Shilpi Modi

Individual differences in trait anxiety are associated with white matter tract integrity in fornix and uncinate fasciculus: Preliminary evidence from a DTI based tractography study

Trait anxiety, a personality dimension that measures an individuals higher disposition to anxiety, has been found to be associated with many functional consequences viz. increased distractibility, attentional bias in favor of threat-related information etc. Similarly, volumetric studies have reported morphological changes viz. a decrease in the volume of left uncinate fasciculus (fiber connecting anterior temporal areas including the amygdala with prefrontal-/orbitofrontal cortices) and an increase in the volume of the left amygdala and right hippocampus, to be associated with trait anxiety. The functional and morphological changes associated with trait anxiety might also be associated with the changes in the integrity of WM tracts in relation with the trait anxiety levels of the subjects. Therefore, in the present diffusion tensor tractography (DTT) study, we investigated the possible relationship between the diffusion tensor imaging (DTI) derived indices of a wide array of fiber tracts and the trait anxiety scores in our subject group. A positive correlation between trait anxiety scores and the mean fractional anisotropy (FA) value was obtained in fornix and left uncinate fasciculus. The study provides first account of a positive relation between sub-clinical anxiety levels of subjects and the FA of fornix thereby providing interesting insights into the biological foundation of sub-clinical anxiety.

Assessment of the metabolic profile in Type 2 diabetes mellitus and hypothyroidism through proton MR spectroscopy

The metabolic changes in the brain of patients affected with Type 2 diabetes mellitus (DM) alone, both Type 2 DM and hypothyroidism and hypothyroidism only were investigated using proton magnetic resonance spectroscopy ((1)H MRS). Single-voxel spectroscopy was carried out in right and left frontal lobe white matter, left parietal white matter and left occipital gray matter. Choline (Cho)/creatine (Cr) value was found to be increased in the left occipital gray matter of the subjects affected with Type 2 DM and both Type 2 DM and hypothyroidism as compared to controls. No significant change in the Cho/Cr value in the occipital gray matter was observed in hypothyroid subjects as compared to controls. However, they showed an increased level of Cho/Cr in the frontal white matter. High Cho is associated with altered membrane phospholipid metabolism. The high Cho in frontal white matter in hypothyroids and occipital gray matter in diabetic patients suggests that, though both the diseases are endocrine disorders, they differ from each other in terms of regional brain metabolite changes.

Aberrant functional connectivity of resting state networks associated with trait anxiety

Trait anxiety, a personality dimension, has been characterized by functional consequences such as increased distractibility, attentional bias in favor of threat-related information and hyper-responsive amygdala. However, literature on the association between resting state brain functional connectivity, as studied using resting state functional magnetic resonance imaging (rs-fMRI), and reported anxiety levels in the sub-clinical population is limited. In the present study, we employed rs-fMRI to investigate the possible alterations in the functional integrity of Resting State Networks (RSNs) associated with trait anxiety of the healthy subjects (15 high anxious and 14 low anxious). The rs-fMRI data was analyzed using independent component analysis and a dual regression approach that was applied on 12 RSNs that were identified using FSL. High anxious subjects showed significantly reduced functional connectivity in regions of the default mode network (posterior cingulate gyrus, middle and superior temporal gyrus, planum polare, supramarginal gyrus, temporal pole, angular gyrus and lateral occipital gyrus) which has been suggested to be involved in episodic memory, theory of mind, self-evaluation, and introspection, and perceptual systems including medial visual network, auditory network and another network involving temporal, parieto-occipital and frontal regions. Reduction in resting state connectivity in regions of the perceptual networks might underlie the perceptual, attentional and working memory deficits associated with trait anxiety. To our knowledge, this is the first study to relate trait anxiety to resting state connectivity using independent component analysis.

Glutamate level in anterior cingulate predicts anxiety in healthy humans: A magnetic resonance spectroscopy study

Anxiety, a personality dimension in healthy humans, has been found to be associated with many functional consequences such as increased distractibility and attentional bias in favour of threat-related information, along with morphological and microstructural changes in the brain. The associated metabolic/neurochemical alterations are sparsely studied. In the present magnetic resonance spectroscopy (MRS) study, we investigated the possible relationship between regional brain chemistry within anterior cingulate cortex (4-cm(3) voxel) and hippocampus (2.5-cm(3) voxel) and anxiety (measured by State-Trait Anxiety Inventory) in our subject group. In the anterior cingulate cortex, multivariate analysis of covariance showed an increase in myo-inositol and combined glutamate and glutamine levels in the high anxiety subject group as compared with the low anxiety group. In the partial correlation analysis between neurochemicals and anxiety, glutamate and combined glutamate and glutamine also showed a predictive value for anxiety. On analysing the trait anxiety sub-score separately, we found glutamate, inositol and combined glutamate and glutamine levels to be increased in the high trait anxiety group as compared with the low trait anxiety group. All three resonances also had a predictive value for trait anxiety. In the hippocampus, none of the neurochemicals showed significant difference between high and low anxiety groups. The study provides a first account of alterations in anterior cingulate cortex neurochemistry in relation to anxiety in healthy subjects. The study thus contributes to the limited literature available on altered metabolism and neural mechanisms underlying sub-clinical anxiety.

Motor function deficits in schizophrenia: an fMRI and VBM study

IntroductionTo investigate whether the motor functional alterations in schizophrenia (SZ) are also associated with structural changes in the related brain areas using functional magnetic resonance imaging (fMRI) and voxel-based morphometry (VBM).MethodsA sample of 14 right-handed SZ patients and 14 right-handed healthy control subjects matched for age, sex, and education were examined with structural high-resolution T1-weighted MRI; fMRI images were obtained during right index finger-tapping task in the same session.ResultsfMRI results showed reduced functional activation in the motor areas (contralateral precentral and postcentral gyrus) and ipsilateral cerebellum in SZ subjects as compared to healthy controls (n = 14). VBM analysis also revealed reduced grey matter in motor areas and white matter reduction in cerebellum of SZ subjects as compared to controls.ConclusionThe present study provides an evidence for a possible association between structural alterations in the motor cortex and disturbed functional activation in the motor areas in persons affected with SZ during a simple finger-tapping task.

Effect of visual experience on structural organization of the human brain: A voxel based morphometric study using DARTEL

OBJECTIVE To investigate structural reorganization in the brain with differential visual experience using Voxel-Based Morphometry with Diffeomorphic Anatomic Registration Through Exponentiated Lie algebra algorithm (DARTEL) approach. MATERIALS AND METHODS High resolution structural MR images were taken in fifteen normal sighted healthy controls, thirteen totally blind subjects and six partial blind subjects. The analysis was carried out using SPM8 software on MATLAB 7.6.0 platform. RESULTS VBM study revealed gray matter volume atrophy in the cerebellum and left inferior parietal cortex in total blind subjects and in left inferior parietal cortex, right caudate nucleus, and left primary visual cortex in partial blind subjects as compared to controls. White matter volume loss was found in calcarine gyrus in total blind subjects and Thlamus-somatosensory region in partially blind subjects as compared to controls. Besides, an increase in Gray Matter volume was also found in left middle occipital and middle frontal gyrus and right entorhinal cortex, and an increase in White Matter volume was found in superior frontal gyrus, left middle temporal gyrus and right Heschls gyrus in totally blind subjects as compared to controls. Comparison between total and partial blind subjects revealed a greater Gray Matter volume in left cerebellum of partial blinds and left Brodmann area 18 of total blind subjects. CONCLUSION Results suggest that, loss of vision at an early age can induce significant structural reorganization on account of the loss of visual input. These plastic changes are different in early onset of total blindness as compared to partial blindness.

Brain metabolite changes in alcoholism: localized proton magnetic resonance spectroscopy study of the occipital lobe.

Chronic alcoholism is associated with altered brain metabolism, morphology and cognitive abilities. Besides deficits in higher order cognitive functions, alcoholics also show a deficit in the processing of basic sensory information viz. visual stimulation. To assess the metabolic changes associated with this deficit, (1)H MRS was carried out in the occipital lobe of alcohol dependents. A significant increase in Cho/Cr ratio (p<0.015) was observed in occipital lobe in the alcoholic group indicating altered cell membrane metabolism, which may probably be associated with the alterations in the cognitive abilities associated with vision.

Functional and structural abnormalities associated with empathy in patients with schizophrenia: An fMRI and VBM study

Empathy deficit is a core feature of schizophrenia which may lead to social dysfunction. The present study was carried out to investigate functional and structural abnormalities associated with empathy in patients with schizophrenia using functional magnetic resonance imaging (fMRI) and voxel-based morphometry (VBM). A sample of 14 schizophrenia patients and 14 healthy control subjects matched for age, sex and education were examined with structural high-resolution T1-weighted MRI; fMRI images were obtained during empathy task in the same session. The analysis was carried out using SPM8 software. On behavioural assessment, schizophrenic patients (83.00±29.04) showed less scores for sadness compared to healthy controls (128.70±22.26) (p<0.001). fMRI results also showed reduced clusters of activation in the bilateral fusiform gyrus, left lingual gyrus, left middle and inferior occipital gyrus in schizophrenic subjects as compared to controls during empathy task. In the same brain areas, VBM results also showed reduced grey and white matter volumes. The present study provides an evidence for an association between structural alterations and disturbed functional brain activation during empathy task in persons affected with schizophrenia. These findings suggest a biological basis for social cognition deficits in schizophrenics.

Altered brain metabolism after whole body irradiation in mice: A preliminary in vivo 1H MRS study

Abstract Purpose: In the classical description of acute radiation syndrome, the role of central nervous system (CNS) is underestimated. It is now well recognised that ionising radiation-induced oxidative stress may bring about functional changes in the brain. In this study, we prospectively evaluated metabolic changes in the brain after whole body irradiation in mice using in vivo proton (1H) nuclear magnetic resonance spectroscopy (MRS). Material and methods: Young adult mice were exposed to whole body irradiation of 8 Gy and controls were sham irradiated. In vivo 1H MRS from cortex-hippocampus and hypothalamic-thalamic region of brain at different time points, i.e., as early as 6 hours, day 1, 2, 3, 5 and 10 post irradiation was carried out at 7 Tesla animal magnetic resonance imaging system. Brain metabolites were measured and quantitative analysis of detectable metabolites was performed by linear combination of model (LCModel). Results: Significant reduction in myoinositol (p = 0.03) and taurine (p = 0.02) ratios were observed in cortex-hippocampus region as early as day 2 post irradiation compared to controls. These metabolic alterations remained sustained over day 10 post irradiation. Conclusions: The results of this preliminary study suggest that the alteration/reduction in the mI and Tau concentration may be associated with physiological perturbations in astrocytes or radiation induced neuro-inflammatory response triggered in microglial cell.

T2 relaxation time alterations underlying neurocognitive deficits in alcohol-use disorders (AUD) in an Indian population: A combined conventional ROI and voxel-based relaxometry analysis

Long-term heavy alcohol consumption has traditionally been associated with impaired cognitive abilities, such as deficits in abstract reasoning, problem solving, verbal fluency, memory, attention, and visuospatial processing. The present study aimed at exploring these neuropsychological deficits in alcohol-use disorders (AUD) in an Indian population using the Postgraduate Institute Battery of Brain Dysfunction (PGIBBD) and their possible correlation with alterations in T2 relaxation times (T2-RT), using whole-brain voxel-based relaxometry (VBR) and conventional region of interest (ROI) approach. Multi-echo T2 mapping sequence was performed on 25 subjects with AUD and 25 healthy controls matched for age, education, and socioeconomic status. Whole-brain T2-RT measurements were conducted using VBR and conventional ROI approach. The study was carried out on a 3T whole-body MR scanner. Post processing for VBR and ROI analysis was performed using SPM 8 software and vendor-provided software, respectively. A PGIBBD test battery was conducted on all subjects to assess their cognitive abilities, and the results were reported as raw scores. VBR and ROI results revealed that AUD subjects showed prolonged T2-RTs in cerebellum bilaterally, parahippocampal gyrus bilaterally, right anterior cingulate cortex, left superior temporal gyrus, left middle frontal gyrus, and left calcarine gyrus. A significant correlation was also observed between the neuropsychological test raw scores and alterations in T2-RT in AUD subjects. Our results are consistent with previous studies suggesting tissue disruption or gliosis or demyelination as a possible reason for prolonged T2-RTs. This damage to brain tissue, which is evident as prolonged T2-RT, could possibly be associated with impaired cognitive abilities noticeable in AUD subjects.