Gyrus White Matter Research Articles

Alteration of the Cortex Shape as a Proxy of White Matter Swelling in Severe Cerebral Small Vessel Disease.

CADASIL is a monogenic small vessel disease characterized by the accumulation of brain tissue lesions of microvascular origin leading to strokes and cognitive deficits. Both cortical and parenchymal alterations have been described using various MRI markers. However, relationships between cortical and subcortical alterations remain largely unexplored. While brain atrophy is a preponderant feature in cerebral small vessel disease, recent results in CADASIL suggest slightly larger brain volumes and increased white matter water content at early stages of the disease by comparison to controls. We hypothesized in this study that increased water content in gyral white matter balances expected brain atrophy. Direct white matter volume computation is challenging in these patients given widespread subcortical alterations. Instead, our approach was that a gyral white matter swelling would translate into a modification of the shape of cortical gyri. Our goal was then to assess the relationship between subcortical lesions and possible alteration of the cortex shape. More specifically, aims of this work were to assess 1) morphometric differences of the cortex shape between CADASIL patients and controls 2) the relationship between the cortex shape and the volume of white matter hyperintensities (WMH), a reflect of white matter alterations. Twenty-one patients at the early stage of the disease and 28 age- and sex-matched controls were included. Cortical surfaces were reconstructed from 3D-T1-weighted images. Folding power assessed from spectral analysis of gyrification and cortical morphometry using curvedness and shape index were computed as proxies of the cortex shape. Influence of segmentation errors were evaluated through the simulation of WMH in controls. As a result, patients had larger folding power and curvedness compared to controls. They also presented lower shape indices both related to sulci and gyri. In patients, the volume of WMH was associated with decreased gyral shape index. These results suggest that the cortex shape of CADASIL patients is different compared to controls and that the enlargement of gyri is related to the extent of white matter alterations. The study of the cortex shape might be another way to evaluate subcortical swelling or atrophy in various neurological disorders.

Micro- and Macrostructural White Matter Integrity in Never-Treated and Currently Unmedicated Patients With Schizophrenia and Effects of Short-Term Antipsychotic Treatment

BackgroundSchizophrenia is associated with progressive white matter changes, but it is unclear whether antipsychotic medications contribute to these. Our objective was to characterize effects of short-term treatment with risperidone on white matter diffusion indices. MethodsWe recruited 42 patients with schizophrenia (30 never treated and 12 currently untreated) and 42 matched healthy control subjects in this prospective case-control neuroimaging study. Patients received a 6-week trial of risperidone. Using diffusion tensor imaging, we assessed microstructural (fractional anisotropy, mean diffusivity, and radial diffusivity) and macrostructural (radial fiber trophy) white matter integrity deficits in unmedicated patients compared with control subjects and change in white matter integrity in patients before and after antipsychotic treatment (mean risperidone dose at end point was 3.73 ± 1.72 mg). ResultsAt baseline, fractional anisotropy was decreased in the left medial temporal white matter (cluster extent: 123 voxels; Montreal Neurological Institute peak coordinates: x = −51, y = −44, z = −7; α < .05), and mean diffusivity was increased in the fusiform/lingual gyrus white matter extending to the hippocampal part of the cingulum (cluster extent: 185 voxels; peak coordinates: x = −27, y = −49, z = 2; α < .04) in patients compared with control subjects. Radial diffusivity and macrostructure were not abnormal. None of the diffusion indices showed a significant change after 6 weeks of treatment with both voxelwise and whole-brain white matter analyses. ConclusionsWe demonstrate microstructural white matter integrity abnormalities in the absence of macrostructural impairment in unmedicated patients with primarily early-stage schizophrenia. In our data, we found no significant white matter changes after short-term treatment with risperidone.

Longitudinal Clinical and Neuroimaging Evaluation of Symptomatic Concussion in 10- to 14-year-old Youth Athletes.

This study longitudinally assessed 10- to 14-year-old patients with sports and recreational concussion (n = 22) who remained symptomatic 3 to 4weeks post-injury compared with typically developing controls (n = 24). Examination by multi-modal magnetic resonance imaging (MRI) and multi-domain clinical outcome measures was completed at 1-month and 6-months post-injury. Concussion patients showed evidence of improvement by 6-month follow-up in domains of cognitive function, whereas measures of psychological health were less resolved with patients exhibiting sustained symptoms of depression, behavior impairment, and concussion symptoms. Quantitative neuroimaging measures identified measures indicative of chronic injury with regional reductions observed by both volumetric segmentation and white matter fractional anisotropy (FA) from diffusion tensor imaging (DTI). Volumetric reductions (p < 0.01) were observed in the middle anterior and posterior portions of the corpus callosum, and right caudal anterior cingulate cortex of patients, although none held after strict correction. Examination of the FA data identified significant reductions in the left middle frontal gyrus white matter (p = 0.0003). Linear regression analysis on the 6-month depression outcome variable using the initial clinical, demographic, and imaging measures identified the top predictive models to include concussion diagnosis, and initial symptoms of depression, concussion symptoms, and sleep impairment with additional contribution from other measures of mental health, behavior impairment, and quality of life depending on the model (adjusted r-squared = 0.69 indicating strong predictive ability). This study supports further inclusion of mental health rehabilitation and imaging supplementing traditional cognitive rehabilitation strategies employed in these young athletes.

Diffusion tensor magnetic resonance imaging in the diagnosis of white matter lesion in middle-aged patients with uncomplicated essential hypertension

Diffusion tensor magnetic resonance imaging (DT-MRI) is the only noninvasive technique that makes it possible to study white matter microstructure in vivo and to quantify the images obtained. Objective : to study white matter in middle-aged treatment-naХ ve patients with uncomplicated grade 1–2 essential hypertension (EH), by using DT-MRI. Patients and methods . The investigation enrolled 82 people aged 40–59 years (41 patients with EH and 41 healthy individuals (a control group)). Twenty-four blood pressure monitoring and brain MRI were performed in different modes (T1 MPRAGE, T2 TSE, T2 FLAIR, and DTI). Results . White matter hyperintensities (WMHs) were found in 7.3% of the healthy individuals and in 53.7% of the hypertensive patients (p=0.0002). The latter had significantly lower fractional anisotropy (FA) values in the white matter of the left inferior frontal gyrus than the healthy individuals (0.39±0.06 and 0.45±0.09, respectively; p<0.001). FA was lower in the hypertensive patients than in the healthy individuals not only in the presence of WMHs (the left inferior frontal gyrus white matter was 0.397±0.071 and 0.45±0.09, respectively; p=0.009; the genu of the corpus callosum was 0.79±0.04 and 0.81±0.05, respectively; p=0.045), but also in the absence of WMHs (the left inferior frontal gyrus white matter was 0.378±0.073 and 0.45±0.09, respectively; p=0.0007). Discussion. The treatment-naХ ve patients with uncomplicated grade 1–2 EH with short-term (2,3 year) duration were found to have significantly lower FA values in the left inferior frontal gyrus white matter than the healthy normotensive subjects of the same age. Thus, the microstructural integrity of white matter is impaired in middle-aged hypertensive patients even at the earliest disease stages. Conclusion. Middle-aged treatment-naive patients with uncomplicated grade 1–2 EH have lower FA in the left inferior frontal gyrus white matter even in the absence of WMHs.

Compensatory Shift of Subcallosal Area and Paraterminal Gyrus White Matter Parameters on DTI in Patients with Alzheimer Disease.

Alzheimer disease is traditionally conceptualized as a disease of brain gray matter, however, studies with diffusion tensor imaging have demonstrated that Alzheimer disease also involves alterations in white matter integrity. We measured number of tracts, tracts length, tract volume, quantitative anisotropy and general fractional anisotropy of neuronal tracts in subcallosal area, paraterminal gyrus and fornix in patients with Alzheimer disease and healthy age-matched controls. Our hypothesis was that patients with Alzheimer disease should exhibit decrease in the integrity of these white matter structures that are crucial for semantic memory function. For our study were selected 24 patients with confirmed Alzheimer disease diagnosis and 24 healthy controls (AD center, Department of Neurology, Charles University, Prague, Czech Republic). Statistically significant differences between the patients with Alzheimer disease and the control group were found both on the left and right fornices but only concerning the tract numbers and tract length. The subcallosal area and paraterminal gyrus showed statistically significant differences between the patients with Alzheimer disease and the control group, but only on the left side and only associated with the tract volume and quantitative anisotropy. Our explanation for these findings lies in the severe hippocampal atrophy (and subsequent loss of function) with compensatory hypertrophy of the subcallosal area and paraterminal gyrus neuronal fibers that occurs in Alzheimer's disease, as an adaptation to the loss of projection from the hippocampal formation via fornix.

Characterization of White Matter Tracts by Diffusion MR Tractography in Cat and Ferret that Have Similar Gyral Patterns.

The developmental relationships between gyral structures and white matter tracts have long been debated, but it is still difficult to discern whether they influence each other's development or are causally related. To explore this topic, this study used cats and ferrets as models for species that share similar gyral folding patterns and imaged with diffusion magnetic resonance imaging to compare white matter innervations in homologous gyri and other brain regions. Adult cat and ferret brains were analyzed via diffusion spectrum imaging tractography and homologous regions of interest were compared. Although similar genetic lineage and gyral structures would suggest analogous white matter tracts, tractography reveals significantly differing white matter connectivity in both the visual and auditory cortices. Similarities in connectivity were concentrated primarily in the highly conserved cerebellar region. These results correlate well with existing histological and functional studies of both species. Our results indicate that, while the 2 species may share similar gyral structures, they utilize different white matter connectivity; suggesting that while species may share similar gyral structures, they can develop different underlying white matter connectivity.

Distinct white-matter aberrations in 22q11.2 deletion syndrome and patients at ultra-high risk for psychosis.

Patients with a deletion at chromosome 22q11.2 (22q11DS) have 30% lifetime risk of developing a psychosis. People fulfilling clinical criteria for ultra-high risk (UHR) for psychosis have 30% risk of developing a psychosis within 2 years. Both high-risk groups show white-matter (WM) abnormalities in microstructure and volume compared to healthy controls (HC), which have been related to psychotic symptoms. Comparisons of WM pathology between these two groups may specify WM markers related to genetic and clinical risk factors. Fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD) and mean diffusivity (MD) were assessed using diffusion tensor magnetic resonance imaging (MRI), and WM volume with structural MRI, in 23 UHR patients, 21 22q11DS patients, and 33 HC. Compared to UHR patients 22q11DS patients had (1) lower AD and RD in corpus callosum (CC), cortical fasciculi, and anterior thalamic radiation (ATR), (2) higher FA in CC and ATR, and (3) lower occipital and superior temporal gyrus WM volume. Compared to HC, 22q11DS patients had (1) lower AD and RD throughout cortical fasciculi and (2) higher FA in ATR, CC and inferior fronto-occipital fasciculus. Compared to HC, UHR patients had (1) higher mean MD, RD, and AD in CC, ATR and cortical fasciculi, (2) no differences in FA. UHR and 22q11DS patients share a susceptibility for developing psychosis yet were characterized by distinct patterns of WM alterations relative to HC. While UHR patients were typified by signs suggestive of aberrant myelination, 22q11DS subjects showed signs suggestive of lower axonal integrity.

White matter alterations in youth with acute mild traumatic brain injury

To examine acute alterations in white matter (WM) diffusion based on diffusion tensor imaging (DTI) in youth with mild traumatic brain injury (mTBI) relative to orthopedic injury (OI) controls. A prospective cohort study of 23 patients with mTBI and 20 OI controls ages 11-16 years were recruited from the emergency department (ED). DTI was performed within 96 hours. Voxel based analysis quantified group differences for DTI indices: fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD). The Post Concussion Symptom Scale assessed symptom burden. Youth with mTBI had significantly higher symptom burdens in the ED and at scanning than controls. The mTBI group had significantly higher levels of FA and AD in several WM regions including the middle temporal gyrus WM, superior temporal gyrus WM, anterior corona radiata, and superior longitudinal fasciculus. The mTBI group had significantly lower levels of MD and/or RD in a few WM regions including the middle frontal gyrus WM and anterior corona radiata. Diffusion alterations correlated poorly with acute symptom burden. Alterations of diffusivity were detected in spatially heterogeneous WM regions shortly after mTBI in youth. The pattern of alterations may reflect restrictive water diffusion in WM early post-injury.

Inferior frontal gyrus white matter abnormalities in obsessive-compulsive disorder.

The aim of the present study is to explore obsessive-compulsive disorder (OCD)-related abnormalities in white matter connectivity in OCD for a core region associated with inhibitory control [i.e. inferior frontal gyrus (IFG)]. Fifteen patients with OCD (11 men) and 15 healthy controls (nine men) underwent diffusion tensor imaging scanning to study four diffusivity indexes of white matter integrity [fractional anisotropy, mean diffusivity (MD), axial diffusivity and radial diffusivity (RD)]. The results showed that persons with OCD manifested significantly lower fractional anisotropy levels in the bilateral IFG as well as its parcellations in the pars opercularis, pars triangularis, and pars orbitalis. Significantly higher levels of MD, RD were evident for the OCD group in the IFG as a whole as well as in the bilateral subregions of the pars triangularis and pars opercularis (for MD and RD), the right side of the pars orbitalis (for RD), and the left side of the pars triangularis and right side pars opercularis (for axial diffusivity). Overall, the results suggest significant alterations in structural connectivity, probably associated with myelination and axonal abnormalities in the IFG of OCD patients.

Oligodendrocyte morphometry and expression of myelin – Related mRNA in ventral prefrontal white matter in major depressive disorder

White matter disturbance in the ventral prefrontal cortex (vPFC) in major depressive disorder (MDD) has been noted with diffusion tensor imaging (DTI). However, the cellular and molecular pathology of prefrontal white matter in MDD and potential influence of antidepressant medications is not fully understood. Oligodendrocyte morphometry and myelin-related mRNA and protein expression was examined in the white matter of the vPFC in MDD. Sections of deep and gyral white matter from the vPFC were collected from 20 subjects with MDD and 16 control subjects. Density and size of CNPase-immunoreactive (-IR) oligodendrocytes were estimated using 3-dimensional cell counting. While neither density nor soma size of oligodendrocytes was significantly affected in deep white matter, soma size was significantly decreased in the gyral white matter in MDD. In rhesus monkeys treated chronically with fluoxetine there was no significant effect on oligodendrocyte morphometry. Using quantitative RT-PCR to measure oligodendrocyte-related mRNA for CNPase, PLP1, MBP, MOG, MOBP, Olig1 and Olig2, in MDD there was a significantly reduced expression of PLP1 mRNA (which positively correlated with smaller sizes) and increased expression of mRNA for CNPase, OLIG1 and MOG. The expression of CNPase protein was significantly decreased in MDD. Altered expression of four myelin genes and CNPase protein suggests a mechanism for the degeneration of cortical axons and dysfunctional maturation of oligodendrocytes in MDD. The change in oligodendrocyte morphology in gyral white matter may parallel altered axonal integrity as revealed by DTI.

The Subventricular Zone in the Immature Piglet Brain: Anatomy and Exodus of Neuroblasts into White Matter after Traumatic Brain Injury

Stimulation of postnatal neurogenesis in the subventricular zone (SVZ) and robust migration of neuroblasts to the lesion site in response to traumatic brain injury (TBI) is well established in rodent species; however, it is not yet known whether postnatal neurogenesis plays a role in repair after TBI in gyrencephalic species. Here we describe the anatomy of the SVZ in the piglet for the first time and initiate an investigation into the effect of TBI on the SVZ architecture and the number of neuroblasts in the white matter. Among all ages of immaturity examined the SVZ contained a dense mesh network of neurogenic precursor cells (doublecortin+) positioned directly adjacent to the ependymal cells (ventricular SVZ, Vsvz) and neuroblasts organized into chains that were distinct from the Vsvz (abventricular SVZ, Asvz). Though the architecture of the SVZ was similar among ages, the areas of Vsvz and Asvz neuroblast chains declined with age. At postnatal day (PND) 14 the white matter tracts have a tremendous number of individual neuroblasts. In our scaled cortical impact model, lesion size increased with age. Similarly, the response of the SVZ to injury was also age dependent. The younger age groups that sustained the proportionately smallest lesions had the largest SVZ areas, which further increased in response to injury. In piglets that were injured at 4 months of age and had the largest lesions, the SVZ did not increase in response to injury. Similar to humans, swine have abundant gyri and gyral white matter, providing a unique platform to study neuroblasts potentially migrating from the SVZ to the lesioned cortex along these white matter tracts. In piglets injured at PND 7, TBI did not increase the total number of neuroblasts in the white matter compared to uninjured piglets, but redistribution occurred with a greater number of neuroblasts in the white matter of the hemisphere ipsilateral to the injury compared to the contralateral hemisphere. At 7 days after injury, less than 1% of neuroblasts in the white matter were born in the 2 days following injury. These data show that the SVZ in the piglet shares many anatomical similarities with the SVZ in the human infant, and that TBI had only modest effects on the SVZ and the number of neuroblasts in the white matter. Piglets at an equivalent developmental stage to human infants were equipped with the largest SVZ and a tremendous number of neuroblasts in the white matter, which may be sufficient in lesion repair without the dramatic stimulation of neurogenic machinery. It has yet to be determined whether neurogenesis and migrating neuroblasts play a role in repair after TBI and/or whether an alteration of normal migration during active postnatal population of brain regions is beneficial in species with gyrencephalic brains.

Voxel-based analysis of fractional anisotropy in post-stroke apathy.

ObjectiveTo explore the structural basis of post-stroke apathy by using voxel-based analysis (VBA) of fractional anisotropy (FA) maps.MethodsWe enrolled 54 consecutive patients with ischemic stroke during convalescence, and divided them into apathy (n = 31) and non-apathy (n = 23) groups. We obtained magnetic resonance images of their brains, including T1, T2 and DTI sequences. Age, sex, education level, Hamilton Depression Scale (HAMD) scores, Mini-Mental State Examination (MMSE) scores, National Institutes of Health Stroke Scale (NIHSS) scores, and infarct locations for the two groups were compared. Finally, to investigate the structural basis of post-stroke apathy, VBA of FA maps was performed in which we included the variables that a univariate analysis determined had P-values less than 0.20 as covariates.ResultsHAMD (P = 0.01) and MMSE (P<0.01) scores differed significantly between the apathy and non-apathy groups. After controlling for age, education level, HAMD scores, and MMSE scores, significant FA reduction was detected in four clusters with peak voxels at the genu of the corpus callosum (X = −16, Y = 30, Z = 8), left anterior corona radiata (−22, 30, 10), splenium of the corpus callosum (−24, −56, 18), and right inferior frontal gyrus white matter (52, 24, 18), after family-wise error correction for multiple comparisons.ConclusionsPost-stroke apathy is related to depression and cognitive decline. Damage to the genu of the corpus callosum, left anterior corona radiata, splenium of the corpus callosum, and white matter in the right inferior frontal gyrus may lead to apathy after ischemic stroke.

Effects of VRK2 (rs2312147) on white matter connectivity in patients with schizophrenia.

Recent genome-wide association studies of schizophrenia reported a novel risk variant, rs2312147 at vaccinia-related kinase 2 gene (VRK2), in multiple Asian and European samples. However, its effect on the brain structure in schizophrenia is little known. We analyzed the brain structure of 36 schizophrenia patients and 18 healthy subjects with regard to rs2312147 genotype groups. Brain magnetic resonance scans for gray matter (GM) and white matter (WM) analysis, and genotype analysis for VRK2 rs2312147, were conducted. The Positive and Negative Syndrome Scale and the Digit Symbol Test were assessed for schizophrenia patients. There was no significant difference in either GM volume or WM connectivity with regard to rs2312147 genotype in healthy subjects. In contrast, we found significant differences in the WM connectivity between rs2312147 CC and CT/TT genotype groups of schizophrenia patients. The related brain areas included the splenium of corpus callosum, the left occipital lobe WM, the internal capsule (left anterior limb and right retrolenticular part), the bilateral temporal lobe WM, the left fornix/stria terminalis, the left cingulate gyrus WM, and the left parietal lobe WM. Voxelwise correlation analysis revealed that the Digit Symbol Test scores (age corrected) correlated with the fractional anisotropy in WM tracts that previously showed significant group differences between the CT/TT and CC genotypes in the rs2312147 CT/TT genotype group, while no significant correlation was found in the CC genotype group. Our data may provide evidence for the effect of VRK2 on WM connectivity in patients with schizophrenia.

Developmental dynamics of radial vulnerability in the cerebral compartments in preterm infants and neonates.

The developmental vulnerability of different classes of axonal pathways in preterm white matter is not known. We propose that laminar compartments of the developing cerebral wall serve as spatial framework for axonal growth and evaluate potential of anatomical landmarks for understanding reorganization of the cerebral wall after perinatal lesions. The 3-T MRI (in vivo) and histological analysis were performed in a series of cases ranging from 22 postconceptional weeks to 3 years. For the follow-up scans, three groups of children (control, normotypic, and preterms with lesions) were examined at the term equivalent age and after the first year of life. MRI and histological abnormalities were analyzed in the following compartments: (a) periventricular, with periventricular fiber system; (b) intermediate, with periventricular crossroads, sagittal strata, and centrum semiovale; (c) superficial, composed of gyral white matter, subplate, and cortical plate. Vulnerability of thalamocortical pathways within the crossroads and sagittal strata seems to be characteristic for early preterms, while vulnerability of long association pathways in the centrum semiovale seems to be predominant feature of late preterms. The structural indicator of the lesion of the long association pathways is the loss of delineation between centrum semiovale and subplate remnant, which is possible substrate of the diffuse periventricular leukomalacia. The enhanced difference in MR signal intensity of centrum semiovale and subplate remnant, observed in damaged children after first year, we interpret as structural plasticity of intact short cortico-cortical fibers, which grow postnatally through U-zones and enter the cortex through the subplate remnant. Our findings indicate that radial distribution of MRI signal abnormalities in the cerebral compartments may be related to lesion of different classes of axonal pathways and have prognostic value for predicting the likely outcome of prenatal and perinatal lesions.

Fibrillary astrocytes are decreased in the subgenual cingulate in schizophrenia

Decreases in astrocyte density and in glial fibrillary acid protein (GFAP) mRNA in the anterior cingulate cortex have been reported changed in mood and affective disorders. Our study examines the relative density and frequency of fibrillary and gemistocytic astrocytes in the white matter of the subgenual cingulate cortex in 11 schizophrenia, 16 bipolar disorder, 20 major depression and 20 normal control cases. Serial coronal sections were stained with H&E for anatomical guidance and GFAP immunohistochemistry for astrocyte identification. Astrocyte density was measured using systematic anatomical distinctions and randomised counting methods previously reported. Astrocytes were classified as fibrillary or gemistocytic based on staining and morphometric criteria and were measured in the crown and base of the gyral white matter. Fibrillary astrocytes were decreased in the base of the cingulate white matter in schizophrenia (p = 0.046), with no change in the density of gemistocytic astrocytes. There was no change in density of gemistocytic astrocytes. This suggests that the previously reported decrease in astrocytes in schizophrenia in the subgenual cingulate is accounted for only by a change in fibrillary astrocytes. With recent findings suggesting fibrillary astrocytes regulate synaptic glutamate this morphological change may relate to disregulation of function of the subgenual cingulate cortex.

Executive deficits, not processing speed relates to abnormalities in distinct prefrontal tracts in amyotrophic lateral sclerosis

Cognitive impairment in amyotrophic lateral sclerosis is characterized by deficits on tests of executive function; however, the contribution of abnormal processing speed is unknown. Methods are confounded by tasks that depend on motor speed in patients with physical disability. Structural and functional magnetic resonance imaging studies have revealed multi-system cerebral involvement, with evidence of reduced white matter volume and integrity in predominant frontotemporal regions. The current study has two aims. First, to investigate whether cognitive impairments in amyotrophic lateral sclerosis are due to executive dysfunction or slowed processing speed using methodology that accommodates motor disability. This is achieved using a dual-task paradigm and tasks that manipulate stimulus presentation times and do not rely on response motor speed. Second, to identify relationships between specific cognitive impairments and the integrity of distinct white matter tracts. Thirty patients with amyotrophic lateral sclerosis and 30 age- and education-matched control subjects were administered an experimental dual-task procedure that combined a visual inspection time task and digit recall. In addition, measures of executive function (including letter fluency) and processing speed (visual inspection time and rapid serial letter identification) were administered. Integrity of white matter tracts was determined using region of interest analyses of diffusion tensor magnetic resonance imaging data. Patients with amyotrophic lateral sclerosis did not show impairments on tests of processing speed, but executive deficits were revealed once visual inspection time was combined with digit recall (dual-task) and in letter fluency. In addition to the corticospinal tracts, significant differences in fractional anisotropy and mean diffusivity were found between groups in a number of prefrontal and temporal white matter tracts including the anterior cingulate, anterior thalamic radiation, uncinate fasciculus and hippocampal portion of the cingulum bundles. Significant differences also emerged in the anterior corona radiata as well as in white matter underlying the superior, medial and inferior frontal gyri and the temporal gyri. Dual-task performance significantly correlated with fractional anisotropy measures in the middle frontal gyrus white matter and anterior corona radiata. Letter fluency indices significantly correlated with fractional anisotropy measures of the inferior frontal gyrus white matter and corpus callosum in addition to the corticospinal tracts and mean diffusivity measures in the white matter of the superior frontal gyrus. The current study demonstrates that cognitive impairment in amyotrophic lateral sclerosis is not due to generic slowing of processing speed. Moreover, different executive deficits are related to distinct prefrontal tract involvement in amyotrophic lateral sclerosis with dual-task impairment associating with dorsolateral prefrontal dysfunction and letter fluency showing greater dependence on inferolateral prefrontal dysfunction.

The Human Cerebral Cortex Flattens during Adolescence

The human cerebral cortex appears to shrink during adolescence. To delineate the dynamic morphological changes involved in this process, 52 healthy male and female adolescents (11-17 years old) were neuroimaged twice using magnetic resonance imaging, approximately 2 years apart. Using a novel morphometric analysis procedure combining the FreeSurfer and BrainVisa image software suites, we quantified global and lobar change in cortical thickness, outer surface area, the gyrification index, the average Euclidean distance between opposing sides of the white matter surface (gyral white matter thickness), the convex ("exposed") part of the outer cortical surface (hull surface area), sulcal length, depth, and width. We found that the cortical surface flattens during adolescence. Flattening was strongest in the frontal and occipital cortices, in which significant sulcal widening and decreased sulcal depth co-occurred. Globally, sulcal widening was associated with cortical thinning and, for the frontal cortex, with loss of surface area. For the other cortical lobes, thinning was related to gyral white matter expansion. The overall flattening of the macrostructural three-dimensional architecture of the human cortex during adolescence thus involves changes in gray matter and effects of the maturation of white matter.

A 1H-magnetic resonance spectroscopy imaging study on frontal gyrus, anterior cingulate cortex and hippocampus of patients with generalized anxiety disorder

Objective To study the feature of brain functional in front gyrus, anterior cingulate cortex and hippocampus of patients with generalized anxiety disorder (GAD). Methods 19 patients with GAD and 20 healthy volunteers were scanned on brain using proton magnetic resonance spectroscopic imaging (1H-MRS). The levels of Choline (Cho), Creatine (Cr), N-acetyl-aspartate(NAA) were measured in the frontal gyrus, anterior cingulate cortex and hippocampus of all subjects.The 1H-MRS data were compared between two groups. Results Compared with the healthy matched control, the levels of Cho(7.22±1.99), Cr(5.44±1.68), NAA(12.09±2.30)in right frontal gyrus white matter, the levels of Cho(9.89±2.40), Cr(8.59±1.71)in right anterior cingulate cortex and the levels of NAA in left anterior cingulate cortex were significantly high (P 0.05). Conclusion The brain substance metabolisms of the patients with GAD are abnormal and asymmetrical between left and right brain, especially occurred in right brain. Key words: 1H-Magnetic resonance spectroscopy; Generalized anxiety disorder; Frontal gyrus; Anterior cingulate cortex; Hippocampus

White matter microstructure correlates of inhibition and task-switching in adolescents

Although protracted prefrontal gray matter development is associated with concomitant executive function (EF) development in adolescents, few studies have explored the relationship between white matter and EF. This study examined the relationship between white matter microstructure and two aspects of EF, inhibition and task-switching, in a sample of 84 adolescents using diffusion tensor imaging (DTI). Tract-Based Spatial Statistics (TBSS) were used to examine fractional anisotropy (FA) and mean diffusivity (MD). Adolescents completed the Color-Word Interference task from the Delis–Kaplan Executive Function System, a clinical version of the Stroop task. Inhibition and task-switching performance were group normalized and measured using both reaction time and errors. Performance and the interaction of age and performance were regressed on FA and MD white matter skeletons, controlling for age and IQ, separately for inhibition and task-switching. Follow up analyses examined the relative contributions of axial and radial diffusivities. Greater FA in the anterior corona radiata (ACR) was associated with better inhibition, independent of age. Greater FA in the SCR and precentral gyrus white matter were associated with better task-switching, regardless of age, whereas an association between FA in the ACR and task-switching was dependent on age. There were no significant associations between MD and performance. Results suggest better inhibition and task-switching are associated with greater integrity of white matter microstructure in regions supporting cross-cortical and cortical–subcortical connections stemming from the prefrontal cortex. These findings are consistent with functional studies of cognitive control and models of EF that propose separate, yet related, latent factors.

Longitudinal Heschl's gyrus growth during childhood and adolescence in typical development and autism.

Heightened auditory sensitivity and atypical auditory processing are common in autism. Functional studies suggest abnormal neural response and hemispheric activation to auditory stimuli, yet the neurodevelopment underlying atypical auditory function in autism is unknown. In this study, we model longitudinal volumetric growth of Heschl's gyrus gray matter and white matter during childhood and adolescence in 40 individuals with autism and 17 typically developing participants. Up to three time points of magnetic resonance imaging data, collected on average every 2.5 years, were examined from individuals 3-12 years of age at the time of their first scan. Consistent with previous cross-sectional studies, no group differences were found in Heschl's gyrus gray matter volume or asymmetry. However, reduced longitudinal gray matter volumetric growth was found in the right Heschl's gyrus in autism. Reduced longitudinal white matter growth in the left hemisphere was found in the right-handed autism participants. Atypical Heschl's gyrus white matter volumetric growth was found bilaterally in the autism individuals with a history of delayed onset of spoken language. Heightened auditory sensitivity, obtained from the Sensory Profile, was associated with reduced volumetric gray matter growth in the right hemisphere. Our longitudinal analyses revealed dynamic gray and white matter changes in Heschl's gyrus throughout childhood and adolescence in both typical development and autism.