in four children: partial trisomy of chromosome 13, partial duplication of the long arm of chromosome 10, Aicardi's

Elzbieta Marszal; Ewa Jamroz; Jacek Pilch; Ewa Kluczewska; Halina Jablecka-Deja; Robert Krawczyk

2000-01-01

109

Secondary corpus callosum abnormalities associated with antiepileptic drugs in temporal lobe epilepsy. A diffusion tensor imaging study.  

PubMed

Epilepsy is more than a grey-matter disorder affecting large white matter connections of the brain with seizure generation and propagation. The mechanism for such changes remains unclear. The purpose of this study was to investigate the microstructural changes in the corpus callosum in temporal lobe epilepsy (TLE) patients and whether these abnormalities are related to antiepileptic drug (AED) therapy. Ten TLE patients receiving AED therapy, ten TLE patients with no therapy and ten controls were included in the study. The regions of interest in the corpus callosum were outlined to each Witelson region (WR). Fractional anisotrophy (FA), apparent diffusion coefficient (ADC), three main diffusivity values (?1, ?2, ?3) and tractography were acquired from each WR. DTI indices of these tracts and each WR were compared between the three subject groups and correlates examined with clinical variables that included duration of epilepsy, gender, AED type and AED therapy exposure. In TLE subjects with receiving AED therapy significantly (p<0.05) decreased FA and increased ADC values of corpus callosum were obtained when compared to the other groups. There was no significant relationship between AED type and DTI indices. Analysis of eigen values in the splenium of corpus callosum (WR7) showed ?1 values were significantly decreased in relation to AED medication duration (p<0.05). FA values of rostrum and corpus showed a reduction with duration of epilepsy. TLE is associated with abnormal integrity of corpus callosum white matter tracts. AED therapy may cause additional damage on secondary degeneration and medication time effects especially on the splenium of corpus callosum. PMID:24059625

Günbey, H P; Ercan, K; F?nd?ko?lu, A S; Bilir, E; Karaoglanoglu, M; Komurcu, F; Alhan, A

2011-05-11

110

MR spectroscopy and diffusion tensor imaging of the brain in congenital muscular dystrophy with merosin deficiency: metabolite level decreases, fractional anisotropy decreases, and apparent diffusion coefficient increases in the white matter.  

PubMed

Brain magnetic resonance spectroscopy (MRS) and diffusion tensor imaging (DTI) in one patient with merosin-deficient congenital muscular dystrophy (MDCMD) revealed significant metabolite (choline, creatine, N-acetyl aspartate) level reductions, fractional anisotropy (FA) reduction and increased apparent diffusion coefficient (ADC) in the white matter (p<0.01, all). In the gray matter, the MRS properties did not differ significantly from those in controls. The ADC and FA, however, differed significantly as in the white matter, although the differences were less pronounced. This is the first quantitative MR study of the brain in a patient with MDCMD, which revealed that the concentrations of all MRS measured metabolites were decreased only in the white matter. This observation, combined with the DTI observed ADC increases and FA decrease, indicated a presence of vasogenic edema in the white matter. PMID:17113260

Sijens, P E; Fock, J M; Meiners, L C; Potze, J H; Irwan, R; Oudkerk, M

2006-11-17

111

Corpus callosum and P300 in schizophrenia.  

PubMed

Functional abnormalities in the interhemispheric transfer via the corpus callosum in schizophrenia may result in filtering problems and information processing problems, which may in turn be related to the synchronization of cortical event-related activity. To explore whether a relationship exists between corpus callosum (CC) size, measured with in-vivo magnetic resonance imaging, and late auditory event-related P300 potentials, 50 patients with schizophrenia as well as 50 healthy controls were examined. The absolute CC size and subregional areas, as well as the CC areas adjusted for total brain volume, were not significantly different between patients with schizophrenia and controls. While no significant group differences were observed for P3a-, P3b-, PSW-amplitudes and P3b-latencies, P3a- and PSW-latencies were significantly prolonged for patients with schizophrenia. Absolute CC total size was significantly correlated with P3b-amplitudes in healthy controls (r=0.29; P=0.044). In patients with schizophrenia, significant correlations were observed between the subregion of the posterior body of the CC and positive slow wave (PSW; r=0.47; P=0.001). P3a-, P3b- and PSW-latencies were not significantly correlated to CC size in either patients with schizophrenia or healthy controls. The results are discussed in terms of the possibility that abnormalities in interhemispheric transfer may underlie the mechanisms of schizophrenia. PMID:11343870

Frodl, T; Meisenzahl, E M; Müller, D; Greiner, J; Juckel, G; Leinsinger, G; Hahn, H; Möller, H J; Hegerl, U

2001-04-15

112

CMB anisotropies due to cosmological magnetosonic waves  

SciTech Connect

We study scalar mode perturbations (magnetosonic waves) induced by a helical stochastic cosmological magnetic field and derive analytically the corresponding cosmic microwave background (CMB) temperature and polarization anisotropy angular power spectra. We show that the presence of a stochastic magnetic field, or an homogeneous magnetic field, influences the acoustic oscillation pattern of the CMB anisotropy power spectrum, effectively acting as a reduction of the baryon fraction. We find that the scalar magnetic energy density perturbation contribution to the CMB temperature anisotropy is small compared to the contribution to the CMB E-polarization anisotropy.

Kahniashvili, Tina [Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, Kansas 66506 (United States); CCPP, Department of Physics, New York University, 4 Washington Place, New York 10003 (United States); National Abastumani Astrophysical Observatory, 2A Kazbegi Ave, GE-0160 Tbilisi (Georgia); Ratra, Bharat [Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, Kansas 66506 (United States)

2007-01-15

113

Quantitative diffusion tensor MR imaging of the brain: field strength related variance of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) scalars  

Microsoft Academic Search

The objectives were to study the “impact” of the magnetic field strength on diffusion tensor imaging (DTI) metrics and also to determine whether magnetic-field-related differences in T2-relaxation times of brain tissue influence DTI measurements. DTI was performed on 12 healthy volunteers at 1.5 and 3.0 Tesla (within 2 h) using identical DTI scan parameters. Apparent diffusion coefficient (ADC) and fractional

Thierry A. G. M. Huisman; Thomas Loenneker; Gerd Barta; Matthias E. Bellemann; Juergen Hennig; Joachim E. Fischer; Kamil A. Il’yasov

2006-01-01

114

Insights into the functional specificity of the human corpus callosum.  

PubMed

Patient VP underwent complete callosotomy for the control of intractable epilepsy at the age of 27 years. Subsequent MRI, however, revealed spared callosal fibres in the rostral and splenial ends of the corpus callosum. We report a series of experiments designed to determine whether these fibres support functional transfer of information between the two cerebral hemispheres. Although we found no evidence for transfer of colour, shape or size information, there is good evidence for transfer of word information. This suggests that the spared splenial fibres in VP's corpus callosum are material-specific. The results of these experiments illustrate the remarkable degree of functional specificity within the corpus callosum PMID:10775537

Funnell, M G; Corballis, P M; Gazzaniga, M S

2000-05-01

115

Corpus callosum agenesis and rehabilitative treatment.  

PubMed

Corpus callosum agenesis is a relatively common brain malformation. It can be isolated or included in a complex alteration of brain (or sometimes even whole body) morphology. It has been associated with a number of neuropsychiatric disorders, from subtle neuropsychological deficits to Pervasive Developmental Disorders.Etiology and pathogenetic mechanisms have been better understood in recent years, due to the availability of more adequate animal models and the relevant progresses in developmental neurosciences. These recent findings are reviewed (through a MedLine search including papers published in the last 5 years and most relevant previously published papers) in view of the potential impact on children's global functioning and on the possible rehabilitative treatment, with an emphasis on the possibility to exploit brain plasticity and on the use of the ICF-CY framework. PMID:20849621

Chiappedi, Matteo; Bejor, Maurizio

2010-09-17

116

Corpus Callosum Shape Analysis with Application to Dyslexia  

PubMed Central

Morphometric studies of the corpus callosum suggest its involvement in a number of psychiatric conditions. In the present study we introduce a novel pattern recognition technique that offers a point-by-point shape descriptor of the corpus callosum. The method uses arc lengths of electric field lines in order to avoid discontinuities caused by folding anatomical contours. We tested this technique by comparing the shape of the corpus callosum in a series of dyslexic men (n = 16) and age-matched controls (n = 14). The results indicate a generalized increase in size of the corpus callosum in dyslexia with a concomitant diminution at its rostral and caudal poles. The reported shape analysis and 2D-reconstruction provide information of anatomical importance that would otherwise passed unnoticed when analyzing size information alone.

Casanova, Manuel F.; El-Baz, Ayman; Elnakib, Ahmed; Giedd, Jay; Rumsey, Judith M.; Williams, Emily L.; Switala, Andrew E.

2012-01-01

117

Anatomy of corpus callosum in prenatally malnourished rats.  

PubMed

The effect of prenatal malnutrition on the anatomy of the corpus callosum was assessed in adult rats (45-52 days old). In the prenatally malnourished animals we observed a significant reduction of the corpus callosum total area, partial areas, and perimeter, as compared with normal animals. In addition, the splenium of corpus callosum (posterior fifth) showed a significant decrease of fiber diameters in the myelinated fibers without changing density. There was also a significant decrease in diameter and a significant increase in density of unmyelinated fibers. Measurements of perimeter's fractal dimensions from sagittal sections of the brain and corpus callosum did not show significant differences between malnourished and control animals. These findings indicate that cortico-cortical connections are vulnerable to the prenatal malnutrition, and suggest this may affect interhemispheric conduction velocity, particularly in visual connections (splenium). PMID:22688989

Olivares, Ricardo; Morgan, Carlos; Pérez, Hernán; Hernández, Alejandro; Aboitiz, Francisco; Soto-Moyano, Rubén; Gil, Julio; Ortiz, Alexis; Flores, Osvaldo; Gimeno, Miguel; Laborda, Jesús

2012-01-01

118

Sex Differences in the Human Corpus Callosum: Myth or Reality?  

Microsoft Academic Search

BISHOP, K.M. AND WAHLSTEN, D. Sex differences in the human corpus callosum: myth or reality? NEUROSCI BIOBEHAV REV 21(5) 581-601 1997.—It has been claimed that the human corpus callosum shows sex differences, and in particular that the splenium (the posterior portion) is larger in women than in men. Data collected before 1910 from cadavers indicate that, on average, males have

KATHERINE M. BISHOP; DOUGLAS WAHLSTEN

1997-01-01

119

Classification of acquired lesions of the corpus callosum with MRI  

Microsoft Academic Search

MRI has facilitated diagnostic assessment of the corpus callosum. Diagnostic classification of solitary or multiple lesions\\u000a of the corpus callosum has not attracted much attention, although signal abnormalities are not uncommon. Our aim was to identify\\u000a characteristic imaging features of lesions frequently encountered in practice. We reviewed the case histories of 59 patients\\u000a with lesions shown on MRI. The nature

S. A. Friese; M. Bitzer; D. Freudenstein; K. Voigt; W. Küker

2000-01-01

120

Sexual Dimorphism of Human Corpus Callosum Using Quantitative MRI  

Microsoft Academic Search

Background : To investigate the sexual dimorphism in human corpus callosum (CC), we measured the mid-sagittal area of corpus callosum and its seven sub-regions. Methods : Eighteen men (23.0±9.1 years) and 16 women (27.3±11.3 years) underwent 1.6 mm thickness SPGR (spoiled gradient recalled in the steady state) MRI. All subjects are right handed and had no neurological or psychiatric diseases.

Woo Suk Tae; Seung Bong Hong

2002-01-01

121

Agenesis of the Corpus Callosum Is Associated With Feeding Difficulties  

Microsoft Academic Search

Our objective was to characterize the common occurrence of feeding and swallowing disorders noticed by our speech therapy department among patients with agenesis of the corpus callosum. All patients with suspected or presumed agenesis of the corpus callosum undergoing therapy for feeding and\\/or swallowing disorders, including oral and\\/or pharyngeal dysphagia and oral-sensory disorder, were identified. Their brain magnetic resonance imaging

Yu-tze Ng; Colleen M. McCarthy; Theodore J. Tarby; John B. Bodensteiner

2004-01-01

122

X linked recessive inheritance of agenesis of the corpus callosum  

Microsoft Academic Search

A 2-year-old boy with psychomotor retardation, congenital unilateral ptosis, bilateral adducted thumbs, weakness of upper limbs, and Hirschsprung's disease (aganglionosis), with complete agenesis of the corpus callosum and hypoplasia of the inferior vermis and cerebellum is reported. His 24-year-old maternal uncle, with severe psychomotor retardation but none of the other physical problems, also has agenesis of the corpus callosum demonstrated

P Kaplan

1983-01-01

123

Corpus Callosum Area in Children and Adults with Autism.  

PubMed

Despite repeated findings of abnormal corpus callosum structure in autism, the developmental trajectories of corpus callosum growth in the disorder have not yet been reported. In this study, we examined corpus callosum size from a developmental perspective across a 30-year age range in a large cross-sectional sample of individuals with autism compared to a typically developing sample. Midsagittal corpus callosum area and the 7 Witelson subregions were examined in 68 males with autism (mean age 14.1 years; range 3-36 years) and 47 males with typical development (mean age 15.3 years; range 4-29 years). Controlling for total brain volume, increased variability in total corpus callosum area was found in autism. In autism, increased midsagittal areas were associated with reduced severity of autism behaviors, higher intelligence, and faster speed of processing (p=0.003, p=0.011, p=0.013, respectively). A trend toward group differences in isthmus development was found (p=0.029, uncorrected). These results suggest that individuals with autism benefit functionally from increased corpus callosum area. Our cross-sectional examination also shows potential maturational abnormalities in autism, a finding that should be examined further with longitudinal datasets. PMID:23130086

Prigge, Molly B D; Lange, Nicholas; Bigler, Erin D; Merkley, Tricia L; Neeley, E Shannon; Abildskov, Tracy J; Froehlich, Alyson L; Nielsen, Jared A; Cooperrider, Jason R; Cariello, Annahir N; Ravichandran, Caitlin; Alexander, Andrew L; Lainhart, Janet E

2012-11-01

124

Neuronal fiber composition of the corpus callosum within some odontocetes.  

PubMed

Odontocetes (toothed whales) evolved from terrestrial mammals approximately 55 million years ago and have since remained on a unique evolutionary trajectory. This study used formalin-fixed tissue and light microscopy to quantify the size and number of fibers along the corpus callosum of the bottlenose dolphin (n = 8). Two other species, the Amazon River dolphin (n = 1) and the killer whale (n = 1), were included for comparison. A large amount of variation in the shape and area of the corpus callosum was observed. The odontocete corpus callosum is a heterogeneous structure with variation in fiber size and density along the length of the corpus callosum in all specimens examined. Using the species with the largest sample size, the bottlenose dolphin, comparisons by sex and age (sexually mature verses immature) were made for the area of the corpus callosum, five subregions, and fiber densities. Although no sex differences were detected, age appeared to affect the size, shape, and fiber composition of the bottlenose dolphin corpus callosum. PMID:18493931

Keogh, Mandy J; Ridgway, Sam H

2008-07-01

125

Automated measurement of the human corpus callosum using MRI.  

PubMed

The corpus callosum includes the majority of fibers that connect the two cortical hemispheres. Studies of cross-sectional callosal morphometry and area have revealed developmental, gender, and hemispheric differences in healthy populations and callosal deficits associated with neurodegenerative disease and brain injury. However, accurate quantification of the callosum using magnetic resonance imaging is complicated by intersubject variability in callosal size, shape, and location and often requires manual outlining of the callosum in order to achieve adequate performance. Here we describe an objective, fully automated protocol that utilizes voxel-based images to quantify the area and thickness both of the entire callosum and of different callosal compartments. We verify the method's accuracy, reliability, robustness, and multisite consistency and make comparisons with manual measurements using public brain-image databases. An analysis of age-related changes in the callosum showed increases in length and reductions in thickness and area with age. A comparison of older subjects with and without mild dementia revealed that reductions in anterior callosal area independently predicted poorer cognitive performance after factoring out Mini-Mental Status Examination scores and normalized whole brain volume. Open-source software implementing the algorithm is available at www.nitrc.org/projects/c8c8. PMID:22988433

Herron, Timothy J; Kang, Xiaojian; Woods, David L

2012-09-12

126

Impairment in explicit visuomotor sequence learning is related to loss of microstructural integrity of the corpus callosum in multiple sclerosis patients with minimal disability.  

PubMed

Sequence learning can be investigated by serial reaction-time (SRT) paradigms. Explicit learning occurs when subjects have to recognize a test sequence and has been shown to activate the frontoparietal network in both contralateral and ipsilateral hemispheres. Thus, the left and right superior longitudinal fasciculi (SLF), connecting the intra-hemispheric frontoparietal circuits, could have a role in explicit unimanual visuomotor learning. Also, as both hemispheres are involved, we could hypothesize that the corpus callosum (CC) has a role in this process. Pathological damage in both SLF and CC has been detected in patients with Multiple Sclerosis (PwMS), and microstructural alterations can be quantified by Diffusion Tensor Imaging (DTI). In light of these findings, we inquired whether PwMS with minimal disability showed impairments in explicit visuomotor sequence learning and whether this could be due to loss of white matter integrity in these intra- and inter-hemispheric white matter pathways. Thus, we combined DTI analysis with a modified version of SRT task based on finger opposition movements in a group of PwMS with minimal disability. We found that the performance in explicit sequence learning was significantly reduced in these patients with respect to healthy subjects; the amount of sequence-specific learning was found to be more strongly correlated with fractional anisotropy (FA) in the CC (r=0.93) than in the left (r=0.28) and right SLF (r=0.27) (p for interaction=0.005 and 0.04 respectively). This finding suggests that an inter-hemispheric information exchange between the homologous areas is required to successfully accomplish the task and indirectly supports the role of the right (ipsilateral) hemisphere in explicit visuomotor learning. On the other hand, we found no significant correlation of the FA in the CC and in the SLFs with nonspecific learning (assessed when stimuli are randomly presented), supporting the hypothesis that inter-hemispheric integrity is specifically relevant for explicit sequence learning. PMID:21549844

Bonzano, L; Tacchino, A; Roccatagliata, L; Sormani, M P; Mancardi, G L; Bove, M

2011-04-30

127

Diffusion Tensor Magnetic Resonance Imaging Finding of Discrepant Fractional Anisotropy Between the Frontal and Parietal Lobes After Whole-Brain Irradiation in Childhood Medulloblastoma Survivors: Reflection of Regional White Matter Radiosensitivity?  

SciTech Connect

Purpose: To test the hypothesis that fractional anisotropy (FA) is more severely reduced in white matter of the frontal lobe compared with the parietal lobe after receiving the same whole-brain irradiation dose in a cohort of childhood medulloblastoma survivors. Methods and Materials: Twenty-two medulloblastoma survivors (15 male, mean [{+-} SD] age = 12.1 {+-} 4.6 years) and the same number of control subjects (15 male, aged 12.0 {+-} 4.2 years) were recruited for diffusion tensor magnetic resonance imaging scans. Using an automated tissue classification method and the Talairach Daemon atlas, FA values of frontal and parietal lobes receiving the same radiation dose, and the ratio between them were quantified and denoted as FFA, PFA, and FA{sub f/p}, respectively. The Mann-Whitney U test was used to test for significant differences of FFA, PFA, and FA{sub f/p} between medulloblastoma survivors and control subjects. Results: Frontal lobe and parietal lobe white matter FA were found to be significantly less in medulloblastoma survivors compared with control subjects (frontal p = 0.001, parietal p = 0.026). Moreover, these differences were found to be discrepant, with the frontal lobe having a significantly larger difference in FA compared with the parietal lobe. The FA{sub f/p} of control and medulloblastoma survivors was 1.110 and 1.082, respectively (p = 0.029). Conclusion: Discrepant FA changes after the same irradiation dose suggest radiosensitivity of the frontal lobe white matter compared with the parietal lobe. Special efforts to address the potentially vulnerable frontal lobe after treatment with whole-brain radiation may be needed so as to balance disease control and treatment-related morbidity.

Qiu Deqiang [Department of Diagnostic Radiology, Queen Mary Hospital, University of Hong Kong, Hong Kong (China); Kwong, Dora [Department of Clinical Oncology, Queen Mary Hospital, University of Hong Kong, Hong Kong (China); Chan, Godfrey [Department of Pediatric and Adolescent Medicine, Queen Mary Hospital, University of Hong Kong, Hong Kong (China); Leung, Lucullus [Department of Oncology, Princess Margaret Hospital, Hong Kong (China); Khong, P.-L. [Department of Diagnostic Radiology, Queen Mary Hospital, University of Hong Kong, Hong Kong (China)], E-mail: plkhong@hkucc.hku.hk

2007-11-01

128

Longitudinal Changes in the Corpus Callosum following Pediatric Traumatic Brain Injury  

PubMed Central

Background Atrophy of the corpus callosum (CC) is a documented consequence of moderate-to-severe traumatic brain injury (TBI), which has been expressed as volume loss using quantitative magnetic resonance imaging (MRI). Other advanced imaging modalities such as diffusion tensor imaging (DTI) have also detected white matter microstructural alteration following TBI in the CC. The manner and degree to which macrostructural changes such as volume and microstructural changes develop over time following pediatric TBI, and their relation to a measure of processing speed is the focus of this longitudinal investigation. As such, DTI and volumetric changes in the CC in participants with TBI and a comparison group at approximately 3 and 18 months after injury as well as their relation to processing speed were determined. Methods Forty-eight children and adolescents aged 7–17 years who sustained either complicated mild or moderate-to-severe TBI (n = 23) or orthopedic injury (OI; n = 25) were studied. The participants underwent brain MRI and were administered the Eriksen flanker task at both time points. Results At 3 months after injury, there were significant group differences in DTI metrics in the total CC and its subregions (genu/anterior, body/central and splenium/posterior), with the TBI group demonstrating significantly lower fractional anisotropy (FA) and a higher apparent diffusion coefficient (ADC) in comparison to the OI group. These group differences were also present at 18 months after injury in all CC subregions, with lower FA and a higher ADC in the TBI group. In terms of longitudinal changes in DTI, despite the group difference in mean FA, both groups generally demonstrated a modest increase in FA over time though this increase was only significant in the splenium/posterior subregion. Interestingly, the TBI group also generally demonstrated ADC increases from 3 to 18 months though the OI group demonstrated ADC decreases over time. Volumetrically, the group differences at 3 months were marginal for the midanterior and body/central subregions and total CC. However, by 18 months, the TBI group demonstrated a significantly decreased volume in all subregions except the splenium/posterior area relative to the OI group. Unlike the OI group, which showed a significant volume increase in subregions of the CC over time, the TBI group demonstrated a significant and consistent volume decrease. Performance on a measure of processing speed did not differentiate the groups at either visit, and only the OI group showed significantly improved performance over time. Processing speed was related to FA in the splenium/posterior and total CC only in the TBI group on both occasions, with a stronger relation at 18 months. Conclusion In response to TBI, macrostructural volume loss in the CC occurred over time; yet, at the microstructural level, DTI demonstrated both indicators of continued maturation and development even in the damaged CC, as well as evidence of potential degenerative change. Unlike volumetrics, which likely reflects the degree of overall neuronal loss and axonal damage, DTI may reflect some aspects of postinjury maturation and adaptation in white matter following TBI. Multimodality imaging studies may be important to further understand the long-term consequences of pediatric TBI.

Wu, Trevor C.; Wilde, Elisabeth A.; Bigler, Erin D.; Li, Xiaoqi; Merkley, Tricia L.; Yallampalli, Ragini; McCauley, Stephen R.; Schnelle, Kathleen P.; Vasquez, Ana C.; Chu, Zili; Hanten, Gerri; Hunter, Jill V.; Levin, Harvey S.

2011-01-01

129

The corpus callosum, interhemisphere interactions, and the function of the right hemisphere of the brain  

Microsoft Academic Search

A complex clinical-neuropsychological study was performed by the Luriya method before and after surgery in 36 patients with arteriovenous malformations (AVM) of the corpus callosum. The symptoms of local lesions to the various parts of the corpus callosum are described. Symptoms of partial lesioning of the corpus callosum were found to be modality-specific, though only relatively. The symptoms of dyscopia

S. B. Buklina

2005-01-01

130

Corpus Callosum Morphology and Its Relationship to Cognitive Function in Neurofibromatosis Type 1  

Microsoft Academic Search

Neurofibromatosis type 1 (NF1) is associated with cognitive dysfunction and structural brain abnormalities such as an enlarged corpus callosum. This study aimed to determine the relationship between corpus callosum morphology and cognitive function in children with neurofibromatosis type 1 using quantitative neuroanatomic imaging techniques. Children with neurofibromatosis type 1 (n = 46) demonstrated a significantly larger total corpus callosum and

Natalie Pride; Jonathan M. Payne; Richard Webster; E. Arthur Shores; Caroline Rae; Kathryn N. North

2010-01-01

131

Marchiafava-Bignami disease: serial changes in corpus callosum on MRI  

Microsoft Academic Search

Serial MRI findings of changes in corpus callosum lesions in two cases of Marchiafava-Bignami disease are presented. In both, MRI displayed diffuse swelling of the corpus callosum in the acute stage, thought to represent oedema and demyelination. In the chronic stage, in addition to atrophy of the corpus callosum with presumed focal necrosis, previously undescribed focal hypointensity on T2-weighted images,

K. H. Changl; S. H. Chal; M. H. Han; S. H. Park; D. L. Nah; J. H. Hong

1992-01-01

132

Characterization of the corpus callosum in very preterm and full-term infants utilizing MRI  

Microsoft Academic Search

The corpus callosum is the largest white matter tract, important for interhemispheric communication. The aim of this study was to investigate and compare corpus callosum size, shape and diffusion characteristics in 106 very preterm infants and 22 full-term infants. Structural and diffusion magnetic resonance images were obtained at term equivalent. The corpus callosum was segmented, cross-sectional areas were calculated, and

Deanne K. Thompson; Terrie E. Inder; Nathan Faggian; Leigh Johnston; Simon K. Warfield; Peter J. Anderson; Lex W. Doyle; Gary F. Egan

2011-01-01

133

Corpus callosum in aging and dementia.  

PubMed

The overarching objective of the thesis was to investigate the morphological changes in the corpus callosum (CC) in aging and dementia in relation to its role in cognitive and motor decline. The CC is the largest white matter tract in the brain, containing upwards of 200 million axons, and is believed important for communication and interaction between the two cerebral hemispheres. Historically, the role of white matter, including the CC, in relation to cognitive function has often been eclipsed by the predominance of the cortex, and led to a "corticocentric" view of the brain and cognitive function. However, from the 1960s and onwards, the role of lesions in the white matter in the appearence of cognitive deficits and diseases such as dementia has become increasingly evident. Many studies have indicated that AD is associated with CC atrophy, but the precise pattern of subregional CC atrophy in different disease stages remains undetermined. In study I, we establish that atrophy is present primarily in the posterior CC early in AD, and that atrophy of the CC is associated with faster disease progression. This finding supports a model where posterior atrophy is the earliest changes in the CC in AD patients, with atrophy of anterior CC being a later pathological event. To further elucidate the role of CC atrophy in dementia, we examined a population of 329 elderly subjects, and found that a higher rate of tissue loss in posterior CC is associated with an increased risk of dementia. This study represents the first to examine CC in elderly subjects longitudinally. In the same cohort, we investigated whether impairment in specific cognitive domains was associated with CC tissue loss. Previous studies had shown that processing speed and executive functions may be particularly reliant on the CC. Our findings indicated that CC tissue loss leads to selective impairment of processing speed but not memory or executive function deficits. Finally, CC tissue loss was also associated with impairment of motor function. Overall, the present findings confirm and extend the role of the CC in dementia and age-associated cognitive and motor deficits. PMID:24083533

Frederiksen, Kristian Steen

2013-10-01

134

Microstructural Integrity of the Corpus Callosum Linked with Neuropsychological Performance in Adolescents  

ERIC Educational Resources Information Center

|Background: Diffusion tensor imaging (DTI) has revealed microstructural aspects of adolescent brain development, the cognitive correlates of which remain relatively uncharacterized. Methods: DTI was used to assess white matter microstructure in 18 typically developing adolescents (ages 16-18). Fractional anisotropy (FA) and mean diffusion (MD)…

Fryer, Susanna L.; Frank, Lawrence R.; Spadoni, Andrea D.; Theilmann, Rebecca J.; Nagel, Bonnie J.; Schweinsburg, Alecia D.; Tapert, Susan F.

2008-01-01

135

Perspectives on Dichotic Listening and the Corpus Callosum  

ERIC Educational Resources Information Center

|The present review summarizes historic and recent research which has investigated the role of the corpus callosum in dichotic processing within the context of audiology. Examination of performance by certain clinical groups, including split brain patients, multiple sclerosis cases, and other types of neurological lesions is included.…

Musiek, Frank E.; Weihing, Jeffrey

2011-01-01

136

Sex differences in the corpus callosum of patients with schizophrenia  

Microsoft Academic Search

The corpus callosum (CC) has been of interest in schizophrenia research because of its possible role in reduced lateralization and because of its sexually dimorphic characteristics. The literature has been replete with structural brain studies that have yielded equivocal results because of failure to address sex differences, handedness, and overall reductions in total brain volume (TBV) associated with schizophrenia. We

Matthew S. Panizzon; Anne L. Hoff; Thomas E. Nordahl; William S. Kremen; Barbara Reisman; Mary Wieneke; Debra Harris; Chris Goodman; Scott Espinoza; William Liu; Kelvin Lim

2003-01-01

137

Social cognition in individuals with agenesis of the corpus callosum  

Microsoft Academic Search

Past research has revealed that individuals with agenesis of the corpus callosum (ACC) have deficits in interhemispheric transfer, complex novel problem-solving, and the comprehension of paralinguistic aspects of language. Case studies and family reports also suggest problems in social cognition. The performance of 11 individuals with complete ACC and with normal intelligence was compared to that of 13 IQ- and

Scott H. Symington; Lynn K. Paul; Melissa F. Symington; Makoto Ono; Warren S. Brown

2010-01-01

138

Corpus Callosum Differences Associated with Persistent Stuttering in Adults  

ERIC Educational Resources Information Center

|Recent studies have implicated anatomical differences in speech-relevant brain regions of adults who stutter (AWS) compared to normally fluent adults (NFA). The present study focused on the region of the corpus callosum (CC) which is involved in interhemispheric processing between the left and right cerebral hemispheres. Two-dimensional…

Choo, Ai Leen; Kraft, Shelly Jo; Olivero, William; Ambrose, Nicoline G.; Sharma, Harish; Chang, Soo-Eun; Loucks, Torrey M.

2011-01-01

139

A factor analysis of the rat's corpus callosum  

Microsoft Academic Search

Previous work from our laboratory (Berrebi et al., Brain Research, 438 (1988) 216-224) demonstrated region-specific sexual dimorphisms in the size of the rat's corpus callosum, which are modifiable by extra stimulation in early life. These differences are assumed to reflect regional corticocortical fibers of passage which are altered differentially by gender and our experimental manipulations. In this paper, we report

Victor H. Denenberg; Albert S. Berrebi; Roslyn H. Fitch

1989-01-01

140

Perspectives on Dichotic Listening and the Corpus Callosum  

ERIC Educational Resources Information Center

The present review summarizes historic and recent research which has investigated the role of the corpus callosum in dichotic processing within the context of audiology. Examination of performance by certain clinical groups, including split brain patients, multiple sclerosis cases, and other types of neurological lesions is included. Maturational,…

Musiek, Frank E.; Weihing, Jeffrey

2011-01-01

141

A computerized approach for morphological analysis of the corpus callosum  

Microsoft Academic Search

A new technique for analyzing the morphology of the corpus callosum is presented, and it is applied to a group of elderly subjects. The proposed approach normalizes subject data into the Talairach space using an elastic deformation transformation. The properties of this transformation are used as a quantitative description of the callosal shape with respect to the Talairach atlas, which

C. Davatzikos; M. Vaillant; S. Letovsky; J. L. Prince; S. M. Resnick

1996-01-01

142

Commissurotomy of the Corpus Callosum and the Remedial Reader.  

ERIC Educational Resources Information Center

Testimony presented at a congressional hearing on illiteracy (March 1986) indicated that good readers use their myelinated corpus callosum fibers (which connect the left and right hemispheres of the brain) at millisecond speeds to coordinate the two brain hemispheres. Students taught using the whole-word recognition method (also called the…

Albert, Elaine

143

Autism Traits in Individuals with Agenesis of the Corpus Callosum  

ERIC Educational Resources Information Center

|Autism spectrum disorders (ASD) have numerous etiologies, including structural brain malformations such as agenesis of the corpus callosum (AgCC). We sought to directly measure the occurrence of autism traits in a cohort of individuals with AgCC and to investigate the neural underpinnings of this association. We screened a large AgCC cohort (n =…

Lau, Yolanda C.; Hinkley, Leighton B. N.; Bukshpun, Polina; Strominger, Zoe A.; Wakahiro, Mari L. J.; Baron-Cohen, Simon; Allison, Carrie; Auyeung, Bonnie; Jeremy, Rita J.; Nagarajan, Srikantan S.; Sherr, Elliott H.; Marco, Elysa J.

2013-01-01

144

Characterization of sexual dimorphism in the human corpus callosum  

Microsoft Academic Search

Despite decades of research, there is still no agreement over the presence of gender-based morphologic differences in the human corpus callosum. We approached the problem using a highly precise computational technique for shape comparison. Starting with a prospectively acquired sample of cranial MRIs of healthy volunteers (age ranges 18–84), the variations of individual callosa are quantified with respect to a

Abraham Dubb; Ruben Gur; Brian Avants; James Gee

2003-01-01

145

Interhemispheric Neuroepithelial Cyst Associated with Agenesis of the Corpus callosum  

Microsoft Academic Search

This report describes a neonatal case in whom a large interhemispheric cyst associated with agenesis of the corpus callosum was revealed by fetal ultrasonography and demonstrated by MRI to be multilobulated. Endoscopic fenestration of cysts was initially designed in view of the development of the patient’s brain and surgical invasiveness. One year later, when motor paresis of the left arm

Yuji Uematsu; Kenji Kubo; Toshiki Nishibayashi; Fuminori Ozaki; Kunio Nakai; Toru Itakura

2000-01-01

146

Agenesis of the Corpus Callosum in Two Sisters  

Microsoft Academic Search

Two sisters are described. They are offspring of Arabic parents who are both first and second cousins, through both sets of grandparents; additionally the father's parents are first cousins. The diagnosis of agenesis of the corpus callosum in the propositae was made by the characteristic picture on the pneumoencephalogram.The clinical symptoms in the two sisters varied considerably. The older sister

Yehuda Shapira; Tirza Cohen

1973-01-01

147

Outcome in Prenatally Diagnosed Fetal Agenesis of the Corpus callosum  

Microsoft Academic Search

This study of the outcome and prognostic factors in prenatally diagnosed agenesis of the corpus callosum (ACC) was undertaken to see if there are any differences between subgroups, what relationship they have to neurodevelopmental outcome and whether this information aids the counselling of parents of fetuses with the condition. The outcome of 14 prenatally diagnosed fetuses with ACC and 61

P. W. A. Goodyear; C. M. Bannister; S. Russell; S. Rimmer

2001-01-01

148

Congenital asymmetric crying facies and agenesis of corpus callosum  

Microsoft Academic Search

Although association of congenital asymmetric crying facies (CACF) with major congenital anomalies of central nervous system (CNS) has been described, brain magnetic resonance imaging (MRI) studies have not been reported. Two children who had CACF associated with agenesis of corpus callosum (ACC) diagnosed by MRI are described. Neurofibromatosis type 1 (NF-1) was diagnosed in one case. Both patients had developmental

Konstantinos A Voudris; Angeliki Skardoutsou; Eleni A Vagiakou

2003-01-01

149

Anisotropy of Iron-Series Permanent Magnets  

NASA Astrophysics Data System (ADS)

Element-strategic considerations have sparked renewed interest in rare-earth-free permanent magnets, but the prediction of the magnetocrystalline anisotropy from the atomic structure is still in its infancy, and there are no rules predicting the d anisotropy as function of the atomic structure. We have obtained tight-binding estimates for a variety of clusters and etxtended structures of different symmetry and d-band filling. A expected, the anisotropy strongly oscillates as a function of the d-band filling. Our calculations indicate that nearly filled d bands tend to yield anisotropy parallel to the pair axis. Sites with trigonal symmetry support bigger anisotropies than cubic and tetragonal environments, but this is a crystal- field effect similar to that in BaFe12O19 rather than a band-structure effect. Shape anisotropy is important in alnico- type nanostructured permanent magnets. We find a maximum of the energy product as a function of packing fraction, namely a maximum value of ?oMs^2/12 realized at a volume fraction of 2/3. For Fe65Co35, this yields an upper limit of 390 kJ/m^3 [49 MGOe].

Skomski, Ralph; Hadjipanayis, G. C.; Sellmyer, D. J.

2010-03-01

150

Age-related decline in brain white matter anisotropy measured with spatially corrected echo-planar diffusion tensor imaging.  

PubMed

Echo planar (EP) diffusion tensor imaging (DTI) permits in vivo identification of the orientation and coherence of brain white matter tracts but suffers from field inhomogeneity-induced geometric distortion. To reduce spatial distortion, polynomial warping corrections were applied and the effects tested on measures of fractional anisotropy (FA) in the genu and splenium of corpus callosum. Implementation entailed spatially warping EP images obtained without diffusion weighting (b = 0) to long-echo T(2)-weighted fast spin echo images, collected for anatomical delineation, tissue segmentation, and coregistration with the diffusion images. Using the optimal warping procedure (third-order polynomial), the effects of age on FA and a quantitative measure of intervoxel coherence (C) in the genu, splenium, centrum semiovale, and frontal and parietal pericallosal white matter were examined in 31 healthy men (23-76 years). FA declined significantly with age in all regions except the splenium, whereas intervoxel coherence positively correlated with age in the genu. Magn Reson Med 44:259-268, 2000. PMID:10918325

Pfefferbaum, A; Sullivan, E V; Hedehus, M; Lim, K O; Adalsteinsson, E; Moseley, M

2000-08-01

151

Biomarkers of increased diffusion anisotropy in semi-acute mild traumatic brain injury: a longitudinal perspective.  

PubMed

Mild traumatic brain injury is the most prevalent neurological insult and frequently results in neurobehavioural sequelae. However, little is known about the pathophysiology underlying the injury and how these injuries change as a function of time. Although diffusion tensor imaging holds promise for in vivo characterization of white matter pathology, both the direction and magnitude of anisotropic water diffusion abnormalities in axonal tracts are actively debated. The current study therefore represents both an independent replication effort (n = 28) of our previous findings (n = 22) of increased fractional anisotropy during semi-acute injury, as well as a prospective study (n = 26) on the putative recovery of diffusion abnormalities. Moreover, new analytical strategies were applied to capture spatially heterogeneous white matter injuries, which minimize implicit assumptions of uniform injury across diverse clinical presentations. Results indicate that whereas a general pattern of high anisotropic diffusion/low radial diffusivity was present in various white matter tracts in both the replication and original cohorts, this pattern was only consistently observed in the genu of the corpus callosum across both samples. Evidence for a greater number of localized clusters with increased anisotropic diffusion was identified across both cohorts at trend levels, confirming heterogeneity in white matter injury. Pooled analyses (50 patients; 50 controls) suggested that measures of diffusion within the genu were predictive of patient classification, albeit at very modest levels (71% accuracy). Finally, we observed evidence of recovery in lesion load in returning patients across a 4-month interval, which was correlated with a reduction in self-reported post-concussive symptomatology. In summary, the corpus callosum may serve as a common point of injury in mild traumatic brain injury secondary to anatomical (high frequency of long unmyelinated fibres) and biomechanics factors. A spatially heterogeneous pattern of increased anisotropic diffusion exists in various other white matter tracts, and these white matter anomalies appear to diminish with recovery. This macroscopic pattern of diffusion abnormalities may be associated with cytotoxic oedema following mechanical forces, resulting in changes in ionic homeostasis, and alterations in the ratio of intracellular and extracellular water. Animal models more specific to the types of mild traumatic brain injury typically incurred by humans are needed to confirm the histological correlates of these macroscopic markers of white matter pathology. PMID:22505633

Ling, Josef M; Peña, Amanda; Yeo, Ronald A; Merideth, Flannery L; Klimaj, Stefan; Gasparovic, Charles; Mayer, Andrew R

2012-04-01

152

Biomarkers of increased diffusion anisotropy in semi-acute mild traumatic brain injury: a longitudinal perspective  

PubMed Central

Mild traumatic brain injury is the most prevalent neurological insult and frequently results in neurobehavioural sequelae. However, little is known about the pathophysiology underlying the injury and how these injuries change as a function of time. Although diffusion tensor imaging holds promise for in vivo characterization of white matter pathology, both the direction and magnitude of anisotropic water diffusion abnormalities in axonal tracts are actively debated. The current study therefore represents both an independent replication effort (n = 28) of our previous findings (n = 22) of increased fractional anisotropy during semi-acute injury, as well as a prospective study (n = 26) on the putative recovery of diffusion abnormalities. Moreover, new analytical strategies were applied to capture spatially heterogeneous white matter injuries, which minimize implicit assumptions of uniform injury across diverse clinical presentations. Results indicate that whereas a general pattern of high anisotropic diffusion/low radial diffusivity was present in various white matter tracts in both the replication and original cohorts, this pattern was only consistently observed in the genu of the corpus callosum across both samples. Evidence for a greater number of localized clusters with increased anisotropic diffusion was identified across both cohorts at trend levels, confirming heterogeneity in white matter injury. Pooled analyses (50 patients; 50 controls) suggested that measures of diffusion within the genu were predictive of patient classification, albeit at very modest levels (71% accuracy). Finally, we observed evidence of recovery in lesion load in returning patients across a 4-month interval, which was correlated with a reduction in self-reported post-concussive symptomatology. In summary, the corpus callosum may serve as a common point of injury in mild traumatic brain injury secondary to anatomical (high frequency of long unmyelinated fibres) and biomechanics factors. A spatially heterogeneous pattern of increased anisotropic diffusion exists in various other white matter tracts, and these white matter anomalies appear to diminish with recovery. This macroscopic pattern of diffusion abnormalities may be associated with cytotoxic oedema following mechanical forces, resulting in changes in ionic homeostasis, and alterations in the ratio of intracellular and extracellular water. Animal models more specific to the types of mild traumatic brain injury typically incurred by humans are needed to confirm the histological correlates of these macroscopic markers of white matter pathology.

Ling, Josef M.; Pena, Amanda; Yeo, Ronald A.; Merideth, Flannery L.; Klimaj, Stefan; Gasparovic, Charles

2012-01-01

153

Complete Corpus Callosum Agenesis: Can It Be Mild?  

PubMed Central

Corpus callosum agenesis is a relatively common brain malformation. It can be isolated or included in a complex alteration of brain (or sometimes even whole body) morphology. Etiology and pathogenetic mechanisms have been better understood in recent years due to the availability of more adequate animal models and the relevant progresses in developmental neurosciences. We present the case of a girl with a complete agenesis of the corpus callosum discovered at birth. She had mild learning difficulties, but reached satisfactory levels of autonomy after an individually tailored rehabilitative treatment. Her story is discussed in light of recent findings, which emphasize the possibility to exploit brain plasticity and the utility of an individually tailored approach, defined on the basis of a dialogue with the family and the patient.

Chiappedi, Matteo; Fresca, Anna; Baschenis, Ilaria Maria Carlotta

2012-01-01

154

Agenesis of corpus callosum: prenatal diagnosis and prognosis  

Microsoft Academic Search

IntroductionAgenesis of corpus callosum (ACC) is commonly diagnosed prenatally. When isolated, it appears to carry a good prognosis but studies are often retrospective and follow-up short. We report a prospective study of 17 children (11 boys, 6 girls) with prenatally diagnosed isolated ACC.MethodsNeuropsychological evaluation was performed each year and results at the ages of 2, 4, and 6 years were compared.ResultsFebrile

Marie-Laure Moutard; Virginie Kieffer; Josué Feingold; François Kieffer; Fanny Lewin; Catherine Adamsbaum; Antoinette Gélot; Jaume Campistol i Plana; Patrick van Bogaert; Monique André; Gérard Ponsot

2003-01-01

155

A critical re-examination of sexual dimorphism in the corpus callosum microstructure  

Microsoft Academic Search

Recent diffusion-tensor imaging (DTI) studies suggest sexual dimorphism in the micro-structural architecture of the corpus callosum. However, the corpus callosum is also found to be larger in males than in females, a fact that might introduce a systematic bias to the analysis of DTI parameters. Diffusion parameters obtained in the larger male corpus callosum could be less affected by partial-volume

René Westerhausen; Kristiina Kompus; Margaretha Dramsdahl; Liv E. Falkenberg; Renate Grüner; Helene Hjelmervik; Karsten Specht; Kerstin Plessen; Kenneth Hugdahl

2011-01-01

156

Diffusion tensor imaging of normal white matter maturation from late childhood to young adulthood: Voxel-wise evaluation of mean diffusivity, fractional anisotropy, radial and axial diffusivities, and correlation with reading development  

Microsoft Academic Search

Using diffusion tensor MR imaging (DTI) and advanced voxel-wise analysis tools, we study diffusivity and anisotropy changes of white matter from late childhood to young adulthood, and correlate quantitative diffusion indices with Chinese and English reading performance scores. Seventy-five normal healthy school going ethnic Chinese students and young adults of three age groups were recruited (group 1, n=24, mean±SD=7.4±0.3 years; group

Deqiang Qiu; Li-Hai Tan; Ke Zhou; Pek-Lan Khong

2008-01-01

157

Magnetic multilayer interface anisotropy  

NASA Astrophysics Data System (ADS)

Ni/Mo and Ni/V multilayer magnetic anisotropy has been investigated as a function of Ni layer thickness, frequency and temperature. Variable frequency ferromagnetic resonance (FMR) measurements show, for the first time, significant frequency dependence associated with the multilayer magnetic anisotropy. The thickness dependence allows one to extract the interface contribution from the total anisotropy. Temperature dependent FMR (9 GHz) and room temperature magnetization indicate that strain between Ni and the non-magnetic layers is contributing significantly to the source of the interface anisotropy and the state of the interfacial magnetization. In order to examine the interface properties of other transition metal multilayer systems, investigations on Fe/Cu are underway and CoCr/Ag is being proposed. ESR measurements have been reported on Gd substituted YBaCuO superconductors and a novel quasi-equilibrium method has been developed to determine quickly and precisely the transition temperature.

Pechan, M. J.

158

Magnetic multilayer interface anisotropy  

SciTech Connect

Ni/Mo and Ni/V multilayer magnetic anisotropy has been investigated as a function of Ni layer thickness, frequency and temperature. Variable frequency ferromagnetic resonance (FMR) measurements show, for the first time, significant frequency dependence associated with the multilayer magnetic anisotropy. The thickness dependence allows one to extract the interface contribution from the total anisotropy. Temperature dependent FMR (9 GHz) and room temperature magnetization indicate that strain between Ni and the non-magnetic layers is contributing significantly to the source of the interface anisotropy and the state of the interfacial magnetization. In order to examine the interface properties of other transition metal multilayer systems, investigations on Fe/Cu are underway and CoCr/Ag is being proposed. ESR measurements have been reported on Gd substituted YBaCuO superconductors and a novel quasi-equilibrium method has been developed to determine quickly and precisely the ransition temperature.

Pechan, M.J.

1992-01-01

159

The Role of Corpus Callosum Development in Functional Connectivity and Cognitive Processing  

Microsoft Academic Search

The corpus callosum is hypothesized to play a fundamental role in integrating information and mediating complex behaviors. Here, we demonstrate that lack of normal callosal development can lead to deficits in functional connectivity that are related to impairments in specific cognitive domains. We examined resting-state functional connectivity in individuals with agenesis of the corpus callosum (AgCC) and matched controls using

Leighton B. N. Hinkley; Elysa J. Marco; Anne M. Findlay; Susanne Honma; Rita J. Jeremy; Zoe Strominger; Polina Bukshpun; Mari Wakahiro; Warren S. Brown; Lynn K. Paul; A. James Barkovich; Pratik Mukherjee; Srikantan S. Nagarajan; Elliott H. Sherr

2012-01-01

160

Regional Pattern of Increased Water Diffusivity in Hippocampus and Corpus Callosum in Mild Cognitive Impairment  

Microsoft Academic Search

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),

Huali Wang; Min-Ying Su

2006-01-01

161

Corpus Callosum and Prefrontal Functions in Adolescents with History of Very Preterm Birth  

ERIC Educational Resources Information Center

Very preterm (VPT) birth can account for thinning of the corpus callosum and poorer cognitive performance. Research findings about preterm and VPT adolescents usually describe a small posterior corpus callosum, although our research group has also found reductions of the anterior part, specifically the genu. The aim of the present study was to…

Narberhaus, Ana; Segarra, Dolors; Caldu, Xavier; Gimenez, Monica; Pueyo, Roser; Botet, Francesc; Junque, Carme

2008-01-01

162

A quantitative MRI study of the corpus callosum in children and adolescents  

Microsoft Academic Search

Total midsagittal area and seven subdivisions of the corpus callosum were measured on magnetic resonance images of 114 healthy boys and girls, aged 4 to 18. Striking variability of size was noted for all measures. Total midsagittal corpus callosum area increased in a robust and linear fashion from ages 4 to 18 (slope = 13.1 mm2\\/year, P = 0.0001 and

Jay N. Giedd; Judith M. Rumsey; F. Xavier Castellanos; Jagath C. Rajapakse; Debra Kaysen; A. Catherine Vaituzis; Yolanda C. Vauss; Susan D. Hamburger; Judith L. Rapoport

1996-01-01

163

Spatial frequency thresholds of single striate cortical cells in neonatal corpus callosum sectioned cats  

Microsoft Academic Search

Following section of the corpus callosum at 1–6 postnatal weeks in cats, behavioral visual acuity was measured binocularly and monocularly from 6–29 postnatal weeks; physiological determination of spatial frequency thresholds of single striate cortical cells was performed when the cats were at least 8 months old. Results were compared between cats with callosum section at each postnatal week, as well

A. J. Elberger

1990-01-01

164

Three sibs with microcephaly, clubfeet and agenesis of corpus callosum: a new genetic syndrome?  

PubMed

Clubfoot is a common birth deformity, and agenesis of the corpus callosum is one of the most prevalent brain malformations. We describe three sibs of Arab origin, who were born with clubfeet, agenesis of corpus callosum, and minor anomalies. Two of them were born with microcephaly. This phenotype may represent a novel autosomal recessive genetic condition. PMID:21465661

Shkalim, Vered; Ben-Sira, Liat; Inbar, Dov; Kaadan, Walid; Basel-Vanagaite, Lina; Straussberg, Rachel

2011-04-04

165

Sexual dimorphism in the human corpus callosum? A comparison of methodologies  

Microsoft Academic Search

Mid-sagittal magnetic resonance images of 104 normal individuals were analyzed to assess whether or not the corpus callosum or parts thereof is sexually dimorphic in favor of females. Subjects were 56 males and 48 females, both groups being closely age matched. The outline of the corpus callosum was divided into seven sub-areas, using three different orientations. A comparison was made

Deborah Constant; Heinz Ruther

1996-01-01

166

Cross-sectional area of the elephant corpus callosum: comparison to other eutherian mammals  

Microsoft Academic Search

The current study reports our findings of the relationship between cross-sectional area of the corpus callosum and brain mass in over 100 eutherian mammal species. We were specifically interested in determining whether the elephant had a corpus callosum the size that would be expected for eutherian mammal with a brain mass of approximately 5000 g, or whether a different morphology

P. R. Manger; J. Hemingway; M. Haagensen; E. Gilissen

2010-01-01

167

Developmental Dyslexia: ReEvaluation of the Corpus callosum in Male Adults  

Microsoft Academic Search

Using a new method based upon the measurement of four angles, we analyzed the corpus callosum of 23 adult male dyslexics and 25 age-matched controls on MRI sagittal scans. Two out of the four angles measured showed significant differences between the groups that are consistent with previous findings concerning the size of the corpus callosum in dyslexics. In particular, posterior

Fabrice Robichon; Pascal Bouchard; Jean-François Démonet; Michel Habib

2000-01-01

168

Spatial attention in agenesis of the corpus callosum: shifting attention between visual fields  

Microsoft Academic Search

The role of the corpus callosum in spatially selective visual attention is uncertain. Research using commissurotomy and callosotomy patients has attempted to determine if the corpus callosum plays a role in reorienting attention between visual fields, as if spatial attention is unitary or divisible between the cerebral hemispheres. Reorienting of selective visuospatial attention within versus between visual fields was tested

Robert J Hines; Lynn K Paul; Warren S Brown

2002-01-01

169

Hypoplasia of the Corpus Callosum: A Study of 445 Consecutive MRI Scans  

Microsoft Academic Search

The size of the corpus callosum was assessed visually and by computer-assisted image analysis in a series of 445 consecutive magnetic resonance imaging (MRI) scans in children under 17 years of age. Fifty individuals were subjectively identified with small corpora callosa on visual inspection of the MRI scans. Seven patients had true hypoplasia of the corpus callosum after comparing the

John Bodensteiner; G. B. Schaefer; Lisa Breeding; Linda Cowan

1994-01-01

170

A Case of Schizophrenia with Complete Agenesis of the Corpus Callosum  

Microsoft Academic Search

Objective: To describe the case of a person with schizophrenia and agenesis of the corpus callosum.Conclusion: A 24-year-old Caucasian woman with schizophrenia was incidentally found to have complete agenesis of the corpus callosum. A comprehensive neuropsychiatric assessment allowed management to be specifically tailored to the patient's unique clinical profile.

Dhamodharan Chinnasamy; Rebecca Rudd; Dennis Velakoulis

2006-01-01

171

Gelastic epilepsy, hypothalamic hamartoma, precocious puberty, and agenesis of the corpus callosum: a new association  

Microsoft Academic Search

We describe a boy who has gelastic epilepsy, precocious puberty, hypothalamic hamartoma, and agenesis of the corpus callosum. We believe that this is the first documented case in which agenesis of the corpus callosum has been associated with hypothalamic hamartoma and gelastic epileptic syndrome in a child.

Alikchan A Alikchanov; Andrey S Petrukhin; Konstantin Yu Mukhin; Alexander Yu Nikanorov

1998-01-01

172

A case of hypocontractile neurogenic bladder associated with agenesis of corpus callosum  

Microsoft Academic Search

A case of hypocontractile neurogenic bladder associated with agenesis of the corpus callosum is presented. Not only detrusor pressure but the urethral and anal pressures were also very weak. Although no abnormality could be detected on cervical, thoracic and lumbar magnetic resonance imaging and myelography, dysgenesis of the spinal cord or peripheral nerves associated with agenesis of corpus callosum was

Hirofumi Oyama; Shigeaki Yokoi; Yoshinari Ono; Yoshihisa Kida

1998-01-01

173

Antenatal ultrasonographic findings differentiating complete from partial agenesis of the corpus callosum  

Microsoft Academic Search

Four cases of complete (three) and partial (one) agenesis were evaluated ultrasonographically. The frontal lobe\\/biparietal diameter ratio were evaluated in 113 normal fetuses and compared with those ratios in fetuses with corpus callosum agenesis. In the presence of the classic ultrasonographic features of agenesis of the corpus callosum, frontal lobe shortening, along with absence of the cavum septi pellucidi, might

Ron Tepper; Yaron Zalel; Eti Gaon; Moshe Fejgin; Y. Beyth

1996-01-01

174

Electroanatomy of the corpus callosum radiation according to the facts of stereotactic stimulation in man  

Microsoft Academic Search

Following exploratory electrical stimulation varying portions of fibres of the Corpus callosum were coagulated in a group of epileptic patients in order to interrupt the interhemispheric spreading of electrical discharges. The stimulation experiments revealed that the central fibres of the Corpus callosum are arranged according to a somatotopic pattern somewhat similar to the topology of the second motor region. The

G. SCtIALTENBRAND; H. Spuler; W. Wahren

1970-01-01

175

Anisotropy of sandstone permeability  

Microsoft Academic Search

Small-scale probe permeability measurements on differently oriented faces of highly compacted and quartz-cemented Viking Formation sandstones yield detailed permeability distributions that appear to be diagnostic of the grain- and lamina-scale fabric of the samples. Permeability anisotropy of a single 'structureless'-appearing sample is low, reflected by a kV \\/ kH-ratio of 0.7; corresponding k-distributions are homogeneous. Permeability anisotropy of a strongly

Rudi Meyer

176

A magnetic resonance imaging study of corpus callosum size in familial schizophrenic subjects,their relatives, and normal controls  

Microsoft Academic Search

The corpus callosum is one of several brain regions thought to be abnormal in schizophrenia. We sought to investigate whether the size of the corpus callosum would be abnormally small in schizophrenic subjects from families with familial schizophrenia and their healthy relatives. We wished to determine whether an abnormal corpus callosum size is found in healthy relatives who are genetically

S. E. Chua; T. Sharma; N. Takei; R. M. Murray; P. W. R. Woodruff

2000-01-01

177

Corpus Callosum Differences associated with Persistent Stuttering in Adults  

PubMed Central

Recent studies have implicated anatomical differences in speech-relevant brain regions of adults who stutter (AWS) compared to normally fluent adults (NFA). The present study focused on the region of the corpus callosum (CC) which is involved in interhemispheric processing between the left and right cerebral hemispheres. Two-dimensional segmentation of area and voxel based morphometry were used to evaluate the corpus callosum. Results revealed that the rostrum and anterior midbody of the CC was larger in AWS than NFA. In addition, the overall callosa area was larger in AWS than NFA. The group comparison of white matter volume showed a cluster of increased white matter volume predominantly encompassing the rostrum across the midline portion in AWS. These results potentially reflect anatomical changes associated with differences in the hemispheric distribution of language processes that has been reported previously in AWS. Educational objectives After reading this article, the reader will be able to: (1) summarize research findings on functional and anatomical differences between AWS and NFA; (2) summarize research findings on anatomical anomalies observed in AWS; (3) discuss the possible relationships between functional and anatomical aberrations in AWS; and (4) discuss how the findings of the present study may support results of previous behavioral investigations (e.g. dichotic listening) in AWS.

Choo, Ai Leen; Kraft, Shelly Jo; Olivero, William; Ambrose, Nicoline G.; Sharma, Harish; Chang, Soo-Eun; Loucks, Torrey

2011-01-01

178

Reduced area of the corpus callosum in posttraumatic stress disorder.  

PubMed

Magnetic resonance imaging (MRI) studies have revealed decreases in the mid-sagittal area of the corpus callosum (CC) in pediatric posttraumatic stress disorder (PTSD), but at present no data are available in adult PTSD patients. We have previously reported decreased whole-brain white matter (WM) volume in adults with PTSD and now report corpus callosum area from the same sample. MRI was used to obtain whole-brain images in 12 adult patients with PTSD and 10 matched controls. Total parenchyma (white matter plus gray matter [GM]) volume, mid-sagittal area of the CC and seven sub-regions of this structure were calculated. In PTSD patients, the total CC area, absolute and normalized to total brain parenchyma, was smaller compared with control values. Several absolute and normalized CC sub-regions were also smaller in PTSD patients: genu (region 2), mid-body (region 5) and isthmus (region 6). There was also a trend for the anterior mid-body (area 4) to be smaller in PTSD patients. No differences were found in the rostrum (region 1), rostral body (region 3) or splenium (region 7). Adult patients with PTSD had decreased CC area after correcting for total brain tissue, indicating that these differences are not attributable to generalized white matter atrophy. These findings are similar to previous results in children with PTSD and suggest specific changes in the CC. PMID:15465292

Villarreal, Gerardo; Hamilton, Derek A; Graham, David P; Driscoll, Ira; Qualls, Clifford; Petropoulos, Helen; Brooks, William M

2004-09-15

179

Magnetic multilayer interface anisotropy  

SciTech Connect

Ni/Mo and Ni/V multilayer magnetic anisotropy has been investigated as a function of Ni layer thickness, frequency and temperature. Variable frequency ferromagnetic resonance (FMR) measurements show, for the first time, significant frequency dependence associated with the multilayer magnetic anisotropy. The thickness dependence allows one to extract the interface contribution from the total anisotropy. Temperature dependent FMR (9 GHz) and room temperature magnetization indicate that strain between Ni and the non-magnetic layers is contributing significantly to the source of the interface anisotropy and the state of the interfacial magnetization. In order to examine the interface properties of other transition metal multilayer systems, investigations on Fe/Cu are underway and CoCr/Ag is being proposed. ESR measurements have been reported on Gd substituted YBaCuO superconductors and a novel quasi-equilibrium method has been developed to determine quickly and precisely the transition temperature. During the next project period the P.I. proposes to (1) extend the variable frequency FMR measurements to low temperature, where extremely large interface anisotropies are known to obtain in Ni/Mo and Ni/V and are proposed to exist in Ni/W; (2) obtain accurate dc anisotropies via a novel, variable temperature torque magnetometer currently under construction; (3) expand upon his initial findings in Fe/Cu multilayer investigations; (4) begin anisotropy investigations on Co/Ag and CoCr/Ag multilayers where the easy magnetization direction depends upon the Cr concentration; (4) make and characterize Bi based superconductors according to resistivity, thermal conductivity and thermoelectric power and construct YBaCuO based superconducting loop-gap'' resonators for use in his magnetic resonance work.

Pechan, M.J.

1990-01-01

180

Magnetic anisotropy of chloritoid  

NASA Astrophysics Data System (ADS)

The magnetocrystalline anisotropy of monoclinic chloritoid, a relatively common mineral in aluminum-rich, metapelitic rocks, has been determined for the first time by measuring the high-field anisotropy of magnetic susceptibility (HF-AMS), using two independent approaches, i.e., (a) directional magnetic hysteresis measurements and (b) torque magnetometry, on a collection of single crystals collected from different tectonometamorphic settings worldwide. Magnetic remanence experiments show that all specimens contain ferromagnetic (s.l.) impurities, being mainly magnetite. The determined HF-AMS ellipsoids have a highly oblate shape with the minimum susceptibility direction subparallel to the crystallographic c-axis of chloritoid. In the basal plane of chloritoid, though the HF-AMS can be considered isotropic. The degree of anisotropy is found to be 1.47, which is significantly higher than the anisotropy of most paramagnetic silicates and even well above the frequently used upper limit (i.e., 1.35) for the paramagnetic contribution to the AMS of siliciclastic rocks. The obtained values for the paramagnetic Curie temperature parallel (??) and perpendicular (??) to the basal plane indicate that this pronounced magnetocrystalline anisotropy is related to strong antiferromagnetic exchange interactions in the direction of the crystallographic c-axis (?? < 0) and rather weak ferromagnetic exchange interactions within the basal plane (?? > 0). As a consequence, chloritoid-bearing metapelites with a pronounced mineral alignment can have a high degree of anisotropy without the need of invoking a significant contribution of strongly anisotropic, ferromagnetic (s.l.) minerals. The newly discovered magnetocrystalline anisotropy of chloritoid thus calls for a revised approach of magnetic fabric interpretations in chloritoid-bearing rocks.

Haerinck, Tom; Debacker, Timothy N.; Sintubin, Manuel

2013-08-01

181

Magnetic multilayer interface anisotropy  

SciTech Connect

Ni/Mo and Ni/V multilayer magnetic anisotropy has been investigated as a function of Ni layer thickness, frequency and temperature. Variable frequency ferromagnetic resonance (FMR) measurements show, for the first time, significant frequency dependence associated with the multilayer magnetic anisotropy. The thickness dependence allows one to extract the interface contribution from the total anisotropy. Temperature dependant FMR (9 GHz) and room temperature magnetization indicate that strain between Ni and the non-magnetic layers if contributing significantly to the source of the interface anisotropy and the state of the interfacial magnetization. In order to examine the interface properties of other transition metal multilayer systems, investigations on Fe/Cu are underway and CoCr/Ag is being proposed. ESR measurements have been reported on Gd substituted YBaCuO superconductors and a novel quasi-equilibrium method has been developed to determine quickly and precisely the transition temperature. During the next project the P.I. proposes to (1) extend the variable frequency FMR measurements to low temperature, where extremely large interface anisotropies are known to obtain in Ni/Mo and Ni/V and are proposed to exist in Ni/W; (2) obtain accurate dc anisotropies via a novel, variable temperature torque magnetometer currently under construction; (3) expand upon his initial findings in Fe/Cu multilayer investigations; (4) begin anisotropy investigations on Co/Ag and CoCr/Ag multilayers where the easy magnetization direction depends upon the Cr concentration; (4) make and characterize Bi based superconductors according to resistivity, thermal conductivity and thermoelectric power and construct YBaCuO based superconducting loop-gap'' resonators for use in his magnetic resonance work. 2 figs.

Pechan, M.J.

1991-01-01

182

Large amplitude oscillation of magnetic anisotropy engineered by substrate step density  

NASA Astrophysics Data System (ADS)

Large amplitude quantum oscillations of magnetic anisotropy in Fe films grown on Ag surfaces of high step density are reported. Distortion of the film structure by the steps is found to be responsible for the anisotropy modification which oscillates with increasing film thickness. The larger the distorted fraction of the film volume, the larger the observed amplitude of the anisotropy oscillations. Such dependence of the anisotropy oscillations on the step density offers an easy tool to manipulate the strength of the anisotropy and orientation of the easy magnetization axis.

Bauer, U.; Przybylski, M.

2010-04-01

183

Corpus callosum signal intensity in patients with bipolar and unipolar disorder  

PubMed Central

Background: Anatomical abnormalities in the corpus callosum have been reported in magnetic resonance imaging (MRI) studies in patients with bipolar but not unipolar disorder. MRI signal intensity can be used as a putative index of corpus callosum myelination. Objectives: To measure MRI signal intensity in patients with bipolar and unipolar disorder to investigate abnormalities of corpus callosum myelination. Methods: The study involved 29 DSM-IV bipolar patients (mean (SD) age, 35 (11) years; 16 male, 13 female), 23 DSM-IV unipolar patients (41 (10) years; 4 male, 19 female), and 36 healthy controls (37 (10) years; 23 male, 13 female). A 1.5T GE Signa magnet was employed, with a fast spin echo sequence. Corpus callosum signal intensity was obtained blindly using the semiautomated software NIH Image 1.62. Results: Bipolar patients had lower corpus callosum signal intensity for all callosal subregions (genu, anterior and posterior body, isthmus, splenium) than healthy controls (ANCOVA, age and sex as covariates, p<0.05). No significant differences were found between unipolar and healthy subjects (ANCOVA, age and sex as covariates, p>0.05). Conclusions: The findings suggest abnormalities in corpus callosum white matter in bipolar but not unipolar patients, possibly because of altered myelination. Such abnormalities could lead to impaired interhemispheric communication in bipolar disorder. Longitudinal MRI studies involving first episode and early onset bipolar patients will be necessary for a better understanding of the potential role of abnormalities of corpus callosum myelination in the pathophysiology of bipolar disorder.

Brambilla, P; Nicoletti, M; Sassi, R; Mallinger, A; Frank, E; Keshavan, M; Soares, J

2004-01-01

184

Corpus callosum size and shape alterations in adolescent inhalant users.  

PubMed

Inhalants, frequently abused during adolescence, are neurotoxic to white matter. We investigated the impact of inhalant misuse on the morphology of the corpus callosum (CC), the largest white matter bundle in the brain, in an adolescent sample of inhalant users [n = 14; mean age = 17.3; standard deviation (SD) = 1.7], cannabis users (n = 11; mean age = 19.7; SD = 1.7) and community controls (n = 9; mean age = 19.5; SD = 2.6). We identified significant morphological differences in the CC among inhalant users compared with community controls. There were no morphological differences between inhalant and cannabis users. Our findings may represent the early stages of neurobiological damage associated with chronic inhalant misuse. PMID:21955104

Takagi, Michael; Lubman, Dan I; Walterfang, Mark; Barton, Sarah; Reutens, David; Wood, Amanda; Yücel, Murat

2011-09-29

185

Diffusion Tensor Quantification and Cognitive Correlates of the Macrostructure and Microstructure of the Corpus Callosum in Typically Developing Children and Dyslexics  

PubMed Central

Noninvasive quantitative magnetic resonance imaging methods such as diffusion tensor imaging (DTI), can offer insights into structure/function relationships in human developmental brain disorders. In this report, we quantified macrostructural and microstructural attributes of the corpus callosum (CC) in children with dyslexia and typically developing readers of comparable age and gender. Diffusion anisotropy, mean, radial and axial diffusivities of cross-sectional CC sub-regions were computed using a validated DTI methodology. The normalized posterior CC area was enlarged in children with dyslexia compared to typically developing children. Moreover, the callosal microstructural attributes, such as mean diffusivity of the posterior middle sector of the CC, significantly correlated with measures of word reading and reading comprehension. Reading group differences in FA, MD, and RD were observed in the posterior CC (CC5). This study demonstrates the utility of regional DTI measurements of the CC in understanding the neurobiology of reading disorders.

Hasan, Khader M.; Molfese, David L.; Walimuni, Indika S.; Stuebing, Karla K.; Papanicolaou, Andrew C.; Narayana, Ponnada A.; Fletcher, Jack M.

2012-01-01

186

Magnetic anisotropy data of CHP  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume C `Diamagnetic Susceptibility and Magnetic Anisotropy of Organic Compounds' of Volume 27 `Diamagnetic Susceptibility and Anisotropy' of Landolt-Börnstein - Group II Molecules and Radicals.

Kumar, M.; Gupta, R.

187

SELECTIVELY DIMINISHED CORPUS CALLOSUM FIBERS IN CONGENITAL CENTRAL HYPOVENTILATION SYNDROME  

PubMed Central

Congenital central hypoventilation syndrome (CCHS), a condition associated with mutations in the PHOX2B gene, is characterized by loss of breathing drive during sleep, insensitivity to CO2 and O2, and multiple somatomotor, autonomic, neuropsychological, and ophthalmologic deficits, including impaired intrinsic and extrinsic eye muscle control. Brain structural studies show injury in peri-callosal regions and the corpus callosum (CC), which has the potential to affect functions disturbed in the syndrome; however, the extent of CC injury in CCHS is unclear. Diffusion tensor imaging (DTI)-based fiber tractography procedures display fiber directional information and allow quantification of fiber integrity. We performed DTI in 13 CCHS children (age, 18.2±4.7 years; 8 male) and 31 control (17.4±4.9 years; 18 male) subjects using a 3.0-Tesla magnetic resonance imaging scanner; CC fibers were assessed globally and regionally with tractography procedures, and fiber counts and densities compared between groups using analysis-of-covariance (covariates; age and sex). Global CC evaluation showed reduced fiber counts and densities in CCHS over control subjects (CCHS vs controls; fiber-counts, 4490±854 vs 5232±777, p<0.001; fiber-density, 10.0±1.5 vs 10.8±0.9 fibers/mm2, p<0.020), and regional examination revealed that these changes are localized to callosal axons projecting to prefrontal (217±47 vs 248±32, p<0.005), premotor (201±51 vs 241±47, p<0.012), parietal (179±64 vs 238±54, p<0.002), and occipital regions (363±46 vs 431±82, p<0.004). Corpus callosum fibers in CCHS are compromised in motor, cognitive, speech, and ophthalmologic regulatory areas. The mechanisms of fiber injury are unclear, but may result from hypoxia or perfusion deficits accompanying the syndrome, or from consequences of PHOX2B action.

Kumar, Rajesh; Macey, Paul M.; Woo, Mary A.; Harper, Ronald M.

2011-01-01

188

Selectively diminished corpus callosum fibers in congenital central hypoventilation syndrome.  

PubMed

Congenital central hypoventilation syndrome (CCHS), a condition associated with mutations in the PHOX2B gene, is characterized by loss of breathing drive during sleep, insensitivity to CO2 and O2, and multiple somatomotor, autonomic, neuropsychological, and ophthalmologic deficits, including impaired intrinsic and extrinsic eye muscle control. Brain structural studies show injury in peri-callosal regions and the corpus callosum (CC), which has the potential to affect functions disturbed in the syndrome; however, the extent of CC injury in CCHS is unclear. Diffusion tensor imaging (DTI)-based fiber tractography procedures display fiber directional information and allow quantification of fiber integrity. We performed DTI in 13 CCHS children (age, 18.2±4.7 years; eight male) and 31 control (17.4±4.9 years; 18 male) subjects using a 3.0-Tesla magnetic resonance imaging scanner; CC fibers were assessed globally and regionally with tractography procedures, and fiber counts and densities compared between groups using analysis-of-covariance (covariates; age and sex). Global CC evaluation showed reduced fiber counts and densities in CCHS over control subjects (CCHS vs. controls; fiber-counts, 4490±854 vs. 5232±777, P<0.001; fiber-density, 10.0±1.5 vs. 10.8±0.9 fibers/mm2, P<0.020), and regional examination revealed that these changes are localized to callosal axons projecting to prefrontal (217±47 vs. 248±32, P<0.005), premotor (201±51 vs. 241±47, P<0.012), parietal (179±64 vs. 238±54, P<0.002), and occipital regions (363±46 vs. 431±82, P<0.004). Corpus callosum fibers in CCHS are compromised in motor, cognitive, speech, and ophthalmologic regulatory areas. The mechanisms of fiber injury are unclear, but may result from hypoxia or perfusion deficits accompanying the syndrome, or from consequences of PHOX2B action. PMID:21256194

Kumar, R; Macey, P M; Woo, M A; Harper, R M

2011-01-19

189

Agenesis of corpus callosum and emotional information processing in schizophrenia.  

PubMed

Corpus callosum (CC) is essential in providing the integration of information related to perception and action within a subcortico-cortical network, thus supporting the generation of a unified experience about and reaction to changes in the environment. Its role in schizophrenia is yet to be fully elucidated, but there is accumulating evidence that there could be differences between patients and healthy controls regarding the morphology and function of CC, especially when individuals face emotionally laden information. Here, we report a case study of a patient with partial agenesis of corpus callosum (agCC patient with agenesis of the anterior aspect, above the genu) and we provide a direct comparison with a group of patients with no apparent callosal damage (CC group) regarding the brain activity during the processing of emotionally laden information. We found that although the visual cortex activation in response to visual stimuli regardless of their emotional content was comparable in agCC patient and CC group both in terms of localization and intensity of activation, we observed a very large, non-specific and non-lateralized cerebral activation in the agCC patient, in contrast with the CC group, which showed a more lateralized and spatially localized activation, when the emotional content of the stimuli was considered. Further analysis of brain activity in the regions obtained in the CC group revealed that the agCC patient actually had an opposite activation pattern relative to most participants with no CC agenesis, indicating a dysfunctional response to these kind of stimuli, consistent with the clinical presentation of this particular patient. Our results seem to give support to the disconnection hypothesis which posits that the core symptoms of schizophrenia are related to aberrant connectivity between distinct brain areas, especially when faced with emotional stimuli, a fact consistent with the clinical tableau of this particular patient. PMID:22347194

Lungu, Ovidiu; Stip, Emmanuel

2012-02-03

190

Magnetic Anisotropy and Paleomagnetism  

Microsoft Academic Search

The natural remanent magnetization of certain Welsh slates lies in the cleavage plane, which was found to be a plane of high susceptibility defined by the alignment of aniso- tropic crystals of pyrrhotite. A correlation between the magnitude of susceptibility anisotropy and the bulk susceptibility of the slates has been observed. This is interpreted as a partial masking of the

M. D. Fuller

1963-01-01

191

Killing vectors and anisotropy  

NASA Astrophysics Data System (ADS)

We consider an action that can generate fluids with three unequal stresses for metrics with a spacelike Killing vector. The parameters in the action are directly related to the stress anisotropies. The field equations following from the action are applied to an anisotropic cosmological expansion and an extension of the Gott-Hiscock cosmic string.

Krisch, J. P.; Glass, E. N.

2009-08-01

192

Killing vectors and anisotropy  

SciTech Connect

We consider an action that can generate fluids with three unequal stresses for metrics with a spacelike Killing vector. The parameters in the action are directly related to the stress anisotropies. The field equations following from the action are applied to an anisotropic cosmological expansion and an extension of the Gott-Hiscock cosmic string.

Krisch, J. P.; Glass, E. N. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2009-08-15

193

What does anisotropy measure? Insights from increased and decreased anisotropy in selective fiber tracts in schizophrenia  

PubMed Central

Schizophrenia is a common, severe, and chronically disabling mental illness of unknown cause. Recent MRI studies have focused attention on white matter abnormalities in schizophrenia using diffusion tensor imaging (DTI). Indices commonly derived from DTI include (1) mean diffusivity, independent of direction, (2) fractional anisotropy (FA) or relative anisotropy (RA), (3) axial diffusivity, and (4) radial diffusivity. In cerebral white matter, contributions to these indices come from fiber arrangements, degree of myelination, and axonal integrity. Relatively pure deficits in myelin result in a modest increase in radial diffusivity, without affecting axial diffusivity and with preservation of anisotropy. Although schizophrenia is not characterized by gross abnormalities of white matter, it does involve a profound dysregulation of myelin-associated gene expression, reductions in oligodendrocyte numbers, and marked abnormalities in the ultrastructure of myelin sheaths. Since each oligodendrocyte myelinates as many as 40 axon segments, changes in the number of oligodendrocytes (OLG), and/or in the integrity of myelin sheaths, and/or axoglial contacts can have a profound impact on signal propagation and the integrity of neuronal circuits. Whereas a number of studies have revealed inconsistent decreases in anisotropy in schizophrenia, we and others have found increased FA in key subcortical tracts associated with the circuits underlying symptom generation in schizophrenia. We review data revealing increased anisotropy in dopaminergic tracts in the mesencephalon of schizophrenics and their unaffected relatives, and discuss the possible biological underpinnings and physiological significance of this finding.

Alba-Ferrara, L. M.; de Erausquin, Gabriel A.

2012-01-01

194

Azimuthal Anisotropy and the QGP  

SciTech Connect

Study of azimuthal anisotropy have played very important role at RHIC(Relativistic Heavy Ion Collider) Physics. The large azimuthal anisotropy is the proof of very early thermalization of the system which cannot be obtained without introducing interactions at the partonic level. Quark number scaling of the azimuthal anisotropy suggests a new particle production mechanism characteristic in dense matter.

Miake, Yasuo [Institute of Physics, University of Tsukuba, Tsukuba, 305-8571 (Japan)

2006-11-02

195

Quantitative Analysis of the Shape of the Corpus Callosum in Autistic Individuals  

PubMed Central

Multiple studies suggest that the corpus callosum in patients with autism is reduced in size. This study attempts to elucidate the nature of this morphometric abnormality by analyzing the shape of this structure in 17 high-functioning patients with autism and an equal number of comparison participants matched for age, sex, IQ, and handedness. The corpus callosum was segmented from T1 weighted images acquired with a Siemens 1.5 T scanner. Transformed coordinates of the curvilinear axis were aggregated into a parametric map and compared across series to derive regions of statistical significance. Our results indicate that in subjects with autism reduction in size of the corpus callosum occurs over all of its subdivisions (genu, body, splenium) with a small area of overgrowth at its caudal pole. Since the commisural fibers that traverse the different anatomical compartments of the corpus callosum originate in disparate brain regions our results suggest the presence of widely distributed cortical abnormalities in people with autism.

Casanova, Manuel F.; El-Baz, Ayman; Elnakib, Ahmed; Switala, Andrew E.; Williams, Emily L.; Williams, Diane L.; Minshew, Nancy J.; Conturo, Thomas E.

2012-01-01

196

Whole-exome sequencing identifies mutated c12orf57 in recessive corpus callosum hypoplasia.  

PubMed

The corpus callosum is the principal cerebral commissure connecting the right and left hemispheres. The development of the corpus callosum is under tight genetic control, as demonstrated by abnormalities in its development in more than 1,000 genetic syndromes. We recruited more than 25 families in which members affected with corpus callosum hypoplasia (CCH) lacked syndromic features and had consanguineous parents, suggesting recessive causes. Exome sequence analysis identified C12orf57 mutations at the initiator methionine codon in four different families. C12orf57 is ubiquitously expressed and encodes a poorly annotated 126 amino acid protein of unknown function. This protein is without significant paralogs but has been tightly conserved across evolution. Our data suggest that this conserved gene is required for development of the human corpus callosum. PMID:23453666

Akizu, Naiara; Shembesh, Nuri M; Ben-Omran, Tawfeg; Bastaki, Laila; Al-Tawari, Asma; Zaki, Maha S; Koul, Roshan; Spencer, Emily; Rosti, Rasim Ozgur; Scott, Eric; Nickerson, Elizabeth; Gabriel, Stacey; da Gente, Gilberto; Li, Jiang; Deardorff, Matthew A; Conlin, Laura K; Horton, Margaret A; Zackai, Elaine H; Sherr, Elliott H; Gleeson, Joseph G

2013-02-28

197

Whole-Exome Sequencing Identifies Mutated C12orf57 in Recessive Corpus Callosum Hypoplasia  

PubMed Central

The corpus callosum is the principal cerebral commissure connecting the right and left hemispheres. The development of the corpus callosum is under tight genetic control, as demonstrated by abnormalities in its development in more than 1,000 genetic syndromes. We recruited more than 25 families in which members affected with corpus callosum hypoplasia (CCH) lacked syndromic features and had consanguineous parents, suggesting recessive causes. Exome sequence analysis identified C12orf57 mutations at the initiator methionine codon in four different families. C12orf57 is ubiquitously expressed and encodes a poorly annotated 126 amino acid protein of unknown function. This protein is without significant paralogs but has been tightly conserved across evolution. Our data suggest that this conserved gene is required for development of the human corpus callosum.

Akizu, Naiara; Shembesh, Nuri M.; Ben-Omran, Tawfeg; Bastaki, Laila; Al-Tawari, Asma; Zaki, Maha S.; Koul, Roshan; Spencer, Emily; Rosti, Rasim Ozgur; Scott, Eric; Nickerson, Elizabeth; Gabriel, Stacey; da Gente, Gilberto; Li, Jiang; Deardorff, Matthew A.; Conlin, Laura K.; Horton, Margaret A.; Zackai, Elaine H.; Sherr, Elliott H.; Gleeson, Joseph G.

2013-01-01

198

Microelectrode Analysis of Transfer of Visual Information by the Corpus Callosum.  

National Technical Information Service (NTIS)

Responses to patterned visual stimuli were recorded with tungsten microelectrodes from single fibers of the posterior third of the corpus callosum in midpontine pretrigeminal cats. Visual receptive fields of these units were similar to those observed with...

G. Berlucchi M. S. Gazzaniga G. Rizzolatti

1967-01-01

199

Hypohidrotic ectodermal dysplasia, primary hypothyroidism, and agenesis of the corpus callosum.  

PubMed Central

In this report we present the unique combination of hypohidrotic ectodermal dysplasia, primary hypothyroidism, and agenesis of the corpus callosum in a two year old, severely mentally retarded boy. Images

Fryns, J P; Chrzanowska, K; Van den Berghe, H

1989-01-01

200

Morphometric analysis of the human corpus callosum fails to reveal sex-related differences.  

PubMed

No observations of sex differences in the splenium of the human corpus callosum are made. In the data there is no support for the concept that sex related functional hemispherical discrepancies are due to differences in area and width of the splenium of corpus callosum. However variability within a sex is often larger than the variability between the two sexes. The results are discussed with regard to a neurobiological theory of schizophrenia. PMID:3722806

Weber, G; Weis, S

1986-01-01

201

Anisotropy of HARDI Diffusion Profiles Based on the L 2 Norm  

Microsoft Academic Search

\\u000a The fractional anisotropy (FA) value for Diffusion Tensor Imaging is widely used to determine the anisotropy of diffusion\\u000a in a given voxel. As the FA value is based on the tensor’s eigenvectors it is not possible to calculate this quantity for\\u000a HARDI diffusion profiles. In this paper we introduce an anisotropy index for HARDI data that utilizes the L2-norm as

Philipp Landgraf; Dorit Merhof; Mirco Richter

202

Segmentation of corpus callosum using diffusion tensor imaging: validation in patients with glioblastoma  

PubMed Central

Background This paper presents a three-dimensional (3D) method for segmenting corpus callosum in normal subjects and brain cancer patients with glioblastoma. Methods Nineteen patients with histologically confirmed treatment naïve glioblastoma and eleven normal control subjects underwent DTI on a 3T scanner. Based on the information inherent in diffusion tensors, a similarity measure was proposed and used in the proposed algorithm. In this algorithm, diffusion pattern of corpus callosum was used as prior information. Subsequently, corpus callosum was automatically divided into Witelson subdivisions. We simulated the potential rotation of corpus callosum under tumor pressure and studied the reproducibility of the proposed segmentation method in such cases. Results Dice coefficients, estimated to compare automatic and manual segmentation results for Witelson subdivisions, ranged from 94% to 98% for control subjects and from 81% to 95% for tumor patients, illustrating closeness of automatic and manual segmentations. Studying the effect of corpus callosum rotation by different Euler angles showed that although segmentation results were more sensitive to azimuth and elevation than skew, rotations caused by brain tumors do not have major effects on the segmentation results. Conclusions The proposed method and similarity measure segment corpus callosum by propagating a hyper-surface inside the structure (resulting in high sensitivity), without penetrating into neighboring fiber bundles (resulting in high specificity).

2012-01-01

203

Corpus callosum morphology and its relationship to cognitive function in neurofibromatosis type 1.  

PubMed

Neurofibromatosis type 1 (NF1) is associated with cognitive dysfunction and structural brain abnormalities such as an enlarged corpus callosum. This study aimed to determine the relationship between corpus callosum morphology and cognitive function in children with neurofibromatosis type 1 using quantitative neuroanatomic imaging techniques. Children with neurofibromatosis type 1 (n = 46) demonstrated a significantly larger total corpus callosum and corpus callosum index compared with control participants (n = 30). A larger corpus callosum index in children with neurofibromatosis type 1 was associated with significantly lower IQ, reduced abstract concept formation, reduced verbal memory, and diminished academic ability, specifically reading and math. Our results suggest an enlarged corpus callosum in children with neurofibromatosis type 1 is associated with cognitive impairment and may provide an early structural marker for the children at risk of cognitive difficulties. Cognitive deficits associated with structural brain abnormalities in neurofibromatosis type 1 are unlikely to be reversible and so may not respond to proposed pharmacological therapies for neurofibromatosis type 1-related cognitive impairments. PMID:20142468

Pride, Natalie; Payne, Jonathan M; Webster, Richard; Shores, E Arthur; Rae, Caroline; North, Kathryn N

2010-02-08

204

Focal transient lesions of the corpus callosum in systemic lupus erythematosus.  

PubMed

Focal lesions limited to the splenium of the corpus callosum are rare and little is known about their etiology. We describe three patients with systemic lupus erythematosus (SLE) that presented transient lesions of the corpus callosum. We reviewed three patients with SLE whose magnetic resonance imaging (MRI) results revealed focal lesions in the splenum of corpus callosum. The medical records, including clinical, serological, and treatment features, were reviewed to determine the etiology of these lesions. Of 115 patients who had MRI for research purposes, three patients with focal nonhemorrhagic lesions of the corpus callosum were identified. All patients had active SLE at the time of MRI. One patient had other findings on MRI, including cerebral venous thrombosis. On follow-up MRI, patients had an inactive disease and the corpus callosum lesions disappeared. A transient lesion in the splenium of corpus callosum seems to be a nonspecific endpoint of different disease processes leading to vasogenic edema. The complete and rapid reversibility in all cases with disease control is emphasized and any invasive diagnostic or therapeutic approach is discouraged. PMID:16404495

Appenzeller, Simone; Faria, Andreia; Marini, Roberto; Costallat, Lilian Tereza Lavras; Cendes, Fernando

2006-01-11

205

Local anisotropy in globally isotropic granular packings.  

PubMed

We report on two-dimensional computer simulations of frictionless granular packings at various area fractions ? above the jamming point ?(c). We measure the anisotropy in coarse-grained stress ?(s) and shear modulus ?(m) as functions of coarse-graining scale, R. ?(s) can be collapsed onto a master curve after rescaling R by a characteristic length scale ? and ?(s) by an anisotropy magnitude A. Both A and ? accelerate as ???(c) from above, consistent with a divergence at ?(c). ?(m) shows no characteristic length scale and has a nontrivial power-law form, ?(m)~R(-0.62), over almost the entire range of R at all ?. These results suggest that the force chains present in the spatial structure of the quenched stress may be governed by different physics than the anomalous elastic response near jamming. PMID:22243184

Karimi, K; Maloney, C E

2011-12-23

206

Local Anisotropy in Globally Isotropic Granular Packings  

NASA Astrophysics Data System (ADS)

We report on two-dimensional computer simulations of frictionless granular packings at various area fractions ? above the jamming point ?c. We measure the anisotropy in coarse-grained stress ?s and shear modulus ?m as functions of coarse-graining scale, R. ?s can be collapsed onto a master curve after rescaling R by a characteristic length scale ? and ?s by an anisotropy magnitude A. Both A and ? accelerate as ???c from above, consistent with a divergence at ?c. ?m shows no characteristic length scale and has a nontrivial power-law form, ?m˜R-0.62, over almost the entire range of R at all ?. These results suggest that the force chains present in the spatial structure of the quenched stress may be governed by different physics than the anomalous elastic response near jamming.

Karimi, K.; Maloney, C. E.

2011-12-01

207

Wilkinson Microwave Anisotropy Probe  

NASA Astrophysics Data System (ADS)

The Wilkinson Microwave Anisotropy Probe (WMAP) is a NASA space mission that has put fundamental theories of the nature of the universe to a precise test. Since August 2001, WMAP has continually surveyed the full sky, mapping out tiny differences in the temperature of the cosmic microwave background (CMB) radiation, which is the radiant heat from the Big Bang. A fossil remnant of the hot big bang, the CMB permeates the universe and is seen today with an average temperature of only 2.725 Kelvin. Tiny variations about this average temperature were first discovered by NASA's Cosmic Background Explorer (COBE) mission. WMAP followed up on the COBE results by characterizing the detailed statistical nature of the CMB temperature variations (called "anisotropy"), revealing a wealth of detail about the global properties of the universe.

Bennett, Charles L.

2005-10-01

208

Texture and anisotropy  

NASA Astrophysics Data System (ADS)

A large number of polycrystalline materials, both manmade and natural, display preferred orientation of crystallites. Such alignment has a profound effect on anisotropy of physical properties. Preferred orientation or texture forms during growth or deformation and is modified during recrystallization or phase transformations and theories exist to predict its origin. Different methods are applied to characterize orientation patterns and determine the orientation distribution, most of them relying on diffraction. Conventionally x-ray pole-figure goniometers are used. More recently single orientation measurements are performed with electron microscopes, both SEM and TEM. For special applications, particularly texture analysis at non-ambient conditions, neutron diffraction and synchrotron x-rays have distinct advantages. The review emphasizes such new possibilities. A second section surveys important texture types in a variety of materials with emphasis on technologically important systems and in rocks that contribute to anisotropy in the earth. In the former group are metals, structural ceramics and thin films. Seismic anisotropy is present in the crust (mainly due to phyllosilicate alignment), the upper mantle (olivine), the lower mantle (perovskite and magnesiowuestite) and the inner core (egr-iron) and due to alignment by plastic deformation. There is new interest in the texturing of biological materials such as bones and shells. Preferred orientation is not restricted to inorganic substances but is also present in polymers that are not discussed in this review.

Wenk, H.-R.; Van Houtte, P.

2004-08-01

209

Counseling in fetal medicine: agenesis of the corpus callosum.  

PubMed

In this Review, we aim to provide up-to-date and evidence-based answers to common questions regarding the diagnosis and prognosis of prenatally detected agenesis of the corpus callosum (ACC). A systematic literature search was performed to identify all reports of ACC and reference lists of articles were identified. ACC involves partial or complete absence of the main commissural pathway that connects the two cerebral hemispheres, and can be isolated (with no other abnormalities) or complex (coexisting with other abnormalities). It is a rare finding and the prevalence is difficult to estimate because of selection bias in reported series. The corpus callosum (CC) can be assessed on ultrasound by direct visualization, but indirect features, such as ventriculomegaly, absence of the cavum septi pellucidi or widening of interhemispheric fissure, are often the reason for detection in a screening population. Careful imaging in a center with a high level of expertise is required to make a full assessment and to exclude coexisting abnormalities, which occur in about 46% of fetuses. When available, magnetic resonance imaging appears to be an important adjunct as it allows direct visualization. It can reduce false-positive rates on ultrasound and can confirm ACC, it can assess whether this is complete or partial and it can help in detecting coexisting brain abnormalities not seen on ultrasound. The overall rate of chromosomal abnormality in fetuses with ACC is 18%, but this high rate includes both isolated and complex ACC; more recent studies suggest that chromosomal abnormalities are rare in isolated cases. Nevertheless, postnatal follow-up studies suggest that about 15% of cases thought to be isolated prenatally were found to have associated abnormalities after birth. Neurodevelopmental outcome in isolated ACC was recently reported in a systematic review and suggested normal outcome in about 65-75% of cases. Findings need to be considered in light of the several limitations of existing studies, in terms of study design, selection bias, varying definitions and imaging protocols, ascertainment bias and lack of control groups. These uncertainties mean that antenatal counseling is difficult and further large prospective studies are needed. PMID:23024003

Santo, S; D'Antonio, F; Homfray, T; Rich, P; Pilu, G; Bhide, A; Thilaganathan, B; Papageorghiou, A T

2012-11-01

210

Regional density of glial cells in the rat corpus callosum.  

PubMed

Axons and glial cells are the main components of white matter. The corpus callosum (CC) is the largest white matter tract in mammals; in rodents, 99% of the cells correspond to glia after postnatal day 5 (P5). The area of the CC varies through life and regional differences related to the number of axons have been previously described. Whether glial cell density varies accordingly is unknown; thus the aim of this study was to estimate glial cell density for the genu, body and splenium -the three main regions of CC-, of P6 and P30 rats. Here we report that the density of CC glial cells reduced by ~10% from P6 to P30. Even so, the density of astrocytes showed a slight increase (+6%), probably due to differentiation of glioblasts. Interestingly, glial cell density decreased for the genu (-21%) and the body (-13%), while for the splenium a minor increase (+5%) was observed. The astrocyte/glia ratio increased (from P6 to P30) for the genu (+27%), body (+17%) and splenium (+4%). Together, our results showed regional differences in glial cell density of the CC. Whether this pattern is modified in some neuropathologies remains to be explored. PMID:23760411

Reyes-Haro, Daniel; Mora-Loyola, Ernesto; Soria-Ortiz, Berenice; García-Colunga, Jesús

2013-01-01

211

Detecting corpus callosum abnormalities in autism based on anatomical landmarks  

PubMed Central

Autism is a severe developmental disorder whose neurological basis is largely unknown. Autism is a subtype of autism that displays more homogeneous features within group. The aim of this study was to identify the shape differences of the corpus callosum between patients with autism and the controls. Anatomical landmarks were collected from mid-sagittal MRI of 25 patients and 18 controls. Euclidean distance matrix analysis and thin-plate spline were used to analyze the landmark forms. Point-by-point shape comparison was performed both globally and locally. A new local shape comparison scheme was proposed which compared each part of the shape in its local coordinate system. Point correspondence was established among individual shapes based on the inherent landmark correspondence. No significant difference was found in the landmark form between patients and controls, but the distance between interior genu and posterior most was found significantly shorter in patients. Thin-plate spline analysis showed significant group difference between the landmark configurations in terms of the deformation from the overall mean configuration. Significant global shape differences were found in the anterior lower body and posterior bottom, and local shape difference existed in the anterior bottom. This study can serve as both clinical reference and a detailed procedure guideline for similar studies in the future.

He, Qing; Duan, Ye; Karsch, Kevin; Miles, Judith

2010-01-01

212

The structure of the corpus callosum in obsessive compulsive disorder.  

PubMed

Abnormal brain connectivity has recently been reported in obsessive compulsive disorder (OCD). However, structural differences in the corpus callosum (CC), the primary structure connecting the two hemispheres, have not been extensively studied. In this case-control study, we recruited 30 patients with OCD and 30 healthy control subjects carefully matched for age, sex and handedness. Combining surface-based mesh-modeling and voxel-based morphometry (VBM), we compared callosal thickness and white matter (WM) density in patients and controls. We investigated associations between callosal structure and cortical gray matter (GM) density, and we related CC measures to neuropsychological performance in OCD. OCD patients showed small anterior and posterior callosal regions compared to healthy control subjects. In the OCD group, anterior callosal thickness was positively correlated with GM density of the right mid-dorso-lateral prefrontal (BA 9/46) area, while posterior callosal thickness was positively correlated with GM density in the left supramarginal gyrus (BA 40). Moreover, posterior callosal WM density was positively correlated with verbal memory, visuo-spatial memory, verbal fluency, and visuo-spatial reasoning performances. Callosal attributes were related to GM density in cortical areas innervated by the CC, and were also related to performance in cognitive domains impaired in the disorder. The CC may therefore be integrally involved in OCD. PMID:23078960

Di Paola, M; Luders, E; Rubino, I A; Siracusano, A; Manfredi, G; Girardi, P; Martinotti, G; Thompson, P M; Chou, Y-Y; Toga, A W; Caltagirone, C; Spalletta, G

2012-10-15

213

Explaining Function with Anatomy: Language Lateralization and Corpus Callosum Size  

PubMed Central

The anatomy of the corpus callosum (CC) has been advocated as a potential marker for functional lateralization because its size is supposedly proportional to the number of fibers connecting the hemispheres. Previous morphometric studies of this relationship have compared CC size in groups of subjects who are more or less likely to show differences in their lateralization (e.g., left vs right handers). The findings, however, have been inconsistent, and to our knowledge, no previous study has directly compared CC size with lateralization assessed by functional imaging data. We therefore combined anatomical measurements of CC size with left versus right hemisphere language activation in 74 normal subjects. After controlling for perceptual and motor output effects, as well as for global white-matter volume, handedness, gender and age, we found that subjects who had a larger CC showed more left lateralization for language in posterior temporal and inferior frontal regions. Examination of these effects revealed that, as CC size increased, stronger lateralization resulted from more left hemisphere activation in both regions as well as reduced right hemisphere activation in the posterior temporal region. Our observations provide the first clear evidence in normal subjects that the midsagittal surface area of the CC contributes to the degree to which language is functionally lateralized. We discuss the complex interhemispheric processes that might underlie this effect.

Josse, Goulven; Seghier, Mohamed L.; Kherif, Ferath; Price, Cathy J.

2009-01-01

214

Explaining function with anatomy: language lateralization and corpus callosum size.  

PubMed

The anatomy of the corpus callosum (CC) has been advocated as a potential marker for functional lateralization because its size is supposedly proportional to the number of fibers connecting the hemispheres. Previous morphometric studies of this relationship have compared CC size in groups of subjects who are more or less likely to show differences in their lateralization (e.g., left vs right handers). The findings, however, have been inconsistent, and to our knowledge, no previous study has directly compared CC size with lateralization assessed by functional imaging data. We therefore combined anatomical measurements of CC size with left versus right hemisphere language activation in 74 normal subjects. After controlling for perceptual and motor output effects, as well as for global white-matter volume, handedness, gender and age, we found that subjects who had a larger CC showed more left lateralization for language in posterior temporal and inferior frontal regions. Examination of these effects revealed that, as CC size increased, stronger lateralization resulted from more left hemisphere activation in both regions as well as reduced right hemisphere activation in the posterior temporal region. Our observations provide the first clear evidence in normal subjects that the midsagittal surface area of the CC contributes to the degree to which language is functionally lateralized. We discuss the complex interhemispheric processes that might underlie this effect. PMID:19109495

Josse, Goulven; Seghier, Mohamed L; Kherif, Ferath; Price, Cathy J

2008-12-24

215

Equivalent Fractions  

NSDL National Science Digital Library

This lesson helps students discover how to obtain equal fractions by using both fraction strips and playing a fraction matching game. Students will learn that to obtain equal fractions they may multiply the numerator and denominator by the same number.

Alabama Learning Exchange (alex)

2009-03-23

216

Fantastic Fractions  

NSDL National Science Digital Library

Play these games to practice your knowledge of fractions! Have fun! Travel to Ancient Egypt with the Fraction Cats to practice adding fractions. Follow this link toAdd like fractions using circles Practice your estimation and Find Grampy ...

Cate, Ms.

2008-04-12

217

Is diffusion anisotropy an accurate monitor of myelination?  

Microsoft Academic Search

We compare T2-relaxation and diffusion tensor data from normal human brain. The relationships between myelin-water fraction (MWF) and various diffusion tensor measures [e.g., fractional anisotropy (FA), perpendicular diffusivity (ADC?) and mean diffusivity ] in white matter (WM) and gray matter (GM) structures in the brain were examined in 16 normal volunteers at 1.5 T and 6 normal subjects at 3.0

Burkhard Mädler; Sylvia A. Drabycz; Shannon H. Kolind; Kenneth P. Whittall; Alexander L. MacKay

2008-01-01

218

Fraction Fun  

NSDL National Science Digital Library

In this lesson you will learn about equivalent fractions, how to add fractions, and factoring Learn how to create equivalent fractions Equivalent Fractions In this game you will practice using smaller pieces or fractions to fill the larger circle Equivalent Fractions Practice adding fractions with unlike denominators. Adding Fractions Identify the Least Common Multiple and Greatest Common Factor LCM and GCF Plug in a number and find the Least Common Multiple or Greatest Common ...

Evans, Miss

2007-10-03

219

Separating intrinsic and apparent anisotropy  

NASA Astrophysics Data System (ADS)

Seismic anisotropy plays a key role in studies of the Earth's rheology and deformation because of its relation to flow-induced lattice-preferred orientation (LPO) of intrinsically anisotropic minerals. In addition to LPO, small-scale heterogeneity produces apparent anisotropy that need not be related to deformation in the same way as intrinsic anisotropy. Quantitative interpretations of observed anisotropy therefore require the separation of its intrinsic and apparent components. We analyse the possibility to separate intrinsic and apparent anisotropy in media with hexagonal symmetry - typically used in surface wave tomography and SKS splitting studies. Our analysis is on the level of the wave equation, which makes it general and independent of specific data types or tomographic techniques. We find that observed anisotropy can be explained by isotropic heterogeneity when elastic parameters take specific combinations of values. In practice, the uncertainties of inferred anisotropy are large enough to ensure that such a combination is always within the error bars. It follows that commonly observed anisotropy can always be explained completely by a purely isotropic laminated medium unless all anisotropic parameters are known with unrealistic accuracy. Most importantly, minute changes in the poorly constrained P wave anisotropy and the parameter ? can switch between the possible or impossible existence of an isotropic equivalent. Important implications of our study include: (1) Intrinsic anisotropy over tomographically resolved length scales is never strictly required when reasonable error bars for anisotropic parameters are taken into account. (2) Currently available seismic observables provide weak constraints on the relative contributions of intrinsic and apparent anisotropy. (3) Therefore, seismic observables alone are not sufficient to constrain the magnitude of mantle flow. (4) Quantitative interpretations of anisotropy in terms of mantle flow require combined seismic/geodynamic inversions, as well as the incorporation of additional data such as topography, gravity and scattered waves.

Fichtner, Andreas; Kennett, Brian L. N.; Trampert, Jeannot

2013-06-01

220

Effects of anisotropy and dissipation on the primordial light-isotope abundances  

SciTech Connect

Account is taken of the dissipation of anisotropy due to neutrino viscosity and nearly collisionless radiation in a Bianchi type-I cosmology during primordial nucleosynthesis. For experimentally allowed cross sections, and for moderate anisotropy, the final /sup 4/He mass fraction is significantly less than in the standard model, while the D fraction increases much less than would be expected in a low-helium isotropic cosmology.

Rothman, T.; Matzner, R.

1982-05-31

221

Structural changes of the corpus callosum in tinnitus  

PubMed Central

Objectives: In tinnitus, several brain regions seem to be structurally altered, including the medial partition of Heschl's gyrus (mHG), the site of the primary auditory cortex. The mHG is smaller in tinnitus patients than in healthy controls. The corpus callosum (CC) is the main interhemispheric commissure of the brain connecting the auditory areas of the left and the right hemisphere. Here, we investigate whether tinnitus status is associated with CC volume. Methods: The midsagittal cross-sectional area of the CC was examined in tinnitus patients and healthy controls in which an examination of the mHG had been carried out earlier. The CC was extracted and segmented into subregions which were defined according to the most common CC morphometry schemes introduced by Witelson (1989) and Hofer and Frahm (2006). Results: For both CC segmentation schemes, the CC posterior midbody was smaller in male patients than in male healthy controls and the isthmus, the anterior midbody, and the genou were larger in female patients than in female controls. With CC size normalized relative to mHG volume, the normalized CC splenium was larger in male patients than male controls and the normalized CC splenium, the isthmus and the genou were larger in female patients than female controls. Normalized CC segment size expresses callosal interconnectivity relative to auditory cortex volume. Conclusion: It may be argued that the predominant function of the CC is excitatory. The stronger callosal interconnectivity in tinnitus patients, compared to healthy controls, may facilitate the emergence and maintenance of a positive feedback loop between tinnitus generators located in the two hemispheres.

Diesch, Eugen; Schummer, Verena; Kramer, Martin; Rupp, Andre

2012-01-01

222

Fraction Review  

NSDL National Science Digital Library

Review fraction concepts by playing games on any 3 of the following websites. When you're done write down the names of the games you played on a piece of paper and hand it in to the math box. Equivalent fractions Find fractional parts of a set Cross the River by matching fractions to pictures Fraction Practice (choose equivalent fractions please) matching fractions to pictures ...

Benson, Mrs.

2010-01-26

223

Fractions 1  

NSDL National Science Digital Library

This lesson is a review of fractions. dsd video 1. Start at the district web page 2. Go to My DSD 3. Click on OnDemand 4. In the custom search box, type "fractions" 5. Watch the "Fun with Fractions, Math all Around us" video. Visual Fractions Follow this link to explore fractions. Click on "Identify Fractions". Work on identifying fractions with lines until you have done at ...

Taylor, Mrs.

2010-09-28

224

Fractions Fun!  

NSDL National Science Digital Library

Fractions tell about parts of something. Let's play some games to learn more about fractions. We have learned about fractions in math class. Let's learn about them a different way. Click on this link for the first lesson. CoolMath4Kids introduction to fractions Now let's look at fractions that are equal to one. CoolMath4Kids fractions equal to one Do you remember doing this in our math class? We have been working with equivalent fractions. ...

Hedrich, Anne

2009-05-26

225

Asthenospheric Anisotropy Beneath North America  

Microsoft Academic Search

We are studying how anisotropy varies from the lithosphere to the asthenosphere using teleseismic body and surface waves in eastern and central North America, and we are investigating the relationship of observed asthenospheric anisotropy to numerical models of asthenospheric flow. Surface wave inversions and migration of teleseismic scattered waves define a decrease in lithospheric thickness from more than 200 km

K. M. Fischer; C. M. McCarthy; S. E. Zaranek; C. A. Rychert; A. Li

2005-01-01

226

Wavelet Analysis of Permeability Anisotropy  

Microsoft Academic Search

Since the permeability of porous media is anisotropic, an accurate representation of anisotropy is needed in order to reliably predict the movement of fluids and contaminants in the subsurface. We use wavelet analysis to identify principal axes of anisotropy in a porous medium and to identify the boundaries between regions with different principal axes. Wavelet analysis uses an integral transform

K. L. Powell; R. M. Neupauer

2003-01-01

227

Quantitative analysis of the corpus callosum in children with cerebral palsy and developmental delay: correlation with cerebral white matter volume  

Microsoft Academic Search

Background: The direct quantitative correlation between thickness of the corpus callosum and volume of cerebral white matter in children with cerebral palsy and developmental delay has not been demonstrated. Objective: This study was conducted to quantitatively correlate the thickness of the corpus callosum with the volume of cerebral white matter in children with cerebral palsy and developmental delay. Material and

Ashok Panigrahy; Patrick D. Barnes; Robert L. Robertson; Lynn A. Sleeper; James W. Sayre

2005-01-01

228

Transient lesion in the splenium of the corpus callosum: three further cases in epileptic patients and a pathophysiological hypothesis  

Microsoft Academic Search

OBJECTIVEFocal lesions limited to the splenium of the corpus callosum (SCC) are rare and little is known about their aetiology. Three patients were examined for presurgical evaluation in epilepsy with a transient lesion in the SCC and a pathophysiological hypothesis is presented.METHODSThree patients were identified with a circumscribed lesion in the centre of the corpus callosum. Follow up MRI was

T Polster; M Hoppe; A Ebner

2001-01-01

229

Corpus Callosum Segment Circumference Is Associated With Response Control in Children With Attention-Deficit Hyperactivity Disorder (ADHD)  

Microsoft Academic Search

Response control is impaired in attention-deficit hyperactivity disorder (ADHD). Given the corpus callosum’s role in response control, we compared callosal morphology in 64 children with ADHD and 64 typically developing children, aged 7 to 13 years, and investigated the relationships between callosal morphology and response control. Area and circumference of 5 callosal segments (genu, rostral body, midbody, isthmus, and splenium)

Melanie A. McNally; Deana Crocetti; E. Mark Mahone; Martha B. Denckla; Stacy J. Suskauer; Stewart H. Mostofsky

2010-01-01

230

The missing pericallosal artery on sonography: a sign of agenesis of the corpus callosum in the neonatal brain?  

Microsoft Academic Search

The sonographic findings in five newborn infants with agenesis of the corpus callosum are reported. Besides abnormal shape and position of the lateral and third ventricles of the brain, it was noted that echoreflections from the pericallosal artery were missing in all infants. Normally the pericallosal artery, which follows the surface of the corpus callosum, can be easily detected in

R. Baarsma; A. Martijn; A. Oklen

1987-01-01

231

Pattern-evoked cortical potentials and nuclear magnetic resonance imaging in total and partial agenesis of the corpus callosum  

Microsoft Academic Search

We have examined two cases of agenesis of the corpus callosum without any associated abnormalities. They were accidentally detected in X-ray-computed tomography. Total agenesis of the corpus callosum could be differentiated by nuclear magnetic resonance imaging from partial agenesis.

Yonetsugu Kakisu; Emiko Adachi-Usami; Noriko Kuroda; Mitsuru Kawamura; Keizo Hirayama

1985-01-01

232

Thermal conductivity anisotropy of rocks  

NASA Astrophysics Data System (ADS)

The interior heat of the lithosphere of the Earth is mainly transferred by conduction that depends on thermal conductivity of rocks. Many sedimentary and metamorphic rocks have thermal conductivity anisotropy, i.e. heat is preferentially transferred in the direction parallel to the bedding and foliation of these rocks. Deming (JGR, 1994) proposed an empirical relationship between K(perp) and anisotropy (K(par)/K(perp)) using 89 measurements on rock samples from literatures. In Deming's model, thermal conductivity is almost isotropic for K(perp) > 4 W/mK, but anisotropy is exponentially increasing with decreasing K(perp), with final anisotropy of ~2.5 at K(perp) < 1.0 W/mK. However, Davis et al. (JGR, 2007) argued that there is little evidence for Deming's suggestion that thermal conductivity anisotropy of all rocks increases systematically to about 2.5 for rocks with low thermal conductivity. Davis et al. insisted that Deming's increase in anisotropy for 1 < K(perp) < 4 W/mK with decreasing K(perp) could be due to the fractures filled with air or water, which causes thermal conductivity anisotropy. To test Deming's suggestion and Davis et al.'s argument on thermal conductivity anisotropy, we measured thermal conductivity parallel (K(par)) and perpendicular (K(perp)) to bedding or foliation and performed analytical & numerical modeling. Our measurements on 53 rock samples show the anisotropy range from 0.79 to 1.36 for 1.84 < K(prep) < 4.06 W/mK. Analytical models show that anisotropy can increase or stay the same at the range of 1 < K(perp) < 4 W/mK. Numerical modeling for gneiss shows that anisotropy ranges 1.21 to 1.36 for 2.5 < K(perp) < 4.8 W/mK. Another numerical modeling with interbedded coal layers in high thermal conductivity rocks (3.5 W/mK) shows anisotropy of 1.87 when K(perp) is 1.7 W/mK. Finally, numerical modeling with fractures indicates that the fractures does not seem to affect thermal conductivity anisotropy significantly. In conclusion, our preliminary results imply that thermal conductivity anisotropy can increase or stay at low value in the range of 1.0 < K(perp) < 4.0 W/mK. Both cases are shown to be possible through lab measurements and analytical & numerical modeling.

Lee, Youngmin; Keehm, Youngseuk; Shin, Sang Ho

2013-04-01

233

Fraction Match  

NSDL National Science Digital Library

In this online game students must match the fraction to a model of the fraction (rectangular, triangular, or circular). For each fraction several representations match and each one must be chosen before a new fraction appears. Each round of the game is timed for 1-minute and score is tracked to see how many fraction matches can be made in that time frame.

Games, Mari

2013-01-01

234

Equivalent Fractions  

NSDL National Science Digital Library

What is an equivalent fraction? Students, I want you to create song about fractions. Here is a fraction song video to help you get and idea. Remember your song should be at least five sentences long. Math Song- Equivalent Fractions Students, I want you to click on the website below and the play the fraction game. Let's see how many ...

Ogle, Miss

2012-04-05

235

Fraction Quiz  

NSDL National Science Digital Library

Test your fraction skills by answering questions. This quiz asks you to simplify fractions, convert fractions to decimals and percentages, and answer algebra questions involving fractions. Choose difficulty level, question types, and time. Fraction Quiz is one of the Interactivate assessment quizzes.

236

The gene responsible for a severe form of peripheral neuropathy and agenesis of the corpus callosum maps to chromosome 15q  

SciTech Connect

Peripheral neuropathy with or without agenesis of the corpus callosum (ACCPN) is a devastating neurodegenerative disorder that is transmitted as an autosomal recessive trait. Genealogical studies in a large number of affected French Canadian individuals suggest that ACCPN results from a single founder mutation. A genomewide search using 120 microsatellite DNA markers in 14 French Canadian families allowed the mapping of the ACCPN gene to a 5-cM region on chromosome 15q13-q15 that is flanked by markers D15S1040 and D15S118. A maximum two-point LOD score of 11.1 was obtained with the marker D15S971 at a recombination fraction of 0. Haplotype analysis and linkage disequilibrium support a founder effect. These findings are the first step in the identification of the gene responsible for ACCPN, which may shed some light on the numerous conditions associated with progressive peripheral neuropathy or agenesis of the corpus callosum. 28 refs., 2 figs., 3 tabs.

Casaubon, L.K.; Melanson, M.; Marineau, C. [McGill Univ., Quebec (Canada)]|[Montreal General Hospital Research Institute (Canada)] [and others

1996-01-01

237

Corpus Callosum and Inferior Forebrain White Matter Microstructure Are Related to Functional Outcome from Raised Intracranial Pressure in Child Traumatic Brain Injury  

Microsoft Academic Search

In severe paediatric traumatic brain injury (TBI), a common focus of treatment is raised intracranial pressure (ICP). We have previously reported frontal cerebral vulnerability with executive deficits from raised ICP in paediatric TBI. Now, using diffusion tensor imaging (DTI) in a different population, we have examined fractional anisotropy (FA), and mean, axial and radial diffusivity (MD, AD, RD) in 4

Robert C. Tasker; Amber Gunn Westland; Deborah K. White; Guy B. Williams

2010-01-01

238

Fraction Pointer  

NSDL National Science Digital Library

Determine the value of two given fractions represented as points on a number line. Then find a fraction whose value is between the two given fractions (using an arrow on the number line as a guide) and determine its value. Fraction Pointer is one of the Interactivate assessment explorers.

239

Fractional Wall  

NSDL National Science Digital Library

This problem with multiple solutions is an opportunity for students to practice finding equivalent fractions using a visual fraction bar model. The goal is for the student to develop a deep understanding of equivalent fractions using the model in order to determine a rule for finding equivalent fractions without a model. A Teacher's Note page, hints, possible solutions, and a printable page are provided.

2005-10-01

240

Social and Behavioral Problems of Children with Agenesis of the Corpus Callosum  

ERIC Educational Resources Information Center

|Archival data from a survey of parent observations was used to determine the prevalence of social and behavioral problems in children with agenesis of the corpus callosum (ACC). Parent observations were surveyed using the Child Behavior Checklist (CBCL) for 61 children with ACC who were selected from the archive based on criteria of motor…

Badaruddin, Denise H.; Andrews, Glena L.; Bolte, Sven; Schilmoeller, Kathryn J.; Schilmoeller, Gary; Paul, Lynn K.; Brown, Warren S.

2007-01-01

241

Quantitative Analysis of the Shape of the Corpus Callosum in Patients with Autism and Comparison Individuals  

ERIC Educational Resources Information Center

|Multiple studies suggest that the corpus callosum in patients with autism is reduced in size. This study attempts to elucidate the nature of this morphometric abnormality by analyzing the shape of this structure in 17 high-functioning patients with autism and an equal number of comparison participants matched for age, sex, IQ, and handedness. The…

Casanova, Manuel F.; El-Baz, Ayman; Elnakib, Ahmed; Switala, Andrew E.; Williams, Emily L.; Williams, Diane L.; Minshew, Nancy J.; Conturo, Thomas E.

2011-01-01

242

Corpus Callosum Size is Linked to Dichotic Deafness and Hemisphericity, Not Sex or Handedness  

ERIC Educational Resources Information Center

|Individuals differ in the number of corpus callosum (CC) nerve fibers interconnecting their cerebral hemispheres by about threefold. Early reports suggested that males had smaller CCs than females. This was often interpreted to support the concept that the male brain is more "lateralized" or "specialized," thus accounting for presumed male…

Morton, Bruce E.; Rafto, Stein E.

2006-01-01

243

Orofaciodigital syndrome type I associated with polycystic kidneys and agenesis of the corpus callosum  

Microsoft Academic Search

We report a female case of orofaciodigital syndrome type I (OFD I) associated with polycystic kidneys and agenesis of the corpus callosum. She had chronic renal failure requiring maintenance dialysis and significant neurological deficits. Her mother had less severe OFD I associated with polycystic kidneys but her renal function was normal and there was no clinical or radiological evidence of

A A Connacher; C C Forsyth; W K Stewart

1987-01-01

244

Longitudinal Changes in the Corpus Callosum following Pediatric Traumatic Brain Injury  

Microsoft Academic Search

Background: Atrophy of the corpus callosum (CC) is a documented consequence of moderate-to-severe traumatic brain injury (TBI), which has been expressed as volume loss using quantitative magnetic resonance imaging (MRI). Other advanced imaging modalities such as diffusion tensor imaging (DTI) have also detected white matter microstructural alteration following TBI in the CC. The manner and degree to which macrostructural changes

Trevor C. Wu; Elisabeth A. Wilde; Erin D. Bigler; Xiaoqi Li; Tricia L. Merkley; Ragini Yallampalli; Stephen R. McCauley; Kathleen P. Schnelle; Ana C. Vasquez; Zili Chu; Gerri Hanten; Jill V. Hunter; Harvey S. Levin

2010-01-01

245

Corpus callosum size in adults with high-functioning autism and the relevance of gender  

Microsoft Academic Search

The goal of the study was to investigate the size of the corpus callosum (CC) and its subsegments in relation to total brain volume (TBV) as an empirical indicator of impaired connectivity in autism with special respect to gender. In MRI data sets of 29 adults with high-functioning autism (HFA) and 29 age-, gender- and IQ-matched control subjects, the TBV

Ralf Tepest; Esther Jacobi; Astrid Gawronski; Barbara Krug; Walter Möller-Hartmann; Fritz G. Lehnhardt; Kai Vogeley

2010-01-01

246

The Brain Connection: The Corpus Callosum is Larger in Left-Handers.  

ERIC Educational Resources Information Center

Discusses the neurobiological basis for functional specialization of the cerebral hemispheres, indicating that the size of the corpus callosum is correlated with the neurophysiological measure of hand preference. In postmortem examinations of 42 subjects there were no sex differences, but mixed-handers had significantly larger total areas of the…

Witelson, Sandra F.

1985-01-01

247

Variations in Human Corpus Callosum Do Not Predict Gender: A Study Using Magnetic Resonance Imaging  

Microsoft Academic Search

Controversy exists in the neuropsychological literature concerning the existence of gender-associated differences in cognitive functioning and in hemispheric lateralization of cognitive functions. A recent study, based on 14 brains obtained at autopsy, reported sex differences in the splenium of the human corpus callosum and suggested that the larger splenium in females reflects less hemispheric lateralization, or \\

William Byne; Ruth Bleier; Lanning Houston

1988-01-01

248

Agenesis of the Corpus Callosum: Assessment and Remediation of School-Related Problems.  

ERIC Educational Resources Information Center

The paper examines three cases of children born with brain damage (absence of corpus callosum). Common problems (attentional, cognitive, visuo-motor, and motor deficits) are noted, and the impact of secondary emotional involvement is considered. Intervention approaches with two of the children are described as inconsistent and inadequate, while…

Puente, Antonio, E.

249

Postnatally Induced Formation of the Corpus Callosum in Acallosal Mice on Glia-Coated Cellulose Bridges  

Microsoft Academic Search

Developing axons of the corpus callosum of mice are guided across the cerebral midline by a slinglike glial structure that forms transiently between the hemispheres. If the ``sling'' is cut at precallosal stages, the would-be callosal fibers whirl into paired neuromas adjacent to the longitudinal cerebral fissure. In experiments on such surgically acallosal animals, the aberrant commissural axons maintained a

Jerry Silver; Michael Y. Ogawa

1983-01-01

250

Quantitative Analysis of the Shape of the Corpus Callosum in Patients with Autism and Comparison Individuals  

ERIC Educational Resources Information Center

Multiple studies suggest that the corpus callosum in patients with autism is reduced in size. This study attempts to elucidate the nature of this morphometric abnormality by analyzing the shape of this structure in 17 high-functioning patients with autism and an equal number of comparison participants matched for age, sex, IQ, and handedness. The…

Casanova, Manuel F.; El-Baz, Ayman; Elnakib, Ahmed; Switala, Andrew E.; Williams, Emily L.; Williams, Diane L.; Minshew, Nancy J.; Conturo, Thomas E.

2011-01-01

251

Cerebral specialization and interhemispheric communication: Does the corpus callosum enable the human condition?  

Microsoft Academic Search

Summary The surgical disconnection of the cerebral hemispheres half-brain. By having the callosum serve as the great communication link between redundant systems, a pre- creates an extraordinary opportunity to study basic existing system could be jettisoned as new functions neurological mechanisms: the organization of the sensory developed in one hemisphere, while the other hemisphere and motors systems, the cortical representation

Michael S. Gazzaniga

2000-01-01

252

Axon Overproduction and Elimination in the Corpus Callosum of the Developing Rhesus Monkey  

Microsoft Academic Search

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 166 million at birth (E165). Thus, the number of callosal ax- ons in newborn monkeys

A.-S. LaMantia; P. Rakic

1990-01-01

253

Social and Behavioral Problems of Children with Agenesis of the Corpus Callosum  

ERIC Educational Resources Information Center

Archival data from a survey of parent observations was used to determine the prevalence of social and behavioral problems in children with agenesis of the corpus callosum (ACC). Parent observations were surveyed using the Child Behavior Checklist (CBCL) for 61 children with ACC who were selected from the archive based on criteria of motor…

Badaruddin, Denise H.; Andrews, Glena L.; Bolte, Sven; Schilmoeller, Kathryn J.; Schilmoeller, Gary; Paul, Lynn K.; Brown, Warren S.

2007-01-01

254

Corpus Callosum Morphology in Attention Deficit-Hyperactivity Disorder: Morphometric Analysis of MRI.  

ERIC Educational Resources Information Center

Morphometric analysis of magnetic resonance imaging scans revealed that, compared to nondisabled controls, the seven children with attention deficit hyperactivity disorder had a smaller corpus callosum. Results suggest that subtle differences may exist in the brains of these children and that deviations in normal corticogenesis may underlie the…

Hynd, George W.; And Others

1991-01-01

255

A 23-Year Review of Communication Development in an Individual with Agenesis of the Corpus Callosum.  

ERIC Educational Resources Information Center

Twenty-three years of observation and testing of the communication skills of a male with agenesis of the corpus callosum and normal IQ revealed initial weakness in language. Difficulties with fluent speech persisted into young adulthood. With intensive intervention, communication and academic skills developed and the participant completed high…

Stickles, Judith L.; Schilmoeller, Gary L.; Schilmoeller, Kathryn J.

2002-01-01

256

Holoprosencephaly and agenesis of the corpus callosum: Frequency of Associated Malformations  

Microsoft Academic Search

Review of 28 autopsy cases of holoprosencephaly (HPE) and 50 cases of agenesis of corpus callosum (ACC) (16 complete and 34 partial) revealed a high incidence of associated abnormalities in both the CNS and other organs. Craniofacial dysplasias were present in 92.8% of the HPE and in 37.8% of the cases with ACC; most frequent were microcephaly, hypotelorism, hypertelorism, and

K. Jellinger; H. Gross; E. Kaltenbäck; W. Grisold

1981-01-01

257

A Two-Year Longitudinal MRI Study of the Corpus Callosum in Autism  

ERIC Educational Resources Information Center

|A growing body of literature has identified size reductions of the corpus callosum (CC) in autism. However, to our knowledge, no published studies have reported on the growth of CC volumes in youth with autism. Volumes of the total CC and its sub-divisions were obtained from 23 male children with autism and 23 age- and gender-matched controls at…

Frazier, Thomas W.; Keshavan, Matcheri S.; Minshew, Nancy J.; Hardan, Antonio Y.

2012-01-01

258

Altered white matter microstructure in the corpus callosum in Huntington's disease: Implications for cortical “disconnection”  

Microsoft Academic Search

The corpus callosum (CC) is the major conduit for information transfer between the cerebral hemispheres and plays an integral role in relaying sensory, motor and cognitive information between homologous cortical regions. The majority of fibers that make up the CC arise from large pyramidal neurons in layers III and V, which project contra-laterally. These neurons degenerate in Huntington's disease (HD)

H. Diana Rosas; Stephanie Y. Lee; Alexander C. Bender; Alexandra K. Zaleta; Mark Vangel; Peng Yu; Bruce Fischl; Vasanth Pappu; Christina Onorato; Jang-Ho Cha; David H. Salat; Steven M. Hersch

2010-01-01

259

Morphometry of the corpus callosum in monozygotic twins discordant for schizophrenia: a magnetic resonance imaging study.  

PubMed Central

The corpus callosum (CC) has been the focus of several morphometric studies of patients with schizophrenia, but the results of these studies have been contradictory. In an attempt to improve the reliability of morphometric measurements of the corpus callosum, a computerised image analysis system was used to measure the shape, area, thickness and length of the CC on magnetic resonance imaging (MRI) in 12 pairs of monozygotic twins discordant for schizophrenia (SC). No differences in CC area (anterior, middle, posterior thirds and total), length or vertical thickness of the CC body (at three levels) were demonstrated by t test comparisons of the affected SC and unaffected twins. Statistical analysis of a Fourier expansion series suggested differences in shape between normal and SC cotwins in the second harmonic of the anterior and middle segments and effects of gender on posterior CC shape. These results fail to replicate previous findings of altered length, thickness and area in the schizophrenic CC, but implicate disease-related shape differences in the anterior and middle segment of the corpus callosum and gender-related differences in splenium shape. The disease-related shape distortion suggest ventriculomegaly rather than an intrinsic abnormality of the corpus callosum. Images

Casanova, M F; Sanders, R D; Goldberg, T E; Bigelow, L B; Christison, G; Torrey, E F; Weinberger, D R

1990-01-01

260

MRI study of corpus callosum in children and adolescents with bipolar disorder  

Microsoft Academic Search

This structural magnetic resonance imaging study examined the length, areas, and circularity of the corpus callosum (CC) in 16 children and adolescents with bipolar disorder and 21 healthy controls. Bipolar disorder patients had lower circularity of the CC splenium compared with healthy controls. No significant differences in CC length or area were observed, suggesting that reported CC abnormalities appear late

A. Sibel Yasar; E. Serap Monkul; Roberto B. Sassi; David Axelson; Paolo Brambilla; Mark A. Nicoletti; John P. Hatch; Matcheri Keshavan; Neal Ryan; Boris Birmaher; Jair C. Soares

2006-01-01

261

Diencephalic epilepsy in a patient with agenesis of the corpus callosum confirmed by computerised axial tomography  

PubMed Central

A case of diencephalic epilepsy is described in whom stereotyped attacks of spontaneous hypothermia and diaphoresis occurred over a 20 year period. No abnormality of the hypothalamo-pituitary-adrenal axis was found, and there was no evidence of an intracranial mass lesion. Pneumoencephalography and computerised axial tomography (EMI scan) demonstrated agenesis of the corpus callosum. Images

Carr-Locke, David; Millac, Paul

1977-01-01

262

Status epilepticus, hypothermia and metabolic chaos in a man with agenesis of the corpus callosum.  

PubMed Central

A case of hypothermia and metabolic derangement in a 60-year-old man following a period of status epilepticus is reported. A CT head scan performed subsequently demonstrated agenesis of the corpus callosum. Hypercalcaemia which has not been reported before was a prominent abnormality in the metabolic profile. Images

Johnson, M H; Jones, S N

1985-01-01

263

Reduced White Matter Connectivity in the Corpus Callosum of Children with Tourette Syndrome  

ERIC Educational Resources Information Center

|Background: Brain imaging studies have revealed anatomical anomalies in the brains of individuals with Tourette syndrome (TS). Prefrontal regions have been found to be larger and the corpus callosum (CC) area smaller in children and young adults with TS compared with healthy control subjects, and these anatomical features have been understood to…

Plessen, Kerstin J.; Gruner, Renate; Lundervold, Arvid; Hirsch, Jochen G.; Xu, Dongrong; Bansal, Ravi; Hammar, Asa; Lundervold, Astri J.; Wentzel-Larsen, Tore; Lie, Stein Atle; Gass, Achim; Peterson, Bradley S.; Hugdahl, Kenneth

2006-01-01

264

Reduced white matter connectivity in the corpus callosum of children with Tourette syndrome  

Microsoft Academic Search

Background: Brain imaging studies have revealed anatomical anomalies in the brains of individuals with Tourette syndrome (TS). Prefrontal regions have been found to be larger and the corpus callosum (CC) area smaller in children and young adults with TS compared with healthy control subjects, and these anatomical features have been understood to reflect neural plasticity that helps to attenuate the

Kerstin J. Plessen; Renate Grüner; Arvid Lundervold; Jochen G. Hirsch; Dongrong Xu; Ravi Bansal; Åsa Hammar; Astri J. Lundervold; Tore Wentzel-Larsen; Stein Atle Lie; Achim Gass; Bradley S. Peterson; Kenneth Hugdahl

2006-01-01

265

Midsagittal structural differences and sexual dimorphism of the corpus callosum in obsessive-compulsive disorder  

Microsoft Academic Search

Neurobiological abnormalities in various brain regions, including the orbitofrontal cortex, basal ganglia, and thalamus, have been found in patients with obsessive–compulsive disorder (OCD), and impairment in white matter connectivity in these regions has recently been suggested. To investigate structural connectivity in OCD, we used the midsagittal area and thickness to assess the morphology of the corpus callosum (CC), the largest

Hye Yoon Park; Jun Sung Park; Sun Hyung Kim; Joon Hwan Jang; Wi Hoon Jung; Jung-Seok Choi; Do-Hyung Kang; Jong-Min Lee; Jun Soo Kwon

2011-01-01

266

Congenital and Acquired Abnormalities of the Corpus Callosum: A Pictorial Essay  

PubMed Central

The purpose of this review is to illustrate the wide spectrum of lesions in the corpus callosum, both congenital and acquired: developmental abnormalities, phakomatoses, neurometabolic disorders, demyelinating diseases, infection and inflammation, vascular lesions, neoplasms, traumatic and iatrogenic injury, and others. Cases include fetuses, children, and adults with rich iconography from the authors' own archive.

Krupa, Katarzyna; Bekiesinska-Figatowska, Monika

2013-01-01

267

Demyelination and remyelination in anatomically distinct regions of the corpus callosum following cuprizone intoxication.  

PubMed

Multiple sclerosis is a chronic demyelinating disease of the central nervous system. Spontaneous remyelination during early disease stages is thought to preserve and partially restore function. However, this process ceases in later stages despite the presence of pre-oligodendrocytes. Cuprizone-induced demyelination is a useful model with which to study the remyelination process. Previous studies have demonstrated heterogeneities in demyelination in individual animals. Here we investigated regional differences in demyelination and remyelination within the corpus callosum. C57BL/6 mice were fed 0.2% cuprizone for 5 weeks to induce demyelination. Remyelination was examined 2-5 weeks after cuprizone withdrawal. Immunohistochemistry and electron microscopy were used to quantify regional differences in demyelination, gliosis, and remyelination. We found that, while demyelination was limited in the rostral region of corpus callosum, nearly complete demyelination occurred in the caudal callosum, beginning at approximately -0.5mm from bregma. Astrogliosis and microgliosis were correlated with demyelination and differed between the rostral and caudal callosal structures. Remyelination upon cessation of cuprizone ensued at different rates with splenium remyelinating faster than dorsal hippocampal commissure. Our data show anatomical differences of cuprizone-induced demyelination and remyelination in the corpus callosum and the importance of examining specific callosal regions in myelin repair studies using this model. PMID:22015947

Steelman, Andrew J; Thompson, Jeffrey P; Li, Jianrong

2011-10-12

268

Hereditary spastic paraplegia with hypoplastic corpus callosum in a Turkish family.  

PubMed

Hereditary spastic paraplegia is composed of a heterogeneous group of neurodegenerative disorders and is classified as pure or complicated due to its clinical variability. Autosomal recessive hereditary spastic paraplegia with hypoplastic corpus callosum is a rare form of complicated hereditary spastic paraplegia. In complicated hereditary spastic paraplegia, autosomal dominant, autosomal recessive, and X-linked modes of inheritance have been noted. The diagnostic criteria of autosomal recessive hereditary spastic paraplegia with hypoplastic corpus callosum are inheritance consistent with autosomal recessive trait, slowly progressive spastic paraparesis and mental detoriation, hypoplasia of corpus callosum revealed by brain computerized tomography or magnetic resonance imaging, and exclusion of other disorders by magnetic resonance imaging of the spine and brain as well as other laboratory tests. In this report, the authors present the case of 3 affected siblings in a family from Turkey, whereas 1 child and the con-sanguineous parents were healthy. To the authors' knowledge, it is the first reported case of autosomal recessive hereditary spastic paraplegia with hypoplastic corpus callosum from Turkey. PMID:17621486

Gucuyener, Kivilcim; Hirfanoglu, Tugba; Ok, Ikbal; Cansu, Ali; Serdaroglu, Ayse

2007-02-01

269

The prognosis of agenesis of the corpus callosum might mostly be favourable  

Microsoft Academic Search

The post-natal development of 6 patients with complete agenesis of the corpus callosum was as- sessed. The diagnosis of agenesis of the corpus cal- losum had been suspected prenatally in 3 cases. In the remaining 3 cases diagnostic neuro-imaging was performed because of partial seizures (n = 2) and pendular nystagmus (n = 1). The neurological examination was normal in

G. P. Ramelli; N. Zanda; M. Wyttenbach; L. Bronz; A. Schnider

270

Unlayered polymicrogyria and agenesis of the corpus callosum: a relevant association?  

Microsoft Academic Search

Three anatomical cases of unlayered polymicrogyria associated with agenesis of the corpus callosum and heterotopias are presented. The cortical dysplasia includes: (1) thin unlayered cortical mantle with radial disposition but no horizontal organisation of the neurons; (2) microgyria with fused molecular layers; and (3) persisting transitory cells in the molecular layer (Cajal-Retzius cells, subpial granular layer). A Golgi study of

T. Billette de Villemeur; C. Chiron; O. Robain

1992-01-01

271

Integrated cognitive retraining in agenesis of corpus callosum: a single case study  

Microsoft Academic Search

Individuals with Agenesis of corpus callosum (ACC) have deficits in areas of cogni- tive functions, social, emotional processing and communication. The aims of the study were to examine: (a) the neuropsychological profile pre- and post-intervention; (b) to study the effects of the integrated integrative cognitive retraining in patient with ACC. We employed a single case experimental study with pre- and

Rajakumari P. Reddy; Rajan Jamuna; Lata Hemchand

2010-01-01

272

Single forebrain ventricle without prosencephaly: agenesis of the corpus callosum with dehiscent fornices  

Microsoft Academic Search

Coalescence of the cerebral ventricles with formation of a single forebrain ventricle is described in an unusual case of agenesis of the corpus callosum with dehiscent fornices and severe hydrocephalus. The cerebral hemispheres were fully cleaved. The detached fornices were widely separated from the thalami. The membrana tectoria was retroverted over the midbrain and cerebellum, where it joined the fornices

Guillermo A. de León; Mary Ann Radkowski; Francisco A. Gutierrez

1995-01-01

273

Agenesis of the corpus callosum: a United Kingdom series of 56 cases  

Microsoft Academic Search

A survey of cases of agenesis of the corpus callosum was carried out to examine its associations, utilising the British Neurological Surveillance Unit (BNSU). Fifty six cases were reported (36 male), 37 were adults. Nearly two thirds had epilepsy; half of the adult cases had intellectual impairment as estimated clinically, and a third a psychiatric disorder. Nine cases (five adults)

M Taylor; A S David

1998-01-01

274

Decreased Interhemispheric EEG Coherence during Sleep in Agenesis of the Corpus Callosum  

Microsoft Academic Search

Inter- and intrahemispheric EEG coherence was studied in 4 subjects with agenesis of the corpus callosum (ACC) and in 4 matched controls through different states of the sleep\\/wakefulness cycle. Interhemispheric coherence was calculated between homologous prefrontal, frontal, central, parietal and occipital electrode pairs whereas intrahemispheric coherence was calculated between all adjacent, unihemispheric electrode pairs. EEG samples were recorded from stage

Tore Nielsen; Jacques Montplaisir; Maryse Lassonde

1993-01-01

275

Social processing deficits in agenesis of the corpus callosum: narratives from the Thematic Apperception Test  

Microsoft Academic Search

Clinical observations suggest that individuals with agenesis of the corpus callosum (ACC) and normal IQ may have deficits in social intelligence. This study analyzed responses by normally intelligent individuals with ACC to pictures from the Thematic Apperception Test. A rating system was developed to assess three elements of story-generation: story logic, social understanding, and common content. Six individuals with ACC

Lynn K Paul; Beatrix Schieffer; Warren S Brown

2004-01-01

276

Appearance of an Interhemispheric Cyst Associated with Agenesis of the Corpus Callosum  

Microsoft Academic Search

Summary: We describe a fetus with agenesis of the corpus callosum (ACC) and Dandy-Walker malformation that de- veloped a frontal paramidline cyst late in gestation. The interval appearance of the cyst occurred in concert with increasing size of the lateral ventricles, which supports the hypothesis that cysts associated with ACC can develop with increasing intraventricular pressure. Recognition of the potential

Annemarie Stroustrup Smith; Deborah Levine

277

Diencephalic epilepsy in a patient with agenesis of the corpus callosum confirmed by computerised axial tomography  

Microsoft Academic Search

A case of diencephalic epilepsy is described in whom stereotyped attacks of spontaneous hypothermia and diaphoresis occurred over a 20 year period. No abnormality of the hypothalamo-pituitary-adrenal axis was found, and there was no evidence of an intracranial mass lesion. Pneumoencephalography and computerised axial tomography (EMI scan) demonstrated agenesis of the corpus callosum.

David Carr-Locke; Paul Millac

1977-01-01

278

Communicative deficits in agenesis of the corpus callosum: Nonliteral language and affective prosody  

Microsoft Academic Search

While some individuals with agenesis of the corpus callosum can perform normally on standardized intelligence tests, clinical observations suggest that they nevertheless have deficits in the domains of fluid and social intelligence. Particularly important for social competence is adequate understanding and use of paralinguistic information. This study examined the impact of callosal absence on the processing of pragmatic and paralinguistic

Lynn K Paul; Diana Van Lancker-Sidtis; Beatrix Schieffer; Rosalind Dietrich; Warren S Brown

2003-01-01

279

Relativistic Strange Stars with Anisotropy  

NASA Astrophysics Data System (ADS)

We study a compact star comprising strange matter content in the presence of pressure anisotropy. Considering strange matter with equation of state p = (?-4B)/3, where B is Bag parameter, we analyze the effect of pressure anisotropy on the Bag parameter for a compact star described by Vaidya-Tikekar metric. The values of B inside and on surface of the star are determined for different anisotropy parameter ?. It is found that in the vicinity of the center of a compact star, B parameter is almost constant. However, away from the center B varies with the radial distance and finally at the surface B attains a value independent of the anisotropy. It is also noted that for some values of ?, B remains constant throughout the star. Given ? and spheriodicity a, B is found to be decreasing with the increase in compactness factor. The models admitting B increasing with ? for a given spheriodicity parameter (a) and compactness are also found.

Paul, B. C.; Chattopadhyay, P. K.; Karmakar, S.; Tikekar, R.

280

Neutrino anisotropies after Planck  

NASA Astrophysics Data System (ADS)

We present new constraints on the rest-frame sound speed, ceff2, and the viscosity parameter, cvis2, of the cosmic neutrino background from the recent measurements of the cosmic microwave background anisotropies provided by the Planck satellite. While broadly consistent with the expectations of ceff2=cvis2=1/3 in the standard scenario, the Planck data set hints at a higher value of the viscosity parameter, with cvis2=0.60±0.18 at 68% C.L., and a lower value of the sound speed, with ceff2=0.304±0.013 at 68% C.L. We find a correlation between the neutrino parameters and the lensing amplitude of the temperature power spectrum AL. When the latter parameter is allowed to vary, we find a better consistency with the standard model with cvis2=0.51±0.22, ceff2=0.311±0.019, and AL=1.08±0.18 at 68% C.L. This result indicates that the anomalous large value of AL measured by Planck could be connected to nonstandard neutrino properties. Including additional data sets from baryon acoustic oscillation surveys and the Hubble Space Telescope constraint on the Hubble constant, we obtain cvis2=0.40±0.19, ceff2=0.319±0.019, and AL=1.15±0.17 at 68% C.L.; including the lensing power spectrum, we obtain cvis2=0.50±0.19, ceff2=0.314±0.015, and AL=1.025±0.076 at 68% C.L. Finally, we investigate further degeneracies between the clustering parameters and other cosmological parameters.

Gerbino, Martina; Di Valentino, Eleonora; Said, Najla

2013-09-01

281

Fraction Game  

NSDL National Science Digital Library

This interactive game provides an opportunity for students to think about how fractions are related to a unit whole, compare fractional parts of a whole, and find equivalent fractions. Players move markers a total distance that is less than or equal to the random target fraction, along their choice of seven parallel number line tracks, which are divided into different fractional parts. The goal is to move each of the seven markers to the right side of the game board using as few fraction target cards as possible. Instructions and exploration questions are included.

2011-01-01

282

Fractional Clothesline  

NSDL National Science Digital Library

Astring will be stretched across the classroom and various points will be marked for 0, 1, 2, 3, and 4. This classroom number line will be used to show that all proper fractions are grouped between 0 and 1, and that improper fractions or mixed numbers are all grouped above 1. Students clip index cards with various proper fractions, improper fractions, and mixed numbers on the clothesline to visually see groupings. Students then play an estimation game with groups using the same principle. Encouraging students to look at fractions in various ways will help foster their conceptual fraction sense.

Mathematics, Illuminations N.

2009-07-23

283

Fractional Clothesline  

NSDL National Science Digital Library

This lesson fosters a student's conceptual fraction sense with proper fractions, improper fractions, and mixed numbers by placing thirty fraction cards in order between given whole numbers on a number line clothesline. Users will visually identify that all proper fractions are grouped between zero and one, and that improper fractions or mixed numbers are all grouped above one. Users also play an estimation game with groups using the same principle. Instructional plan, questions for the students, assessment options, extensions, and teacher reflections are given.

Heitschmidt, Corey

2008-01-01

284

Equivalent Fractions!  

NSDL National Science Digital Library

How good at determining equivalent fractions are you? Test your skills with these various fraction games to find out! You have recently been learning about fractions and their equivalency. Try this game to test your knowledge of Equivalent Fractions!! Be sure to notice the "hints" under some of the questions to help you get the correct answer. Good Luck! Continue to master your skills by playing the Dirt Bike Proportions! game. How quickly you ...

Pearce, Ms.

2011-11-06

285

Ordering Fractions  

NSDL National Science Digital Library

This interactive Flash applet develops a student's fractional understanding and provides practice with comparing and ordering fractions. The learner is given five fractions in "frames" and must place them on the wall hooks in order from least to greatest. If help is needed, a student can enter the Testing Room and manipulate a pair of pipes to see and/or compare the two fractions side by side.

Bunker, Dan

2011-01-01

286

Fraction Frenzy  

NSDL National Science Digital Library

In this interactive shockwave game, students match equivalent fractions by making fraction pairs. During each round, the student receives more cards with greater difficulty of fraction equivalencies to match, all while being timed. The goal is to beat the time and get as many correct matches as possible in order to get the highest score.

2010-01-01

287

Asthenospheric Anisotropy Beneath North America  

NASA Astrophysics Data System (ADS)

We are studying how anisotropy varies from the lithosphere to the asthenosphere using teleseismic body and surface waves in eastern and central North America, and we are investigating the relationship of observed asthenospheric anisotropy to numerical models of asthenospheric flow. Surface wave inversions and migration of teleseismic scattered waves define a decrease in lithospheric thickness from more than 200 km in Proterozoic regions to less than 100 km at the eastern continental margin. Shear-wave splitting in SKS phases indicates significant anisotropy beneath the region, but alone these data cannot constrain the depth at which the anisotropy occurs. In an area of the northeastern United States and southeastern Canada that is relatively densely sampled by permanent broadband stations and past temporary broadband arrays, inversion of Rayleigh waves reveals very little azimuthal anisotropy at lithospheric depths; when the Rayleigh waves are integrated with observations of roughly 1 s of SKS splitting, significant asthenospheric anisotropy is required. Further insight on the asthenosphere in this area comes from inversions of Ps phases which reveal a very rapid drop in shear velocity across the lithosphere-asthenosphere boundary (3-11% over less than 11 km). This velocity gradient is too sharp to be explained by purely thermal models, but is consistent with an asthenosphere that contains a few per cent partial melt or that is enriched in volatiles relative to the lithosphere. Evidence for azimuthal anisotropy in the asthenosphere has also been obtained across a broader region of the eastern and central United States. Love and Rayleigh wave inversions along portions of the Florida to Edmonton (FLED) IRIS/PASSCAL array show that Love wave velocities are fast relative to Rayleigh wavespeeds, similar to the findings of Gaherty (2004) using data from the Missouri to Massachusetts (MOMA) IRIS/PASSCAL array. Given that these linear arrays are orthogonal with respect to each other, and that SKS splitting fast directions in the region are fairly consistent and parallel to the MOMA array, the surface waves are most simply explained by radial anisotropy (a fast horizontal plane and a slow vertical axis) in the upper 200 km of the mantle, again requiring azimuthal anisotropy in the sub-lithospheric mantle to produce the SKS splitting. These results suggest that deformation fabrics in the lithosphere and asthenosphere are fundamentally different. The orientations of observed SKS fast directions are in general consistent with the direction of asthenospheric flow around the base of the lithosphere predicted by models in which flow is dominated by plate motion.

Fischer, K. M.; McCarthy, C. M.; Zaranek, S. E.; Rychert, C. A.; Li, A.

2005-12-01

288

Validation of the anisotropy index ellipsoidal area ratio in diffusion tensor imaging  

Microsoft Academic Search

A new diffusion anisotropy index, ellipsoidal area ratio (EAR), was described recently and proved to be less noise-sensitive than fractional anisotropy (FA) by theory and simulation. Here we show that EAR has higher signal-to-noise ratios than FA in average diffusion tensor imaging data from 40 normal subjects. EAR was also more sensitive than FA in detecting white matter abnormalities in

Xiaojian Kang; Timothy J. Herron; David L. Woods

2010-01-01

289

Teaching Fractions  

NSDL National Science Digital Library

This research guide provides suggestions for specialists and teachers looking to improve fraction instruction in their classrooms or schools. The guide starts with ideas for introducing fraction concepts in kindergarten and early elementary school and continues with activities and teaching strategies designed to help older students understand fraction magnitudes and computational procedures involving fractions. It then examines ways of helping students use fractions to solve rate, ratio, and proportion problems. Each recommendation includes a brief summary of supporting research and descriptions of classroom activities that can be used to implement the recommendation.

Fazio, Lisa; Siegler, Robert

2012-01-01

290

Fraction finder  

NSDL National Science Digital Library

Each problem generated by this applet states two fractional endpoints for a line segment. The student representations each fraction by subdividing and coloring areas displayed as either circles or squares. The applet indicates if a colored area correctly represents the fraction. Finally, the student must model and name in the lowest terms a fraction between the two given fractions. The applet allows students to either work with circles or squares and can keep the student's score for a series of problems. From the applet page, What, How, and Why buttons open sections that explain the activity's purpose, function, and where the mathematics fits into the curriculum, as well as lists the related NCTM standards. Also included are student handouts and discussion questions about approximating fractions and whether it is easier to reduce a fraction expressed as a square or circle. Copyright 2005 Eisenhower National Clearinghouse

Foundation, Shodor E.

2004-01-01

291

Developmental malformation of the corpus callosum: a review of typical callosal development and examples of developmental disorders with callosal involvement  

Microsoft Academic Search

This review provides an overview of the involvement of the corpus callosum (CC) in a variety of developmental disorders that\\u000a are currently defined exclusively by genetics, developmental insult, and\\/or behavior. I begin with a general review of CC\\u000a development, connectivity, and function, followed by discussion of the research methods typically utilized to study the callosum.\\u000a The bulk of the review

Lynn K. Paul

2011-01-01

292

Wavelet Analysis of Permeability Anisotropy  

NASA Astrophysics Data System (ADS)

Since the permeability of porous media is anisotropic, an accurate representation of anisotropy is needed in order to reliably predict the movement of fluids and contaminants in the subsurface. We use wavelet analysis to identify principal axes of anisotropy in a porous medium and to identify the boundaries between regions with different principal axes. Wavelet analysis uses an integral transform that extracts local information at multiple scales and orientations. We have tested the technique on hypothetical two-dimensional permeability fields, and we have conducted a preliminary evaluation of the technique using laboratory-measured permeability data from a block of Massillon sandstone. We demonstrate the wavelet analysis technique for identifying principal axes of anisotropy, and we evaluate the effects of sparse data on the results.

Powell, K. L.; Neupauer, R. M.

2003-12-01

293

Shape analysis of corpus callosum in phenylketonuria using a new 3D correspondence algorithm  

NASA Astrophysics Data System (ADS)

Statistical shape analysis of brain structures has gained increasing interest from neuroimaging community because it can precisely locate shape differences between healthy and pathological structures. The most difficult and crucial problem is establishing shape correspondence among individual 3D shapes. This paper proposes a new algorithm for 3D shape correspondence. A set of landmarks are sampled on a template shape, and initial correspondence is established between the template and the target shape based on the similarity of locations and normal directions. The landmarks on the target are then refined by iterative thin plate spline. The algorithm is simple and fast, and no spherical mapping is needed. We apply our method to the statistical shape analysis of the corpus callosum (CC) in phenylketonuria (PKU), and significant local shape differences between the patients and the controls are found in the most anterior and posterior aspects of the corpus callosum.

He, Qing; Christ, Shawn E.; Karsch, Kevin; Peck, Dawn; Duan, Ye

2010-03-01

294

Boomerang sign: Clinical significance of transient lesion in splenium of corpus callosum  

PubMed Central

Transient signal abnormality in the splenium of corpus callosum on magnetic resonance imaging (MRI) is occasionally encountered in clinical practice. It has been reported in various clinical conditions apart from patients with epilepsy. We describe 4 patients with different etiologies presenting with signal changes in the splenium of corpus callosum. They were diagnosed as having progressive myoclonic epilepsy (case 1), localization-related epilepsy (case 2), hemicrania continua (case 3), and postinfectious parkinsonism (case 4). While three patients had complete involvement of the splenium on diffusion-weighted image (“boomerang sign”), the patient having hemicrania continua showed semilunar involvement (“mini-boomerang”) on T2-weighted and FLAIR image. All the cases had noncontiguous involvement of the splenium. We herein, discuss these cases with transient splenial involvement and stress that such patients do not need aggressive diagnostic and therapeutic interventions. An attempt has been made to review the literature regarding the pathophysiology, etiology, and outcome of such lesions.

Malhotra, Hardeep Singh; Garg, Ravindra Kumar; Vidhate, Mukund R.; Sharma, Pawan Kumar

2012-01-01

295

Age at developmental cortical injury differentially Alters corpus callosum volume in the rat  

PubMed Central

Background Freezing lesions to developing rat cortex induced between postnatal day (P) one and three (P1 – 3) lead to malformations similar to human microgyria, and further correspond to reductions in brain weight and cortical volume. In contrast, comparable lesions on P5 do not produce microgyric malformations, nor the changes in brain weight seen with microgyria. However, injury occurring at all three ages does lead to rapid auditory processing deficits as measured in the juvenile period. Interestingly, these deficits persist into adulthood only in the P1 lesion case [1]. Given prior evidence that early focal cortical lesions induce abnormalities in cortical morphology and connectivity [1-4], we hypothesized that the differential behavioral effects of focal cortical lesions on P1, P3 or P5 may be associated with underlying neuroanatomical changes that are sensitive to timing of injury. Clinical studies indicate that humans with perinatal brain injury often show regional reductions in corpus callosum size and abnormal symmetry, which frequently correspond to learning impairments [5-7]. Therefore, in the current study the brains of P1, 3 or 5 lesion rats, previously evaluated for brain weight, and cortical volume changes and auditory processing impairments (P21-90), were further analyzed for changes in corpus callosum volume. Results Results showed a significant main effect of Treatment on corpus callosum volume [F (1,57) = 10.2, P < .01], with lesion subjects showing significantly smaller callosal volumes as compared to shams. An Age at Treatment × Treatment interaction [F(2,57) = 3.2, P < .05], indicated that corpus callosum size decreased as the age of injury decreased from P5 to P1. Simple effects analysis showed significant differences between P1 and P3 [F(1,28) = 8.7, P < .01], and P1 and P5 [F(1,28) = 15.1, P < .001], subjects. Rats with P1 injury resulting in microgyria had the greatest reduction in corpus callosum volume (22% reduction), followed by the P3 group (11% reduction), which showed a significant reduction in corpus callosum volume compared to shams [F(1,31) = 5.9, P < .05]. Finally, the P5 lesion group did not significantly differ from the sham subjects in callosal volume. Conclusion Decrements in corpus callosum volume in the P1 and 3 lesion groups are consistent with the reductions in brain weight and cortical volume previously reported for microgyric rats [1,8]. Current results suggest that disruption to the cortical plate during early postnatal development may lead to more widely dispersed neurovolumetric anomalies and subsequent behavioral impairments [1], compared with injury that occurs later in development. Further, these results suggest that in a human clinical setting decreased corpus callosum volume may represent an additional marker for long-term behavioral outcome.

Threlkeld, Steven W; Rosen, Glenn D; Fitch, R Holly

2007-01-01

296

Boomerang sign: Clinical significance of transient lesion in splenium of corpus callosum.  

PubMed

Transient signal abnormality in the splenium of corpus callosum on magnetic resonance imaging (MRI) is occasionally encountered in clinical practice. It has been reported in various clinical conditions apart from patients with epilepsy. We describe 4 patients with different etiologies presenting with signal changes in the splenium of corpus callosum. They were diagnosed as having progressive myoclonic epilepsy (case 1), localization-related epilepsy (case 2), hemicrania continua (case 3), and postinfectious parkinsonism (case 4). While three patients had complete involvement of the splenium on diffusion-weighted image ("boomerang sign"), the patient having hemicrania continua showed semilunar involvement ("mini-boomerang") on T2-weighted and FLAIR image. All the cases had noncontiguous involvement of the splenium. We herein, discuss these cases with transient splenial involvement and stress that such patients do not need aggressive diagnostic and therapeutic interventions. An attempt has been made to review the literature regarding the pathophysiology, etiology, and outcome of such lesions. PMID:22566735

Malhotra, Hardeep Singh; Garg, Ravindra Kumar; Vidhate, Mukund R; Sharma, Pawan Kumar

2012-04-01

297

A Case of Corpus Callosum Agenesis Presenting with Recurrent Brief Depression  

PubMed Central

Agenesis of corpus callosum can have various neuropsychiatric manifestations. Following case report highlights the case of a young man presenting with features of recurrent brief depressive disorder, each lasting for about 3 to 7 days, for over a year. He had history of occasional headache and episodes of swooning attack in between, usually precipitated by emotional events. His neuroimaging revealed agenesis of corpus callosum. He was experiencing swooning attacks as he became aware that some ‘unusual’ findings were present in his reports. Recurrent brief depression can be a manifestation of this congenital anomaly, and conversion disorder can be present as comorbid diagnosis perhaps due to ignorance and fear of this apparently innocuous congenital malformation.

Bhattacharyya, Ranjan; Sanyal, Debasish; Chakraborty, Suddhendu; Bhattacharyya, Sumita

2009-01-01

298

Corpus Callosum Anatomy in Right-Handed Homosexual and Heterosexual Men  

Microsoft Academic Search

The results of several studies have shown that homosexual men have an increased prevalence of non-right-handedness and atypical\\u000a patterns of hemispheric functional asymmetry. Non-right-handedness in men has been associated with increased size of the corpus\\u000a callosum (CC), particularly of the isthmus, which is the posterior region of the callosal body connecting parietotemporal\\u000a cortical regions. We hypothesized that isthmal area would

Sandra F. Witelson; Debra L. Kigar; Anton Scamvougeras; David M. Kideckel; Brian Buck; Peter L. Stanchev; Michael Bronskill; Sandra Black

2008-01-01

299

Age-related signal intensity changes in the corpus callosum: assessment with three orthogonal FLAIR images  

Microsoft Academic Search

The presence of age-related hyperintensities of the corpus callosum has not been thoroughly evaluated. Fifty-two patients of 50 years of age or older (mean, 71 years; range, 50–87 years) were included in this study. Fluid-attenuated inversion recovery images were obtained in three orthogonal planes. Periventricular hyperintensities (PVHs) and deep white matter hyperintensities (DWMHs) were graded according to Fazekas’ rating scale.

Akira Yamamoto; Yukio Miki; Hidekazu Tomimoto; Mitsunori Kanagaki; Takahiro Takahashi; Yasutaka Fushimi; Junya Konishi; Tabassum Laz Haque; Kaori Togashi

2005-01-01

300

CORPUS CALLOSUM AND EXPERIMENTAL STROKE: STUDIES IN CALLOSOTOMIZED RATS AND ACALLOSAL MICE  

PubMed Central

Background and Purpose Interhemispheric inhibition via the corpus callosum has been proposed as an exacerbating factor in outcome from stroke. Methods We measured infarct volume and behavioral outcome following middle cerebral artery occlusion in callosotomized rats and acallosal mice. Results Neither callosotomy in rats nor callosal agenesis in mice improved infarct volume or behavioral outcome after middle cerebral artery occlusion. Conclusions These findings argue against a role for transcallosal projections in exacerbating focal cerebral ischemia.

Jin, Kunlin; Xie, Lin; Sun, Fen; Mao, XiaoOu; Greenberg, David A.

2011-01-01

301

Lipoma of corpus callosum associated with dysraphic lesions and trisomy 13  

SciTech Connect

We report on a further case of corpus callosal lipoma and frontal cranial defects. Most cases in the literature of corpus callosal lipoma in association with {open_quotes}dysraphic{close_quotes} lesions have been frontal in location. Malformation of the corpus callosum is said to be associated with 50% of these lipomas. Trisomy 13 was confirmed by the 13q14 cosmid probe on paraffin-embedded liver tissue. 19 refs., 5 figs.

Wainwright, H.; Bowen, R.; Radcliffe, M. [Univ. of Cape Town Medical School (South Africa)

1995-05-22

302

Development of the human corpus callosum during childhood and adolescence: A longitudinal MRI study  

Microsoft Academic Search

1.1. Interest in the morphologic development of the corpus callosum (CC) during childhood and adolescence stems from adolescent changes in cognitive functions subserved by the CC, reports of CC anomalies for a wide variety of childhood neuropsychiatrie illnesses, and controversy regarding sexual dimorphism.2.2. Characterization of the normal developmental pattern of the CC is hindered by enormous variability of its size.

Jay N. Gbedd; Jonathan Blumenthal; Neal O. Jeffries; Jagath C. Rajapakse; A. Catherine Vaituzis; Hong Liu; Yolanda C. Berry; Maureen Tobin; Jean Nelson; F. Xavier Castellanos

1999-01-01

303

The critical period for corpus callosum section to affect cortical binocularity  

Microsoft Academic Search

Summary  The period of time during which surgical section of the corpus callosum (CC) is effective in altering the physiological properties of cells in cat striate cortex was investigated. Cats which had the CC transected between 13 days and 24 weeks of age were studied using extracellular, single-unit recording procedures. Analysis of the results from 1,747 cortical units indicate that when

A. J. Elberger; E. L. Smith

1985-01-01

304

Interactive Color Embedding-based Corpus Callosum Segmentation and Fiber Clustering in DTI  

Microsoft Academic Search

We propose an inter-discipl inary project to develop a new interactive tool for color embedding-based corpus callosum segmentation. By integrating color-coding of tractography paths, our tool will allow user to interactively adjust the clustering and segmentation based on their observation of the fiber tracks. The tool will be developed and evaluated in close collaboration with neuropsychologists studying abnormal changes in

Wenjin Zhou; Peter G. Sibley; David F. Tate; Song Zhang

305

Detecting functional magnetic resonance imaging activation in white matter: Interhemispheric transfer across the corpus callosum  

Microsoft Academic Search

Background  It is generally believed that activation in functional magnetic resonance imaging (fMRI) is restricted to gray matter. Despite\\u000a this, a number of studies have reported white matter activation, particularly when the corpus callosum is targeted using interhemispheric\\u000a transfer tasks. These findings suggest that fMRI signals may not be neatly confined to gray matter tissue. In the current\\u000a experiment, 4 T

Erin L Mazerolle; Ryan CN D'Arcy; Steven D Beyea

2008-01-01

306

A novel locus on proximal chromosome 18 associated with agenesis of the corpus callosum in mice  

Microsoft Academic Search

Agenesis of the corpus callosum (ACC) is a congenital abnormality of the brain structure. We have produced transgenic mice\\u000a expressing both reverse tetracycline-controlled transactivator (rtTA) and transcriptional silencer (tTS) ubiquitously. Although\\u000a the transgene products do not affect development of the mouse brain, one of the founder lines, TAS, showed ACC, suggesting\\u000a transgenic disruption of endogenous gene(s). To identify the causative

Seiya Mizuno; Atsushi Mizobuchi; Hiroyoshi Iseki; Saori Iijima; Yoichi Matsuda; Satoshi Kunita; Fumihiro Sugiyama; Ken-ichi Yagami

2010-01-01

307

Social and Behavioral Problems of Children with Agenesis of the Corpus Callosum  

Microsoft Academic Search

Archival data from a survey of parent observations was used to determine the prevalence of social and behavioral problems\\u000a in children with agenesis of the corpus callosum (ACC). Parent observations were surveyed using the Child Behavior Checklist\\u000a (CBCL) for 61 children with ACC who were selected from the archive based on criteria of motor development suggesting a relatively\\u000a high general

Denise H. Badaruddin; Glena L. Andrews; Sven Bölte; Kathryn J. Schilmoeller; Gary Schilmoeller; Lynn K. Paul; Warren S. Brown

2007-01-01

308

Agenesis of the corpus callosum: genetic, developmental and functional aspects of connectivity  

Microsoft Academic Search

Agenesis of the corpus callosum (AgCC), a failure to develop the large bundle of fibres that connect the cerebral hemispheres, occurs in 1:4000 individuals. Genetics, animal models and detailed structural neuroimaging are now providing insights into the developmental and molecular bases of AgCC. Studies using neuropsychological, electroencephalogram and functional MRI approaches are examining the resulting impairments in emotional and social

Warren S. Brown; Ralph Adolphs; J. Michael Tyszka; Linda J. Richards; Pratik Mukherjee; Lynn K. Paul; Elliott H. Sherr

2007-01-01

309

Organizational effects of fetal testosterone on human corpus callosum size and asymmetry.  

PubMed

Previous theory and research in animals has identified the critical role that fetal testosterone (FT) plays in organizing sexually dimorphic brain development. However, to date there are no studies in humans directly testing the organizational effects of FT on structural brain development. In the current study we investigated the effects of FT on corpus callosum size and asymmetry. High-resolution structural magnetic resonance images (MRI) of the brain were obtained on 28 8-11-year-old boys whose exposure to FT had been previously measured in utero via amniocentesis conducted during the second trimester. Although there was no relationship between FT and midsaggital corpus callosum size, increasing FT was significantly related to increasing rightward asymmetry (e.g., Right>Left) of a posterior subsection of the callosum, the isthmus, that projects mainly to parietal and superior temporal areas. This potential organizational effect of FT on rightward callosal asymmetry may be working through enhancing the neuroprotective effects of FT and result in an asymmetric distribution of callosal axons. We suggest that this possible organizational effect of FT on callosal asymmetry may also play a role in shaping sexual dimorphism in functional and structural brain development, cognition, and behavior. PMID:19833443

Chura, Lindsay R; Lombardo, Michael V; Ashwin, Emma; Auyeung, Bonnie; Chakrabarti, Bhismadev; Bullmore, Edward T; Baron-Cohen, Simon

2010-01-01

310

Expression of retinoid X receptor ? is induced in astrocytes during corpus callosum demyelination.  

PubMed

The experimental activation of retinoid receptors reduces pathological symptoms in animal models of multiple sclerosis. In order to assess the involvement of endogenous retinoid signaling during the process of demyelination we investigated retinoic acid synthesizing enzymes and nuclear receptors using the mouse model of cuprizone toxicity. The initiation of myelin degradation in the corpus callosum was accompanied with a local increase of retinaldehyde dehydrogenase (RALDH) immunoreactivity. On the level of receptors we observed a striking increase in protein expression of the retinoid X receptor (RXR)-? in the affected corpus callosum. The RXR? immunoreactivity appeared exclusively in astrocytes, where it reached a maximum at five weeks of treatment, following the RALDH response. In the cerebral cortex and basal ganglia of affected mice RXR? was also observed in neurons. Among nuclear receptor antigens RAR? showed a cuprizone associated increase in the corpus callosum. Quantitative RT-PCR revealed strong basal expression of RXR? and a significant, over 20-fold upregulation of the peroxisome proliferator-activated receptor-? during demyelination. The results indicate that compensatory mechanisms during central demyelination may engage nuclear receptor dimers with an RXR? partner. PMID:22306550

König, René; Stillfried, Milena; Aperdannier, Philipp; Clarner, Tim; Beyer, Cordian; Kipp, Markus; Mey, Jörg

2012-01-28

311

Cosmic Ray Anisotropy with KASCADE  

Microsoft Academic Search

The anisotropy of cosmic rays with energies in the region of the knee in the energy spectrum is investigated in three different persp ectives based on the arrival directions of about 150 Mio. extensive air showers measured by KASCADE. The different analyses are a harmonic analysis of the right ascension distribution and a point source search of showers above 0.5

G. Maier; T. Antoni; W. D. Apel; F. Badea; K. Bekk; A. Bercuci; H. Blümer; H. Bozdog; I. M. Brancus; C. Büttner; A. Chilingarian; K. Daumiller; P. Doll; R. Engel; J. Engler; F. Feßler; H. J. Gils; R. Glasstetter; A. Haungs; D. Heck; J. R. Hörandel; A. Iwan; K. H. Kampert; H. O. Klages; H. J. Mathes; H. J. Mayer; J. Milke; M. Müller; R. Obenland; J. Oehlschläger; S. Ostapchenko; M. Petcu; H. Rebel; M. Risse; G. Schatz; H. Schieler; J. Scholz; T. Thouw; H. Ulrich; J. van Buren; A. Vardanyan; A. Weindl; J. Wochele; J. Zabierowski

2003-01-01

312

Degree Scale Anisotropy: Current Status  

Microsoft Academic Search

The Cosmic Background Radiation gives us one of the few probes into the density perturbations in the early universe that should later lead to the formation of structure we now observe. Recent advances in degree scale anisotropy measurements have allowed us to begin critically testing cosmological models. Combined with the larger scale measurements from COBE we are now able to

P. M. Lubin

1994-01-01

313

Anisotropy in the Indian lithosphere  

Microsoft Academic Search

We present the analysis of shear-wave splitting of the mantle phases and modelling of the partitioning of the energy on the radial and tangential components of the receiver function for the anisotropy in the Indian crust and upper mantle. We estimated the crustal contribution in the shear-wave splitting by the analysis of Moho converted Ps phases and removed this effect

A. Rai; K. Priestley; S. Rai; D. Srinagesha; V. Gaur

2003-01-01

314

Microhardness anisotropy of lamellar bone  

Microsoft Academic Search

The Knoop microhardness test has been utilised to observe in-plane microhardness anisotropy of rat tibiae. The elongated rhombohedral geometry of the Knoop indenter enables the Knoop microhardness (HK) to be calculated for a given indenter orientation. Two indenter orientations were used the major axis of the indenter was aligned along the length of, and across the mid-sagittal section. The statistical

P. E. Riches; N. M. Everitt; A. R. Heggie; D. S. McNally

1997-01-01

315

Seismic anisotropy in Western Tibet  

Microsoft Academic Search

Using data obtained during the 2001 French-Chinese lithoscope passive teleseismic experiment, we investigated the fabric and anisotropy of the crust and mantle of Western Tibet, along profiles cutting major strike-slip faults (Altyn Tagh and Gozha faults) and sutures (Kudi, Bangong, and Shiquanhe sutures). Broadband stations were deployed across the high plateau along the road between Yecheng, at the southern edge

G. Herquel; P. Tapponnier; G. Wittlinger; G. Poupinet; J. Mei

2003-01-01

316

What fraction?  

NSDL National Science Digital Library

This collection of 22 Flash applets, intended for use with a projector or interactive whiteboard (IWB), gives the educator the ability to display and alter questions about fractions of a group. The teacher chooses from among a variety of graphics and a fixed or varying denominator (group size) and clicks to alter the numerator (subset size). The question is "What fraction?"

Blundred, A.

2012-01-01

317

Fraction Conversion  

NSDL National Science Digital Library

This lesson is designed to develop students' abilities to convert between fractions and decimals. This lesson provides links to discussions and activities related to fraction conversion as well as suggested ways to integrate them into the lesson. Finally, the lesson provides links to follow-up lessons designed for use in succession with the current one.

2010-01-01

318

Kakooma - Fractions  

NSDL National Science Digital Library

In this online game created by Greg Tang, students complete a puzzle by finding the number that is the sum of two others fractions within each grouping. The application allows for a variety of abilities by allowing a choice between easy or hard, depending on the number of equivalent fractions and five levels of challenge, depending on the number of shapes within the puzzle.

Tang, Greg

2013-01-01

319

Fraction Tutorial  

NSDL National Science Digital Library

This site provides an introduction to fractions, including the concept of equivalency, and shows how to reduce, decompose, multiply, divide, add, and subtract them. Illustrations cover all these concepts, beginning with the idea of fractions as parts of a whole, continuing through equivalency, addition and subtraction with like denominators, and finishing with multiplication of mixed numbers. Practice exercises are offered at all levels.

Webb, B. J.

2000-01-01

320

Intrinsic versus extrinsic seismic anisotropy: The radial anisotropy in reference Earth models  

NASA Astrophysics Data System (ADS)

anisotropy usually arises from different mechanisms, which include lattice or crystallographic preferred orientation (LPO, CPO), alignment of cracks with or without fluid inclusions, fine layering, or partial melting. This makes the interpretation of anisotropy in terms of "intrinsic" (produced by LPO, CPO) versus "extrinsic" (produced by other mechanisms) properties difficult and nonunique. The radial anisotropy in the one-dimensional, global spherically symmetric reference Earth is usually claimed to be intrinsic. Here we explore whether the radial anisotropy in one-dimensional reference Earth models including preliminary reference Earth model (PREM) and the constrained reference Earth model ACY400 contains extrinsic anisotropy, especially in relation to fine layering. We conclude that as well as intrinsic anisotropy, extrinsic anisotropy introduced by finely layered models, can be considered to explain the lithospheric anisotropy in PREM, but cannot explain alone its asthenospheric anisotropy. We also find that radial anisotropy in model ACY400 is mainly intrinsic due to its petrological constraints.

Wang, Nian; Montagner, Jean-Paul; Fichtner, Andreas; Capdeville, Yann

2013-08-01

321

Imaging of Stratified Upper Mantle Anisotropy  

NASA Astrophysics Data System (ADS)

Global tomographic models have been improved over years not only by an increase in the number of data but more importantly by using more general parameterizations, now including anisotropy (radial anisotropy and then general slight anisotropy) and anelasticity. The imaging of seismic anisotropy renews our vision of upper mantle dynamics because different physical processes (cracks or fluid inclusions, lattice preferred orientation of crystals, fine layering) give rise to observable seismic anisotropy (S-wave splitting, surface wave radial and azimuthal anisotropy). Surface waves provide an almost uniform lateral and azimuthal coverages, particularly below oceanic areas and are used to image large scale (>1000km) lateral heterogeneities of velocity and anisotropy in the upper mantle (0-660km depth). The interpretation of anisotropy makes it possible to relate surface geology and plate tectonics to underlying mantle convection processes, and to map at depth the origin of geological objects such as continents, mountain ranges, slabs, ridges and plumes. Usually, several different processes create a complex stratification of anisotropy which can be unraveled by simultaneously taking account of effects of anisotropy on body waves and surface waves. The example of stratification of anisotropy beneath the Horn of Africa will be presented.

Montagner, J.

2008-12-01

322

LPO Induced Seismic Anisotropy in Naturally and Experimentally Deformed UHP Eclogites  

NASA Astrophysics Data System (ADS)

Eclogites with strong plastic deformation often show marked anisotropy of petrophysical properties. We report here seismic velocities and anisotropies of ultra-high-pressure eclogites calculated from the lattice preferred orientations (LPOs) of their constituent minerals (garnet, omphacite, quartz and rutile) and single crystal elastic properties using the Unicef Careware software package. The effects of garnet and omphacite layering in eclogite deformed to high strain were not included in calculation which could underestimate seismic anisotropy. We compared calculated results with measured results in similar eclogites. Our results suggest: 1) All minerals except garnet show strong seismic anisotropy (AVp = 23.0 - 40.9 %, Max. AVs = 18.51 - 47.07 %). The average seismic velocity is high in garnet and rutile, moderate in omphacite and coesite, and low in quartz. 2) The deformed eclogites have Vpmax (8.33 - 8.75 km/s) approximately parallel to foliation and lineation, Vpmin (8.25 - 8.62 km/s) approximately normal to foliation (S) and lineation (L) and Vp anisotropies of 1.0-1.7 %. Their Vs are 4.93-4.97 km/s, with maximum anisotropy (0.73-1.78 %) at ~45° to both S and L and minimum anisotropies normal to L in S. Their Vs1 polarization planes are approximately parallel to S. The Vp and Vs of eclogite under UHP peak metamorphic conditions (P = 3-5 GPa, T = 1173-1373 K) are estimated to be 3.4-7.2 % and 6.3-12.1 % higher than those at ambient pressure and temperature conditions, respectively. 3) Omphacite dominates the anisotropy of eclogite while garnet reduces the anisotropy and increases seismic velocity. The influence of rutile is negligible due to its trivial volume fraction. 4) The seismic velocity of eclogite decreases with volume fraction of omphacite and is minimum in omphacitite. In contrast, the anisotropy of eclogite increases with volume fraction of omphacite and is maximum in omphacitite. Omphacitite has seismic velocities reduced by 6-8 % and anisotropies increased to 3-4 % compared to garnetite. The calculated seismic properties of eclogite are comparable to those measured in the laboratory. Moreover, the calculations provide true 3D information on eclogite seismic properties and the corresponding mineral physical interpretations.

Zhang, J.; Green, H. W.

2006-12-01

323

Fractional distillation  

SciTech Connect

Process and apparatus are provided for the recovery of low, medium and high boiling components from feed streams containing same wherein reboiler fouling, gumming and the like are minimized, via the control of fractionator reboiler temperatures.

Brand, M. J.; Callejas, R. J.

1985-10-08

324

Fractional distillation  

Microsoft Academic Search

Process and apparatus are provided for the recovery of low, medium and high boiling components from feed streams containing same wherein reboiler fouling, gumming and the like are minimized, via the control of fractionator reboiler temperatures.

M. J. Brand; R. J. Callejas

1985-01-01

325

Magnetic anisotropy in nanostructured gadolinium  

NASA Astrophysics Data System (ADS)

This experimental work evaluates the magnetic response of 25-nm-thick Gd thin film and 1400 × 70 × 50 nm3 Gd nanobar structures. Neither the thin film nor the nanobars exhibited single domain behavior at temperatures down to 53 K. The Gd thin film exhibited a magnetocrystalline anisotropy induced spin-reorientation due to a hexagonal close-packed (002) texture, something different from that previously reported on epitaxial Gd thin film. The discrepancy is due to grain boundary induced spin-disorder in the nanosacle. The Gd nanobars had a saturation magnetization 75% smaller than the thin film or bulk and is attributed to oxidation as well as the crystallinity changes from hexagonal close-packed to face-centered cubic caused by stress induced stacking faults. These experimental results for both thin film and nanobar show that the crystallinity has a substantial impact to the magnetic anisotropy of Gd nanostructures as well as the formation of single domain structures.

Hsu, Chin-Jui; Prikhodko, Sergey V.; Wang, Chiu-Yen; Chen, Lih-Juann; Carman, Gregory P.

2012-03-01

326

Elastic anisotropy of tire shreds  

SciTech Connect

This paper deals with anisotropic elastic properties of large-size tire shreds used as lightweight fills in road and embankment construction. The anisotropy is a result of compaction and overburden pressure, which induce a layered structure of the shreds. Laboratory experiments conducted in a novel biaxial apparatus revealed a difference in Young`s moduli perpendicular and parallel to the layered structure; also, Poisson`s ratios differ although their values could not be determined accurately. The out-of-plane shear modulus not readily determined from the tests was assessed by means of a layered material model. The results were used for determining the settlement of two road structures containing a layer of tire shreds modeled as either an isotropic or an anisotropic elastic material. Numerical calculations using the code CIRCLY indicated that the effect of tire shreds` anisotropy on road structure settlements is moderate, and the traditional isotropic elastic analysis overestimates the actual settlements.

Heimdahl, T.C.; Drescher, A. [Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Civil Engineering

1999-05-01

327

Quantifying reflectance anisotropy of photosynthetically active radiation in grasslands  

NASA Astrophysics Data System (ADS)

The fraction of photosynthetically active radiation (PAR) (? = 0.4-0.7 ?m) absorbed (FAPAR) is a critical parameter in canopy processes arid in land surface-atmosphere interactions. FAPAR is typically inferred indirectly through empirical relationships established between hemispheric measurements of PAR and either (1) canopy bidirectional, usually nadir, reflectances in the visible wavelengths or (2) spectral vegetation indices. However, the bidirectional reflectance distribution function (BRDF) of vegetated surfaces has been shown to exhibit angular and spectral anisotropy, complicating the estimation of average surface reflectances, including that of PAR, from remote observations. Quantifying the surface's reflectance anisotropy was an important element of the First ISLSCP Field Experiment (FIFE), since its major objectives focused on retrieval of surface parameters from satellite-derived reflectances. Prior to the experiment reported here, the explicit remote measurements for approximating the BRDF of PAR had not been undertaken. The proper expression of reflectance for BRDFs for retrieval of canopy parameters is assessed. A rationale is given for the expression of reflectances as bidirectional reflectance fractions (RFRs), instead of the conventional bidirectional reflectance factors (RFs), when relating spectral data to canopy states or processes. The characterization of the grassland anisotropy in the solar principal plane is markedly different when expressed as RFRs versus RFs. Whereas RFs are extremely useful in addressing important "remote sensing" issues, the "surface only" BRDF is obscured by pixel-size effects since the projected viewing area increases by a factor of cos(?V)-1 with view angle (?V) for off-nadir views. The BRDF for RFRs exhibited increased absorption by the canopy in the forward scatter directions; the anisotropy is most pronounced at midday, and more isotropic at intermediate sun angles, at which time the nadir observation was adequate for estimating the mean surface PAR reflectance.

Middleton, Elizabeth M.

1992-11-01

328

Equivalent Fractions  

NSDL National Science Digital Library

Teachers can use this interactive tool to help students build conceptual understanding of equivalent fractions by emphasizing how visual models represent equivalence. Students learn the value of multiplying a fraction with a value of one. This page includes a video demonstration of the tool and sample lessons from the Conceptua curriculum. Free registration is required to use the tool. A paid subscription is necessary to access full curriculum and allow full student use.

2011-01-01

329

Fraction Pieces  

NSDL National Science Digital Library

Students use this Java applet to explore pieces representing fractional portions of a circle or square. This virtual manipulative can be used to explore patterns and symmetry with young children, or to develop fluency in fraction operations and equivalency in older students. Instructions for using the applet and teaching ideas for parents/teachers are available through the links at the top of the page.

2005-01-01

330

Fractional distillation  

Microsoft Academic Search

While practically all the fatty acids produced in the fatty acid industry are distilled products, these materials are all,\\u000a at least to some degree, fractionated fatty acids. Rarely indeed are today’s fatty acids suited for any of the many applications\\u000a to which they are put without the quality and homolog distribution improvements which only fractional distillation can guarantee.\\u000a Thus, this

R. Berger; W. McPherson

1979-01-01

331

Fantastic Fractions  

NSDL National Science Digital Library

In this math lesson, learners compare pattern blocks to visually understand halves, thirds, and sixths. First, learners look at all the different ways they can make a hexagon using other pattern block pieces. After the investigation, they represent their solutions using pictures and fractional notation. Then, learners play a game to increase their understanding of equivalence and fractions. The game can be played on its own--with or without the preceding lesson.

Lessonplans, Utah

2012-10-22

332

Association of type I neurons positive for NADPH-diaphorase with blood vessels in the adult monkey corpus callosum.  

PubMed

Sagittal sections through the corpus callosum of adult macaque monkeys (n?=?7) reveal a subpopulation of neurons positive for NADPH-diaphorase (NADPHd). These are sparsely distributed, with 2-12 neurons scored over the anterior two-thirds of the callosum (about 14?mm). Neurons are densely labeled, type 1; but on the basis of soma and dendritic morphology, these neurons exhibit distinct heterogeneity. In one subpopulation, the cell body is narrowly attenuated (7-10??m in width). These have bipolar dendrites, extending 300-800??m from the cell body. One or both of the dendrites is often closely associated with blood vessels and tends to be aligned dorso-ventral, perpendicular to the body of the callosum. Another subpopulation of neurons has a larger soma (typically, 15??m?×?20??m) and more multipolar dendrites, which are not as obviously associated with blood vessels. White matter neurons positive for NADPHd have previously been observed as a transient population, most numerous during development, in the human corpus callosum, as well as in that of other species. Their persistence in the corpus callosum of adult macaques and their close association with blood vessels has not previously been reported and is suggestive of roles other than axon guidance. PMID:22363265

Rockland, Kathleen S; Nayyar, Naema

2012-02-20

333

Association of Type I Neurons Positive for NADPH-Diaphorase with Blood Vessels in the Adult Monkey Corpus Callosum  

PubMed Central

Sagittal sections through the corpus callosum of adult macaque monkeys (n?=?7) reveal a subpopulation of neurons positive for NADPH-diaphorase (NADPHd). These are sparsely distributed, with 2–12 neurons scored over the anterior two-thirds of the callosum (about 14?mm). Neurons are densely labeled, type 1; but on the basis of soma and dendritic morphology, these neurons exhibit distinct heterogeneity. In one subpopulation, the cell body is narrowly attenuated (7–10??m in width). These have bipolar dendrites, extending 300–800??m from the cell body. One or both of the dendrites is often closely associated with blood vessels and tends to be aligned dorso-ventral, perpendicular to the body of the callosum. Another subpopulation of neurons has a larger soma (typically, 15??m?×?20??m) and more multipolar dendrites, which are not as obviously associated with blood vessels. White matter neurons positive for NADPHd have previously been observed as a transient population, most numerous during development, in the human corpus callosum, as well as in that of other species. Their persistence in the corpus callosum of adult macaques and their close association with blood vessels has not previously been reported and is suggestive of roles other than axon guidance.

Rockland, Kathleen S.; Nayyar, Naema

2012-01-01

334

Anisotropies of cosmic microwave background  

NASA Astrophysics Data System (ADS)

Cosmic microwave background (CMB) anisotropies have been recognized as one of the most important observational quantities to understand the early stage of our universe. Here it is shown that temperature fluctuations of CMB contain rich information, i.e., cosmological parameters, geometry of the universe, initial condition of the density perturbations and more. The impact by recent observations of BOOMERanG and MAXIMA is also mentioned.

Sugiyama, Naoshi

2001-07-01

335

Cup-Drawing Behavior of High-Strength Steel Sheets Containing Different Volume Fractions of Martensite  

Microsoft Academic Search

Planar anisotropy and cup-drawing behavior were investigated for high-strength steel sheets containing different volume fractions of martensite. Macrotexture analysis using XRD was conducted to capture the effect of crystallographic orientation on the planar anisotropy of high-strength steel sheets. A phenomenological yield function, Yld96, which accounts for the anisotropy of yield stress and r-values, was implemented into ABAQUS using the user

Shi-Hoon Choi; Dae-Wan Kim; Hoe-Seok Yang; Seong-Ho Han; Jeong Whan Yoon

2010-01-01

336

Mechanical Anisotropy of Ankyrin Repeats  

PubMed Central

Red blood cells are frequently deformed and their cytoskeletal proteins such as spectrin and ankyrin-R are repeatedly subjected to mechanical forces. While the mechanics of spectrin was thoroughly investigated in vitro and in vivo, little is known about the mechanical behavior of ankyrin-R. In this study, we combine coarse-grained steered molecular dynamics simulations and atomic force spectroscopy to examine the mechanical response of ankyrin repeats (ARs) in a model synthetic AR protein NI6C, and in the D34 fragment of native ankyrin-R when these proteins are subjected to various stretching geometry conditions. Our steered molecular dynamics results, supported by AFM measurements, reveal an unusual mechanical anisotropy of ARs: their mechanical stability is greater when their unfolding is forced to propagate from the N-terminus toward the C-terminus (repeats unfold at ?60 pN), as compared to the unfolding in the opposite direction (unfolding force ? 30 pN). This anisotropy is also reflected in the complex refolding behavior of ARs. The origin of this unfolding and refolding anisotropy is in the various numbers of native contacts that are broken and formed at the interfaces between neighboring repeats depending on the unfolding/refolding propagation directions. Finally, we discuss how these complex mechanical properties of ARs in D34 may affect its behavior in vivo.

Lee, Whasil; Zeng, Xiancheng; Rotolo, Kristina; Yang, Ming; Schofield, Christopher J.; Bennett, Vann; Yang, Weitao; Marszalek, Piotr E.

2012-01-01

337

Domain switching anisotropy in textured bismuth titanate ceramics  

NASA Astrophysics Data System (ADS)

In a poled ferroelectric ceramic, the probability of crystallographic poles oriented in any given specimen direction is the multiple of both the initial crystallographic texture and the domain switching fraction. In this paper, the non-180° domain switching fraction is shown to be dependent on the initial crystallographic texture and poling direction in tape cast Na0.5Bi4.5Ti4O15 ceramics. The domain switching fraction is 0.18 out of a maximum of 0.50 when poled in a direction in which most of the possible ferroelastic structural distortions are oriented (tape casting plane) whereas no non-180° domain switching is discernable when poled in a less-preferred direction. The mechanism for domain switching anisotropy in textured bismuth titanate ceramics is suggested to be the synergistic alignment of ferroelastic structural distortions, analogous to the mechanical clamping conditions in poling ferroelastic thin films.

Jones, Jacob L.; Slamovich, Elliott B.; Bowman, Keith J.; Lupascu, Doru C.

2005-11-01

338

Texture and anisotropy of ferroelectric bismuth titanate  

NASA Astrophysics Data System (ADS)

Ferroelectric bismuth titanate, Na0.5Bi4.5 Ti4O15, is a piezoelectric ceramic used as an electromechanical sensor in high temperature environments (T < 655°C). However, the piezoelectric constant, d33, is relatively low in randomly oriented ceramics. Crystallographic texturing is often employed to increase the piezoelectric constant because the spontaneous polarization axes of the grains are better aligned. This research distinguishes between the crystallographic texture induced to the grains from tape casting and crystallographic texture induced to the ferroelectric domains from electrical poling. Novel quantitative approaches describe texture of both types independently using conventional and synchrotron X-ray sources as well as time-of-flight neutron diffraction with multiple detectors. Furthermore, methods are developed to describe the combined effect of a ferroelectric texture superimposed on a paraelectric texture. Texture of the paraelectric crystallographic axes was induced by novel processing approaches. An alternative to using plate-shaped template particles was developed utilizing calcined powder. Paraelectric texture develops from particle settling and strong surface energy anisotropy during sintering. The 00l textures induced from this process are on the order of two to four multiples of a random distribution. These textures create property anisotropies between the casting plane and normal directions of 6.4 and 5.7 in piezoelectric d33 constant and remanent polarization, respectively. Texture of the ferroelectric crystallographic axes was induced by electrical poling at different temperatures and in different orientations. Ceramics with an initial paraelectric texture can exhibit greater change in the domain volume fractions during electrical poling than randomly oriented ceramics. This is demonstrated by applying novel quantitative approaches to reflection X-ray spectra from many sample directions. Because orthorhombic Na0.5Bi 4.5Ti4O15 has two ferroelectric domains that can be resolved by diffraction, the maximum possible fraction of non-180° domains switched during poling (eta200) is 0.5. Textured ceramics poled in a direction in which most of the possible polarization directions are oriented exhibit nearly half of this value in some directions, eta 200 = 0.23, whereas randomly oriented ceramics exhibit only a quarter of the maximum possible, eta200 = 0.13. In other words, textured ceramics can be poled to a larger degree than randomly oriented ceramics.

Jones, Jacob Leo

339

MAXIMA: Observations of CMB anisotropy  

NASA Astrophysics Data System (ADS)

This document describes the Millimeter Anisotropy eXperiment IMaging Array (MAXIMA), a balloon-borne experiment measuring the temperature anisotropy of the Cosmic Microwave Background (CMB) on angular scales of 10 ' to 5°. MAXIMA data are used to discriminate between cosmological models and to determine cosmological parameters. MAXIMA maps the CMB using 16 bolometric detectors observing in spectral bands centered at 150 GHz, 230 GHz, and 410 GHz, with 10 ' resolution at all frequencies. The combined receiver sensitivity to CMB anisotropy is ˜40 ?K sec , the best reported by any CMB experiment. Systematic errors are rejected by using four uncorrelated spatial modulations, multiple independent CMB observations, heavily baffled optics, and strong spectral discrimination. Observation patterns are well cross-linked and optimized for the extraction of cosmological information. Pointing is reconstructed to an accuracy of 1'. Absolute calibration uncertainty of 3 4% is the best achieved by any sub-orbital CMB experiment. Two MAXIMA flights were launched from the National Scientific Balloon Facility in Palestine Texas in 1998 and 1999. During a total of 8.5 hours of CMB observations, 300 deg2 of the sky were mapped, with ˜50 deg2 overlap between the two flights. The observed region was selected for low foreground emission and post-flight data analysis confirms that foreground contamination is negligible. Cosmological results are presented from the 1998 flight, MAXIMA-I , in which 122 deg2 of sky were mapped over 3 hours. A maximum likelihood map with 3' pixelization is obtained from the three most sensitive and best tested detectors. The angular power spectrum derived from this map shows a narrow peak near ? = 200, and is consistent with inflationary Big Bang models. Within these models, cosmological parameters are estimated, including total density ?tot = 0.9+0.18-0.16 , baryon density ?bh2 = 0.033 ± 0.013, and power spectrum normalization C 10 = 690+200- 125mK2 . In combination with recent supernova observations, we obtain additional constrains on the matter density ?m = 0.32+0.14-0.11 and the dark energy density ?? = 0.65+0.15-0.16 . All parameter estimates are presented at 95% confidence. The final chapter is a discussion CMB polarization anisotropy, including an overview of MAXIPOL, the polarization sensitive follow-up to MAXIMA. Measurements of CMB polarization are an essential complement to those of temperature anisotropy.

Rabii, Bahman

340

Introducing Fractions Slideshow- Flowering Fractions  

NSDL National Science Digital Library

This online resource is a story of a girl and her father planting flowers that your children and you interact with. Help them fill in the fractions as they practice dividing the garden up for their flowers!

Center, Beacon L.

2011-10-24

341

Some aspects of amoeboid microglia in the corpus callosum and neighbouring regions of neonatal rats.  

PubMed Central

The distribution and form of amoeboid microglia in the brain of neonatal rats have been studied with the light and electron microscope. With the silver carbonate method of Rio-Hortega, two major 'colonies' of amoeboid microglia are identified: (1) in the supraventricular corpus callosum in which the nerve fibres are widely spaced, and (2) at the medial angle of the lateral ventricle inferior to the corpus callosum. Scattered amoeboid cells are also seen in the cavum septum pellucidum and in the lumen of the lateral ventricle. Associated with the subependyma forming the roof of the lateral ventricle there are also numerous amoeboid cells. Ultrastructural studies show that the subependyma includes cellular elements with features intermediate between those of immature subependymal cells and full-blown amoeboid microglia. It is suggested that the latter are derived from the subependymal cells and that, once they are formed, they leave the subependyma and migrate into the corpus callosum and elsewhere. With the metallic stain, the amoeboid microglia present a wide diversity of appearances, some of which bear a close resemblance to typical microglia. It is therefore suggested that amoeboid microglia change into typical microglia. The present study clearly demonstrates that amoeboid microglia are active phagocytes. Their cytoplasm is heavily loaded with secretory granules (lysosomes) and give a positive reaction with PAS and acid phosphatase. Images Fig. 1 Fig. 2 Fig. 3 Figs. 4-9 Fig. 10 Fig. 11 Fig. 12 Fig. 13 Fig. 14 Fig. 15 Fig. 16 Fig. 17 Fig. 18 Fig. 19 Fig. 20 Fig. 21 Fig. 22 Fig. 23

Ling, E A

1976-01-01

342

Effects of prenatal irradiation on the development of cerebral cortex and corpus callosum of the mouse  

SciTech Connect

Defects of the cerebral cortex and corpus callosum of mice subjected prenatally to gamma irradiation were evaluated as a function of dose and of embryonic age at irradiation. Pregnant mice were exposed to a gamma source at 16, 17, and 19 days of gestation (E16, E17, and E19, respectively), with total doses of 2 Gy and 3 Gy, in order to produce brain defects on their progeny. At 60 postnatal days, the brains of the offspring were analyzed qualitatively and quantitatively and compared with those of nonirradiated animals. Mice irradiated at E16 were all acallosal. Those that were exposed to 2 Gy displayed an aberrant longitudinal bundle typical of other acallosals, but this was not the case in those irradiated with 3 Gy. The corpus callosum of animals irradiated at E17 with 3 Gy was pronouncedly hypotrophic, but milder effects were observed in the other groups. Quantitative analysis confirmed a dependence of callosal midsagittal area upon dose and age at irradiation, and, in addition, indicated an interaction between these variables. The neocortex of irradiated animals was hypotrophic: layers II-III were much more affected than layer V, and this was more affected than layer VI. Quantitative analysis indicated that this effect also depended on dose and age at irradiation and that it was due to a loss of cortical neurons. Furthermore, a positive correlation was found between the number of neurons within layers II-III, and V and the midsagittal area of the corpus callosum. Ectopic neurons were found in the white matter and in layer I of animals irradiated at E16 and E17, indicating that fetal exposure to ionizing radiation interfered with the migration of cortical neuroblasts.

Schmidt, S.L.; Lent, R.

1987-10-08

343

Agenesis of the corpus callosum with Probst bundles owing to haploinsufficiency for a gene in an 8 cM region of 6q25  

Microsoft Academic Search

Agenesis of the corpus callosum (ACC) is a relatively common brain abnormality resulting from developmental defects either limited to the structures leading to the proper formation of the corpus callosum or involving the embryo forebrain more generally. ACC is genetically heterogeneous with autosomal dominant, autosomal recessive, and X linked inheritance and has also been reported in subjects with aneuploidies involving

B Pirola; L Bortotto; S Giglio; E Piovan; A Janes; R Guerrini; O Zuffardi

1998-01-01

344

The K–Cl cotransporter KCC3 is mutant in a severe peripheral neuropathy associated with agenesis of the corpus callosum  

Microsoft Academic Search

Peripheral neuropathy associated with agenesis of the corpus callosum (ACCPN) is a severe sensorimotor neuropathy associated with mental retardation, dysmorphic features and complete or partial agenesis of the corpus callosum. ACCPN is transmitted in an autosomal recessive fashion and is found at a high frequency in the province of Quebec, Canada. ACCPN has been previously mapped to chromosome 15q. The

Heidi C. Howard; David B. Mount; Daniel Rochefort; Nellie Byun; Nicolas Dupré; Jianming Lu; Xuemo Fan; Luyan Song; Jean-Baptiste Rivière; Claude Prévost; Jürgen Horst; Alessandro Simonati; Beate Lemcke; Rick Welch; Roger England; Frank Q. Zhan; Adriana Mercado; William B. Siesser; Alfred L. George; Michael P. McDonald; Jean-Pierre Bouchard; Jean Mathieu; Eric Delpire; Guy A. Rouleau

2002-01-01

345

Fine mapping the candidate region for peripheral neuropathy with or without agenesis of the corpus callosum in the French Canadian population  

Microsoft Academic Search

Peripheral neuropathy with or without agenesis of the corpus callosum (ACCPN [MIM 2180000]) is an autosomal recessive disease characterised by progressive sensorimotor neuropathy, mental retardation, dysmorphic features and complete or partial agenesis of the corpus callosum. The ACCPN gene was mapped in 1996 to a 4 cM region on chromosome 15. We have since collected additional French Canadian (FC) families

Heidi C Howard; Marie-Pierre Dubé; Claude Prévost; Jean-Pierre Bouchard; Jean Mathieu; Guy A Rouleau

2002-01-01

346

Gender-based differences in the shape of the human corpus callosum are associated with allometric variations.  

PubMed

The corpus callosum displays considerable morphological variability between individuals. Although some characteristics are thought to differ between male and female brains, there is no agreement regarding the source of this variation. Biomedical imaging and geometric morphometrics have provided tools to investigate shape and size variation in terms of integration and correlation. Here we analyze variations at the midsagittal outline of the corpus callosum in a sample of 102 young adults in order to describe and quantify the pattern of covariation associated with its morphology. Our results suggest that the shape of the corpus callosum is characterized by low levels of morphological integration, which explains the large variability. In larger brains, a minor allometric component involves a relative reduction of the splenium. Small differences between males and?females are associated with this allometric pattern, induced primarily by size variation rather than gender-specific characteristics. PMID:22296183

Bruner, Emiliano; de la Cuétara, José Manuel; Colom, Roberto; Martin-Loeches, Manuel

2012-02-01

347

Hematoma in the splenium of the corpus callosum in the subacute stage of subarachnoid hemorrhage--three case reports.  

PubMed

Three patients developed hemorrhage in the splenium of the corpus callosum 2 weeks after the onset of subarachnoid hemorrhage (SAH) associated with acute hydrocephalus. Computed tomography performed a few days after the onset showed a low density area in the splenium of corpus callosum in all three patients, and preventive measures against symptomatic vasospasm were begun, including vasodilator administration. Computed tomography showed hemorrhage in the splenium of the corpus callosum 17 to 22 days after onset of SAH, manifesting as mental deterioration or headache. Antivasospasm agents were immediately discontinued, and strict blood control measures were instituted. Splenial hematoma is another potential cause of neurological deterioration after surgery for SAH, in addition to vasospasm, hydrocephalus, and rebleeding. PMID:20339269

Sorimachi, Takatoshi; Yajima, Naoki; Sasaki, Osamu; Koike, Tetsuo; Fujii, Yukihiko

2010-01-01

348

Agenesis of the corpus callosum in fetuses with mild ventriculomegaly: role of MR imaging  

Microsoft Academic Search

Purpose  We evaluated the role of magnetic resonance (MR) imaging in the diagnosis of corpus callosum agenesis — isolated or associated\\u000a with other anomalies — in fetuses with mild cerebral ventriculomegaly, as depicted at prenatal sonography.\\u000a \\u000a \\u000a \\u000a \\u000a Material and methods  Between January 2005 and March 2007, 33 fetuses with a mean gestational age of 28.9 weeks (range 17–37) and mild ventriculomegaly\\u000a diagnosed at

R. Manfredi; A. Tognolini; C. Bruno; R. Raffaelli; M. Franchi; R. Pozzi Mucelli

2010-01-01

349

Matching Fractions  

NSDL National Science Digital Library

In this interactive game similar to Concentration(TM) students match fractions (1/2, 1/3, 3/4, and 5/9) to images that represent those fractions. This game can be played in pairs with the printed out cards or as a whole class on the interactive white board (IWB). This resource includes teacher notes with suggestions for introducing the game, discussion questions, support suggestions, a set of cards to be printed (PDF), a blank set of cards to make your own (PDF), and a full screen version of the game.

Team, Nrich

2012-01-01

350

Mowat-Wilson syndrome in a fetus with antenatal diagnosis of short corpus callosum: advocacy for standard autopsy.  

PubMed

Mowat-Wilson syndrome (MWS) is a genetic disease caused by heterozygous mutations or deletions of the ZEB2 gene rarely diagnosed prenatally and with little fetal description reported. It is mainly characterized by moderate-to-severe intellectual disability, epilepsy, facial dysmorphism and various malformations including Hirschsprung disease and corpus callosum anomalies. Here we report a fetal case of MWS well described, suspected at standard autopsy. The association of a corpus callosum hypoplasia with a histological Hirschsprung disease and a typical facial gestalt allowed the guiding of genetic testing. Classical fetopathological examination still keeps indications in cases of syndromic association in the era of virtual autopsy. PMID:23523603

Spaggiari, Emmanuel; Baumann, Clarisse; Alison, Marianne; Oury, Jean-François; Belarbi, Nadia; Dupont, Céline; Guimiot, Fabien; Delezoide, Anne-Lise

2013-03-21

351

Structural anisotropy and internal magnetic fields in trabecular bone: Coupling solution and solid dipolar interactions  

Microsoft Academic Search

We investigate the use of intermolecular multiple-quantum coherence to probe structural anisotropy in trabecular bone. Despite the low volume fraction of bone, the bone–water interface produces internal magnetic field gradients which modulate the dipolar field, depending on sample orientation, choice of dipolar correlation length, correlation gradient direction, and evolution time. For this system, the probing of internal magnetic field gradients

Louis-S. Bouchard; Felix W. Wehrli; Chih-Liang Chin; Warren S. Warren

2005-01-01

352

Soft to hard magnetic anisotropy in nanostructured magnets  

NASA Astrophysics Data System (ADS)

The effective anisotropy of hard-soft magnetic nanostructures is analyzed using the concept of the exchange correlation length of both phases. The dependence of coercivity on volume fraction, fluctuation length, temperature, and magnetic properties of the components is derived from the degree of magnetic coupling, defined through an effective interphase exchange constant. Coercivity and remanence measurements carried out on devitrified FeZrBCu amorphous alloys point out the transition from an uncoupled to a coupled regime by increasing the temperature in a very diluted system, according to the predictions of the analysis.

Arcas, J.; Hernando, A.; Barandiarán, J. M.; Prados, C.; Vázquez, M.; Marín, P.; Neuweiler, A.

1998-09-01

353

Interface, surface and bulk anisotropies of heterostructures  

Microsoft Academic Search

Heterostructures of bulk-isotropic materials show optical anisotropies of various origins. The anisotropies reported so far can be categorized into four classes: surface-, interface- and confinement-induced anisotropies and bulk effects. Recent experimental results of ZnSe\\/GaAs (lattice matched but valence mismatched), GaN\\/GaAs (valence matched but lattice mismatched) and SiO2\\/Si (amorphous\\/crystalline) are reviewed in this article. The contribution from each class of the

T. Yasuda

1998-01-01

354

Magnetic Anisotropy in the Radula of Chiton  

NASA Astrophysics Data System (ADS)

Radular teeth of chitons were studied by using magnetic torque-meter and transmission electron microscopy (TEM). The magnetic torque curves give clear evidence of presence of strong uni-axial magnetic anisotropy. The easy axis is along the length direction of tongue-like radula. The TEM pattern shows that long chip-like magnetite nano-scaled particles packed in the radular teeth with both uni-axial shape anisotropy and magneto-crystalline anisotropy.

Zhao, Jian-Gao; Qian, Xia; Liu, Wei; Liu, Chuan-Lin; Zhan, Wen-Shan

2000-07-01

355

Plastic anisotropy in aluminium drawn tubes  

Microsoft Academic Search

Developments of plastic anisotropy in aluminium tubes are investigated experimentally and theoretically. Asreceived drawn\\u000a tubes are tensioned or twisted to get speciments having different anisotropies. The tubes are cut and extended into flat sheets.\\u000a The surfaces are removed mechanically and electorochemically into half thickness. The anisotropy is evaluated by flow stress\\u000a and r-value of tensile tests in various directions in

Hiroshi Takahashi; Junji Moro; Shin Tsuchida

1998-01-01

356

Seismic anisotropy in Western Tibet  

NASA Astrophysics Data System (ADS)

Using data obtained during the 2001 French-Chinese lithoscope passive teleseismic experiment, we investigated the fabric and anisotropy of the crust and mantle of Western Tibet, along profiles cutting major strike-slip faults (Altyn Tagh and Gozha faults) and sutures (Kudi, Bangong, and Shiquanhe sutures). Broadband stations were deployed across the high plateau along the road between Yecheng, at the southern edge of the Tarim Basin, and Shiquanhe (Ali) in the upper Indus valley. Aditionnal stations were also installed along a small north-south profile near Hotian to complement the Yecheng-Mazar profile. Seismic anisotropy was measured with SKS shear wave splitting in order to map lithospheric deformation and upper mantle flow. Non null but small anisotropy, caracterized by delays in the 0.2 to 0.6s range, was observed at 9 stations. These values are comparable to those previously found south of the Zangbo suture in SE Tibet. For stations south of the Bangong suture but well north of the Karakorum fault, the fast polarization directions are oriented northeast-southwest, roughly perpendicular to the Himalaya-Karakorum range. It is possible that these FPDs reflect crustal shear in relation with overthrusting. Between Domar and Hotien, the fast polarization directions at stations where the delay is largest are oriented roughly parallel to the Ghoza and Altyn Tagh faults, i.e. N60 and N90°E respectively. Farther westwards, near Yecheng, on either side of the western Kunlun range-front, the FPDs trend N40°E, roughly orthogonal to that front, which would be consistent with crustal shear, due to understhrusting and subduction of the Tarim block beneath Tibet. This interpretation would be in agreement with the results of teleseismic tomography, but would require complete slip-partitionning of the overall relative motion between the Pamir-Tibet block and the Tarim.

Herquel, G.; Tapponnier, P.; Wittlinger, G.; Poupinet, G.; Mei, J.

2003-04-01

357

Global Anisotropy in Galaxy Orientations  

NASA Astrophysics Data System (ADS)

We suggest a new method for investigating the distribution of the orientations of galaxies. This method is used to process data from the UGC and ESO catalogues, and from the catalogue of flat edge-on galaxies compiled by the authors (FGC). A statistically significant anisotropy is detected, and possible reasons for this are analyzed. The orientation distribution is described by a three-axis ellipsoid, showing an excess of about 20 per cent in the direction 4^h^-6^h^, 20^deg^-40^deg^, and a deficit of about 25 per cent in the direction 13^h^-15^h^, 30^deg^- 40^deg^.

Parnovsky, S. L.; Karachentsev, I. D.; Karachentseva, V. E.

1994-06-01

358

Cosmic Ray Anisotropy with KASCADE  

NASA Astrophysics Data System (ADS)

The anisotropy of cosmic rays with energies in the region of the knee in the energy spectrum is investigated in three different persp ectives based on the arrival directions of about 150 Mio. extensive air showers measured by KASCADE. The different analyses are a harmonic analysis of the right ascension distribution and a point source search of showers above 0.5 PeV as well as an auto correlation analysis of showers above 100 PeV. All three analyses agree inside the statistical limits with an isotropic distribution of the arrival directions of cosmic rays.

Maier, G.; Antoni, T.; Apel, W. D.; Badea, F.; Bekk, K.; Bercuci, A.; Blümer, H.; Bozdog, H.; Brancus, I. M.; Büttner, C.; Chilingarian, A.; Daumiller, K.; Doll, P.; Engel, R.; Engler, J.; Feßler, F.; Gils, H. J.; Glasstetter, R.; Haungs, A.; Heck, D.; Hörandel, J. R.; Iwan, A.; Kampert, K. H.; Klages, H. O.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Müller, M.; Obenland, R.; Oehlschläger, J.; Ostapchenko, S.; Petcu, M.; Rebel, H.; Risse, M.; Schatz, G.; Schieler, H.; Scholz, J.; Thouw, T.; Ulrich, H.; van Buren, J.; Vardanyan, A.; Weindl, A.; Wochele, J.; Zabierowski, J.

2003-07-01

359

Magnetic anisotropy and porosity of chondrites  

NASA Astrophysics Data System (ADS)

The measured magnetic anisotropy and porosity of various chondrites are found to be inversely correlated when they are considered by class of chondrites (E, H and L + LL). For chondrites with similar porosities, the anisotropies for H and E chondrites are smaller than for L and LL chondrites, which have lower metal contents. The anisotropy and porosity are not dependent on the metamorphic grade of chondrites. K-Ar ages of strongly anisotropic and/or less porous chondrites are younger than those of less anisotropic and/or more porous chondrites. These observations suggest that impacts which reset the K-Ar ages produced the anisotropy and reduced the porosity of chondrites.

Sugiura, N.; Strangway, D. W.

1983-01-01

360

Saturation-dependent anisotropy in the Hanford subsurface hydraulic conductivity  

NASA Astrophysics Data System (ADS)

In previous work anisotropy in a fracture network was shown to provide a possible explanation for the observed scale-effect in the hydraulic conductivity of a carbonate aquifer. Use was made of a coordinate transformation and reference made to the transverse and longitudinal electrical conductivities of thin (disordered) solid films. An analogous approach is now developed to describe the inferred anisotropy of the hydraulic conductivity as a function of saturation in the Hanford subsurface. Here different soil types play the role of fractures of different apertures, while the spatial anisotropy is generated by soils of higher silt and clay fractions. A quasi- equilibrium condition (equal matric potentials) is implemented at matric potentials believed characteristic of the Hanford subsurface (several hundred centimeters) and theoretical results for the hydraulic conductivity (modified by known values at saturation) are used to develop the distribution of K values at the appropriate potential. The results are hoped to be relevant to the dispersion of a Tc plume. Work was supported by DOE grant DE-FG02-05ER64067 and -06ER64196 and NSF grant EAR 0609884

Blank, L.; Skinner, T.; Hunt, A.

2006-12-01

361

Propagation of Epileptiform Events across the Corpus Callosum in a Cingulate Cortical Slice Preparation  

PubMed Central

We report on a novel mouse in vitro brain slice preparation that contains intact callosal axons connecting anterior cingulate cortices (ACC). Callosal connections are demonstrated by the ability to regularly record epileptiform events between hemispheres (bilateral events). That the correlation of these events depends on the callosum is demonstrated by the bisection of the callosum in vitro. Epileptiform events are evoked with four different methods: (1) bath application of bicuculline (a GABA-A antagonist); (2) bicuculline+MK801 (an NMDA receptor antagonist), (3) a zero magnesium extracellular solution (0Mg); (4) focal application of bicuculline to a single cortical hemisphere. Significant increases in the number of epileptiform events, as well as increases in the ratio of bilateral events to unilateral events, are observed during bath applications of bicuculline, but not during applications of bicuculline+MK-801. Long ictal-like events (defined as events >20 seconds) are only observed in 0Mg. Whole cell patch clamp recordings of single neurons reveal strong feedforward inhibition during focal epileptiform events in the contralateral hemisphere. Within the ACC, we find differences between the rostral areas of ACC vs. caudal ACC in terms of connectivity between hemispheres, with the caudal regions demonstrating shorter interhemispheric latencies. The morphologies of many patch clamped neurons show callosally-spanning axons, again demonstrating intact callosal circuits in this in vitro preparation.

Quach-Wong, Bonnie; Sonnenfeld, Julian; Aaron, Gloster

2012-01-01

362

Propagation of epileptiform events across the corpus callosum in a cingulate cortical slice preparation.  

PubMed

We report on a novel mouse in vitro brain slice preparation that contains intact callosal axons connecting anterior cingulate cortices (ACC). Callosal connections are demonstrated by the ability to regularly record epileptiform events between hemispheres (bilateral events). That the correlation of these events depends on the callosum is demonstrated by the bisection of the callosum in vitro. Epileptiform events are evoked with four different methods: (1) bath application of bicuculline (a GABA-A antagonist); (2) bicuculline+MK801 (an NMDA receptor antagonist), (3) a zero magnesium extracellular solution (0Mg); (4) focal application of bicuculline to a single cortical hemisphere. Significant increases in the number of epileptiform events, as well as increases in the ratio of bilateral events to unilateral events, are observed during bath applications of bicuculline, but not during applications of bicuculline+MK-801. Long ictal-like events (defined as events >20 seconds) are only observed in 0Mg. Whole cell patch clamp recordings of single neurons reveal strong feedforward inhibition during focal epileptiform events in the contralateral hemisphere. Within the ACC, we find differences between the rostral areas of ACC vs. caudal ACC in terms of connectivity between hemispheres, with the caudal regions demonstrating shorter interhemispheric latencies. The morphologies of many patch clamped neurons show callosally-spanning axons, again demonstrating intact callosal circuits in this in vitro preparation. PMID:22363643

Walker, Jeffrey; Storch, Gregory; Quach-Wong, Bonnie; Sonnenfeld, Julian; Aaron, Gloster

2012-02-21

363

Unmyelinated Axons Show Selective Rostrocaudal Pathology in the Corpus Callosum Following Traumatic Brain Injury  

PubMed Central

Axonal injury is consistently observed following traumatic brain injury (TBI). Prior research has extensively characterized the post-TBI response in myelinated axons. Despite evidence that unmyelinated axons comprise a numerical majority of cerebral axons, pathological changes in unmyelinated axons following TBI have not been systematically studied. To identify morphological correlates of functional impairment of unmyelinated fibers following TBI, we assessed ultrastructural changes in corpus callosum axons. Adult rats received moderate fluid percussion TBI, which produced diffuse injury with no contusion. Cross-sectional areas of 13,797 unmyelinated, and 3,278 intact myelinated axons were stereologically measured at survival intervals from 3 hours to 15 days post-injury. The mean caliber of unmyelinated axons was significantly reduced at 3 to 7 days, and recovered by 15 days, but the time course of this shrinkage varied among the genu, mid-callosum and splenium. Relatively large unmyelinated axons appeared to be particularly vulnerable. Injury-induced decreases in unmyelinated fiber density were also observed but they were more variable than caliber reductions. By contrast, no significant morphometric changes were observed in myelinated axons. The finding of a preferential vulnerability in unmyelinated axons has implications for current concepts of axonal responses following TBI and for development of specifically targeted therapies.

Reeves, Thomas M.; Smith, Terry L.; Williamson, Judy C.; Phillips, Linda L.

2012-01-01

364

Myelination of the corpus callosum in male and female rats following complex environment housing during adulthood.  

PubMed

Myelination is an important process in brain development, and delays or abnormalities in this process have been associated with a number of conditions including autism, developmental delay, attention deficit disorder, and schizophrenia. Myelination can be sensitive to developmental experience; however, although the adult brain remains highly plastic, it is unknown whether myelination continues to be sensitive to experience during adulthood. Male and female rats were socially housed until four months of age, at which time they were moved into either a complex or "enriched" environment (EC) or an isolated condition (IC). Although the area of the splenium (posterior 20% of the callosum, which contains axons from visual cortical neurons) increased by about 10% following two months of EC housing, the area occupied by myelinated axons was not influenced by adult housing condition. Instead, it was the area occupied by glial cell processes and unmyelinated axons which significantly increased following EC housing. Neither the size nor the myelin content of the genu (anterior 15% of the callosum) was sensitive to manipulations of adult housing condition, but males had more area occupied by myelinated axons in both callosal regions. Finally, the inability of two months of complex environment housing during adulthood to impact the number of myelinated axons in the splenium was confirmed in a subset of animals using quantitative electron microscopy. We conclude that the sensitivity of myelination to experience is reduced in adulthood relative to development in both sexes. PMID:19596280

Markham, Julie A; Herting, Megan M; Luszpak, Agatha E; Juraska, Janice M; Greenough, William T

2009-07-09

365

The Corpus Callosum and the Visual Cortex: Plasticity Is a Game for Two  

PubMed Central

Throughout life, experience shapes and selects the most appropriate brain functional connectivity to adapt to a changing environment. An ideal system to study experience-dependent plasticity is the visual cortex, because visual experience can be easily manipulated. In this paper, we focus on the role of interhemispheric, transcallosal projections in experience-dependent plasticity of the visual cortex. We review data showing that deprivation of sensory experience can modify the morphology of callosal fibres, thus altering the communication between the two hemispheres. More importantly, manipulation of callosal input activity during an early critical period alters developmental maturation of functional properties in visual cortex and modifies its ability to remodel in response to experience. We also discuss recent data in rat visual cortex, demonstrating that the corpus callosum plays a role in binocularity of cortical neurons and is involved in the plastic shift of eye preference that follows a period of monocular eyelid suture (monocular deprivation) in early age. Thus, experience can modify the fine connectivity of the corpus callosum, and callosal connections represent a major pathway through which experience can mediate functional maturation and plastic rearrangements in the visual cortex.

Pietrasanta, Marta; Restani, Laura; Caleo, Matteo

2012-01-01

366

Corpus callosum analysis using MDL-based sequential models of shape and appearance  

NASA Astrophysics Data System (ADS)

This paper describes a method for automatically analysing and segmenting the corpus callosum from magnetic resonance images of the brain based on the widely used Active Appearance Models (AAMs) by Cootes et al. Extensions of the original method, which are designed to improve this specific case are proposed, but all remain applicable to other domain problems. The well-known multi-resolution AAM optimisation is extended to include sequential relaxations on texture resolution, model coverage and model parameter constraints. Fully unsupervised analysis is obtained by exploiting model parameter convergence limits and a maximum likelihood estimate of shape and pose. Further, the important problem of modelling object neighbourhood is addressed. Finally, we describe how correspondence across images is achieved by selecting the minimum description length (MDL) landmarks from a set of training boundaries using the recently proposed method of Davies et al. This MDL-approach ensures a unique parameterisation of corpus callosum contour variation, which is crucial for neurological studies that compare reference areas such as rostrum, splenium, et cetera. We present quantitative and qualitative results that show that the method produces accurate, robust and rapid segmentations in a cross sectional study of 17 subjects, establishing its feasibility as a fully automated clinical tool for analysis and segmentation.

Stegmann, Mikkel B.; Davies, Rhodri H.; Ryberg, Charlotte

2004-05-01

367

fMRI and corpus callosum relationships in monozygotic twins discordant for handedness.  

PubMed

To further investigate brain structure and function in 26 handedness discordant monozygotic twin pairs (MzHd), MRI and behavioural assessments were carried out. These showed significant correlation between language-specific functional laterality in inferior and middle frontal gyri, and anterior corpus callosum. Previous studies of handedness discordant monozygotic twins failed to resolve the issue concerning handedness and hemispheric laterality for language due to methodological disparities. The results would be relevant to genetic theories as well as to brain structure:function explanations. MzHd twins underwent MRI and fMRI scanning as well as behavioural assessment of motor performance and cognition. There were significant differences on MRI and fMRI laterality measures, as well as a significant correlation between anterior callosal widths and functional laterality. LH twins showed higher frequencies of atypical functional laterality. There was no significant within-twin pair correlation on fMRI verbal laterality, nor did results show within-twin pair differences on verbal fluency or IQ. Implications for the field of laterality research pertain to frontal hemispheric equipotentiality for verbal processes in healthy individuals. In particular, there can be an apparent lack of cognitive 'cost' to atypical laterality. An fMRI verbal laterality index correlated significantly with corpus callosum widths near Broca's area. PMID:22527119

Gurd, J M; Cowell, P E; Lux, S; Rezai, R; Cherkas, L; Ebers, G C

2012-04-21

368

Electrical anisotropy of South African lithosphere compared with seismic anisotropy from shear-wave splitting analyses  

Microsoft Academic Search

Electrical anisotropy in southern Africa, inferred from the analysis of magnetotelluric (MT) data recorded as part of the Southern African MT Experiment (SAMTEX), is compared with seismic anisotropy inferred from an SKS shear-wave splitting study in the same region. Given the vastly varying penetration depths in the survey area, electrical anisotropy is derived in terms of approximate depth, rather than

Mark P. Hamilton; Alan G. Jones; Rob. L. Evans; Shane Evans; C. J. S. Fourie; Xavier Garcia; Andy Mountford; Jessica E. Spratt

2006-01-01

369

Double-wave-vector diffusion-weighted imaging reveals microscopic diffusion anisotropy in the living human brain.  

PubMed

Diffusion-tensor imaging is widely used to characterize diffusion in biological tissue, however, the derived anisotropy information, e.g., the fractional anisotropy, is ambiguous. For instance, low values of the diffusion anisotropy in brain white matter voxels may reflect a reduced axon density, i.e., a loss of fibers, or a lower fiber coherence within the voxel, e.g., more crossing fibers. This ambiguity can be avoided with experiments involving two diffusion-weighting periods applied successively in a single acquisition, so-called double-wave-vector or double-pulsed-field-gradient experiments. For a long mixing time between the two periods such experiments are sensitive to the cells' eccentricity, i.e., the diffusion anisotropy present on a microscopic scale. In this study, it is shown that this microscopic diffusion anisotropy can be detected in white matter in the living human brain, even in a macroscopically isotropic region-of-interest (fractional anisotropy = 0). The underlying signal difference between parallel and orthogonal wave vector orientations does not show up in standard diffusion-weighting experiments but is specific to the double-wave-vector experiment. Furthermore, the modulation amplitude observed is very similar for regions-of-interest with different fractional anisotrpy values. Thus, double-wave-vector experiments may provide a direct and reliable access to white matter integrity independent of the actual fiber orientation distribution within the voxel. PMID:22711603

Lawrenz, Marco; Finsterbusch, Jürgen

2012-06-18

370

Magnetic anisotropy of ferrosmectic phases  

NASA Astrophysics Data System (ADS)

A new anisotropic magnetic fluid, called ferrosmectic, is obtained when using a colloidal suspension of submicronic magnetic particles (ferrofluid), as a component in a smectic phase of fluid membranes. These lamellar phases present specific magnetic properties. The anisotropy of their magnetic susceptilities as a function of particles concentration is studied and interpreted : a microscopic mechanism involving a steric hindrance between particles and membranes is used to understand the experimental results. Un nouveau fluide magnétique anisotrope, appelé ferrosmectique, est obtenu lorsque nous utilisons un ferrofluide, c'est-à-dire une suspension colloïdale de particules magnétiques de taille inférieure au micron, comme composant dans la fabrication d'une phase smectique de membranes fluides. Ces phases adoptent des comportements spécifiques sous champ magnétique, et nous présentons ici une étude de l'anisotropie de leur susceptibilité magnétique en fonction de la concentration en particules. Nous interprétons les résultats obtenus par un mécanisme microscopique basé sur l'existence d'une gêne stérique entre membranes et particules.

Ponsinet, Virginie; Fabre, Pascale; Veyssié, Madeleine; Cabanel, Régis

1994-10-01

371

Fraction Reduction through Continued Fractions  

ERIC Educational Resources Information Center

This article presents a method of reducing fractions without factoring. The ideas presented may be useful as a project for motivated students in an undergraduate number theory course. The discussion is related to the Euclidean Algorithm and its variations may lead to projects or early examples involving efficiency of an algorithm.

Carley, Holly

2011-01-01

372

Fraction four  

NSDL National Science Digital Library

In this two-player online game, students combine math skills and strategies to practice simplifying, converting, and multiplying decimals, percentages, and fractions. For each correct answer, the player places a colored ball on a 10-by-10 grid. The first person to place four balls of his or her color together in a row or diagonally wins. Students can choose different difficulty levels, response time limits, and types of questions. Problems range from simple calculations for reducing fractions to solving proportions. From the online game page, What, How, and Why buttons open sections that explain the activity's purpose, function, and where the mathematics fits into the curriculum. Supporting information includes links to related lessons and student discussion questions, which help determine what strategies the winning student used to arrive at the correct answers. Copyright 2005 Eisenhower National Clearinghouse

Foundation, Shodor E.

2004-01-01

373

Thermal stability of anisotropy in TbFe films prepared by dc-magnetron sputtering  

SciTech Connect

We have found that stresses induced during magnetron sputter deposition of amorphous TbFe films are very important in determining the thermal stability of the perpendicular anisotropy, {ital K}{sub {ital u}}. To determine the stress-induced contribution to the anisotropy, the anisotropy was measured with a torque magnetometer before and after peeling films from their substrates. Data clearly show that the fractional change in anisotropy which occurs when the film is peeled from its substrate, {Delta}{ital K}{sub {ital u}}/{ital K}{sub {ital u}}, decreases with increasing Ar pressures. Furthermore, annealing studies reveal that the thermal stability of {ital K}{sub {ital u}} improves with increasing Ar sputtering pressure{minus}a trend which is in conflict with the tendency for films sputtered under low Ar pressure to be more oxidation resistant. This trend is attributed to the large stress-induced anisotropy component which exists at low argon pressures and its tendency to decrease as a result of long-term annealing. Measurements of the anisotropy of films which had been annealed at 200 {degree}C for 815 h showed that the residual {ital K}{sub {ital u}} after annealing increased with argon pressure. Measurements of the width of the peak in coercivity around {ital T}{sub comp} in these films shows that {ital H}{sub {ital c}} increases monotonically with argon pressure. This monotonic increase in {ital H}{sub {ital c}} is attributed to larger local variations in anisotropy caused by the less dense microstructure and the more random local anisotropy produced by the larger angle of incidence of adatoms which results from the increased scattering in the higher pressure sputtering gas.

Cheng, S.N.; Kryder, M.H. (Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania (USA))

1991-11-15

374

Corpus Callosum Morphology in Normal Controls and Traumatic Brain Injury: Sex Differences, Mechanisms of Injury, and Neuropsychological Correlates  

Microsoft Academic Search

This study examined the relative cross-sectional area of the corpus callosum (CC) from MRI scans of 166 normal controls and 97 patients who have suffered traumatic brain injury (TBI). The issue of sex differences in the normal CC is addressed with regard to methodological limitations of many previous conflicting reports. Women had larger CC relative to cranial volume than did

Sterling C. Johnson; James B. Pinkston; Erin D. Bigler; Duane D. Blatter

1996-01-01

375

Gender differences in brain volume and size of corpus callosum and amygdala of rhesus monkey measured from MRI images  

Microsoft Academic Search

While it has been established that the weight of the female rhesus monkey brain is less than that of the male, the sexual dimorphism of specific brain structures has not been well-documented. To further understand potential sex differences, we measured the whole brain volume and the size of the corpus callosum (mid-sagittal) and amygdala (largest coronal section) in MRI images

Michael S. Franklin; Gary W. Kraemer; Steven E. Shelton; Eva Baker; Ned H. Kalin; Hideo Uno

2000-01-01

376

Topography of the human corpus callosum revisited—Comprehensive fiber tractography using diffusion tensor magnetic resonance imaging  

Microsoft Academic Search

Several tracing studies have established a topographical distribution of fiber connections to the cortex in midsagittal cross-sections of the corpus callosum (CC). The most prominent example is Witelson's scheme, which defines five vertical partitions mainly based on primate data. Conventional MRI of the human CC does not reveal morphologically discernable structures, although microscopy techniques identified myelinated axons with a relatively

Sabine Hofer; Jens Frahm

2006-01-01

377

The size and fibre composition of the corpus callosum with respect to gender and schizophrenia: a post-mortem study  

Microsoft Academic Search

Summary In this study the cross-sectional area (in n J 14 female controls, 15 male controls, 11 female patients with schizophrenia, 15 male patients with schizophrenia) and fibre composition (in n J 11 female controls, 10 male controls, 10 female patients with schizophrenia, 10 male patients with schizophrenia) of the corpus callosum in post-mortem control and schizophrenic brains was examined.

J. Robin Highley; Margaret M. Esiri; Brendan McDonald; Mario Cortina-Borja; Brian M. Herron; Timothy J. Crow

1999-01-01

378

DTI tractography based parcellation of white matter: Application to the mid-sagittal morphology of corpus callosum  

Microsoft Academic Search

Morphology of the corpus callosum (CC) at the mid-sagittal level has been a target of extensive studies. However, the lack of internal structures and its polymorphism make it a challenging task to quantitatively analyze shape differences among subjects. In this paper, diffusion tensor Imaging (DTI) and tract tracing technique were applied to incorporate cortical connectivity information to the morphological study.

Hao Huang; Jiangyang Zhang; Hangyi Jiang; Setsu Wakana; Lidia Poetscher; Michael I. Miller; Peter C. M. van Zijl; Argye E. Hillis; Robert Wytik; Susumu Mori

2005-01-01

379

Frequency of Agenesis of the Corpus Callosum in the Developmentally Disabled Population as Determined by Computerized Tomography  

Microsoft Academic Search

Agenesis of the corpus callosum (ACC) is an infrequent congenital abnormality that has been diagnosed by necropsy, surgery, pneumoencephalography, computerized tomography (CT), and magnetic resonance imaging. The reported prevalence has varied as a function of disability status of the population studied and diagnostic technique. This report found 33 cases of ACC in a consecutive series of 1,447 CTs of developmentally

Joseph S. Jeret; David Serur; Krystyna Wisniewski; Clifford Fisch

1986-01-01

380

Biographical Study of a Woman with Agenesis of the Corpus Callosum: A Story of Hope and Inspiration  

Microsoft Academic Search

School psychologists must be knowledgeable about brain development to help students in their care. The human brain has the capability to determine a person's happiness, effectiveness, and positive relationships with others. This biographical study examined how a young woman diagnosed with Agenesis of the Corpus Callosum (ACC) and agenesis of the cerebellum came to live a productive, happy life. ACC

Robin Comerford

2008-01-01

381

Cuprizone demyelination of the corpus callosum in mice correlates with altered social interaction and impaired bilateral sensorimotor coordination  

Microsoft Academic Search

For studies of remyelination in demyelinating diseases, the cuprizone model of CC (corpus callosum) demyelination has experimental advantages that include overall size, prox- imity to neural stem cells of the subventricular zone, and correlation with a lesion predilection site in multiple sclerosis. In addition, cuprizone treatment can be ended to allow more direct analysis of remyelination than with viral or

Norah Hibbits; Ravinder Pannu; T John Wu; Regina C Armstrong

2009-01-01

382

Corpus callosum damage in heavy marijuana use: Preliminary evidence from diffusion tensor tractography and tract-based spatial statistics  

Microsoft Academic Search

Heavy marijuana use has well established long term consequences for cognition and mental health, but the effect on brain structure is less well understood. We used an MRI technique that is sensitive to the structural integrity of brain tissue combined with a white matter mapping tractography technique to investigate structural changes in the corpus callosum (CC). Diffusion tensor imaging (DTI)

D. Arnone; T. R. Barrick; S. Chengappa; C. E. Mackay; C. A. Clark; M. T. Abou-Saleh

2008-01-01

383

Corpus Callosum Size, Reaction Time Speed and Variability in Mild Cognitive Disorders and in a Normative Sample  

ERIC Educational Resources Information Center

|Intra-individual variability in reaction time increases with age and with neurological disorders, but the neural correlates of this increased variability remain uncertain. We hypothesized that both faster mean reaction time (RT) and less intra-individual RT variability would be associated with larger corpus callosum (CC) size in older adults, and…

Anstey, Kaarin J.; Mack, Holly A.; Christensen, Helen; Li, Shu-Chen; Reglade-Meslin, Chantal; Maller, Jerome; Kumar, Rajeev; Dear, Keith; Easteal, Simon; Sachdev, Perminder

2007-01-01

384

A comparative study of corpus callosum size and signal intensity in capuchin monkeys ( Cebus apella) and chimpanzees ( Pan troglodytes)  

Microsoft Academic Search

The evolution of corpus callosum (CC) was integral to the development of higher cognitive processes and hemispheric specialization. An examination of CC morphology and organization across different primate species will further our understanding of the evolution of these specified functions. Using magnetic resonance imaging (MRI) as a non-invasive technique to measure CC size and to approximate the degree of myelination

K. A. Phillips; N. Kapfenberger; W. D. Hopkins

2009-01-01

385

Familial Progressive Sensorimotor Neuropathy with Agenesis of the Corpus callosum (Andermann Syndrome): A Clinical, Neuroradiological and Histopathological Study  

Microsoft Academic Search

Three siblings from consanguineous parents, originating from Tanzania, presented with symptoms of complete or partial agenesis of the corpus callosum. Two males had in addition a sensorimotor neuropathy, moderate mental retardation and skeletal dysmorphism (Andermann syndrome). A study of sural nerve biopsies revealed thickening of the perineurium and reduction in the number of large myelinated fibres with axonal degeneration. Muscle

Dirk Deleu; Sunita A. Bamanikar; David Muirhead; Andre Louon

1997-01-01

386

Median cleft face syndrome in association with hydrocephalus, agenesis of the corpus callosum, holoprosencephaly and choanal atresia  

Microsoft Academic Search

A premature female infant had the characteristic features of the median cleft face syndrome in association with holoprosencephaly, agenesis of the corpus callosum, hydrocephalus and choanal atresia. Whereas the nervous system is rarely affected in patients with the median cleft face syndrome, severe mental retardation has been reported in three previously published cases and is suggested in our own patient.

T. Bömelburg; W. Lenz; T. Eusterbrock

1987-01-01

387

Lissencephaly with agenesis of corpus callosum and rudimentary dysplastic cerebellum: a subtype of lissencephaly with cerebellar hypoplasia  

Microsoft Academic Search

Lissencephaly with agenesis of the corpus callosum and rudimentary dysplastic cerebellum may represent a subset of lissencephaly with cerebellar hypoplasia (LCH) of unknown etiology, one that is distinct from other types of LCH. We present a detailed neuropathological description of an autopsy brain from a 7-day-old neonate born at 38-gestational weeks, presenting with this malformation. The brain was severely hydrocephalic

Hajime Miyata; Dennis J. Chute; James Fink; Pablo Villablanca; Harry V. Vinters

2004-01-01

388

Coulomb relaxation of electron-temperature anisotropy  

Microsoft Academic Search

Hyatt et al. (1987) have carried out an experiment on the collisional relaxation of electron-temperature anisotropy in a laboratory plasma containing singly ionized ions. They observed equalization of the longitudinal and transverse temperature with respect to the external magnetic field as a result of Coulomb electron collisions. A theoretical examination of electron-temperature anisotropy relaxation is carried out in the present

Iu. V. Konikov

1990-01-01

389

AVO and anisotropy from logs and walkaways  

SciTech Connect

AVO (amplitude versus offset) is the seismic technique used for mapping lithology, and modeling is an important step for successful AVO interpretations. Shear velocity measurements are essential, since AVO attempts to exploit the elastic (as opposed to acoustic) nature of seismic wave propagation. A property of seismic wave propagation not often considered is anisotropy. This is probably because the magnitude of the anisotropy has been difficult to measure, and its effect on AVO is not widely known. New technology is helping to improve AVO modeling. Dipole source shear logging tools can now measure very slow shear velocities, increasing the range of applicability of AVO, and new borehole seismic techniques can measure anisotropy. When integrated, these new measurements provide more detailed information about the elastic moduli that govern wave propagation, and bring the possibility for greater reliability in AVO interpretation. Two examples of ray-trace AVO synthetics are shown to illustrate typical AVO responses and the importance of shear velocity information. An overview of anisotropy is given and a new technique to estimate anisotropy from walkaway surveys (multi-offset VSPs) is described. The log and walkaway measurements are then integrated to study the impact of anisotropy on AVO. First, the effect of anisotropy on Ostrander's shale-sand model is investigated, and second, isotropic and anisotropic ray-trace synthetics are compared. The effect of anisotropy on AVO is found to be significant and may be lead to misinterpretations of AVO anomalies.

Leaney, S.W.; Borland, W.E. (Schlumberger Geophysics Nusantara, Jakarta (Indonesia))

1994-07-01

390

Anisotropy of Southern African lithosphere and asthenosphere  

Microsoft Academic Search

Observations of anisotropy, when understood in terms of deformation processes, are critical to illuminating the dynamics of past and present tectonic processes - in particular how continents formed, stabilized and interacted with underlying mantle regions in the past, and how they do so today. Seismology and electromagnetic observations of anisotropy are essential if we are to understand the tectonic history

Mark P. Hamilton; Alan G. Jones; Merrion Square; Louise Collins; Xavier Garcia; Colin Hogg; Clare Horan; David Khoza; Marion Miensopust; Mark Muller; Jessica Spratt; Gerry Wallace; Alan D. Chave; Rob L. Evans; Sue Webb; Janine Cole; Patrick Cole; Raimund Stettler; G. Tshoso; David Hutchins; Shane Evans; Theo Aravanis; Andy Mountford; Wayne Pettit; Stoffel Fourie; Jan Wasborg

391

Mantle structural geology from seismic anisotropy  

Microsoft Academic Search

Seismic anisotropy is a ubiquitous feature of the subcontinental mantle. This can be inferred both from direct seismic observations of shear wave splitting from teleseismic shear waves, as well as the petrofabric analyses of mantle nodules from kimberlite pipes. The anisotropy is principally due to the strain-induced lattice preferred orientation (LPO) of olivine. The combined use of these mantle samples,

PAUL SILVER; DAVID MAINPRICE; WALID BEN ISMAÏL; ANDRÉA TOMMASI; GUILHEM BARRUOL

392

Anisotropy of zigzag chains of palladium  

NASA Astrophysics Data System (ADS)

Ab initio calculations of the biaxial anisotropy of infinite Pd zigzag chains are presented. The simulations were performed with the Vienna Ab-Initio Simulation Package, using a tetragonal unit cell with a supercell approach where the atoms are repeated along the z-direction. The anisotropy is determined from the energies along the three principal directions [001], [100], and [010]. The second-order anisotropy constants K1 and K1' were extracted by fitting the calculated energy values to the phenomenological energy. The easiest magnetization direction is along the wire axis, whereas the hardest direction is perpendicular to the plane of the wire. The calculated anisotropy constants K1 and K1' are 5.5 MJ/m3 and -13.9 MJ/m3, respectively These anisotropies are large, but they are smaller than those of linear chains, because the zigzag shape leads to a quenched orbital moment.

Sahota, P. K.; Skomski, R.; Enders, A.; Sellmyer, D. J.; Kashyap, A.

2011-04-01

393

Optical and diamagnetic anisotropy of graphene oxide  

NASA Astrophysics Data System (ADS)

We have recently shown that graphene oxide (GO) emits a broad photoluminescence (PL) band in both solid and aqueous preparations. The origin of this PL is not yet well understood, but for absorptive and emissive optical processes originating in the two dimensional GO plane, one expects an in-plane polarization. Studies of optical anisotropy can therefore help to clarify the origin of the PL. Here we use a method of optical nanomagnetometry (Torrens, et al, JACS 129, p. 252 (2007)) to extract these quantities, also determining the magnetic anisotropy. We find that when aqueous preparations of GO are placed in a magnetic field, diamagnetically induced alignment leads to marked linear polarization anisotropy of absorbance and photoluminescence. By taking six optical measurements at each magnetic field, we are able to extract the intrinsic polarization anisotropies of optical absorption and emission of GO flakes and to quantify the orbital diamagnetic anisotropy. We discuss how these quantities give insight into electronic delocalization in these systems.

Exarhos, A. L.; Vora, P. M.; Lou, Z.; Johnson, A. T.; Kikkawa, J. M.

2009-03-01

394

Seismic anisotropy observed in upper oceanic crust  

SciTech Connect

Seismic anisotropy in the upper 150Om. of oceanic basement has been observed by polarization analysis of three-component bore-hole seismometer records. The most convincing evidence for the anisotropy is shear wave splitting for explosive sources at four azimuths. Compressional wave particle motion deviations suggestive of anisotropy are also observed but they may be caused by lateral inhomogeneities. The anisotropy was not resolved by travel-time analysis. The observed velocities and particle motions in the horizontal plane can be modelled to within a standard deviation by assuming a perfectly elastic, homogeneous, anisotropic layer 2 with hexagonal symmetry and a horizontal symmetry axis. The most probable cause of the anisotropy is preferred crack orientation.

Stephen, R.A.

1981-08-01

395

Anisotropy in high-resolution diffusion-weighted MRI and anomalous diffusion  

NASA Astrophysics Data System (ADS)

It is shown below that complex diffusion anisotropy observed in diffusion-weighted MRI can be fully accounted for by allowing for non-locality of the spatial operator in the diffusion equation. The anisotropy is represented by a distribution over directions on a sphere. It allows recognition of fiber tracts crossing at arbitrary angles. A simple generalization of the Stejskal-Tanner equation for the determination of the ODF is presented. Furthermore, an explicit solution of the Bloch-Torrey equation for an anisotropic time-fractional diffusion equation is obtained in terms of a generalized Mittag-Leffler type function.

Hanyga, A.; Seredy?ska, M.

2012-07-01

396

Anisotropy in high-resolution diffusion-weighted MRI and anomalous diffusion.  

PubMed

It is shown below that complex diffusion anisotropy observed in diffusion-weighted MRI can be fully accounted for by allowing for non-locality of the spatial operator in the diffusion equation. The anisotropy is represented by a distribution over directions on a sphere. It allows recognition of fiber tracts crossing at arbitrary angles. A simple generalization of the Stejskal-Tanner equation for the determination of the ODF is presented. Furthermore, an explicit solution of the Bloch-Torrey equation for an anisotropic time-fractional diffusion equation is obtained in terms of a generalized Mittag-Leffler type function. PMID:22706028

Hanyga, A; Seredy?ska, M

2012-05-14

397

Azimuthal Anisotropy Results from STAR  

NASA Astrophysics Data System (ADS)

Recent advances in the studies of eventwise azimuthal anisotropy from STAR have been made possible by the high statistics 200 GeV Au + Au datasets taken in 2010 and by the broad range of energies recorded during the first phase of the RHIC beam energy scan. The high statistics full energy Au + Au data have allowed precision studies of flow. These include detailed studies of flow versus non-flow, results of elliptic flow at high pT, the ?2 contributions from jets, and elliptic flow of multi-strange hadrons. Data from the beam energy scan enables STAR to search for evidence of the first order phase transition and the onset of deconfinement through the energy systematics of directed flow, elliptic flow, and azimuthally sensitive HBT.

Cebra, Daniel

2013-05-01

398

Optical anisotropy of (311) superlattices  

NASA Astrophysics Data System (ADS)

We report a calculation of the electronic properties of GaAs/AlAs (311) superlattices through the Brillouin zone using realistic values of the parameters in a tight-binding Hamiltonian. The nature and the localization of the lowest conduction bands for these low-symmetry structures is investigated and its origin is studied with respect to the layer number. A direct-gap-to-indirect-gap transition is evidenced for L=3 nm which is equal to the thickness for which the crossing of ?-X states occurs in the (100) superlattices. The in-plane anisotropy of the optical transitions and the relative intensity is found to be dependent on both the layer number and the nature of the states involved in the transition. Comparison with available experimental data is quite satisfactory.

Jouanin, C.; Hallaoui, A.; Bertho, D.

1994-07-01

399

Psychological correlates of handedness and corpus callosum asymmetry in autism: the left hemisphere dysfunction theory revisited.  

PubMed

Rightward cerebral lateralization has been suggested to be involved in the neuropathology of autism spectrum conditions. We investigated functional and neuroanatomical asymmetry, in terms of handedness and corpus callosum measurements in male adolescents with autism, their unaffected siblings and controls, and their associations with executive dysfunction and symptom severity. Adolescents with autism did not differ from controls in functional asymmetry, but neuroanatomically showed the expected pattern of stronger rightward lateralization in the posterior and anterior midbody based on their hand-preference. Measures of symptom severity were related to rightward asymmetry in three subregions (splenium, posterior midbody and rostral body). We found the opposite pattern for the isthmus and rostrum with better cognitive and less severe clinical scores associated with rightward lateralization. PMID:23179344

Floris, Dorothea L; Chura, Lindsay R; Holt, Rosemary J; Suckling, John; Bullmore, Edward T; Baron-Cohen, Simon; Spencer, Michael D

2013-08-01

400

Role of the corpus callosum in speech comprehension: interfacing syntax and prosody.  

PubMed

The role of the corpus callosum (CC) in the interhemispheric interaction of prosodic and syntactic information during speech comprehension was investigated in patients with lesions in the CC, and in healthy controls. The event-related brain potential experiment examined the effect of prosodic phrase structure on the processing of a verb whose argument structure matched or did not match the prior prosody-induced syntactic structure. While controls showed an N400-like effect for prosodically mismatching verb argument structures, thus indicating a stable interplay between prosody and syntax, patients with lesions in the posterior third of the CC did not show this effect. Because these patients displayed a prosody-independent semantic N400 effect, the present data indicate that the posterior third of the CC is the crucial neuroanatomical structure for the interhemispheric interplay of suprasegmental prosodic information and syntactic information. PMID:17196536

Friederici, Angela D; von Cramon, D Yves; Kotz, Sonja A

2007-01-01

401

The Association between Handedness, Brain Asymmetries, and Corpus Callosum Size in Chimpanzees (Pan troglodytes)  

PubMed Central

It has been suggested from studies in human subjects that sex, handedness, and brain asymmetries influence variation in corpus callosum (CC) size and these differences reflect the degree of connectivity between homotopic regions of the left and right cerebral hemispheres. Here we report that handedness is associated with variation in the size of the CC in chimpanzees. We further report that variation in brain asymmetries in a cortical region homologous to Broca's area is associated with the size of the CC but differs for right- and left-handed individuals. Collectively, the results suggest that individual differences in functional and neuroanatomical asymmetries are associated with CC variation not just in humans but also in chimpanzees and therefore may reflect a common neural basis for laterality in these 2 species.

Dunham, Leslie; Cantalupo, Claudio; Taglialatela, Jared

2007-01-01

402

Callosal disconnection syndrome after corpus callosum infarct: a diffusion tensor tractography study.  

PubMed

We report a patient who presented with callosal disconnection syndrome (CDS) and fiber disconnection on diffusion tensor tractography (DTT) after an infarct of the corpus callosum (CC). A 72-year-old woman presented with manifestations of CDS, including frontal alien hand syndrome (AHS), left agraphia, right hemiparesis, right somatosensory deficit, left neglect, and impaired visual recognition. DTT was performed for the evaluation of CC fibers, followed by comparison with DTT findings of normal subjects. DTT of the normal subject revealed bilateral extension of CC fibers to the frontal, parietal, and occipitotemporal cortices. By contrast, CC fibers of the patient revealed extensive disruption, with the exception of CC fibers passing through the anterior genu and the posterior splenium. The extensive disruption of CC fibers appears to explain the patient's various CDS symptoms. In brief, DTT could be useful for detection of CC lesions in patients with CDS. PMID:23246180

Jang, Sung Ho; Lee, Jun; Yeo, Sang Seok; Chang, Min Cheol

2012-12-12

403

Mobility decline in the elderly relates to lesion accrual in the splenium of the corpus callosum.  

PubMed

In a previous cross-sectional study on baseline data, we demonstrated that the volume of brain white matter hyperintensities (WMH) in the splenium of corpus callosum (SCC) predicted the current mobility function of older persons. The primary aim of this follow-up study was to determine the relation of WMH volume change in SCC (SCC-?WMH) with change in mobility measures. A secondary aim was to characterize the global and regional progression of WMH. Mobility function and WMH burden were evaluated at baseline and at 2 years in 77 community-dwelling individuals (baseline age, 82 ± 4). Regional WMH in SCC, as well as genu and body of corpus callosum, subregions of corona radiata, and superior longitudinal fasciculus were determined using a white matter parcellation atlas. The total WMH volume increased 3.3 ± 3.5 ml/year, mainly through enlargement. Significant WMH increases were observed in all selected regions, particularly within the corona radiata. While at baseline and follow-up we observed correlations between WMH burden and several measures of mobility, longitudinal change correlated only with change in chair rise (CR). SCC-?WMH showed the highest correlation (r =?-0.413, p = 0.0002) and was the best regional predictor of CR decline (OR = 1.5, r(2)?= 0.3). The SCC-?WMH was more than five times larger in the CR-decline group compared to the no-decline group (p = 0.0003). The SCC-?WMH (top quartile) showed a higher sensitivity/specificity for CR decline compared to change in total WMH, 63/88% versus 52/84%, respectively. The findings suggest that accrual of WMHs in posterior areas of the brain supporting inter-hemispheric integration and processing of visual-spatial information is a mechanism contributing to age-related mobility deterioration. PMID:21505765

Moscufo, Nicola; Wolfson, Leslie; Meier, Dominik; Liguori, Maria; Hildenbrand, Peter G; Wakefield, Dorothy; Schmidt, Julia A; Pearlson, Godfrey D; Guttmann, Charles R G

2011-04-20

404

Azimuthal anisotropy of the Pacific region  

NASA Astrophysics Data System (ADS)

Azimuthal anisotropy is the dependence of local seismic properties on the azimuth of propagation. We present the azimuthally anisotropic component of a 3D SV velocity model for the Pacific Ocean, derived from the waveform modeling of over 56,000 multi-mode Rayleigh waves followed by a simultaneous inversion for isotropic and azimuthally anisotropic vsv structure. The isotropic vsv model is discussed in a previous paper (A. Maggi, E. Debayle, K. Priestley, G. Barruol, Multi-mode surface waveform tomography of the Pacific Ocean: a close look at the lithospheric cooling signature, Geophys. J. Int. 166 (3) (2006). doi:10.1111/j.1365-246x.2006.03037.x). The azimuthal anisotropy we find is consistent with the lattice preferred orientation model (LPO): the hypothesis of anisotropy generation in the Earth's mantle by preferential alignment of anisotropic crystals in response to the shear strains induced by mantle flow. At lithospheric depths we find good agreement between fast azimuthal anisotropy orientations and ridge spreading directions recorded by sea-floor magnetic anomalies. At asthenospheric depths we find a strong correlation between fast azimuthal anisotropy orientations and the directions of current plate motions. We observe perturbations in the pattern of seismic anisotropy close to Pacific hot-spots that are consistent with the predictions of numerical models of LPO generation in plume-disturbed plate motion-driven mantle flow. These observations suggest that perturbations in the patterns of azimuthal anisotropy may provide indirect evidence for plume-like upwelling in the mantle.

Maggi, Alessia; Debayle, Eric; Priestley, Keith; Barruol, Guilhem

2006-10-01

405

Neoclassical study of temperature anisotropy in NSTX experiments using the GTC-NEO particle code  

NASA Astrophysics Data System (ADS)

Ion thermal transport in the National Spherical Torus eXperiment (NSTX) is often observed to be close to the neoclassical level. This makes self-consistent neoclassical simulations carried out with the GTC-NEO particle code highly relevant for studying transport-related issues in NSTX. GTC-NEO, which now treats multiple species of ion impurities[1], takes as input the experimental profiles from NSTX discharges and calculates fully non-local, self-consistent neoclassical fluxes and radial electric field. Given that the fraction of trapped particles is high in spherical tokamaks, one remarkable question is that of possible temperature anisotropy, which cannot be determined experimentally with the current diagnostics. Some experimental measurements assume the temperature anisotropy for the interpolation of raw data from diagnostics. This work describes new numerical diagnostics and computational improvements that were implemented in GTC-NEO to enable the study of temperature anisotropy.

Perkins, David; Ethier, Stephane; Wang, Weixing

2012-10-01

406

Local control of single atom magnetocrystalline anisotropy.  

PubMed

Individual Fe atoms on a Cu_{2}N/Cu(100) surface exhibit strong magnetic anisotropy due to the crystal field. We show that we can controllably enhance or reduce this anisotropy by adjusting the relative position of a second nearby Fe atom, with atomic precision, in a low-temperature scanning tunneling microscope. Local inelastic electron tunneling spectroscopy, combined with a qualitative first-principles model, reveal that the change in uniaxial anisotropy is driven by local strain due to the presence of the second Fe atom. PMID:24093296

Bryant, B; Spinelli, A; Wagenaar, J J T; Gerrits, M; Otte, A F

2013-09-17

407

Local Control of Single Atom Magnetocrystalline Anisotropy  

NASA Astrophysics Data System (ADS)

Individual Fe atoms on a Cu2N/Cu(100) surface exhibit strong magnetic anisotropy due to the crystal field. We show that we can controllably enhance or reduce this anisotropy by adjusting the relative position of a second nearby Fe atom, with atomic precision, in a low-temperature scanning tunneling microscope. Local inelastic electron tunneling spectroscopy, combined with a qualitative first-principles model, reveal that the change in uniaxial anisotropy is driven by local strain due to the presence of the second Fe atom.

Bryant, B.; Spinelli, A.; Wagenaar, J. J. T.; Gerrits, M.; Otte, A. F.

2013-09-01

408

Orbital anisotropy in paramagnetic manganese oxide nanostripes  

NASA Astrophysics Data System (ADS)

We have detected a clear magnetic anisotropy in the temperature and field dependent Mn L2,3 magnetic circular dichroism (MCD) spectra of 28 Å wide paramagnetic manganese oxide nanostripes, which we relate to the presence of a largely unquenched orbital moment revealed by MCD sum rule analysis. Polarization, angle, and temperature dependent linear dichroism spectra indicate that the observed anisotropy is related to a depletion of 3d states with ml=±2 orbital quantum number in the ground state of the paramagnetic system. Strongly anisotropic electrostatic coupling provides an internal source of spatial symmetry breaking which might generally yield paramagnetic anisotropy phenomena in 3d oxide nanostructures.

Altieri, S.; Allegretti, F.; Steurer, W.; Surnev, S.; Finazzi, M.; Sessi, V.; Brookes, N. B.; Valeri, S.; Netzer, F. P.

2013-06-01

409

Cosmic Ray Anisotropy with the KASCADE Experiment  

NASA Astrophysics Data System (ADS)

Anisotropies in the arrival directions of cosmic rays reflect their source distribution and propagation properties. In the presented analysis extensive air shower measurements with KASCADE are analyzed with respect to large and small scale anisotropies. The resulting upper limits on large scale anisotropy amplitudes of 10-3 to 10-2 restrict the parameter space of several propagation models. No cosmic ray point sources could be found in a sky survey of the northern hemisphere. Typical upper flux limits for point sources are around 10-10 m-2s-1.

Maier, Gernot; Antoni, T.; Apel, W. D.; Badea, A. F.; Bekk, K.; Bercuci, A.; Blümer, H.; Bozdog, H.; Brancus, I. M.; Büttner, C.; Chilingarian, A.; Daumiller, K.; Doll, P.; Engel, R.; Engler, J.; Feßler, F.; Gils, H. J.; Glasstetter, R.; Haungs, A.; Heck, D.; Hörandel, J. R.; Kampert, K.-H.; Klages, H. O.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Müller, M.; Obenland, R.; Oehlschläger, J.; Ostapchenko, S.; Petcu, M.; Rebel, H.; Risse, A.; Risse, M.; Roth, M.; Schatz, G.; Schieler, H.; Scholz, J.; Thouw, T.; Ulrich, H.; van Buren, J.; Vardanyan, A.; Weindl, A.; Wochele, J.; Zabierowski, J.

410

Haldane Gap and Fractional Oscillations in Gated Josephson Arrays  

NASA Astrophysics Data System (ADS)

An analogy between the twisted quantum xxz model and a gated Josephson junction array is used to predict sharp structure in the critical currents versus gate voltage, and fractional ac Josephson frequencies. We prove selection rules for level crossings which imply fractional periodicities of ground states with varying Aharonov-Bohm flux. Extrapolated numerical diagonalization on ladders indicates a Haldane gap at moderate easy-plane anisotropy, with vanishing superfluid stiffness. Physical parameters for experimental realization of these novel effects are proposed.

Altman, Ehud; Auerbach, Assa

1998-11-01

411

Analysis of the magnetic anisotropy induced by applying a magnetic field during the quenching process in amorphous ribbons  

NASA Astrophysics Data System (ADS)

The magnetic anisotropy induced in amorphous magnetic ribbons by applying a magnetic field to the melt during the solidification process is analyzed. Using a model based on the magnetization curve and on the evolution of the uniaxial torque with the applied magnetic field, the volume fractions of the sample affected by the different magnetic anisotropies are obtained for the ribbons of composition Fe80B20 and Co70Mn5Fe1Mo1Si14B9. The results are compared with those obtained in the ribbons of the same composition but with anisotropies induced by the static magnetic annealing. From these results, the different sources of the field-quenching-induced magnetic anisotropy in those amorphous magnetic ribbons are analyzed.

Tejedor, M.; García, J. A.; Carrizo, J.; Elbaile, L.; Santos, J. D.; Mira, J.; Rivas, J.

2004-11-01

412

Molecular-dynamics simulation of structural anisotropy in glassy metals and its relationship to magnetic anisotropy  

Microsoft Academic Search

Creep-induced magnetic anisotropy in metallic glass was investigated using a molecular-dynamics simulation. A model binary glass structure of 2048 particles interacting via Lennard–Jones potentials was creep deformed below its glass transition temperature. Creep deformation resulted in the bond-orientational anisotropy (BOA) within the first nearest-neighbor shell with a large sixth-order spherical harmonic component. The magnetic anisotropy estimated on the basis of

T. Tomida; T. Egami

1991-01-01

413

Photoionization affected by chemical anisotropy  

SciTech Connect

The kinetic constants of rhodamine 3B quenching by N,N-dimethyl aniline were extracted from the very beginning of the quenching kinetics, recently studied in a few solvents of different viscosities. They were well fitted with the conventional kinetic constant definition, provided the radial distribution function of simple liquids was ascribed to the reactant pair distribution and the contact electron transfer rate was different in all the cases. This difference was attributed to the chemical anisotropy averaging by the rotation of reactants, which is the faster in solvents of lower viscosity. With the proper choice of a space dependent encounter diffusion, the whole quenching kinetics was well fitted with an encounter theory, using the Marcus [J. Chem. Phys. 24, 966 (1956); 43, 679 (1965)] transfer rate instead of the contact Collins-Kimball [J. Colloid. Sci. 4, 425 (1949)] approximation. Not only the beginning and middle part of the quenching were equally well fitted, but the long time (Markovian) rate constant was also found to be the same as previously obtained. Moreover, the concentration dependencies of the fluorescence quantum yield and the Stern-Volmer constant were specified and await their experimental verification.

Gladkikh, V. S.; Burshtein, A. I. [Weizmann Institute of Science, Rehovot 76100 (Israel)

2007-01-07

414

Reduced Anterior Corpus Callosum White Matter Integrity is Related to Increased Impulsivity and Reduced Discriminability in Cocaine-Dependent Subjects: Diffusion Tensor Imaging  

Microsoft Academic Search

Brain imaging studies find evidence of prefrontal cortical dysfunction in cocaine-dependent subjects. Similarly, cocaine-dependent subjects have problems with behaviors related to executive function and impulsivity. Since prefrontal cortical axonal tracts cross between hemispheres in the corpus callosum, it is possible that white matter integrity in the corpus callosum could also be diminished in cocaine-dependent subjects. The purpose of this study

Frederick Gerard Moeller; Khader M Hasan; Joel L Steinberg; Larry A Kramer; Donald M Dougherty; Rafael M Santos; Ignacio Valdes; Alan C Swann; Ernest S Barratt; Ponnada A Narayana

2005-01-01

415

Anisotropy and Microstructure Analysis by Magnetic Measurement.  

National Technical Information Service (NTIS)

Analysis of digital data from the approach-to-saturation region of the hysteresis loop has been made convenient through the use of a microprocessor controlled hysteresigraph. To evaluate microstructure and magnetocrystalline anisotropy effects on the high...

G. F. Dionne J. A. Weiss G. A. Allen

1986-01-01

416

Scattering anisotropy-weighted mesoscopic imaging  

NASA Astrophysics Data System (ADS)

We report that when tissue images are formed via a small solid angle in the backward direction (i.e., back-directional gating), the image intensity is dominantly determined by tissue scattering anisotropy. Thus, this configuration allows for scattering anisotropy-weighted imaging that can provide an intrinsic contrast by capturing tissue structures and organizations. To demonstrate the immediate feasibility, we apply scattering anisotropy-weighted imaging to tissue blocks including basal-cell carcinomas as a pilot study. The main feature of our imaging approach is the high sensitivity to tumor locations and the simplicity for large-area visualization. We further envision that scattering anisotropy-weighted imaging could potentially be used to visualize tissue microenvironments in a mesoscopic (between microscopic and macroscopic) imaging setting.

Xu, Zhengbin; Somani, Ally-Khan; Kim, Young L.

2012-09-01

417

Anisotropy in a non-singular bounce  

NASA Astrophysics Data System (ADS)

Following recent claims relative to the question of large anisotropy production in regular bouncing scenarios, we study the evolution of such anisotropies in a model where an ekpyrotic phase of contraction is followed by domination of a Galileon-type Lagrangian which generates a non-singular bounce. We show that the anisotropies decrease during the phase of ekpyrotic contraction (as expected) and that they can be constrained to remain small during the non-singular bounce phase (a non-trivial result). Specifically, we derive the e-folding number of the phase of ekpyrotic contraction which leads to a present-day anisotropy in agreement with current observational bounds. Communicated by P Singh

Cai, Yi-Fu; Brandenberger, Robert; Peter, Patrick

2013-04-01

418

Tailoring Exchange Bias through Shape Anisotropy  

NASA Astrophysics Data System (ADS)

The exchange bias of Fe lines on top of a continuous FeF2 antiferromagnetic layer was investigated as a function of the orientation of the lines with respect to the cooling field and the applied magnetic field. Fe lines of 300-nm width and 100-?m length were defined by electron-beam lithography and subsequent ion-milling. The orientational dependence of the exchange bias shows that the competition between shape anisotropy and unidirectional exchange bias anisotropy can be used to adjust the exchange bias and the coercivity. Numerical simulations with a coherent rotation model illustrate a rich phase diagram with particularly interesting behavior for the case in which the shape anisotropy is slightly smaller than the unidirectional anisotropy. In this case an exchange bias can even be observed with the applied field perpendicular to the cooling field direction.

Hoffmann, Axel; Grimsditch, M.; Pearson, J. E.; Nogués, J.; Macedo, W. A. A.; Schuller, I. K.

2003-03-01

419

Scattering anisotropy-weighted mesoscopic imaging.  

PubMed

We report that when tissue images are formed via a small solid angle in the backward direction (i.e., back-directional gating), the image intensity is dominantly determined by tissue scattering anisotropy. Thus, this configuration allows for scattering anisotropy-weighted imaging that can provide an intrinsic contrast by capturing tissue structures and organizations. To demonstrate the immediate feasibility, we apply scattering anisotropy-weighted imaging to tissue blocks including basal-cell carcinomas as a pilot study. The main feature of our imaging approach is the high sensitivity to tumor locations and the simplicity for large-area visualization. We further envision that scattering anisotropy-weighted imaging could potentially be used to visualize tissue microenvironments in a mesoscopic (between microscopic and macroscopic) imaging setting. PMID:23085898

Xu, Zhengbin; Somani, Ally-Khan; Kim, Young L

2012-09-01

420

Scattering anisotropy-weighted mesoscopic imaging  

PubMed Central

Abstract. We report that when tissue images are formed via a small solid angle in the backward direction (i.e., back-directional gating), the image intensity is dominantly determined by tissue scattering anisotropy. Thus, this configuration allows for scattering anisotropy-weighted imaging that can provide an intrinsic contrast by capturing tissue structures and organizations. To demonstrate the immediate feasibility, we apply scattering anisotropy-weighted imaging to tissue blocks including basal-cell carcinomas as a pilot study. The main feature of our imaging approach is the high sensitivity to tumor locations and the simplicity for large-area visualization. We further envision that scattering anisotropy-weighted imaging could potentially be used to visualize tissue microenvironments in a mesoscopic (between microscopic and macroscopic) imaging setting.

Xu, Zhengbin; Somani, Ally-Khan; Kim, Young L.

2012-01-01

421

Magnetic anisotropy due to the Casimir effect  

SciTech Connect

We consider the Casimir interaction between a ferromagnetic and a nonmagnetic mirror and show how the Casimir effect gives rise to a magnetic anisotropy in the ferromagnetic layer. The anisotropy is out of plane if the nonmagnetic plate is optically isotropic. If the nonmagnetic plate shows a uniaxial optical anisotropy (with optical axis in the plate plane), we find an in-plane magnetic anisotropy. In both cases, the energetically most favorable magnetization orientation is given by the competition between polar, longitudinal, and transverse contributions to the magneto-optical Kerr effect and will therefore depend on the interplate distance. Numerical results will be presented for a magnetic plate made out of Fe and nonmagnetic plates of Au (optically isotropic), quartz, calcite, and barium titanate (all uniaxially birefringent).

Metalidis, G.; Bruno, P. [Institut fuer Theoretische Festkoerperphysik, Karlsruhe Institut fuer Technologie (KIT), D-76131 Karlsruhe (Germany); European Synchrotron Radiation Facility, Boite Postale 220, F-38043 Grenoble Cedex (France)

2010-02-15

422

Anisotropy of Magnetic Susceptibility of Rocks and Minerals  

Microsoft Academic Search

There are two predominant causes for the anisotropy of magnetic susceptibility of rocks and ferrimagnetic minerals: the shape of the magnetic material and crystalline anisotropy. In general, these factors may operate simultaneously, but in rock magnetism their effects are frequently separable. In the case of shape-effect anisotropy, one can predict the degree of anisotropy by an ellipsoidal approximation, provided that

S. Uyeda; M. D. Fuller; J. C. Belshé; R. W. Girdler

1963-01-01

423

Seismic Anisotropy of Soft Sands, Offshore Western AUstralia  

Microsoft Academic Search

Seismic anisotropy is commonly measured in sand shale environment. Intrinsic polar anisotropy of the shale and its effect on seismic data processing and analysis is well established and reasonably well understood. In sandstone, azimuthal anisotropy is often detected and is typically connected to an in situ stress regime and the brittleness of the rock. This type of anisotropy, commonly referred

M. Urosevic; B. Gurevich

2007-01-01

424

Magnetic Anisotropy of a Single Cobalt Nanocluster  

Microsoft Academic Search

Using a new micro-SQUID setup, we investigate magnetic anisotropy in a single 1000-atom cobalt cluster. This system opens new fields in the characterization and understanding of the origin of magnetic anisotropy in such nanoparticles. For this purpose, we report three-dimensional switching field measurements performed on a 3 nm cobalt cluster embedded in a niobium matrix. We are able to separate

M. Jamet; W. Wernsdorfer; C. Thirion; D. Mailly; V. Dupuis; P. Mélinon; A. Pérez

2001-01-01

425

A reversible lesion of the corpus callosum splenium with adult influenza-associated encephalitis\\/encephalopathy: a case report  

Microsoft Academic Search

ABSTRACT: INTRODUCTION: Influenza virus-associated encephalitis\\/encephalopathy is a severe childhood illness with a poor prognosis. Adult case reports are rare and, to date, there have been no reports of adults with a mild subcortical encephalopathy with reversible lesions of the corpus callosum splenium. CASE PRESENTATION: A previously healthy 35-year-old man presented with acute progressive tetraplegia, transcortical motor aphasia and a mild

En Kimura; Sadahisa Okamoto; Yuji Uchida; Tomoo Hirahara; Tokunori Ikeda; Teruyuki Hirano; Makoto Uchino

2008-01-01

426

Weak or missing paw lateralization in a mouse strain (I\\/LnJ) with congenital absence of the corpus callosum  

Microsoft Academic Search

Ward et al. (Brain Research 424 (1987) 84-88) have reported that reduced size of the corpus callosum (CC) was associated with a lower degree of paw preference in the mouse strain 129\\/J but not in the strain BALB\\/cCF. Both strains show individually different degrees of development of the CC but mice completely lacking CC occur rarely. The mouse strain I\\/LnJ

D Gruber; R Waanders; R L Collins; D P Wolfer; H P Lipp

1991-01-01

427

Novel compound heterozygous mutations of the SPG11 gene in Korean families with hereditary spastic paraplegia with thin corpus callosum  

Microsoft Academic Search

Hereditary spastic paraplegia with thin corpus callosum (HSP-TCC) is one of the most common complicated forms of autosomal\\u000a recessive hereditary spastic paraplegia (HSP). Mutation in SPG11 gene, which is mapped to chromosome 15q21, was recently found to be a major cause of this variant form of HSP. The aim of\\u000a this study is to investigate SPG11 mutations and clinical manifestations

Sung-Min Kim; Jeong-Seon Lee; Suhyun Kim; Hyun-Jung Kim; Man-Ho Kim; Kyoung-Min Lee; Yoon-Ho Hong; Kyung Seok Park; Jung-Joon Sung; Kwang-Woo Lee

2009-01-01

428

Transient splenial lesion of the corpus callosum associated with antiepileptic drugs: evaluation by diffusion-weighted MR imaging  

Microsoft Academic Search

.  \\u000a Transient focal lesions in the splenium of the corpus callosum have been reported in epileptic patients receiving antiepileptic\\u000a drugs. The characteristic imaging features included an oval high signal lesion on T2-weighted images in the central part of\\u000a the splenium, no enhancement on post-contrast MR images, and complete reversibility without specific treatment. We report\\u000a identical MR imaging findings in a

Masayuki Maeda; Takashi Shiroyama; Hirokazu Tsukahara; Taro Shimono; Shigeki Aoki; Kan Takeda

2003-01-01

429

MRI identification of the rostral-caudal pattern of pathology within the corpus callosum in the cuprizone mouse model  

Microsoft Academic Search

Purpose: To characterize and compare histological and MRI-based changes within the corpus callosum (CC) in the cuprizone mouse model of multiple sclerosis (MS). Materials and Methods: A total of 12 C57\\/BL6 mice were fed cuprizone from eight weeks of age for four weeks. One cohort of six cuprizone and two control mice were scanned with a T2-weighted (T2W) sequence. The

Qi-Zhu Wu; Qing Yang; Holly S. Cate; Dennis Kemper; Michele Binder; Hong-Xin Wang; Ke Fang; Melissa J. Quick; Mark Marriott; Trevor J. Kilpatrick; Gary F. Egan

2008-01-01

430

HIV1 gp120Induced Axonal Injury Detected by Accumulation of ?-Amyloid Precursor Protein in Adult Rat Corpus Callosum  

Microsoft Academic Search

HIV-1 brain infection induces neurodegeneration. While most studies focus on HIV-1-mediated neuronal injury, relatively few\\u000a have investigated HIV-1-associated white matter damage. Corpus callosum (CC) is one of frequently involved white matter structures\\u000a in HIV-1-associated white matter damage. Utilizing a model of ex vivo treatment of brain slice containing CC with HIV-1 glycoprotein\\u000a 120 (gp120), we examined axonal injury by analyzing

Jingdong Zhang; Jianuo Liu; Bryan Katafiasz; Howard Fox; Huangui Xiong

431

Diabetes insipidus with impaired osmotic regulation in septo-optic dysplasia and agenesis of the corpus callosum  

Microsoft Academic Search

The clinical and endocrinological findings in 24 children with septo-optic dysplasia and\\/or agenesis of the corpus callosum are described with particular reference to posterior pituitary function. Nine had diabetes insipidus. The prevalence of diabetes insipidus was similar in children with complete and incomplete forms of septo-optic dysplasia. Maintenance of normal osmotic balance was very difficult in six of these children,

N Masera; D B Grant; R Stanhope; M A Preece

1994-01-01

432

Pai syndrome: a further report of a case with bifid nose, lipoma, and agenesis of the corpus callosum  

Microsoft Academic Search

Introduction  Pai syndrome is a rare genetic disorder mainly characterized by the association of complete median cleft of palate and upper\\u000a lip, midline facial cutaneous, and mid-anterior alveolar process polyps, duplicated maxillary median frenulum, bifid nose,\\u000a and midline lipoma(s) of the central nervous system, in particular, the corpus callosum. The incidence of this syndrome is\\u000a much higher in males than in

S. Savasta; S. Chiapedi; S. Perrini; E. Tognato; L. Corsano; A. Chiara

2008-01-01

433

ASSOCIATION OF SEVERE AUTOSOMAL RECESSIVE OSTEOPETROSIS AND DANDY-WALKER SYNDROME WITH AGENESIS OF THE CORPUS CALLOSUM  

Microsoft Academic Search

A severe form of autosomal recessive osteopetrosis associated with Dandy-Walker syndrome and agene- sis of the corpus callosum is reported in a full-term boy born to consanguineous parents. The diagnosis was made shortly after birth. Clinical features were cranio-facial dysmorphy, macrocephaly, hepato- splenomegaly, severe anemia and thrombocytopenia. Skeletal radiographs revealed generalized increase in bone density and abnormal metaphyseal remodeling. Cranial

H. BEN HAMOUDA; M. N. SFAR; R. BRAHAM; M. BEN SALAH; A. AYADI; H. SOUA; H. HAMZA; M. T. SFAR

2001-01-01

434

Calcified meconium balls in a newborn: an unusual case with imperforate anus, rectourinary fistula, colpocephaly, and agenesis of corpus callosum  

Microsoft Academic Search

Calcified intraluminal meconium is a rare finding in newborn infants. It is often associated with communication between the\\u000a urinary and gastrointestinal tracts. Intra-abdominal calcifications are unusual radiographic findings in the newborn and can\\u000a easily be misinterpreted as meconium peritonitis. We report on a newborn infant with anorectal malformation, meconium balls,\\u000a intraluminal calcifications, colpocephaly, and agenesis of the corpus callosum, a

Surasak Puvabanditsin; Eugene Garrow; Nachu Chinnakaruppan; Mayoor Bhatt; Erik Brandsma

2009-01-01

435

Agenesis of the Corpus Callosum Associated With DiGeorge-Velocardiofacial Syndrome: A Case Report and Review of the Literature  

Microsoft Academic Search

We report a patient with clinical and cytogenetic findings consistent with DiGeorge-velocardiofacial syndrome and agenesis of the corpus callosum. This patient represents the first report of a case of DiGeorge-velocardiofacial syndrome associated with such a central nervous system abnormality. This case, together with previous reports in the literature, suggests that structural brain abnormalities, and in particular abnormalities of the corpus

Nathan C. Kraynack; Robert W. Hostoffer; Nathaniel H. Robin

1999-01-01

436

Anterior interhemispheric calcified lipoma together with subcutaneous lipoma and agenesis of corpus callosum: a rare manifestation of midline craniofacial dysraphism.  

PubMed

Frontonasal dysplasia (FND) or craniofacial dysraphism includes a variety of craniofacial defects. FNDs are rarely associated with intracranial lipoma. The majority of intracranial lipomas are incidentally identified on radiological examinations. They are commonly accompanied by other congenital intracranial malformations. Moreover, they are rarely associated with subcutaneous lipoma. We present a rare case of midline craniofacial dysraphism with interhemispheric calcified lipoma together with subcutaneous lipoma and agenesis of the corpus callosum. PMID:23504434

Karakas, Omer; Karakas, Ekrem; Boyac?, Fat?ma Nurefsan; Celik, Bahattin; Cullu, Nesat

2013-03-17

437

Measurements of the cosmic microwave background anisotropies with ARCHEOPS  

NASA Astrophysics Data System (ADS)

ARCHEOPS is a balloon-borne instrument dedicated to measure cosmic microwave background (CMB) temperature anisotropies at high angular resolution (about 10 ') over a large fraction (30%) of the sky in the (sub)millimetre domain (from 143 to 545 GHz). Here, we describe the latest results from the instrument during the last flight that happened during the Arctic night from Kiruna (Sweden) to Russia in February 2002. Various sources of noise are discussed, including atmospheric noise, parasitic noise, photon noise, cosmic variance,... The white noise sensitivity for the eight best bolometers is below 200 ?K CMB s 1/2 per bolometer. Best estimates of the angular power spectrum of the CMB anisotropies are presented, giving for the first time a continuous link between COBE scales and the first acoustic peak. The consequences in terms of cosmological parameters are outlined that reinforce the flatness of the Universe. Other results include the first measurement of polarization and accurate maps of the galactic plane diffuse (sub)millimetre emission.

Beno??t, A.; Archeops Collaboration

2004-01-01

438

Cerebral specialization and interhemispheric communication: does the corpus callosum enable the human condition?  

PubMed

The surgical disconnection of the cerebral hemispheres creates an extraordinary opportunity to study basic neurological mechanisms: the organization of the sensory and motors systems, the cortical representation of the perceptual and cognitive processes, the lateralization of function, and, perhaps most importantly, how the divided brain yields clues to the nature of conscious experience. Studies of split-brain patients over the last 40 years have resulted in numerous insights into the processes of perception, attention, memory, language and reasoning abilities. When the constellation of findings is considered as a whole, one sees the cortical arena as a patchwork of specialized processes. When this is considered in the light of new studies on the lateralization of functions, it becomes reasonable to suppose that the corpus callosum has enabled the development of the many specialized systems by allowing the reworking of existing cortical areas while preserving existing functions. Thus, while language emerged in the left hemisphere at the cost of pre-existing perceptual systems, the critical features of the bilaterally present perceptual system were spared in the opposite half-brain. By having the callosum serve as the great communication link between redundant systems, a pre-existing system could be jettisoned as new functions developed in one hemisphere, while the other hemisphere could continue to perform the previous functions for both half-brains. Split-brain studies have also revealed the complex mosaic of mental processes that participate in human cognition. And yet, even though each cerebral hemisphere has its own set of capacities, with the left hemisphere specialized for language and speech and major problem-solving capacities and the right hemisphere specialized for tasks such as facial recognition and attentional monitoring, we all have the subjective experience of feeling totally integrated. Indeed, even though many of these functions have an automatic quality to them and are carried out by the brain prior to our conscious awareness of them, our subjective belief and feeling is that we are in charge of our actions. These phenomena appear to be related to our left hemisphere's interpreter, a device that allows us to construct theories about the relationship between perceived events, actions and feelings. PMID:10869045

Gazzaniga, M S

2000-07-01

439

Fractional Schrödinger equation.  

PubMed

Some properties of the fractional Schrödinger equation are studied. We prove the Hermiticity of the fractional Hamilton operator and establish the parity conservation law for fractional quantum mechanics. As physical applications of the fractional Schrödinger equation we find the energy spectra of a hydrogenlike atom (fractional "Bohr atom") and of a fractional oscillator in the semiclassical approximation. An equation for the fractional probability current density is developed and discussed. We also discuss the relationships between the fractional and standard Schrödinger equations. PMID:12513557

Laskin, Nick

2002-11-18

440

Tailoring the magnetic anisotropy of thin film permalloy microstrips by combined shape and induced anisotropies  

NASA Astrophysics Data System (ADS)

The sensitivity of magnetic sensors based on the Giant Magneto-Impedance effect can be enhanced using high permeability materials with a well-defined but small transverse anisotropy. We describe an experimental study performed on multilayered, permalloy-based thin films deposited by sputtering under a magnetic field that produces a homogeneous uniaxial anisotropy in the plane of the film. Patterning of the deposit by photolithographic methods into strip-shaped samples (with their long direction perpendicular to the induced anisotropy) establishes a longitudinal shape anisotropy that competes with the transversal one induced at deposition. The combination and competition of the two mutually perpendicular uniaxial anisotropies result in an effective one with a reduced magnitude (the difference between both of them) in the transversal direction. As the strength of the shape anisotropy is determined by the relation between width and length of the stripe, the magnitude of the effective anisotropy can be conveniently modulated by adequately selecting the aspect ratio of the patterned sample. The hysteresis loops measured by Kerr effect magnetometry confirm that the effective transversal anisotropy field can be reduced from 5 to 1 Oe which should concomitantly increase the sensitivity of thin film magneto-impedance sensors.

García-Arribas, Alfredo; Fernández, Eduardo; Svalov, Andrey V.; Kurlyandskaya, Galina V.; Barrainkua, Ane; Navas, David; Barandiaran, José Manuel

2013-04-01

441

Magnetic anisotropy in the trenton limestone: Results of a new technique, anisotropy of anhysteretic susceptibility  

Microsoft Academic Search

A new method for determining magnetic anisotropy using anhysteric remanence susceptibility is described. The magnetic fabric of a collection of Trenton Limestone specimens has been determined using this method, as well as by conventional anisotropy of magnetic susceptibility. The results demonstrate the usefulness of the new method for finding the magnetic fabric of rock units such as the Trenton in

Chad McCabe; Michael Jackson; Brooks B. Ellwood

1985-01-01

442

Montmorillonite alignment induced by magnetic field: Evidence based on the diffusion anisotropy of water molecules  

Microsoft Academic Search

Diffusion coefficients of water in Na-montmorillonite (Na-mon) suspensions have been determined by pulsed-field gradient spin–echo (PGSE) NMR spectroscopy for three directions (x, y, and z), where x and y mean the directions perpendicular to the static magnetic field, and z the direction parallel to it. Diffusion anisotropy was observed in the suspensions with Na-mon weight fractions of 0.63, 1.82, and

Takafumi Takahashi; Takahiro Ohkubo; Yasuhisa Ikeda

2006-01-01

443

Seismic Anisotropy in the Transition Zone  

NASA Astrophysics Data System (ADS)

The transition zone plays a key role in the understanding of mantle convection, particularly the 660km-discontinuity which might inhibit the passage of matter between the upper and the lower mantle. An efficient way for investigating mantle flow circulation is to map seismic anisotropy in this depth range. There are some good evidences of seismic anisotropy in the top 300km of the upper mantle and the bottom D"-layer. Montagner and Kennett (G.J.I., 1996) found that radial anisotropy (transverse isotropy with vertical symmetry axis) is also necessary in the mantle transition zone between 410 and 900km depth for explaining eigenfrequency data. There are also some other evidences of anisotropy by using different kinds of body wave data (P-to-S receiver functions, shear-wave splitting...), demonstrating lateral variations of anisotropy in the transition zone. On a global scale, Trampert and van Heijst} (2002) using overtone data show a long-wavelength azimuthal anisotropic structure in the transition zone. The rms amplitude of their lateral variations is small (about 1%), much smaller than in the uppermost and lowermost mantle. If we want to obtain a global mapping of seismic anisotropy in the upper (410-660km) and lower (660-900km) transition zones, only overtones of surface waves (higher modes) are able to achieve that. We will present some preliminary results of simultaneous inversion of Rayleigh and Love wave overtone data obtained by Beucler et al. (2006) and Visser et al. (2008). We obtain some new determinations of seismic anisotropy in the transition zone, from these higher mode phase velocity measurements. We show that seismic anisotropy is small below most of the transition zones except below subduction zones, all around the Pacific Ocean and beneath eastern Eurasia where the slab is stagnant. Since the presence of anisotropy is due to intense deformation of minerals, it is related to boundary layers and to flow circulation in convective systems. Therefore, the transition zone seems to be a secondary boundary layer within the mantle.

Montagner, J.; Burgos, G.; Beucler, E.; Drilleau, M.; Capdeville, Y.; Mocquet, A.; Trampert, J.

2011-12-01

444

Planum Temporale Asymmetries Correlate with Corpus Callosum Axon Fiber Density in Chimpanzees (Pan troglodytes)  

PubMed Central

The corpus callosum (CC) is the major white matter tract that connects the two cerebral hemispheres. Some have theorized that individual differences in behavioral and brain asymmetries are linked to variation in the density of axon fibers that traverse different sections of the CC. In this study, we examined whether variation in axon fiber density in the CC was associated with variation in asymmetries in the planum temporale (PT) in a sample of 20 post-mortem chimpanzee brains. We further tested for sex differences in small and large CC fiber proportions and density in the chimpanzees. We found that the distribution of small and large fibers within the CC of chimpanzees follows a similar pattern to those reported in humans. We also found that chimpanzees with larger asymmetries in the PT had fewer large fibers in the posterior portion of the CC, particularly among females. As has been reported in human brains, the findings reported here indicate that individual differences in brain asymmetries are associated with variation in interhemispheric connectivity as manifest in axon fiber density and size.

Hopkins, William D.; Pilger, John F.; Storz, Rachel; Ambrose, Alex; Hof, Patrick R.; Sherwood, Chet C.

2012-01-01

445

Investigating the role of the corpus callosum in regulating motor overflow in multiple sclerosis.  

PubMed

The corpus callosum (CC) is commonly affected in multiple sclerosis (MS), however, sensitive behavioral measures of MS-related CC pathology are lacking. The CC is considered a key structure in the mediation of a type of involuntary movement known as motor overflow. In this study, we sought to characterize the impact of CC damage on motor overflow in MS. Twenty MS participants and 20 controls performed a unilateral force production task. Motor overflow (involuntary force) in the non-active hand was measured while the active hand performed the task. CC volume and lesion load were calculated for MS participants using T2-weighted MRI. We found no group differences in motor overflow; however, motor overflow correlated significantly with MS disease severity [Expanded disability status scale (EDSS)]. CC damage (lesions and decreased volume) did not correlate with motor overflow. This study suggests that CC damage may not directly lead to changes in the regulation of motor overflow. Rather, findings support the notion that a wider network of structures may mediate the production and suppression of motor overflow. PMID:23589195

Ternes, Anne-Marie; Maller, Jerome J; Fielding, Joanne; Addamo, Patricia; White, Owen; Georgiou-Karistianis, Nellie

2013-04-16

446

Splenium of Corpus Callosum: Patterns of Interhemispheric Interaction in Children and Adults  

PubMed Central

The splenium of the corpus callosum connects the posterior cortices with fibers varying in size from thin late-myelinating axons in the anterior part, predominantly connecting parietal and temporal areas, to thick early-myelinating fibers in the posterior part, linking primary and secondary visual areas. In the adult human brain, the function of the splenium in a given area is defined by the specialization of the area and implemented via excitation and/or suppression of the contralateral homotopic and heterotopic areas at the same or different level of visual hierarchy. These mechanisms are facilitated by interhemispheric synchronization of oscillatory activity, also supported by the splenium. In postnatal ontogenesis, structural MRI reveals a protracted formation of the splenium during the first two decades of human life. In doing so, the slow myelination of the splenium correlates with the formation of interhemispheric excitatory influences in the extrastriate areas and the EEG synchronization, while the gradual increase of inhibitory effects in the striate cortex is linked to the local inhibitory circuitry. Reshaping interactions between interhemispherically distributed networks under various perceptual contexts allows sparsification of responses to superfluous information from the visual environment, leading to a reduction of metabolic and structural redundancy in a child's brain.

Knyazeva, Maria G.

2013-01-01

447

Correlation between corpus callosum shape and cognitive performance in healthy young adults.  

PubMed

Corpus callosum (CC) might be related to cognitive performance because of its role in interhemispheric communication. Previous research has focused mainly on volumetric analyses of the CC, yielding contradictory results to some extent. Shape is an approach that integrates and extends the data obtained with the volumetric methodology. Here, we analyze the relationships between midsagittal CC shape variation and several cognitive measures. 2D coordinates from 102 MRI-scanned young adult human CCs were superimposed through a Procrustes approach. The residual variation was regressed onto 21 cognitive measures completed by the participants. Most of these measures (including general intelligence, working memory, executive functioning, and mental speed) were unrelated to midsagittal CC morphology. However, attentional control did show consistent and significant correlations with CC shape variation. Slower responses in attentional control were systematically associated with more curved and thinner CC, with consequent rotation of the splenium and the genu. Although the magnitude of the correlations suggests a small relationship of midsagittal CC geometry and attention, the results provide interesting clues regarding the links between brain anatomical configuration and human cognitive function. PMID:22581173

Martín-Loeches, Manuel; Bruner, Emiliano; de la Cuétara, José Manuel; Colom, Roberto

2012-05-13