Fractional Anisotropy In Tracts Research Articles

Cerebellar peduncle injury predicts motor impairments in preterm infants: A quantitative tractography study at term-equivalent age

PurposeCerebellar injury is well established as an important finding in preterm infants with cerebral palsy (CP). In this study, we investigated associations between injury to the cerebellar peduncles and motor impairments in preterm infants using quantitative tractography at term-equivalent age, which represents an early phase before the onset of motor impairments. MethodsWe studied 64 preterm infants who were born at <33 weeks gestational age. These infants were divided into three groups: CP, Non-CP (defined as infants with periventricular leukomalacia but having normal motor function), and a Normal group. Diffusion tensor imaging was performed at term-equivalent age and motor function was assessed no earlier than a corrected age of 2 years. Using tractography, we measured fractional anisotropy (FA) and apparent diffusion coefficient (ADC) of the superior cerebellar peduncles (SCP) and middle cerebellar peduncles (MCP), as well as the motor/sensory tracts. ResultsThe infants in the CP group had significantly lower FA of the SCP and sensory tract than those in the other groups. There was no significant difference in FA and ADC of the motor tract among the three groups. Severity of CP had a significant correlation with FA of the MCP, but not with the FA of other white matter tracts. ConclusionOur results suggested that the infants with CP had injuries of the ascending tracts (e.g. the SCP and sensory tract), and that additional MCP injury might increase the severity of CP. Quantitative tractography assessment at term-equivalent age may be useful for screening preterm infants for prediction of future motor impairments.

Association of Whole-Genome and NETRIN1 Signaling Pathway–Derived Polygenic Risk Scores for Major Depressive Disorder and White Matter Microstructure in the UK Biobank

BackgroundMajor depressive disorder is a clinically heterogeneous psychiatric disorder with a polygenic architecture. Genome-wide association studies have identified a number of risk-associated variants across the genome and have reported growing evidence of NETRIN1 pathway involvement. Stratifying disease risk by genetic variation within the NETRIN1 pathway may provide important routes for identification of disease mechanisms by focusing on a specific process, excluding heterogeneous risk-associated variation in other pathways. Here, we sought to investigate whether major depressive disorder polygenic risk scores derived from the NETRIN1 signaling pathway (NETRIN1-PRSs) and the whole genome, excluding NETRIN1 pathway genes (genomic-PRSs), were associated with white matter microstructure. MethodsWe used two diffusion tensor imaging measures, fractional anisotropy (FA) and mean diffusivity (MD), in the most up-to-date UK Biobank neuroimaging data release (FA: n = 6401; MD: n = 6390). ResultsWe found significantly lower FA in the superior longitudinal fasciculus (β = −.035, pcorrected = .029) and significantly higher MD in a global measure of thalamic radiations (β = .029, pcorrected = .021), as well as higher MD in the superior (β = .034, pcorrected = .039) and inferior (β = .029, pcorrected = .043) longitudinal fasciculus and in the anterior (β = .025, pcorrected = .046) and superior (β = .027, pcorrected = .043) thalamic radiation associated with NETRIN1-PRS. Genomic-PRS was also associated with lower FA and higher MD in several tracts. ConclusionsOur findings indicate that variation in the NETRIN1 signaling pathway may confer risk for major depressive disorder through effects on a number of white matter tracts.

White matter pathways for prosodic structure building: A case study

The relevance of left dorsal and ventral fiber pathways for syntactic and semantic comprehension is well established, while pathways for prosody are little explored. The present study examined linguistic prosodic structure building in a patient whose right arcuate/superior longitudinal fascicles and posterior corpus callosum were transiently compromised by a vasogenic peritumoral edema. Compared to ten matched healthy controls, the patient’s ability to detect irregular prosodic structure significantly improved between pre- and post-surgical assessment. This recovery was accompanied by an increase in average fractional anisotropy (FA) in right dorsal and posterior transcallosal fiber tracts. Neither general cognitive abilities nor (non-prosodic) syntactic comprehension nor FA in right ventral and left dorsal fiber tracts showed a similar pre-post increase. Together, these findings suggest a contribution of right dorsal and inter-hemispheric pathways to prosody perception, including the right-dorsal tracking and structuring of prosodic pitch contours that is transcallosally informed by concurrent syntactic information.

White matter properties associated with pre-reading skills in 6-year-old children born preterm and at term.

To assess associations between white matter properties and pre-reading skills (phonological awareness and receptive and expressive language) in children born preterm and at term at the onset of reading acquisition. Six-year-old children born preterm (n=36; gestational age 22-32wks) and at term (n=43) underwent diffusion magnetic resonance imaging and behavioural assessments. Tracts were selected a priori based on findings from a study of 6-year-old children born at term: the left-hemisphere arcuate fasciculus and superior longitudinal fasciculus, and right-hemisphere uncinate fasciculus. Using linear regression, we assessed associations between fractional anisotropy of tracts and phonological awareness and receptive and expressive language scores. We investigated whether associations were moderated by prematurity. Fractional anisotropy of the left-hemisphere arcuate fasciculus contributed unique variance to phonological awareness across birth groups. The association between fractional anisotropy of the right-hemisphere uncinate fasciculus and receptive and expressive language was significantly moderated by prematurity. A left-hemisphere tract was associated with phonological awareness in both birth groups. A right-hemisphere tract was associated with language only in the term group, suggesting that expressive and receptive language is mediated by different white matter pathways in 6-year-old children born preterm. These findings provide novel insights into similarities and differences of the neurobiology of pre-reading skills between children born preterm and at term at reading onset. White matter properties and pre-reading abilities were associated in children born preterm at the onset of reading. The neurobiology of phonological awareness was similar in children born preterm versus children born at term at 6 years. The neurobiology of language was different in children born preterm versus children born at term at 6 years.

Differential effect of COMT gene methylation on the prefrontal connectivity in subjects with depression versus healthy subjects

Expression of the catechol-O-methyl transferase (COMT) gene mainly determines prefrontal dopaminergic availability. Deficient prefrontal dopaminergic activity leads to loss of interest, energy, and motivation, which are core symptoms of depression. Given the role of stress-environmental interactions in major depressive disorder (MDD), we investigated the impact of COMT gene methylation status on prefrontal connectivity. We measured COMT gene methylation and polymorphisms (Val158Met) at the rs4468 locus in peripheral blood samples of healthy controls (n = 90) and patients with MDD (n = 90). We used diffusion tensor imaging to calculate the fractional anisotropy (FA) and radial diffusivity (RD) of the white matter tracts related to prefrontal cortex. Finally, we examined the effects of COMT gene methylation on the white matter connectivity in patients with MDD. The FA and RD values in the prefrontal white matter tracts of patients with MDD were positively and negatively associated with COMT gene methylation, respectively. In the control group, on the other hand, the association between white matter connectivity and COMT gene methylation showed opposite pattern to those of MDD. COMT gene methylation has a substantial effect on the prefrontal connectivity in patients with MDD. Moreover, COMT gene methylation and prefrontal connectivity showed opposite relationships in patients and controls. Thus, stress-related alterations in dopaminergic neurotransmission have a differential effect on white matter connectivity according to the microenvironment in the brain.

Comparison of Multi-Tensor Diffusion Models' Performance for White Matter Integrity Estimation in Chronic Stroke.

Better insight into white matter (WM) alterations after stroke onset could help to understand the underlying recovery mechanisms and improve future interventions. MR diffusion imaging enables to assess such changes. Our goal was to investigate the relation of WM diffusion characteristics derived from diffusion models of increasing complexity with the motor function of the upper limb. Moreover, we aimed to evaluate the variation of such characteristics across different WM structures of chronic stroke patients in comparison to healthy subjects. Subjects were scanned with a two b-value diffusion-weighted MRI protocol to exploit multiple diffusion models: single tensor, single tensor with isotropic compartment, bi-tensor model, bi-tensor with isotropic compartment. From each model we derived the mean tract fractional anisotropy (FA), mean (MD), radial (RD) and axial (AD) diffusivities outside the lesion site based on a WM tracts atlas. Asymmetry of these measures was correlated with the Fugl-Meyer upper extremity assessment (FMA) score and compared between patient and control groups. Eighteen chronic stroke patients and eight age-matched healthy individuals participated in the study. Significant correlation of the outcome measures with the clinical scores of stroke recovery was found. The lowest correlation of the corticospinal tract FAasymmetry and FMA was with the single tensor model (r = −0.3, p = 0.2) whereas the other models reported results in the range of r = −0.79 ÷ −0.81 and p = 4E-5 ÷ 8E-5. The corticospinal tract and superior longitudinal fasciculus showed most alterations in our patient group relative to controls. Multiple compartment models yielded superior correlation of the diffusion measures and FMA compared to the single tensor model.

Multifocal alterations of white matter accompany the transition from normal cognition to dementia in Parkinson's disease patients.

The purpose of the present study was to investigate the pattern of white matter (WM) changes associated with Parkinson's disease (PD)-related cognitive impairment by using fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) measures. Diffusion Tensor Imaging (DTI) was performed in 21 PD-patients with dementia (PDD) and in an age-matched control group including 40 PD-patients without dementia (PD-CTRL). The Parkinson's disease-Cognitive Rating Scale (PD-CRS) was used for patients' neuropsychological assessment. Local microstructural WM differences associated with the presence of cognitive impairment were tested using tract-based spatial statistics analysis. Multiple regression models investigated the association of DTI indices with total PD-CRS score, PD-CRS raw items and other clinical measures across the whole study sample. Significant FA decreases were found in PDD compared to PD-CTRL patients mainly in the body of corpus callosum, corona radiata and cingulum. Lower PD-CRS score was significantly associated with decreased FA, MD and AD values in multiple WM tracts primarily located in prefrontal and limbic areas as well as across the corpus callosum. Lower performance in specific PD-CRS raw items was also associated with FA decreases in major WM tracts. The results suggest that multifocal microstructural changes of WM accompany the transition from normal to demented cognitive state in PD-patients. The corpus callosum, the corona radiata and the cingulum are among the regions mostly affected during this course. A progressive axonal degeneration is proposed as a key underlying mechanism.

Analyses of regional radiosensitivity of white matter structures along tract axes using novel white matter segmentation and diffusion imaging biomarkers.

Background and purposeBrain radiotherapy (RT) can cause white matter damage and downstream neurocognitive decline. We developed a computational neuroimaging tool to regionally partition individual white matter tracts, then analyze regional changes in diffusion metrics of white matter damage following brain RT.Materials and methodsRT dose, diffusion metrics and white matter tract structures were extracted and mapped to a reference brain for 49 patients who received brain RT, and underwent diffusion tensor imaging pre- and 9–12 months post-RT. Based on their elongation, 23 of 48 white matter tracts were selected. The Tract-Crawler software was developed in MATLAB to create cross-sectional slice planes normal to a tract’s computed medial axis. We then performed slice- and voxel-wise analysis of radiosensitivity, defined as percent change in mean diffusivity (MD) and fractional anisotropy (FA) as a function of dose relative to baseline.ResultsDistinct patterns of FA/MD radiosensitivity were seen for specific tracts, including the corticospinal tract, medial lemniscus, and inferior cerebellar peduncle, in particular at terminal ends. These patterns persisted for corresponding tracts in left and right hemispheres. Local sensitivities were as high as 40%/Gy (e.g., voxel-wise: −39 ± 31%/Gy in right corticospinal tract FA, −45 ± 25%/Gy in right inferior cerebellar peduncle FA), p < 0.05.ConclusionsTract-Crawler, a novel tool to visualize and analyze cuts of white matter structures normal to medial axes, was used to demonstrate that particular white matter tracts exhibit significant regional variations in radiosensitivity based on diffusion biomarkers.

Neural networks in bottom up ‘experiential emotion regulation’

Emotion regulation influences how and when we experience emotion, impacting our sense of self and well being. While previous brain research on emotion regulation has focused on gray matter correlates of emotion regulation, this study represents a first exploratory study on white matter integrity of brain networks of ‘emotional approach’ as a bottom up experiential emotion regulation-strategy. Responding to the gap between cognitive and affective approaches of emotion regulation, pertaining to some of the daily emotional stressors, the present study investigates brain pathways of individual differences in ‘emotional approach’, or the tendency to affectively acknowledge, understand and express emotional experience (cf. [1]). Diffusion tensor magnetic resonance imaging (DTI-MRI) measures of fractional anisotropy (FA) and mean diffusion (MD) evaluated dispositional emotion regulation in a group of 21 women with a ‘high emotional approach’ (HEA) (N = 11) and a ‘low emotional approach’ (LEA) (N = 10). HEA exhibited more FA of the cingulum, supporting emotion processing and emotion regulation, whereas LEA correlated to a higher FA in the right corticospinal tracts, supporting automatic action tendencies and a higher FA in the superior longitudinal fasciculus (SLF), supporting cognitive control and monitoring of emotion. LEA also correlated with an increase in MD in the body (p. = 0.05) and in the splenium of the corpus callosum (CC). A higher FA in the inferior longitudinal fasciculus (IFL) may indicate higher visual- affective integration within emotion processing, whereas more MD in the body and splenium of the CC decreases interhemispheric integration of emotional information within emotion processing and emotion regulation.

White matter microstructural variability mediates the relation between obesity and cognition in healthy adults

Obesity has been linked with structural and functional brain changes. However, the impact of obesity on brain and cognition in aging remains debatable, especially for white matter. We therefore aimed to determine the effects of obesity on white matter microstructure and potential implications for cognition in a well-characterized large cohort of healthy adults. In total, 1255 participants (50% females, 19–80 years, BMI 16.8–50.2 kg/m2) with diffusion-weighted magnetic resonance imaging at 3T were analysed. Tract-based spatial statistics (TBSS) probed whether body mass index (BMI) and waist-to-hip ratio (WHR) were related to fractional anisotropy (FA). We conducted partial correlations and mediation analyses to explore whether obesity or regional FA were related to cognitive performance. Analyses were adjusted for demographic, genetic, and obesity-associated confounders. Results showed that higher BMI and higher WHR were associated with lower FA in multiple white matter tracts (p < 0.05, FWE-corrected). Mediation analyses provided evidence for indirect negative effects of higher BMI and higher WHR on executive functions and processing speed through lower FA in fiber tracts connecting (pre)frontal, visual, and associative areas (indirect paths, |ß| ≥ 0.01; 99% |CI| > 0). This large cross-sectional study showed that obesity is correlated with lower FA in multiple white matter tracts in otherwise healthy adults, independent of confounders. Moreover, although effect sizes were small, mediation results indicated that visceral obesity was linked to poorer executive functions and lower processing speed through lower FA in callosal and associative fiber tracts. Longitudinal studies are needed to support this hypothesis.

Differential White Matter Regional Alterations in Motor Subtypes of Early Drug-Naive Parkinson’s Disease Patients

Background. Parkinson’s disease (PD) can be classified into tremor dominant (TD) and postural instability and gait difficulty (PIGD) subtypes with TD considered as the benign subtype. The neural alterations of the 2 subtypes in the early stages before administration of medications remain elusive. Objective. This study assessed the subtype-related white matter (WM) microstructural features in newly diagnosed and drug-naive PD patients from the Parkinson’s Progression Markers Initiative (PPMI). Methods. Sixty-five early PDs with stable subtypes (52 TD and 13 PIGD patients) and 61 controls underwent diffusion tensor imaging (DTI) scanning and clinical assessment. Tract-based special statistics (TBSS), graph-theoretical and network-based analyses were used to compare WM regional and network features between groups. Results. No differences in disease stages and duration were found between the 2 patient groups. TD patients showed increased fractional anisotropy (FA), but decreased radial and axial diffusivities (RD and AD) in several projection, association, and commissural tracts, compared with PIGD patients and controls. Motor severity had mild-to-moderate correlations with FA and RD of the corpus callosum (genu) in TD, but strong correlations with FA and RD of multiple association tracts in PIGD. Conversely, no significant network changes were noted. Conclusions. TD patients showed regionally increased FA but decreased diffusivities, implying neural reorganization to compensate PD pathology in early stages. PIGD patients, despite having similar disease stages and duration, exhibited more WM degradation. These results demonstrate differential WM regional features between the 2 subtypes in early PD and support the notion of TD being a benign subtype.

Reduced Field-of-View Diffusion Tensor Imaging of the Spinal Cord Shows Motor Dysfunction of the Lower Extremities in Patients With Cervical Compression Myelopathy.

A cross-sectional study. The aim of this study was to quantify spinal cord dysfunction at the tract level in patients with cervical compressive myelopathy (CCM) using reduced field-of-view (rFOV) diffusion tensor imaging (DTI). Although magnetic resonance imaging (MRI) is the standard used for radiological evaluation of CCM, information acquired by MRI does not necessarily reflect the severity of spinal cord disorder. There is a growing interest in developing imaging methods to quantify spinal cord dysfunction. To acquire high-resolution DTI, a new scheme using rFOV has been proposed. We enrolled 10 healthy volunteers and 20 patients with CCM in this study. The participants were studied using a 3.0-T MRI system. For DTI acquisitions, diffusion-weighted spin-echo rFOV single-shot echo-planar imaging was used. Regions-of-interest (ROI) for the lateral column (LC) and posterior column (PC) tracts were determined on the basis of a map of fractional anisotropy (FA) of the spinal cord and FA values were measured. The FA of patients with CCM was compared with that of healthy controls and correlated with Japanese Orthopaedic Association (JOA) score. In LC and PC tracts, FA values in patients with CCM were significantly lower than in healthy volunteers. Total JOA scores correlated moderately with FA in LC and PC tracts. JOA subscores for motor dysfunction of the lower extremities correlated strongly with FA in LC and PC tracts. It is feasible to evaluate the cervical spinal cord at the tract level using rFOV DTI. Although FA values at the maximum compression level were not well correlated with total JOA scores, they were strongly correlated with JOA subscores for motor dysfunction of the lower extremities. Our findings suggest that FA reflects white matter dysfunction below the maximum compression level and FA can be used as an imaging biomarker of spinal cord dysfunction. 4.

Analysis of white matter characteristics with tract-based spatial statistics according to diffusion tensor imaging in early Parkinson’s disease

ObjectiveTo analyze the microstructure of brain white matter according to diffusion tensor imaging (DTI) based on tract-based spatial statistics (TBSS) in early Parkinson's disease (PD). Materials and methodsA total of 31 age- and sex-matched early PD patients and 22 healthy volunteers were recruited in the present study. DTI was performed, and the data analyzed with fsl4.0 software. The fractional anisotropy (FA) was compared between both groups with an independent t test, and the differential area was analyzed. White matter fiber tracts with significant difference in FA between the two groups were selected, and their FAs were measured. Pearson’s correlation analysis was employed to analyze the unified Parkinson’s disease rating scale (UPDRS) score and its association with FA of different tracts. ResultsWhen compared with healthy volunteers, early PD patients had reduced FA in the following areas: bilateral anterior corona radiate, upper corona radiate, fasciculus arcuatus, crus anterius capsulae internae, crus posterius capsulae internae, capsula externa, posterior thalamic radiation, optic radiation, sagittal layer (including fasciculus arcuatus and inferior fronto-occipital fasciculus), crura fornicis, stria terminalis, fornix, genu, body and pad of corpus callosum, left unciform fasciculus, right cingulate bundle, right medipeduncle, and arcuate fibers in the bilateral frontal, temporal, and occipital lobes (P < 0.05). When compared with healthy volunteers, early PD patients showed abnormal FA of fasciculus in the white matter mainly in following areas: bilateral crus anterius capsulae internae, bilateral capsula externa, right anterior corona radiate, body and pad of bilateral corpus callosum, and left sagittal layer (including fasciculi longitudinalis inferior and fasciculus occipitofrontalis inferior) (P < 0.05). In addition, in early PD patients, the UPDRS score and movement score had no relationship with the FA of different fasciculi in the white matter (P > 0.05). ConclusionThere is wide alteration of white matter microstructure in early PD patients, which is characterized by disruption of projection fibers in the descending pathway, limbic system-related fasciculi, corpus callosum, thalamus after radiation, posterior thalamic radiation, Gratiolet's bundle and other fasciculi in the white matter.

White matter abnormalities in 22q11.2 deletion syndrome patients showing cognitive decline.

Decline in cognitive functioning precedes the first psychotic episode in the course of schizophrenia and is considered a hallmark symptom of the disorder. Given the low incidence of schizophrenia, it remains a challenge to investigate whether cognitive decline coincides with disease-related changes in brain structure, such as white matter abnormalities. The 22q11.2 deletion syndrome (22q11DS) is an appealing model in this context, as 25% of patients develop psychosis. Furthermore, we recently showed that cognitive decline also precedes the onset of psychosis in individuals with 22q11DS. Here, we investigate whether the early cognitive decline in patients with 22q11DS is associated with alterations in white matter microstructure. We compared the fractional anisotropy (FA) of white matter in 22q11DS patients with cognitive decline [n = 16; -18.34 (15.8) VIQ percentile points over 6.80 (2.39) years] to 22q11DS patients without cognitive decline [n = 18; 17.71 (20.17) VIQ percentile points over 5.27 (2.03) years] by applying an atlas-based approach to diffusion-weighted imaging data. FA was significantly increased (p < 0.05, FDR) in 22q11DS patients with a cognitive decline in the bilateral superior longitudinal fasciculus, the bilateral cingulum bundle, all subcomponents of the left internal capsule and the left superior frontal-occipital fasciculus as compared with 22q11DS patients without cognitive decline. Within 22q11DS, the early cognitive decline is associated with microstructural differences in white matter. At the mean age of 17.8 years, these changes are reflected in increased FA in several tracts. We hypothesize that similar brain alterations associated with cognitive decline take place early in the trajectory of schizophrenia.

White Matter Microstructural Properties are Related to Inter-Individual Differences in Cognitive Instability after Sleep Deprivation

Several diseases are characterized by cognitive instability, which is amplified in the conditions of sleep deprivation (SD). Cognitive instability in SD can be examined by the number of lapses on the psychomotor vigilance test (PVT), which is considered to be a gold standard in the field. However, the number of PVT lapses widely range according to inter-individual differences, from apparent cognitive resistance to severe cognitive impairment. In this study, tract-based spatial statistical analyses with multiple diffusion tensor imaging-derived characteristics (i.e., fractional anisotropy (FA), mean diffusivity, radial diffusivity, and axial diffusivity) were employed to investigate the relationships between the number of PVT lapses and the diffusion characteristics. A hierarchical linear regression model was then used to assess the contributions of tract-specific FA values in predicting PVT lapses. Finally, dichotomized analysis was used to investigate white matter (WM) differences between resilient and vulnerable groups. Our results showed significant negative correlations between numbers of PVT lapses and FA in multiple WM tracts, with the FA variations in the superior longitudinal fasciculus and splenium of the corpus callosum accounting for nearly 37.5% of individual variability in PVT lapses. In addition, dichotomized analyses indicated that the resilient participants exhibited significantly higher FA values compared with the vulnerable participants. Together, these findings suggest that cognitive instability after SD was closely associated with individual differences in WM integrity.

Damage to the Frontal Aslant Tract Accounts for Visuo-Constructive Deficits in Alzheimer's Disease.

The frontal aslant tract (FAT) has been described as a bundle connecting the Broca's area to the supplementary motor area (SMA) and the pre-SMA in both hemispheres. The functional properties of this tract and its role in degenerative dementia, such as Alzheimer's disease (AD), still need to be fully clarified. The aim of this study was to explore the microstructural integrity of the FAT in patients with AD and its potential relationship with cognitive functioning. Twenty-three patients with AD and 25 healthy subjects (HS) were enrolled. All subjects underwent cognitive and MRI examination. MRI, including diffusion sequences, was used for probabilistic tractography analysis. We reconstructed individual FATs bilaterally and assessed their microstructural integrity using fractional anisotropy (FA), computed as both mean tract value and voxel-wise using SPM-8. Mean FA values were then used to test for correlations with cognitive measures. Mean tract FA and voxel-wise analyses revealed that patients with AD, compared to HS, had decreased FA in the FAT bilaterally. In addition, positive associations were found between FA in the FATs and patients' performance at tests for constructional praxis and visuospatial logical reasoning. The present results reveal a bilateral damage of FAT in AD patients. The association between FATs' microscopic abnormalities and constructive abilities fits well with the knowledge of a functional involvement of SMA and pre-SMA in movement sequences when executing constructive praxis tasks. The FAT is an associative bundle critically involved in the network sub-serving constructional praxis in patients with AD.

Fornix Structural Connectivity and Allostatic Load: Empirical Evidence From Schizophrenia Patients and Healthy Controls.

The fornix is a white matter tract carrying the fibers connecting the hippocampus and the hypothalamus, two essential stress-regulatory structures of the brain. We tested the hypothesis that allostatic load (AL), derived from a battery of peripheral biomarkers indexing the cumulative effects of stress, is associated with abnormalities in brain white matter microstructure, especially the fornix, and that higher AL may help explain the white matter abnormalities in schizophrenia. Using 13 predefined biomarkers, we tested AL in 44 schizophrenic patients and 33 healthy controls. Diffusion tensor imaging was used to obtain fractional anisotropy (FA) values of the fornix and other white matter tracts. AL scores were significantly elevated in patients compared with controls (F(3,77) = 7.87, p = .006). AL was significantly and inversely correlated with FA of fornix in both controls (r = -.58, p = .001) and patients (r = -.36, p = .023). Several nominally significant (p < .05 but did not survive Bonferroni correction for multiple comparison) correlations were also observed between AL and FA of other white matter tracts in schizophrenic patients. However, the fornix was the only tract exhibiting a correlation with AL in both groups. These results provide initial evidence that allostatic processes are linked to fornix microstructure in clinical participants.

Changes to white matter microstructure in transient ischemic attack: A longitudinal diffusion tensor imaging study

Transient ischemic attack (TIA) is associated with localized ischemic changes, identifiable by diffusion-weighted imaging. Past research has not considered whether TIA is also associated with diffuse changes to white matter microstructure; further past work has not tracked changes longitudinally. Here we examine whole-brain changes in fractional anisotropy (FA) in individuals with TIA presenting with sensorimotor symptoms. Twenty individuals with a recent (within 30 days) TIA and 12 healthy older adults were recruited. Participants underwent 3.0T diffusion MRI at baseline; scans were repeated for the TIA group 90 days post-TIA. Track-based spatial statistics (TBSS) was used to conduct a voxel-wise analysis of FA between groups. FA was significantly lower in the TIA group relative to healthy controls, primarily in anterior white matter tracts including: forceps minor, anterior thalamic radiations, cingulum, inferior fronto-occipital fasciculus, and corticospinal tract. TBSS results informed an ROI-based longitudinal examination of FA in the TIA group. There were no changes to TBSS-identified clusters, forceps minor, or the corticospinal tract over time. There was lower FA in the anterior thalamic radiations in the TIA-affected hemisphere at baseline, but no difference between hemispheres at 90days. In summary, individuals with TIA presenting with sensorimotor symptoms have decreased FA in tracts that are also implicated in sensorimotor function, which outlast the clinical symptoms associated with TIA. This suggests a more profound type of brain damage associated with TIA than has been typically described in past work. Diffusion tensor imaging may have utility as a marker of TIA-associated changes to white matter pathways. Hum Brain Mapp 38:5795-5803, 2017. © 2017 Wiley Periodicals, Inc.

Changes in White Matter Integrity following Intensive Voice Treatment (LSVT LOUD®) in Children with Cerebral Palsy and Motor Speech Disorders

Preliminary evidence suggests that intensive voice and speech treatment based on activity-dependent neuroplasticity principles holds promise for affecting positive change in children with cerebral palsy (CP) and motor speech disorders. Diffusion tensor imaging (DTI) allows researchers to make inferences about the integrity of white matter tracks and provides a sensitive measure of neuroplasticity. Previous treatment studies looking at the effects of training on white matter integrity have shown positive results, but these studies have been limited to gross motor function. Eight children with motor speech disorders and CP (3 females; age 8-16 years) and an age- and sex-matched group of typically developing (TD) children participated. Each child with CP completed a full dose of LSVT LOUD® and a 12-week maintenance program. Participants attended 3 recording sessions: before and after treatment, and after the maintenance period. TD children were tested at the same 3 time points. Recording sessions for both groups of children included measures of white matter integrity using DTI and acoustic measures of voice and speech. Fractional anisotropy (FA) was measured for 2 motor tracts and 5 association tracts. In children with CP, we observed an increase in FA in several motor and association tracts immediately following treatment and 12 weeks after treatment. Acoustic data on untrained tasks were correlated with changes in FA detected immediately following treatment and after the 12-week maintenance program. These findings suggest that long-term practice of skills attained during the treatment phase enhances white matter tract integrity in speech production networks.

White matter microstructure in boys with persistent depressive disorder

BackgroundPersistent depressive symptoms in children and adolescents are considered a risk factor for the development of major depressive disorder (MDD) later in life. Previous research has shown alterations in white matter microstructure in pediatric MDD but discrepancies exist as to the specific tracts affected. The current study aimed to improve upon previous methodology and address the question whether previous findings of lower fractional anisotropy (FA) replicate in a sample of children with persistent depressive disorder characterized by mild but more chronic symptoms of depression. MethodsWhite matter microstructure was examined in 25 boys with persistent depressive disorder and 25 typically developing children. Tract specific analysis implemented with the Diffusion Tensor Imaging - ToolKit (DTI-TK) was used to probe fractional anisotropy (FA) in eleven major white matter tracts. ResultsClusters within the left uncinate, inferior fronto-occipital and cerebrospinal tracts showed lower FA in the clinical group. FA in the left uncinate showed a negative association with self-reported symptoms of depression. ConclusionsThe results demonstrate lower FA in several white matter tracts in children with persistent depressive disorder. These findings support the contention that early onset depression is associated with altered white matter microstructure, which may contribute to the maintenance and recurrence of symptoms.