Gray Matter Connectivity Research Articles

Intrinsic gray-matter connectivity of the brain in adults with autism spectrum disorder

Autism spectrum disorders (ASD) are a group of neurodevelopmental conditions that are accompanied by atypical brain connectivity. So far, in vivo evidence for atypical structural brain connectivity in ASD has mainly been based on neuroimaging studies of cortical white matter. However, genetic studies suggest that abnormal connectivity in ASD may also affect neural connections within the cortical gray matter. Such intrinsic gray-matter connections are inherently more difficult to describe in vivo but may be inferred from a variety of surface-based geometric features that can be measured using magnetic resonance imaging. Here, we present a neuroimaging study that examines the intrinsic cortico-cortical connectivity of the brain in ASD using measures of "cortical separation distances" to assess the global and local intrinsic "wiring costs" of the cortex (i.e., estimated length of horizontal connections required to wire the cortex within the cortical sheet). In a sample of 68 adults with ASD and matched controls, we observed significantly reduced intrinsic wiring costs of cortex in ASD, both globally and locally. Differences in global and local wiring cost were predominantly observed in fronto-temporal regions and also significantly predicted the severity of social and repetitive symptoms (respectively). Our study confirms that atypical cortico-cortical "connectivity" in ASD is not restricted to the development of white-matter connections but may also affect the intrinsic gray-matter architecture (and connectivity) within the cortical sheet. Thus, the atypical connectivity of the brain in ASD is complex, affecting both gray and white matter, and forms part of the core neural substrates underlying autistic symptoms.

Functional Networks in Temporal-Lobe Epilepsy: A Voxel-Wise Study of Resting-State Functional Connectivity and Gray-Matter Concentration

Temporal-lobe epilepsy (TLE) involves seizures that typically originate in the hippocampus. There is evidence that seizures involve anatomically and functionally connected brain networks within and beyond the temporal lobe. Many studies have explored the effect of TLE on gray matter and resting-state functional connectivity in the brain. However, the relationship between structural and functional changes has not been fully explored. The goal of this study was to investigate the relationship between gray matter concentration (GMC) and functional connectivity in TLE at the voxel level. A voxel-wise linear regression analysis was performed between GMC maps and whole-brain resting-state functional connectivity maps to both the left thalamus (Lthal) and the left hippocampus (LH) in a group of 15 patients with left TLE. Twenty regions were found that exhibited GMC decreases linearly correlated with resting-state functional connectivity to either the LH or the Lthal in the patient group only. A subset of these regions had significantly reduced GMC, and one of these regions also had reduced functional connectivity to the LH in TLE compared to the controls. These results suggest a network of impairment in left TLE where more severe reductions in GMC accompany decreases (LH, Lthal, right midcingulate gyrus, left precuneus, and left postcentral gyrus) or increases (LH to right thalamus) in resting functional connectivity. However, direct relationships between these imaging parameters and disease characteristics in these regions have yet to be established.

Magnetic Resonance Imaging in Late-Life Depression

Disruption of frontal-subcortical and limbic networks is hypothesized to have a key role in late-life depression (LLD) and can be examined using magnetic resonance imaging (MRI) techniques. Gray matter can be examined using T1-weighted MRI, white matter using T2-weighted MRI and diffusion tensor imaging, and functional connectivity in resting-state networks using functional MRI. Although independent MRI studies have supported gray and white matter abnormalities in frontosubcortical and limbic networks and increased functional connectivity in the default-mode network in depression, no study has concurrently examined gray matter, white matter, and functional connectivity. To examine whether results of different MRI techniques are complementary, multimodal MRI was used to compare gray matter, white matter, and resting-state networks between LLD and control groups. Cross-sectional, case-control, multimodal MRI analysis. University research department. Thirty-six recovered participants with LLD (mean age, 71.8 years) and 25 control participants (mean age, 71.8 years). Gray matter was examined across the whole brain using voxel-based morphometry. Subcortical gray matter structures were also automatically segmented, and volumetric and shape analyses were performed. For white matter analysis, fractional anisotropy, axial diffusivity, and radial diffusivity values were examined using tract-based spatial statistics. For resting-state network analysis, correlation coefficients were compared using independent components analysis followed by dual regression. White matter integrity was widely reduced in LLD, without significant group differences in gray matter volumes or functional connectivity. The present work strongly supports the hypothesis that white matter abnormalities in frontal-subcortical and limbic networks play a key role in LLD even in the absence of changes in resting functional connectivity and gray matter. Factors that could contribute to the lack of significant differences in gray matter and functional connectivity measures, including current symptom severity, medication status, and age of participants with LLD, are discussed.

Altered structural connectivity in neonates at genetic risk for schizophrenia: A combined study using morphological and white matter networks

Recently, an increasing body of evidence suggests that developmental abnormalities related to schizophrenia may occur as early as the neonatal stage. Impairments of brain gray matter and wiring problems of axonal fibers are commonly suspected to be responsible for the disconnection hypothesis in schizophrenia adults, but significantly less is known in neonates. In this study, we investigated 26 neonates who were at genetic risk for schizophrenia and 26 demographically matched healthy neonates using both morphological and white matter networks to examine possible brain connectivity abnormalities. The results showed that both populations exhibited small-world network topology. Morphological network analysis indicated that the brain structural associations of the high-risk neonates tended to have globally lower efficiency, longer connection distance, and less number of hub nodes and edges with relatively higher betweenness. Subgroup analysis showed that male neonates were significantly disease-affected, while the female neonates were not. White matter network analysis, however, showed that the fiber networks were globally unaffected, although several subcortical-cortical connections had significantly less number of fibers in high-risk neonates. This study provides new lines of evidence in support of the disconnection hypothesis, reinforcing the notion that the genetic risk of schizophrenia induces alterations in both gray matter structural associations and white matter connectivity.

Neuroimaging of pain: what does it tell us?

To present an overview of insights into brain mechanisms of pain perception and analgesia based on human brain imaging. The technical advancement made in both functional and structural MRI can be used to delineate the cerebral signature of pain and analgesia, specifically, the brain responses to noxious stimuli and specific pain-related forebrain responses, as well as pain modulatory effects. Neuroimaging has revealed that the brain response to noxious stimuli shares neural resources with other systems that subserve salience detection and reward functions. Recent findings indicate that there is a wide range of individual differences in pain-related brain function and structure due to both pre-existing vulnerabilities and disease-driven factors. Furthermore, several studies now illustrate that the brain is capable of tremendous plasticity both in function and structure due to repeated and ongoing pain. However, emerging data suggest that this plasticity can be reversible after successful pain treatment. Neuroimaging of pain and plasticity can provide a framework to understand the basic mechanisms of pain regarding function, gray and white matter structure and connectivity. This information may also guide future clinical practice. For instance, the time-course of disease-driven brain plasticity and capacity for reversibility may help decide the optimal time frame for chronic pain treatment. Furthermore, findings from functional and structural connectivity studies may indicate potential side effects of targeting specific brain areas in treating chronic pain. Lastly, the correlation between individual factors and functional/structural MRI data may direct individualized treatment plans.

44 White Matter Abnormality is Associated with Volume Reduction in Deep Grey Nuclei Following Preterm Birth

Background. Diffuse white matter disease, which can be seen on MRI as Diffuse Excessive High Signal Intensity (DEHSI) and quantified using apparent diffusion coefficient (ADC) values is the most common abnormality in preterm infants at term equivalent age. We used a computational anatomic approach to survey the brain for structural alterations associated diffuse white matter disease.Methods. Subjects: 62 preterm infants without parenchymal cerebral lesions, born at median 29.7 weeks GA were studied at term equivalent age (median 40.4 weeks GA) together with 12 term born controls. Image acquisition: A 1.5 Tesla MR system was used to acquire high resolution T1-weighted volume datasets with a voxel size 1x1x1.6mm, in addition to conventional and diffusion weighted imaging. Diffuse white matter disease was defined as ADC values > 2 standard deviations above the mean of the control group in one or more white matter region. Image processing: non-rigid image registration was used to transform all images to a reference subject, and voxel-wise volume change values extracted from transformations were analysed with a correction for multiple comparisons.Results. Preterm infants showed volume loss within lentiform and thalamic nuclei (p<0.05), particularly among infants with diffuse white matter disease (p<0.05) and with increasing prematurity at birth (p<0.05), but ADC values in the thalamus and lentiform nuclei were similar to controls.Conclusions. Growth failure within deep grey nuclei occurs in association with diffuse white matter disease and without evidence of acute injury. This suggests deep grey matter connectivity is altered by preterm birth.

Natural history of obsessional states; a study of 150 cases.

<h3>Abstract</h3> <h3>Objectives</h3> Studies have demonstrated that sex differences may play a crucial role in the alternations of brain structures in individuals with bipolar disorder, but findings are not consistent. The current study identified sex differences in brain structure and function among a large sample of individuals with bipolar I disorder (BD-I). <h3>Methods</h3> Structural and functional magnetic resonance imaging datasets were acquired from 105 individuals with BD-I (36 men and 69 women) and 210 healthy adults (72 men and 138 women). A general linear regression model was used for voxel-wise analysis of grey matter (GM) and functional connectivity. Age, sex, diagnosis, and sex-by-diagnosis interaction were defined as predictors. <h3>Results</h3> In GM, the left caudate (<i>p</i> &lt; .001), left thalamus (<i>p</i> &lt; .001), right caudate (<i>p</i> = .003), right thalamus (<i>p</i> &lt; .001), left anterior cingulate gyrus (<i>p</i> = .015), and left middle/posterior cingulate gyrus (<i>p</i> = .022) exhibited sex-by-diagnosis interaction. Furthermore, by using these six brain regions as seeds, we observed sex-by-diagnosis interaction in the alteration of functional connectivity between the left thalamus and right angular gyrus (<i>p</i> = .019). <h3>Conclusions</h3> Our data revealed a sex-by-diagnosis interaction associated with structure and function of the limbic system in individuals with BD-I. These findings may serve as reference for future studies on the pathophysiology of bipolar disorder.