Fractional Anisotropy In Corpus Callosum Research Articles

Corpus callosum and cerebellum participate in semantic dysfunction of Parkinson's disease: a diffusion tensor imaging-based cross-sectional study.

Language dysfunction is common in Parkinson's disease (PD) patients, among which, the decline of semantic fluency is usually observed. This study aims to explore the relationship between white matter (WM) alterations and semantic fluency changes in PD patients. 127 PD patients from the Parkinson's Progression Markers Initiative cohort who received diffusion tensor imaging scanning, clinical assessment and semantic fluency test (SFT) were included. Tract-based special statistics, automated fiber quantification, graph-theoretical and network-based analyses were performed to analyze the correlation between WM structural changes, brain network features and semantic fluency in PD patients. Fractional anisotropy of corpus callosum, anterior thalamic radiation, inferior front-occipital fasciculus, and uncinate fasciculus, were positively correlated with SFT scores, while a negative correlation was identified between radial diffusion of the corpus callosum, inferior longitudinal fasciculus, and SFT scores. Automatic fiber quantification identified similar alterations with more details in these WM tracts. Brain network analysis positively correlated SFT scores with nodal efficiency of cerebellar lobule VIII, and nodal local efficiency of cerebellar lobule X. WM integrity and myelin integrity in the corpus callosum and several other language-related WM tracts may influence the semantic function in PD patients. Damage to the cerebellum lobule VIII and lobule X may also be involved in semantic dysfunction in PD patients.

Significance of Corticospinal, Associative and Inter-Hemispheric Tracts for the Development of Posttraumatic Hemiparesis

Motor disorders are among the most common consequences of severe craniocerebral injury (traumatic brain injury — TBI). Deeper insights into pathophysiological mechanisms of these disorders is important both from a theoretical point of view and in terms of improving neurorehabilitation approaches.The aim of the study was to investigate the correlation of right–sided posttraumatic hemiparesis severity with composite characteristics of fractional anisotropy (FA) in the segments of the corpus callosum (CC), corticospinal tract (CST) and the inferior fronto-occipital fasciculus (IFO) at different stages of traumatic disease (acute, subacute and long-term periods).Material and methods. Cases of 43 patients with TBI were analyzed (28 men and 15 women aged 13 to 59 years, mean age 28±9 years). Forty patients were diagnosed with severe TBI with diffuse axonal damage, three patients had moderate severity TBI. Long-term follow up included continuous clinical and neurological examination with evaluation of patient’s level of consciousness using the CRS-R scale, and the degree of motor deficits in right-sided hemiparesis using a five-point scale. During three post-TBI periods (up to 1 month, from 1 to 6 months, and from 6 to 12 months), patients were examined using diffusion tensor MRI (DTI), tractography and FA. Motor, cortico-spinal tracts and IFO were divided by measurement grid, correlations between FA and scores of right-sided hemiparesis were calculated for each segment.Results. FA correlations (P0.05) with the severity of hemiparesis were established not only for CST motor-specific segments, but also for some CC and IFO segments. In the early period of TBI significant correlations with hemiparesis severity were found not only in the contralateral CST segments, but also in the ipsilateral ones. Significant differences in FA in the related CC and CST segments were found between the groups with good and limited motor recovery: at all stages after TBI, FA was higher in patients with successful recovery.Conclusion. The results of the study provide better insight into pathophysiological mechanisms of post-traumatic motor disorders development, therefore favoring optimization of therapeutic strategies.

Whole Brain and Corpus Callosum Fractional Anisotropy Differences in Patients with Cognitive Impairment.

Diffusion tensor imaging (DTI) is an MRI analysis method that could help assess cognitive impairment (CI) in the ageing population more accurately. In this research, we evaluated fractional anisotropy (FA) of whole brain (WB) and corpus callosum (CC) in patients with normal cognition (NC), mild cognitive impairment (MCI), and moderate/severe cognitive impairment (SCI). In total, 41 participants were included in a cross-sectional study and divided into groups based on Montreal Cognitive Assessment (MoCA) scores (NC group, nine participants, MCI group, sixteen participants, and SCI group, sixteen participants). All participants underwent an MRI examination that included a DTI sequence. FA values between the groups were assessed by analysing FA value and age normative percentile. We did not find statistically significant differences between the groups when analysing CC FA values. Both approaches showed statistically significant differences in WB FA values between the MCI-SCI and MCI-NC groups, where the MCI group participants showed the highest mean FA and highest mean FA normative percentile results in WB.

Tau pathology relates to regional microstructural alterations of cerebral white matter in older adults with diverse cognitive spectrum

AbstractBackgroundGrowing evidences suggest that degeneration of cerebral white matter (WM) occurs in Alzheimer’s disease (AD) independently of cerebrovascular risks or injury. Previous studies using diffusion tensor imaging (DTI) have reported a loss of WM microstructural integrity in the corpus callosum (CC) and cingulum (CG) in AD dementia and mild cognitive impairment (MCI). However, only limited information is available for the relationship of in vivo AD‐specific pathologies including beta‐amyloid (Aβ) and tau accumulation with WM microstructal alterations. Thus, we aimed to examine the association between in vivo AD pathologies and microstructural integrity of the CC and CG through cross‐sectional and longitudinal approaches.MethodA total of 170 (74 cognitively normal, 58 MCI, and 38 AD dementia) older adults from the Korean Brain Aging Study for the Early diagnosis and prediction of Alzheimer’s disease cohort were included. All participants underwent comprehensive clinical assessment and multi‐modal brain imaging including [11C]‐Pittsburgh‐Compound‐B‐positron emission tomography (PET), 18F‐AV‐1451 PET, and DTI. The mean fractional anisotropy (FA) values were obtained for 2 regions of interests, the CC and CG on DTI. The data was analyzed using linear regression model adjusted for age, sex, APOE4 positivity, and vascular risk factor score. Regression‐based mediation analysis was also conducted to assess the mediation of tau for the relationship between Aβ and FA.ResultIn cross‐sectional analyses for baseline data, global tau deposition had a significant negative association with both CC and CG FA (β = ‐0.013, p = 0.004 and β = ‐0.011, p = 0.002), while global Aβ retention showed a negative association with only CG FA (β = ‐0.015, p = 0.004). Longitudinal analyses revealed that higher tau deposition at baseline was associated with both greater reduction of both CC and CG FA over 2 years (β = ‐0.010, p = 0.001 and β = ‐0.005, p = 0.046), whereas Aβ was associated with neither CC nor CG FA change over the period. Additional mediation analysis demonstrated that the cross‐sectional association between Aβ and CG FA was mediated by tau deposition, while there was no direct relationship between the two.ConclusionOur findings suggest that regional alterations of WM microstructural integrity in MCI and AD dementia, which occurs independently of vascular risks, are mainly related with tau pathology rather than amyloid pathology.

Diffusion in the corpus callosum predicts persistence of clinical symptoms after mild traumatic brain injury, a multi-scanner study.

Mild traumatic brain injuries (mTBIs) comprise 80% of all TBI, but conventional MRI techniques are often insensitive to the subtle changes and injuries produced in a concussion. Diffusion tensor imaging (DTI) is one of the most sensitive MRI techniques for mTBI studies with outcome and symptom associations described. The corpus callosum (CC) is one of the most studied fiber tracts in TBI and mTBI, but the comprehensive post-mTBI symptom relationship has not fully been explored. This is a retrospective observational study of how quantitative DTI data of the CC and its sub-regions may relate to clinical presentation of symptoms and timing of resolution of symptoms in patients diagnosed with uncomplicated mTBI. DTI and clinical data were obtained retrospectively from 446 (mean age 42 years, range 13-82) civilian patients. From patient medical charts, presentation of the following common post-concussive symptoms was noted: headache, balance issues, cognitive deficits, fatigue, anxiety, depression, and emotional lability. Also recorded was the time between injury and a visit to the physician when improvement or resolution of a particular symptom was reported. FA values from the total CC and 3 subregions of the CC (genu or anterior, mid body, and splenium or posterior) were obtained from hand tracing on the Olea Sphere v3.0 SP12 free-standing workstation. DTI data was obtained from 8 different 3T MRI scanners and harmonized via ComBat harmonization. The statistical models used to explore the association between regional Fractional Anisotropy (FA) values and symptom presentation and time to symptom resolution were logistic regression and interval-censored semi-parametric Cox proportional hazard models, respectively. Subgroups related to age and timing of first scan were also analyzed. Patients with the highest FA in the total CC (p = 0.01), anterior CC (p < 0.01), and mid-body CC (p = 0.03), but not the posterior CC (p = 0.91) recovered faster from post-concussive cognitive deficits. Patients with the highest FA in the posterior CC recovered faster from depression (p = 0.04) and emotional lability (p = 0.01). There was no evidence that FA in the CC or any of its sub-regions was associated with symptom presentation or with time to resolution of headache, balance issues, fatigue, or anxiety. Patients with mTBI under 40 had higher FA in the CC and the anterior and mid-body subregions (but not the posterior subregion: p = 1.00) compared to patients 40 or over (p ≤ 0.01). There was no evidence for differences in symptom presentation based on loss of consciousness (LOC) or sex (p ≥ 0.18). This study suggests that FA of the CC has diagnostic and prognostic value for clinical assessment of mTBI in a large diverse civilian population, particularly in patients with cognitive symptoms.

White matter microstructural integrity is associated with retinal vascular caliber in adolescents with bipolar disorder

ObjectiveReduced white matter integrity is observed in bipolar disorder (BD), and is associated with cardiovascular risk in adults. This topic is underexplored in youth, and in BD, where novel microvascular measures may help to inform understanding of the vascular-brain connection. We therefore examined the association of retinal vascular caliber with white matter integrity in a cross-sectional sample of adolescents with and without BD. MethodsEighty-four adolescents (n = 42 BD, n = 42 controls) completed retinal imaging, yielding arteriolar and venular caliber. Diffusion tensor imaging measured white matter fractional anisotropy (FA). Multiple linear regression tested associations between retinal vascular caliber and FA in regions-of-interest; corpus callosum, anterior thalamic radiation, uncinate fasciculus, and superior longitudinal fasciculus. Complementary voxel-wise analyses were performed. ResultsArteriolar caliber was elevated in adolescents with BD relative to controls (F(1,79) = 6.15, p = 0.02, η2p = 0.07). In the overall sample, higher venular caliber was significantly associated with lower corpus callosum FA (β = −0.24, puncorrected = 0.04). In voxel-wise analyses, higher arteriolar caliber was significantly associated with lower corpus callosum and forceps minor FA in the overall sample (β = −0.46, p = 0.03). A significant diagnosis-by-venular caliber interaction on FA was noted in 5 clusters including the right retrolenticular internal capsule (β = 0.72, p = 0.03), corticospinal tract (β = 0.72, p = 0.04), and anterior corona radiata (β = 0.63, p = 0.04). In each instance, venular caliber was more positively associated with FA in BD vs. controls. ConclusionRetinal microvascular measures are associated with white matter integrity in BD, particularly in the corpus callosum. This study was proof-of-concept, designed to guide future studies focused on the vascular-brain interface in BD.

The genetic architecture of the corpus callosum and its genetic overlap with common neuropsychiatric diseases

BackgroundThe corpus callosum (CC) is the main structure transferring information between the cerebral hemispheres. Although previous large-scale genome-wide association study (GWAS) has illustrated the genetic architecture of white matter integrity of CC, CC volume is less stressed. MethodsUsing MRI data from 33,861 individuals in UK Biobank, we conducted univariate and multivariate GWAS for CC fractional anisotropy (FA) and volume with PLINK 2.0 and MOSTest. All discovered SNPs in the multivariate framework were functionally annotated in FUMA v1.3.8. In the meanwhile, a series of gene property analyses was conducted simultaneously. In addition, we estimated genetic relationship between CC metrics and other neuropsychiatric traits and diseases. ResultsWe identified a total of 36 and 82 significant genomic loci for CC FA and volume (P < 5 × 10−8). And 53 and 27 genes were respectively mapped by four mapping strategies. For CC volume, gene-set analysis revealed pathways mainly relating to cell migration; cell-type analysis found the top enrichment in neuroglia while for CC FA in GABAergic neurons. Furthermore, we found a lot of genetic overlap and shared loci between CC FA and volume and common neuropsychiatric diseases. DiscussionCollectively, this study helps to better understand the genetic architecture of whole CC and CC subregions. However, the way to divide CC FA and volume in our study restricts the interpretations of our results. Future work will be needed to pay attention to the genetic structure of white matter volume, and an appropriate division of CC may help to better understand CC structure.

Gray and white matter abnormalities in major depressive disorder patients and its associations with childhood adversity

ObjectiveEarly life stress of childhood adversity (CA) may result in major depressive disorder (MDD) by sensitizing individuals to proximal stressors in life events. The neurobiological changes that underlie adult depression may result from the absence of proper care and supervision of caregivers. We aimed to find both gray and white matter abnormalities in MDD patients, who reported the experiences of CA. MethodsThe present study examined cortical alterations in 54 patients with MDD and 167 healthy controls (HCs) using voxel-based morphology and fractional anisotropy (FA) tract-based spatial statistics (TBSS). Both patients and HCs were administered the self-questionnaire clinical scale (the Korean translation of the Childhood Trauma Questionnaire CTQK). Pearson's correlation analysis was performed to find the associations between FA and CTQK. ResultsThe MDD group showed a significant decrease in gray matter (GM) in the left rectus at both the cluster and peak levels after family-wise error correction. The TBSS results showed significantly reduced FA in widespread regions, including the corpus callosum (CC), superior corona radiata, cingulate gyrus, and superior longitudinal fasciculus. The CA was negatively correlated with the FA in CC and crossing pontine tract. ConclusionOur findings demonstrated GM atrophy and white matter (WM) connectivity changes in patients with MDD. The major findings of the widespread FA reduction in WM provided the evidence of brain alterations in MDD. We further propose that the WM would be vulnerable to emotional, physical, and sexual abuse in early childhood during the brain development.

Development of the corpus callosum and cognition after neonatal encephalopathy.

Neonatal imaging studies report corpus callosum abnormalities after neonatal hypoxic-ischaemic encephalopathy (HIE), but corpus callosum development and relation to cognition in childhood are unknown. Using magnetic resonance imaging (MRI), we examined the relationship between corpus callosum size, microstructure and cognitive and motor outcomes at early school-age children cooled for HIE (cases) without cerebral palsy compared to healthy, matched controls. A secondary aim was to examine the impact of HIE-related neonatal brain injury on corpus callosum size, microstructure and growth. Participants aged 6-8 years underwent MRI, the Movement Assessment Battery for Children Second Edition and Wechsler Intelligence Scale for Children Fourth Edition. Cross-sectional area, volume, fractional anisotropy and radial diffusivity of the corpus callosum and five subdivisions were measured. Multivariable regression was used to assess associations between total motor score, full-scale IQ (FSIQ) and imaging metrics. Adjusting for age, sex and intracranial volume, cases (N=40) compared to controls (N=39) demonstrated reduced whole corpus callosum area (β=-26.9, 95% confidence interval [CI]=-53.17, -0.58), volume (β=-138.5, 95% CI=-267.54, -9.56), fractional anisotropy and increased radial diffusivity (P < 0.05) within segments II-V. In cases, segment V area (β=0.18, 95% CI=0.004, 0.35), volume (β=0.04, 95% CI=0.001, 0.079), whole corpus callosum fractional anisotropy (β=13.8 95% CI=0.6, 27.1) and radial diffusivity (β=-11.3, 95% CI=-22.22, -0.42) were associated with FSIQ. Growth of the corpus callosum was restricted in cases with a FSIQ ≤85, and volume was reduced in cases with mild neonatal multifocal injury compared to white matter injury alone. Following neonatal HIE, morphological and microstructural changes in the corpus callosum are associated with reduced cognitive function at early school age.

Ventricular Volume in Infants Born Very Preterm: Relationship with Brain Maturation and Neurodevelopment at Age 4.5 Years

To evaluate the relationship of quantitative ventricular volume with brain maturation and neurodevelopmental outcomes at age 4.5years in children born very preterm. T1-weighted imaging, diffusion tensor imaging, and magnetic resonance spectroscopy were performed shortly after birth (n=212) and at term-equivalent age (TEA) (n=194). Intraventricular hemorrhage (IVH) grade and white matter injury (WMI) volume were measured on early T1-weighted magnetic resonance imaging (MRI) scans. Total cerebral volume and ventricular volume were quantified using the Multiple Automatically Generated Templates-Brain pipeline. At age 4.5years, 178 children (84%) underwent cognitive and motor assessments. Multivariable linear regression was used to examine the relationships between ventricular volume and neurodevelopmental outcomes. Generalized estimating equations were used to account for repeated measures when analyzing neonatal MRI data. All models accounted for sex, postmenstrual age at scan, WMI volume, IVH grade, and total cerebral volume and were corrected for multiple comparisons. On early MRI, 97 infants had IVH (grade 1, n=22; grade 2, n=66; grade 3, n=9), and 68 had WMI (median, 44mm3; IQR, 21-296mm3). IQ at 4.5years was associated with MRI ventricular volume at the early (β=-0.64; P<.001) and TEA (β=-0.44, P<.001) time points. Motor outcomes were associated with ventricular volume at TEA (β=-0.84, P=.01). Greater ventricular volume independently predicted lower fractional anisotropy in corpus callosum (genu: β=-0.0008, P=.002; splenium: β=-0.003, P<.001) and optic radiations (β=-0.001, P=.004); ventricular volume did not predict the N-acetylaspartate/choline ratio. In children born very preterm, neonatal ventricular size was associated with 4.5-year neurodevelopmental outcomes. Our findings suggest that white matter maturation may be abnormal in the setting of enlarged ventricular size beyond that expected from concurrent brain injuries.

White matter abnormalities in first-episode patients with depersonalization/derealization disorder: A tract-based spatial statistics study

BackgroundNeuroimaging studies on depersonalization / derealization disorder (DPD) have revealed that there are structural and functional alterations across numerous brain regions. However, to date, the exact white matter abnormalities that are associated with different clinical symptoms and cognitive impairments in first-episode, drug-naïve patients with DPD remain unclear. MethodsOverall, 25 first-episode, drug-naïve patients with DPD and 23 healthy controls were recruited and underwent DTI scans. The tract-based spatial statistics analysis was conducted in order to determine white matter microstructural changes between the two groups. Correlation analysis was conducted between the fractional anisotropy (FA) of abnormal WM fibers and the total score of the 30-item Cambridge Depersonalization Scale (CDS-30), cognitive assessments. ResultsPatients with DPD demonstrated higher FA in the right corpus callosum (CC), and posterior corona radiate (CR), compared to healthy controls. The FA in the right CC demonstrated a positive correlation with total score of CDS-30, numbing, unreality of self, perceptual alterations, and temporal disintegration, respectively. FA in the right CR region indicated a positive correlation with the total score of CDS-30, unreality of self, perceptual alterations, and temporal disintegration, respectively. Furthermore, FA in the right CR region was found to be negatively correlated with the Continuous Performance Test and the Stroop color-word test. ConclusionThe altered white matter microstructure and cognitive impairments of medication naïve DPD patients were observed. Abnormalities in the integrity of CC and CR were associated with severity of symptoms and cognitive impairments, which may provide a potential biomarker for clinical studies on DPD.

Prenatal antidepressant exposure and sex differences in neonatal corpus callosum microstructure.

Prenatal exposure to selective serotonin reuptake inhibitor (SSRI) antidepressants may influence white matter (WM) development, as previous studies report widespread microstructural alterations and reduced interhemispheric connectivity in SSRI-exposed infants. In rodents, perinatal SSRIs had sex-specific disruptions in corpus callosum (CC) axon architecture and connectivity; yet it is unknown whether SSRI-related brain outcomes in humans are sex specific. In this study, the neonate CC was selected as a region-of-interest to investigate whether prenatal SSRI exposure has sex-specific effects on early WM microstructure. On postnatal day 7, diffusion tensor imaging was used to assess WM microstructure in SSRI-exposed (n=24; 12 male) and nonexposed (n=48; 28 male) term-born neonates. Fractional anisotropy was extracted from CC voxels and a multivariate discriminant analysis was used to identify latent patterns differing between neonates grouped by SSRI-exposure and sex. Analysis revealed localized variations in CC fractional anisotropy that significantly discriminated neonate groups and correctly predicted group membership with an 82% accuracy. Such effects were identified across three dimensions, representing sex differences in SSRI-exposed neonates (genu, splenium), SSRI-related effects independent of sex (genu-to-rostral body), and sex differences in nonexposed neonates (isthmus-splenium, posterior midbody). Our findings suggest that CC microstructure may have a sex-specific, localized, developmental sensitivity to prenatal SSRI exposure.

Integrating Structural and Functional Interhemispheric Brain Connectivity of Gait Freezing in Parkinson's Disease.

Freezing of gait (FOG) has devastating consequences for patients with Parkinson's disease (PD), but the underlying pathophysiological mechanism is unclear. This was investigated in the present study by integrated structural and functional connectivity analyses of PD patients with or without FOG (PD FOG+ and PD FOG–, respectively) and healthy control (HC) subjects. We performed resting-state functional magnetic resonance imaging (fMRI) and diffusion tensor imaging of 24 PD FOG+ patients, 37 PD FOG– patients, and 24 HCs. Tract-based spatial statistics was applied to identify white matter (WM) abnormalities across the whole brain. Fractional anisotropy (FA) and mean diffusivity (MD) of abnormal WM areas were compared among groups, and correlations between these parameters and clinical severity as determined by FOG Questionnaire (FOGQ) score were analyzed. Voxel-mirrored homotopic connectivity (VMHC) was calculated to identify brain regions with abnormal interhemispheric connectivity. Structural and functional measures were integrated by calculating correlations between VMHC and FOGQ score and between FA, MD, and VMHC. The results showed that PD FOG+ and PD FOG– patients had decreased FA in the corpus callosum (CC), cingulum (hippocampus), and superior longitudinal fasciculus and increased MD in the CC, internal capsule, corona radiata, superior longitudinal fasciculus, and thalamus. PD FOG+ patients had more WM abnormalities than PD FOG– patients. FA and MD differed significantly among the splenium, body, and genu of the CC in all three groups (P < 0.05). The decreased FA in the CC was positively correlated with FOGQ score. PD FOG+ patients showed decreased VMHC in the post-central gyrus (PCG), pre-central gyrus, and parietal inferior margin. In PD FOG+ patients, VMHC in the PCG was negatively correlated with FOGQ score but positively correlated with FA in CC. Thus, FOG is associated with impaired interhemispheric brain connectivity measured by FA, MD, and VMHC, which are related to clinical FOG severity. These results demonstrate that integrating structural and functional MRI data can provide new insight into the pathophysiological mechanism of FOG in PD.

Delayed access to conscious processing in multiple sclerosis: Reduced cortical activation and impaired structural connectivity.

Although multiple sclerosis (MS) is frequently accompanied by visuo‐cognitive impairment, especially functional brain mechanisms underlying this impairment are still not well understood. Consequently, we used a functional MRI (fMRI) backward masking task to study visual information processing stratifying unconscious and conscious in MS. Specifically, 30 persons with MS (pwMS) and 34 healthy controls (HC) were shown target stimuli followed by a mask presented 8–150 ms later and had to compare the target to a reference stimulus. Retinal integrity (via optical coherence tomography), optic tract integrity (visual evoked potential; VEP) and whole brain structural connectivity (probabilistic tractography) were assessed as complementary structural brain integrity markers. On a psychophysical level, pwMS reached conscious access later than HC (50 vs. 16 ms, p < .001). The delay increased with disease duration (p < .001, β = .37) and disability (p < .001, β = .24), but did not correlate with conscious information processing speed (Symbol digit modality test, β = .07, p = .817). No association was found for VEP and retinal integrity markers. Moreover, pwMS were characterized by decreased brain activation during unconscious processing compared with HC. No group differences were found during conscious processing. Finally, a complementary structural brain integrity analysis showed that a reduced fractional anisotropy in corpus callosum and an impaired connection between right insula and primary visual areas was related to delayed conscious access in pwMS. Our study revealed slowed conscious access to visual stimulus material in MS and a complex pattern of functional and structural alterations coupled to unconscious processing of/delayed conscious access to visual stimulus material in MS.

Impaired integrity of commissural and association fibers in essential tremor patients: Evidence from a diffusion tensor imaging study

Background/aimThe evolving understanding of essential tremors (ET) has led to a new definition of neurodegenerative disease, pointing to diffuse brain network involvement with a wide spectrum of associated motor and nonmotor symptoms. Considering the fact that white matter should also be affected by the nature of the disease, our study aimed to evaluate the integrity of white matter and its clinical correlations in ET patients. Materials and methodsApproximately 40 patients diagnosed with ET and 40 age-and sex-matched control subjects (ranging between 18–80 years old) were included in the study. The sociodemographic characteristics and clinical features of the patients were recorded. Tremors were assessed using the Fahn-Tolosa-Marin Tremor Rating Scale (FTM-TRS). Diffusion Tensor Imaging (DTI) was performed to evaluate the integrity of white matter. The selected white matter regions used for DTI assessment were the corpus callosum (CC) (i.e., the largest commissural tract in the human brain), the superior longitudinal fasciculus (SLF), and the inferior longitudinal fasciculus (ILF) (i.e., the largest association fiber bundles). Results The mean age of the ET patients and control subjects was 44.23 ± 18.91 and 37.45 ± 10.95 years old (P = 0.542). The fractional anisotropy (FA) values of the CC body (P = 0.003), ILF (p = 0.016), average diffusion coefficient (ADC) values of the CC body (p = 0.001), genu (P = 0.049), SLF (V < 0.001), and ILF (P < 0.001) differed between groups. After controlling for age and sex, there was no correlation between tremor severity and DTI parameters, but impaired integrity in the genu of CC FA (P = 0.035, r = 0.442) and the splenium of CC ADC (P = 0.007, r = 0.543) were related with a longer duration of tremor. Finally, positive family history was correlated with the splenium of CC FA and ADC (P = 0.008, r = 0.536; P = 0.027, r = 0.461) and ILF ADC (P = 0.011, r = –0.519).Conclusion In our study, major white matter structure changes were found in the ET patients. The results suggest that possible neurodegeneration also affects white matter structures in ET patients and that the duration of the tremor and family history are related with impaired integrity of white matter.

White matter changes in empirically derived incident MCI subtypes in the Mayo Clinic Study of Aging.

IntroductionThe aim of this study was to examine white matter hyperintensities (WMH) and fractional anisotropy (FA) in empirically derived incident mild cognitive impairment (MCI) subtypes.MethodsWe evaluated 188 participants with incident MCI in the Mayo Clinic Study of Aging (MCSA) identified as having one of four cluster‐derived subtypes: subtle cognitive impairment, amnestic, dysnomic, and dysexecutive. We used linear regression models to evaluate whole brain and regional WMH volumes. We examined fractional anisotropy (FA) on a subset of 63 participants with diffusion tensor imaging.ResultsAmnestic and dysexecutive subtypes had higher WMH volumes in differing patterns than cognitively unimpaired; the dysexecutive subtype had higher WMH than subtle cognitive impairment. There was widespread WM degeneration in long association and commissural fibers in the amnestic, dysnomic, and dysexecutive subtypes, and corpus callosum FA accounted for significant variability in global cognition.DiscussionWhite matter changes likely contribute to cognitive symptoms in incident MCI.

Onset age of second language acquisition and fractional anisotropy variation in multilingual young adults

The experience of speaking two languages, particularly the age of second language acquisition (L2AoA), has been robustly associated with differences in metrics indicative of white matter structure. However, bilingual language experience is complex, described not only by acquisition but also functional language usage and proficiency. We examined whether the onset age of the second most proficient language (pL2AoA) would indeed be a sensitive measure that incorporates onset age of second language acquisition and self-reported L2 proficiency and correlates with variation in fractional anisotropy in white matter. Thirty-one multilingual young adults with a range of L2AoA and pL2AoA from an English-dominant community participated. After accounting for age, gender, nonverbal IQ, and parental education, both L2AoA and pL2AoA were significantly correlated with fractional anisotropy in the corpus callosum. Furthermore, we show that a larger and more extensive cluster in the corpus callosum was correlated with pL2AoA as compared to the conventional L2AoA. • Multilingualism has been associated with structural brain differences. • We correlated onset age of second language acquisition and white matter structures. • Negative correlations were found between onset age of second language and fractional anisotropy (FA) in corpus callosum. • Similar negative correlations were observed between FA in a larger and more extensive cluster in corpus callosum and the onset age of the second most proficient language.

Functional and structural impairment of transcallosal motor fibres in ALS: a study using transcranial magnetic stimulation, diffusion tensor imaging, and diffusion weighted spectroscopy.

Imaging studies showed that the structure of the corpus callosum (CC) is affected in amyotrophic lateral sclerosis (ALS). Some clinical studies also suggest that interhemispheric connectivity is altered, since mirror movements seem to occur in ALS. Finally, reduced interhemispheric inhibition (IHI), studied by transcranial magnetic stimulation (TMS), has been reported. It is not known whether there is any association between these findings. Here, we studied the integrity of the CC in ALS on the morphological, the functional, the electrophysiological, and the clinical level. Twenty-seven right-handed ALS patients and 21 healthy right-handed controls were included. Mirror activity (MA) was quantified using surface EMG. Diffusion tensor imaging tractography was used to segment the CC and quantify fractional anisotropy (FA). We studied the diffusivity of the intra-axonal markers N-acetylaspartate+N-acetyl aspartyl glutamate D(tNAA) within the CC. IHI was studied as a marker of CC function using a double-pulse TMS protocol. ALS patients showed significantly decreased FA in the motor segment of the CC (p< 0.01), and IHI was significantly reduced compared to controls (p= 0.01). However, no differences were observed regarding D(tNAA) and MA. The morphological as well as the functional integrity of the CC are altered in ALS. IHI was reduced in ALS, associated with decreased FA in the motor CC. Patients did not exhibit increased MA. Also, no differences within the CC were observed using diffusion-weighted spectroscopy. IHI might serve as a marker of transcallosal pathway disruption in ALS, even before clinical deficits become apparent.

Neonatal white matter tract microstructure and 2-year language outcomes after preterm birth

AimTo determine whether variability in diffusion MRI (dMRI) white matter tract metrics, obtained in a cohort of preterm infants prior to neonatal hospital discharge, would be associated with language outcomes at age 2 years, after consideration of age at scan and number of major neonatal complications. Method30 children, gestational age 28.9 (2.4) weeks, underwent dMRI at mean post menstrual age 36.4 (1.4) weeks and language assessment with the Bayley Scales of Infant Development–III at mean age 22.2 (1.7) months chronological age. Mean fractional anisotropy (FA) and mean diffusivity (MD) were calculated for 5 white matter tracts. Hierarchical linear regression assessed associations between tract FA, moderating variables, and language outcomes. ResultsFA of the left inferior longitudinal fasciculus accounted for 17% (p = 0.03) of the variance in composite language and FA of the posterior corpus callosum accounted for 19% (p = 0.02) of the variance in composite language, beyond that accounted for by post-menstrual age at scan and neonatal medical complications. The number of neonatal medical complications moderated the relationship between language and posterior corpus callosum FA but did not moderate the association in the other tract. ConclusionLanguage at age 2 is associated with white matter metrics in early infancy in preterm children. The different pattern of associations by fiber group may relate to the stage of brain maturation and/or the nature and timing of medical complications related to preterm birth. Future studies should replicate these findings with a larger sample size to assure reliability of the findings.

In search of multimodal brain alterations in Alzheimer's and Binswanger's disease.

Structural and functional brain abnormalities have been widely identified in dementia, but with variable replicability and significant overlap. Alzheimer's disease (AD) and Binswanger's disease (BD) share similar symptoms and common brain changes that can confound diagnosis. In this study, we aimed to investigate correlated structural and functional brain changes in AD and BD by combining resting-state functional magnetic resonance imaging (fMRI) and diffusion MRI. A group independent component analysis was first performed on the fMRI data to extract 49 intrinsic connectivity networks (ICNs). Then we conducted a multi-set canonical correlation analysis on three features, functional network connectivity (FNC) between ICNs, fractional anisotropy (FA) and mean diffusivity (MD). Two inter-correlated components show significant group differences. The first component demonstrates distinct brain changes between AD and BD. AD shows increased cerebellar FNC but decreased thalamic and hippocampal FNC. Such FNC alterations are linked to the decreased corpus callosum FA. AD also has increased MD in the frontal and temporal cortex, but BD shows opposite alterations. The second component demonstrates specific brain changes in BD. Increased FNC is mainly between default mode and sensory regions, while decreased FNC is mainly within the default mode domain and related to auditory regions. The FNC changes are associated with FA changes in posterior/middle cingulum cortex and visual cortex and increased MD in thalamus and hippocampus. Our findings provide evidence of linked functional and structural deficits in dementia and suggest that AD and BD have both common and distinct changes in white matter integrity and functional connectivity.