Gray Matter

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Towards joint morphometry of white matter tracts and gray matter surfaces

Towards joint morphometry of white matter tracts and gray matter surfaces

Morphological studies of anatomical structures play an important role in neu- roimaging. For example in the analysis of the circuits connecting sub-cortical areas to the cortical surface one would like to study together gray matter sur- faces and white matter tracts (ber bundles). To the best of our knowledge, there is no generic method to study these objects together.

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Recommendations for the Use of Automated Gray Matter Segmentation Tools: Evidence from Huntington’s Disease

Recommendations for the Use of Automated Gray Matter Segmentation Tools: Evidence from Huntington’s Disease

FigUre 2 | Continued Examples of the gray matter (GM) output from each tool overlaid on one participant from the Track-Huntington’s disease (HD) study. The figure shows three coronal views, with (a) showing the same slices with no segmentation. The first slice shows the frontal and temporal regions, the second slice is toward the middle of the brain, and the last slice shows the occipital lobe. All figures show default probabilistic segmentation maps for each software except for FreeSurfer, which shows volumetric and surface-based regions. For the probabilistic segmentation maps, the brighter the yellow within a voxel, the more likely that the voxel contains GM. The arrow labeled x points to a region of the dura incorrectly classified as occipital GM, and the arrow labeled + points to a region of voxels incorrectly classified as temporal GM. (a) Prior to segmentation. (B) Statistical Parametric Mapping (SPM) 8 Unified Segment, (c) SPM 8 New Segment, (D) SPM 12 Segment, (e) Advanced Normalization Tools (ANTs) Atropos, (F) MALP-EM, (g) FMRIB’s Software Library (FSL) FAST, and (h) FreeSurfer.
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Longitudinal gray matter contraction in three variants of primary progressive aphasia : a tensor-based morphometry study

Longitudinal gray matter contraction in three variants of primary progressive aphasia : a tensor-based morphometry study

91 disease pathology with an atypical presentation may be responsible 92 for lvPPA ( Josephs et al., 2008 ; Mesulam et al., 2008 ; Rabinovici et al., 93 2008b ; Rohrer et al., 2012 , 2013 ). 94 PPA syndromes can be quite heterogeneous in terms of disease dura- 95 tion and symptom progression. A better understanding of anatomical 96 disease progression could significantly help predict the time course of 97 the disease, the symptoms that may arise in these patients and could 98 also have a major impact on caregiver education and support. Further- 99 more, tracking the disease over time could shed light on the possible 100 mechanisms involved in the spreading of the disease. In this frame- 101 work, the characterization of the pattern of atrophy progression rep- 102 resents a major challenge in the study of PPA patients. To date, only a 103 few studies have investigated the progression of gray matter atrophy 104 over time in a single variant of PPA, such as svPPA ( Brambati et al.,
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Gray matter hypertrophy and thickening with obstructive sleep apnea in middle-aged and older adults

Gray matter hypertrophy and thickening with obstructive sleep apnea in middle-aged and older adults

3. Vulnerability of specific brain regions to OSA In the present study, markers of OSA severity were associated with increased thickness or volume in the lateral prefrontal cortex, the parietal lobules, and posterior cingulate cortex as well as the amygdala. Interestingly, previous studies on OSA showed both increased and decreased gray matter volume and/or thickness in the same or adjacent regions as those reported in the present study (9, 11, 13-15, 30-32, 43, 44). Therefore, these regions may be especially vulnerable to OSA and be preferentially affected by both swelling and atrophic processes. It is also important to highlight that we found trends for association between OSA markers of severity and increased gray matter in contralateral brain regions. It would be interesting to follow this cohort in order to verify whether these trends will reach significance over time.
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Perfusion shift from white to gray matter may account for processing speed deficits in schizophrenia.

Perfusion shift from white to gray matter may account for processing speed deficits in schizophrenia.

matter (WM). Patients with schizophrenia show significant deficits in WM integrity, as indexed by fractional anisotropy (FA) of water diffusion, and measured using diffusion tensor imaging (DTI). Reduced speed of information processing and reduced cerebral FA values are highly replicable findings in this disorder that are likely interlinked [Alba-Ferrara and de Erausquin, 2013; Ellison-Wright and Bullmore, 2009; Friedman et al., 2008; Glahn et al., 2013; Kubicki et al., 2007; Nazeri et al., 2013; Penke et al., 2010; Perez-Iglesias et al., 2011; Phillips et al., 2012]. In this study, we examined the link between processing speed (PS) and WM integrity in the context of the energy consumption. Specifically, we hypothesized that reduced WM integrity in patients may lead to alterations in the energy utilization between WM and gray matter (GM) compartments and this, in turn, may modulate functional deficits. The specificity of this effect was tested using two additional neuropsychological tests: working memory and Wechsler adult intelligence scale.
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Regional volumes and spatial volumetric distribution of gray matter in the gender dysphoric brain.

Regional volumes and spatial volumetric distribution of gray matter in the gender dysphoric brain.

Postmortem studies have observed sex-atypical volumes and neuronal numbers in hypothalamic nuclei in the brains of individuals with GD ( Garcia-Falgueras and Swaab, 2008; Kruijver et al., 2000; Zhou et al., 1995 ). Brain structure in individuals with GD has also been investigated in vivo. MRI studies examining white matter tracts using diffusion ten- sor imaging have shown deviations from the natal sex in white matter microstructure in both female-to-males (FM) and male-to-females (MF) ( Rametti et al., 2011a,b ). A few neuroimaging studies have investigated gray matter (GM) in individuals with GD, observing both regional volumet- ric properties in line with the natal sex and others in line with the gender identity of the GD groups ( Luders et al., 2009b, 2012; Savic and Arver, 2011; Zubiaurre-Elorza et al., 2012; Simon et al., 2013 ). A recent study by Zubiaurre-Elorza et al. (2012) was the first to examine GM in FM ( Zubiaurre- Elorza et al., 2012 ). Interestingly, they observed signs of subcortical masculinization in female-to-male adults and of cortical feminization in male-to-female adults, providing the first insights into the developmental processes under- lying GD in both sexes.
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Cortical gray-matter thinning is associated with age-related improvements on executive function tasks

Cortical gray-matter thinning is associated with age-related improvements on executive function tasks

improvements (Casey et al., 2005; Sowell et al., 2004; Tau and Peterson, 2009). Here we explored the role of gray-matter thinning in age-related improvements in cognitive control and working memory span in children ages 5–10, using structural MRI. Many studies have identified substantial decreases in gray-matter thickness in prefrontal and parietal cortices beginning in early childhood and continuing into adolescence (Gogtay et al., 2004; O’Donnell et al., 2005; Pfefferbaum et al., 1994; Sowell et al., 2004; Wilke et al., 2007). These studies include both cross-sectional examinations using automatic gray-white matter parcellation techniques similar to those used in the current paper (Ostby et al., 2009) and longitudinal examinations of children 5–10 years old (Sowell et al., 2004). In contrast to these studies reporting age-related cortical thinning, a few studies have observed non-linear patterns of cortical thickening in early childhood followed by thinning in later childhood or adolescence (e.g. Shaw et al., 2006, 2008). Other studies found that developmental
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Geometrical variations in white and gray matter affect the biomechanics of spinal cord injuries more than the arachnoid space

Geometrical variations in white and gray matter affect the biomechanics of spinal cord injuries more than the arachnoid space

Le´o Fradet 1,2 , Pierre-Jean Arnoux 2,3 , Virginie Callot 2,4 and Yvan Petit 2,5 Abstract Traumatic spinal cord contusions lead to loss of quality of life, but their pathomechanisms are not fully understood. Previous studies have underlined the contribution of the cerebrospinal fluid in spinal cord protection. However, it remains unclear how important the contribution of the cerebrospinal fluid is relative to other factors such as the white/ gray matter ratio. A finite element model of the spinal cord and surrounding morphologic features was used to investi- gate the spinal cord contusion mechanisms, considering subarachnoid space and white/gray matter ratio. Two vertebral segments (T6 and L1) were impacted transversely at 4.5 m s 21 , which demonstrated three major results:
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Changes in gray matter volume and functional connectivity in dementia with Lewy bodies compared to Alzheimer's disease and normal aging: implications for fluctuations

Changes in gray matter volume and functional connectivity in dementia with Lewy bodies compared to Alzheimer's disease and normal aging: implications for fluctuations

However, when investigating more directly the correl- ation between patients’ fluctuation scores and gray mat- ter volume in the DLB group, we found a weak negative correlation in the left inferior parietal lobule, the left and right cerebellum, the midbrain, the bilateral prefrontal cortex, and to a lesser extent, the right thalamus. These regions did not correspond to those showing gray matter loss in DLB patients compared to control subjects, which suggests that the relative atrophy of frontal and insular cortices may not be directly involved in the oc- currence of fluctuations. Moreover, the effect of fluctu- ation scores on regional gray matter volume seemed to follow a particular pattern, as the corresponding brain regions were part of the cholinergic system. This system plays an important role in attention and conscious awareness [ 43 , 44 ] and was shown to be more affected in DLB than in AD [ 45 , 46 ]. The disturbances identified in DLB patients notably include deficits in ChAT [ 47 ] and AChE [ 48 ] and changes in nicotinic and muscarinic receptors density [ 49 – 51 ] compared to AD patients and healthy elderly subjects. Several studies reviewed by Aarsland et al. [ 52 ] also demonstrated that cholinester- ase inhibitors have a positive effect on cognition and neuropsychiatric symptoms in DLB patients, including fluctuating attention, unresponsiveness, and daytime somnolence [ 53 ]. Similarly, neuropathological analyses comparing fluctuating and non-fluctuating DLB patients reported significant cholinergic impairments in thalamic
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Brain Metabolism but Not Gray Matter Volume Underlies the Presence of Language Function in the Minimally Conscious State (MCS): MCS+ Versus MCS− Neuroimaging Differences

Brain Metabolism but Not Gray Matter Volume Underlies the Presence of Language Function in the Minimally Conscious State (MCS): MCS+ Versus MCS− Neuroimaging Differences

frontoparietal hypometabolism was reported in 69% of the MCS- patients against 24% of the MCS+ patients, showing the overall difference between the 2 subgroups. However, it also means that our results are not systematically observable at the subject level. The main novelty of this study is to combine functional and structural analyses in MCS- and MCS+ patients at group level in a representative sample. While functional measurements provide an accurate picture of the functioning brain areas and networks, structural data give information on the location of tissue’s damage. 46 We did not find any gray matter volume difference between MCS-
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Numerical Transcoding Proficiency in 10-Year-Old Schoolchildren is Associated with Gray Matter Inter-Individual Differences: A Voxel-Based Morphometry Study

Numerical Transcoding Proficiency in 10-Year-Old Schoolchildren is Associated with Gray Matter Inter-Individual Differences: A Voxel-Based Morphometry Study

Are individual differences in numerical performance sustained by variations in gray matter volume in schoolchildren? To our knowledge, this challenging question for neuroeducation has not yet been investigated in typical development. We used the Voxel-Based Morphom- etry method to search for possible structural brain differences between two groups of 10-year-old schoolchildren (N = 22) whose performance differed only in numerical transcod- ing between analog and symbolic systems. The results indicated that children with low numerical proficiency have less gray matter volume in the parietal (particularly in the left intraparietal sulcus and the bilateral angular gyri) and occipito-temporal areas. All the identi- fied regions have previously been shown to be functionally involved in transcoding between analog and symbolic numerical systems. Our data contribute to a better understanding of the intertwined relationships between mathematics learning and brain structure in healthy schoolchildren.
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Numerical Transcoding Proficiency in 10-Year-Old Schoolchildren is Associated with Gray Matter Inter-Individual Differences: A Voxel-Based Morphometry Study

Numerical Transcoding Proficiency in 10-Year-Old Schoolchildren is Associated with Gray Matter Inter-Individual Differences: A Voxel-Based Morphometry Study

Are individual differences in numerical performance sustained by variations in gray matter volume in schoolchildren? To our knowledge, this challenging question for neuroeducation has not yet been investigated in typical development. We used the Voxel-Based Morphom- etry method to search for possible structural brain differences between two groups of 10-year-old schoolchildren (N = 22) whose performance differed only in numerical transcod- ing between analog and symbolic systems. The results indicated that children with low numerical proficiency have less gray matter volume in the parietal (particularly in the left intraparietal sulcus and the bilateral angular gyri) and occipito-temporal areas. All the identi- fied regions have previously been shown to be functionally involved in transcoding between analog and symbolic numerical systems. Our data contribute to a better understanding of the intertwined relationships between mathematics learning and brain structure in healthy schoolchildren.
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Associations between daily mood states and brain gray matter volume, resting-state functional connectivity and task-based activity in healthy adults

Associations between daily mood states and brain gray matter volume, resting-state functional connectivity and task-based activity in healthy adults

Psychoeducation, University of Montreal, Montreal, QC, Canada, 5 Department of Psychology and Pediatrics, University of Montreal, Montreal, QC, Canada, 6 School of Public Health, Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland Numerous studies have shown differences in the functioning in the areas of the frontal- limbic circuitry between depressed patients and controls. However, current knowledge on frontal-limbic neural substrates of individual differences in mood states in everyday life in healthy individuals is scarce. The present study investigates anatomical, resting-state, and functional neural correlates of daily mood states in healthy individuals. We expected to observe associations between mood and the frontal-limbic circuitry and the default- mode network (DMN). A total of 42 healthy adults (19 men, 23 women; 34 ± 1.2 years) regularly followed for behavior and psychosocial functioning since age of 6, underwent a functional magnetic resonance imaging scan, and completed a daily diary of mood states and related cognitions for 5 consecutive days. Results showed that individuals with smaller left hippocampal gray matter volumes experienced more negative mood and rumination in their daily life. Greater resting-state functional connectivity (rsFC) within the DMN, namely between posterior cingulate cortex (PCC) and medial prefrontal cortex regions as well as between PCC and precuneus, was associated with both greater negative and positive mood states in daily life. These rsFC results could be indicative of the role of the DMN regional functioning in emotional arousal, irrespective of valence. Lastly, greater daily positive mood was associated with greater activation in response to negative emotional stimuli in the precentral gyri, previously linked to emotional interference on cognitive control. Altogether, present findings might reflect neural mechanisms underlying daily affect and cognition among healthy individuals.
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Indetermination-free cytoarchitecture measurements in brain gray matter via a forward diffusion MRI signal separation method

Indetermination-free cytoarchitecture measurements in brain gray matter via a forward diffusion MRI signal separation method

Such non-invasive measurement of cellular characteristics has the potential to quantify tissue cytoarchitecture, in a unique-solution system, which has so far been accessible only through histology. Our contribution focuses on the human brain gray matter, which can be decomposed into three compartments, somas and processes that are modeled by spheres and 0-radius tubes, and extra-cellular water. This work shows the feasibility to extract factor that reflects the averaged diameter of the somas in the voxel with a unique solution. Our three-compartment model, under the hypothesis that there is no exchange between the three compartments , is as follow :
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Abnormal structural and functional brain connectivity in gray matter heterotopia

Abnormal structural and functional brain connectivity in gray matter heterotopia

Keywords malformation; tractography; fMRI; epilepsy; dyslexia Introduction In many forms of epilepsy, aberrant neuronal connections are likely to be important in pathogenesis (Scharfman 2007). Unfortunately, our ability to probe these changes noninvasively in human patients has been limited. Periventricular nodular heterotopia (PNH), one of the most commonly encountered epileptic brain malformations (Sisodiya 2004), is an ideal substrate for the study of epileptogenic processes (Dubeau et al. 1995; Li et al. 1997; Aghakhani et al. 2005). Although PNH patients are not homogeneous, being characterized by different clinical and radiological features (Battaglia et al. 2006), the disorder is defined by gray matter nodules located along or extending from the walls of the lateral ventricles, and usually presents with the clinical triad of normal intelligence, epilepsy, and reading dysfluency (Chang et al. 2005; Chang et al. 2007; Battaglia & Granata 2008). Just under half of cases have mutations in the FLNA (filamin A) gene on Xq28 (Fox et al. 1998).
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Cytoarchitecture Measurements in Brain Gray Matter using Likelihood-Free Inference

Cytoarchitecture Measurements in Brain Gray Matter using Likelihood-Free Inference

Current microstructure models are predominantly based on the two com- partment Standard Model (SM) [18, 11]. Recent evidence shows that the SM, mainly used in white matter, does not hold for grey matter microstructure anal- ysis [17]. Several assumptions aim at explaining this issue such as increased permeability in neurite membranes [17], or curvy projections along with longer pulse duration [11]. We follow the hypothesis that the SM doesn’t hold due to an abundance of cell bodies in gray matter [13]. Our proposed biophysical model is then based on three compartments [13]: neurites; somas; and extra-cellular space (ECS). Despite its increased complexity, the main advantage of such model is the possibility to jointly estimate the characteristic features of each compartment.
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Brain gray matter MRI morphometry for neuroprognostication after cardiac arrest

Brain gray matter MRI morphometry for neuroprognostication after cardiac arrest

We hypothesize that the use of cortical thickness measurement and subcortical gray matter quantitative volumetry could provide an accurate in vivo assessment of the impact of anoxic/hypoxic insult induced by CA. We speculate that cortical and subcortical volume atrophy measurements provided by these approaches could be used as accurate predictors of long-term neurologic out- come in this setting. To test this hypothesis, we prospectively stud- ied a large and multicenter cohort of anoxic comatose patients. All patients were prospectively recruited and managed according to standard of care recommendations (5) by clinical practitio- ners blinded to MRI data, to avoid bias related to self-fulfilling prophecies. Patients were scanned during the acute phase follow- ing the CA, exclusively during coma state, in standardized clinical
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Transcriptomics of cortical gray matter thickness decline during normal aging.

Transcriptomics of cortical gray matter thickness decline during normal aging.

Neurodegenerative aging is characterized by an abrupt decline in cognition and is associated with increased neuroinflammation, microglial activation, and accumulation of neuroinflammatory proteins and beta-amyloid plaques (Capell et al., 2007; Dodge et al., 2011; Kirkpatrick et al., 2008; Royall et al., 2011; Salthouse, 2009; Schillerstrom et al., 2008; Wolkowitz et al., 2011). Neuroinflammation was assumed to be minimal in healthy aging; yet more recent observations suggest that activation of innate immune pathways may still occur even in healthy cerebral aging (Berchtold et al., 2008; Cribbs et al., 2011). Familial history explains a very large proportion (40–80%) of the variance in individual trajectories in many imaging-based phenotypes of in cerebral aging, including cortical gray matter thickness (GMT) and others (Chiang et al., 2011; DeStefano et al., 2006; Kent et al., 2012; Kochunov et al., 2010a; Kochunov et al., 2009a; Turner et al., 2005; Winkler et al., 2010). However, the search for specific genotypes leading to aging-related disorders had so far identified candidate genes that explain only a small proportion (1–2%) of the total risk (Biffi et al., 2011; Chouliaras et al., 2010). The risk of neurodegenerative aging is likely to be modulated by both genotype and environment, and genome-wide association analyses generally cannot account for their interaction (Chouliaras et al., 2010; Kamboh et al., 2011; Kent et al., 2012; Tanzi, 2012; Weinstein et al., 2011). In contrast, transcriptional profiling analyses that measure the expression of genes are sensitive to both genotype and
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Cortical spreading depression decreases Fos expression in rat periaqueductal gray matter

Cortical spreading depression decreases Fos expression in rat periaqueductal gray matter

NSL 30944 1–6 B.V. Bogdanov et al. / Neuroscience Letters xxx (2014) xxx–xxx 3 Fig . 1. Top: scheme of segmentation into dorso-medial PAG, dorso-lateral PAG, and ventro-lateral PAG (periaqueductal gray matter) segments and Edinger – Westphal nucleus, EWn/3 N areas on a Fos-Ir transverse section of the region of interest (bregma −6.5 mm). Bottom: illu strative camera lucida drawings of Fos-Ir nuclei identified in transverse sections of rostral (bregma −6.5 m m) and caudal parts (bregma −8 m m) of the PAG in an animal belonging to the sham-operated, CSD- stimulated and NaCl-treated, or CSD-stimulated and lamotrigine (LTG)-treated groups. Three sections separated by 360 ␮ m are shown for the two PAG levels.
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Deep Learning Methods for MRI Spinal Cord Gray Matter Segmentation

Deep Learning Methods for MRI Spinal Cord Gray Matter Segmentation

Despite these difficulties, there have been major improvements in acquisition and analysis methods in recent years, making it possible to obtain reliable GM segmentations. From the acquisition standpoint, the advances in coil sensitivity [65], multi-echo gradient echo sequences [66], and phase-sensitive inversion recovery sequences [67] drastically improved the contrast-to-noise-ratio between the white and gray matter in the cord. From the analysis standpoint, the scientific community recently organized a collaboration effort called "Spinal Cord Gray Matter Segmentation Challenge" (SCGM Challenge) [2] to characterize the state- of-the-art and compare six independent developed methods [7,10,11,15,16,68] on a public available standard dataset created through the collaboration of four internationally recognized spinal cord imaging research groups (University College London, Polytechnique Montreal, University of Zurich and Vanderbilt University), providing therefore a ground basis for method comparison that was previously unfeasible.
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