Erratum: Figure Correction.

[This corrects the article on p. 68 in vol. 13, PMID: 25912540.].

A systematic examination of brain volumetric abnormalities in recent-onset schizophrenia using voxel-based, surface-based and region-of-interest-based morphometric analyses.

BACKGROUND: Brain morphometric abnormalities in schizophrenia have been extensively reported in the literature. Whole-brain volumetric reductions are almost universally reported by most studies irrespective of the characteristics of the samples studied (e.g., chronic/recent-onset; medicated/neuroleptic-naïve etc.). However, the same cannot be said of the reported regional morphometric abnormalities in schizophrenia. While certain regional morphometric abnormalities are more frequently reported than others, there are no such abnormalities that are universally reported across studies. Variability of socio-demographic and clinical characteristics across study samples as well as technical and methodological issues related to acquisition and analyses of brain structural images may contribute to inconsistency of brain morphometric findings in schizophrenia. The objective of the present study therefore was to systematically examine brain morphometry in patients with recent-onset schizophrenia to find out if there are significant whole-brain or regional volumetric differences detectable at the appropriate significance threshold, after attempting to control for various confounding factors that could impact brain volumes. METHODS: Structural magnetic resonance images of 90 subjects (schizophrenia = 45; healthy subjects = 45) were acquired using a 3 Tesla magnet. Morphometric analyses were carried out following standard analyses pipelines of three most commonly used strategies, viz., whole-brain voxel-based morphometry, whole-brain surface-based morphometry, and between-group comparisons of regional volumes generated by automated segmentation and parcellation. RESULTS: In our sample of patients having recent-onset schizophrenia with limited neuroleptic exposure, there were no significant whole brain or regional brain morphometric abnormalities noted at the appropriate statistical significance thresholds with or without including age, gender and intracranial volume or total brain volume in the statistical analyses. CONCLUSIONS: In the background of the conflicting findings in the literature, our findings indicate that brain morphometric abnormalities may not be directly related to the schizophrenia phenotype. Analysis of the reasons for the inconsistent results across studies as well as consideration of alternate sources of variability of brain morphology in schizophrenia such as epistatic and epigenetic mechanisms could perhaps advance our understanding of structural brain alterations in schizophrenia.

Effect of polymorphisms of three genes mediating monoamine signalling on brain morphometry in schizophrenia and healthy subjects.

OBJECTIVE: We examined the effect of risk alleles of polymorphisms of three schizophrenia risk genes that mediate monoamine signalling in the brain on regional brain volumes of schizophrenia and healthy control subjects. The risk alleles and the gene polymorphisms studied were: Val allele of catechol o-methyltransferase (COMT) rs4680 polymorphism; short allele of 5-hydroxy tryptamine transporter linked polymorphic region (5HTTLPR) polymorphism; and T allele of 5-hydroxy tryptamine 2A (5HT2A) rs6314 polymorphism. METHODS: The study was carried out on patients with recent onset schizophrenia (n=41) recruited from the outpatient department of National Institute of Mental Health and Neurosciences, Bangalore, India and healthy control subjects (n=39), belonging to South Indian Dravidian ethnicity. Individual and additive effects of risk alleles of the above gene polymorphisms on brain morphometry were explored using voxel-based morphometry. RESULTS: Irrespective of phenotypes, individuals with the risk allele T of the rs6314 polymorphism of 5HT2A gene showed greater (at cluster-extent equivalent to family wise error-correction [FWEc] p<0.05) regional brain volumes in the left inferior temporal and left inferior occipital gyri. Those with the risk alleles of the other two polymorphisms showed a trend (at p<0.001, uncorrected) towards lower regional brain volumes. A trend (at p<0.001, uncorrected) towards additive effects of the above 3 risk alleles (subjects with 2 or 3 risk alleles vs. those with 1 or no risk alleles) on brain morphology was also noted. CONCLUSIONS: The findings of the present study have implications in understanding the role of individual and additive effects of genetic variants in mediating regional brain morphometry in health and disease.

Endogenous-cue prospective memory involving incremental updating of working memory: an fMRI study.

INTRODUCTION: Prospective memory paradigms are conventionally classified on the basis of event-, time-, or activity-based intention retrieval. In the vast majority of such paradigms, intention retrieval is provoked by some kind of external event. However, prospective memory retrieval cues that prompt intention retrieval in everyday life are commonly endogenous, i.e., linked to a specific imagined retrieval context. We describe herein a novel prospective memory paradigm wherein the endogenous cue is generated by incremental updating of working memory, and investigated the hemodynamic correlates of this task. METHODS: Eighteen healthy adult volunteers underwent functional magnetic resonance imaging while they performed a prospective memory task where the delayed intention was triggered by an endogenous cue generated by incremental updating of working memory. Working memory and ongoing task control conditions were also administered. RESULTS: The 'endogenous-cue prospective memory condition' with incremental working memory updating was associated with maximum activations in the right rostral prefrontal cortex, and additional activations in the brain regions that constitute the bilateral fronto-parietal network, central and dorsal salience networks as well as cerebellum. In the working memory control condition, maximal activations were noted in the left dorsal anterior insula. CONCLUSIONS: Activation of the bilateral dorsal anterior insula, a component of the central salience network, was found to be unique to this 'endogenous-cue prospective memory task' in comparison to previously reported exogenous- and endogenous-cue prospective memory tasks without incremental working memory updating. Thus, the findings of the present study highlight the important role played by the dorsal anterior insula in incremental working memory updating that is integral to our endogenous-cue prospective memory task.

An exploratory association study of the influence of dysbindin and neuregulin polymorphisms on brain morphometry in patients with schizophrenia and healthy subjects from South India.

Multiple genetic risk variants may act in a convergent manner leading on to the pathophysiological alterations of brain structure and function in schizophrenia. We examined the effect of polymorphisms of two candidate genes that mediate glutamatergic signaling, viz., dysbindin (rs1011313) and neuregulin (rs35753505), on brain morphometry in patients with schizophrenia (N=38) and healthy subjects (N=37) from South India. Patients with schizophrenia showed trend-level (p<0.001 uncorrected, 20 voxel extent correction) volumetric reductions in multiple brain regions when compared to healthy control subjects. Trend-level volumetric differences were also noted between homozygotes of the risk allele (AA) of the neuregulin (NRG1) polymorphism and heterozygotes (AG), as well as homozygotes of the risk allele (CC) of the dysbindin (DTNBP1) polymorphism and heterozygotes (TC), irrespective of diagnosis. Moreover, an additive effect of the risk alleles on brain morphometry was also noted. These preliminary findings highlight the possible influence of polymorphisms of risk genes on brain morphometry in schizophrenia.

Single-trial EEG classification using logistic regression based on ensemble synchronization.

In this paper, we propose an ensemble synchronization measure across all EEG channel pairs of a cluster based on Frobenius norm of the phase synchronization matrix, in a 0-1 scale enabling a direct comparison between clusters with different number of channels. Using this metric, we studied the intrahemispheric EEG synchronization in the lower gamma band (30-40 Hz) during 1229 single trials of an audio-visual integration cross modal task (CMT) recorded from five patients with schizophrenia and five healthy control subjects. Using ensemble synchronization measure and response latency of single trials recorded during the CMT as features for logistic regression, we could classify each single trial of EEG as belonging to a patient with schizophrenia or a healthy control subject with 73% accuracy, with an area under receiver operating characteristics curve of 0.83. We also propose a likelihood rating to denote the possibility of a subject belonging to the schizophrenia group.

Utility of a computerized, paced semantic verbal fluency paradigm in differentiating schizophrenia and healthy subjects.

Functional magnetic resonance imaging (fMRI) paradigms designed to study word generation traditionally utilize a computerized paced version of the verbal fluency task (VFT) comprising 'blocks' of word generation and a baseline word repetition task. The utility of the above paced VFT paradigm in differentiating neuropsychiatric patients from healthy subjects has not been systematically examined. We administered a computerized, paced version of the semantic VFT comprising word generation and word repetition blocks to 24 schizophrenia and 24 matched healthy subjects, both before and during fMRI acquisition. The performance of patients with schizophrenia was significantly inferior to that of healthy control subjects in both the 'pre-scan' and 'intra-scan' sessions of the computerized paced semantic VFT. Specifically, schizophrenia patients generated significantly fewer total responses (VFTR) as well as correct responses (VFCR), but a larger number of 'no response' trials. However, there were no significant group differences in perseverative responses in the pre-scan session or 'intra-scan' sessions. The above computerized task has been reported by us previously to generate a behavioral performance index with hemodynamic correlates (John et al., 2011). Thus, our findings support the use of computerized paced VFT comprising word generation and word repetition blocks in both clinical and research settings.

Relationship of clinical and cognitive variables with brain morphometric abnormalities in Alzheimer's disease: a voxel based morphometric study using 3-tesla MRI.

Alzheimer's disease (AD) is associated with widespread structural and functional brain alterations. The current study examined the gray matter (GM) voxel based morphometric (VBM) correlates of cognitive and clinical severity scores in patients with AD. The study included 34 patients with AD according to NINCDS/ADRDA AD criteria and 28 matched elderly controls. All subjects were clinically evaluated using Hindi Mental Status Examination (HMSE), Everyday Abilities Scale for India (EASI) and the Clinical Dementia Rating (CDR) scale. The structural Magnetic Resonance Imaging (MRI) data were acquired using a 3 Tesla MRI scanner and VBM analysis was performed using VBM5.1 toolbox. The patients with AD had significantly lower GM volume, white matter volume and total brain volume as compared to controls. The HMSE scores were positively correlated (p=0.009) and EASI (p=0.04) & CDR (p=0.0004) were negatively correlated with the total GM volumes in patients with AD. The VBM analysis revealed diffuse GM atrophy in patients with AD. Frontal& temporal GM volumes were positively correlated with the HMSE scores. Thus the results of the study replicate the previous observations of generalized GM atrophy, in an Indian sample with AD. The cognitive decline, clinical dementia severity and impairment in activities of daily living were correlated whole brain GM and WM volumes as well as with specific brain regional atrophy in AD. However further studies with larger samples & with more detailed cognitive evaluation are required for confirmation & validation of the relationship between regional morphometric abnormalities and cognitive deficits in AD.

Apolipoprotein E4 and brain white matter integrity in Alzheimer's disease: tract-based spatial statistics study under 3-Tesla MRI.

INTRODUCTION: Apolipoprotein E4 (ApoE ε4) polymorphism is a known genetic risk factor for Alzheimer's disease (AD). OBJECTIVES: To evaluate the role of ApoE ε4 on white matter structural integrity in AD. METHODS: Subjects were 32 patients with probable AD (ApoE ε4-positive: n = 15) and 18 matched controls (ApoE ε4-positive: n = 6). All subjects were right-handed, evaluated using standard scales and genotyped at the ApoE locus. Diffusion tensor imaging was performed with a 3-tesla MRI scanner and analyzed using the tract-based spatial statistics method. RESULTS: AD patients had significantly lower fractional anisotropy (FA) in bilateral temporoparietal, limbic and parahippocampal regions in comparison to healthy comparison subjects. ApoE ε4 carriers among both AD and healthy comparison subjects showed lower FA in limbic and medial temporal regions. CONCLUSIONS: There is a modest association between ApoE ε4 carrier status and reduction in white matter tract integrity at medial temporal and limbic regions in both healthy and AD subjects.

Regional brain activation/deactivation during word generation in schizophrenia: fMRI study.

BACKGROUND: Examination of the brain regions that show aberrant activations and/or deactivations during semantic word generation could pave the way for a better understanding of the neurobiology of cognitive dysfunction in schizophrenia. AIMS: To examine the pattern of functional magnetic resonance imaging blood oxygen level dependent activations and deactivations during semantic word generation in schizophrenia. METHOD: Functional magnetic resonance imaging was performed on 24 participants with schizophrenia and 24 matched healthy controls during an overt, paced, 'semantic category word generation' condition and a baseline 'word repetition' condition that modelled all the lead-in/associated processes involved in the performance of the generation task. RESULTS: The brain regions activated during word generation in healthy individuals were replicated with minimal redundancies in participants with schizophrenia. The individuals with schizophrenia showed additional activations of temporo-parieto-occipital cortical regions as well as subcortical regions, despite significantly poorer behavioural performance than the healthy participants. Importantly, the extensive deactivations in other brain regions during word generation in healthy individuals could not be replicated in those with schizophrenia. CONCLUSIONS: More widespread activations and deficient deactivations in the poorly performing participants with schizophrenia may reflect an inability to inhibit competing cognitive processes, which in turn could constitute the core information-processing deficit underlying impaired word generation in schizophrenia.

Transplantation of hippocampal cell lines restore spatial learning in rats with ventral subicular lesions.

We have demonstrated in our previous studies that ventral subicular lesion induces neurodegeneration of the hippocampus and produces cognitive impairment in rats. In the present study, the efficacy of transplanted green fluorescent protein (GFP)-labeled hippocampal cell line (H3-GFP) cells in establishing functional recovery in ventral subicular lesioned rats has been evaluated. The survival of H3-GFP transplants and their ability to express trophic factors in vivo were also investigated. Adult male Wistar rats were subjected to selective lesioning of ventral subiculum and were transplanted with H3-GFP cells into the cornu ammonis 1 (CA1) hippocampus. The transplants settled mainly in the dentate gyrus and expressed neurotrophic factors, brain-derived neurotrophic factor (BDNF), and basic fibroblast growth factor (bFGF). The ventral subicular lesioned (VSL) rats with H3-GFP transplants showed enhanced expression of BDNF in the hippocampus and performed well in eight-arm radial maze and Morris water maze tasks. The VSL rats without hippocampal transplants continued to show cognitive impairment in task learning. The present study demonstrated the H3-GFP transplants mediated recovery of cognitive functions in VSL rats. Our study supports the notion of graft meditated host regeneration and functional recovery through trophic support, although these mechanisms require further investigation.

Complexity analysis of EEG in patients with schizophrenia using fractal dimension.

We computed Higuchi's fractal dimension (FD) of resting, eyes closed EEG recorded from 30 scalp locations in 18 male neuroleptic-naïve, recent-onset schizophrenia (NRS) subjects and 15 male healthy control (HC) subjects, who were group-matched for age. Schizophrenia patients showed a diffuse reduction of FD except in the bilateral temporal and occipital regions, with the reduction being most prominent bifrontally. The positive symptom (PS) schizophrenia subjects showed FD values similar to or even higher than HC in the bilateral temporo-occipital regions, along with a co-existent bifrontal FD reduction as noted in the overall sample of NRS. In contrast, this increase in FD values in the bilateral temporo-occipital region was absent in the negative symptom (NS) subgroup. The regional differences in complexity suggested by these findings may reflect the aberrant brain dynamics underlying the pathophysiology of schizophrenia and its symptom dimensions. Higuchi's method of measuring FD directly in the time domain provides an alternative for the more computationally intensive nonlinear methods of estimating EEG complexity.

Differential relationship of frontal pole and whole brain volumetric measures with age in neuroleptic-naïve schizophrenia and healthy subjects.

Brodmann's area (BA) 10, which occupies the frontal pole (FP) of the human brain, has been proven to play a central role in the executive control of cognitive operations. Previous in vivo morphometric studies of the FP have been limited by the lack of an accepted boundary of its posterior limit. We studied the FP gray matter volume in 23 healthy subjects who were age-, sex-, and education-matched to 23 neuroleptic-naïve recent-onset schizophrenia subjects in the age span 20-40 years, using a cytoarchitectonically and functionally valid landmark-based definition of its posterior boundary that we proposed recently (John, J.P., Yashavantha, B.S., Gado, M., Veena, R., Jain, S., Ravishankar, S., Csernansky, J.G., 2007. A proposal for MRI-based parcellation of the frontal pole. Brain Struct. Funct. 212, 245-253. 2007). Additionally, we examined the relationship between FP volume and age in both healthy and schizophrenia subjects to examine evidence for a possible differential relationship between these variables across the samples. A major finding of the study was the absence of a group-level difference in frontal pole gray volumes between the healthy and schizophrenia participants. However, a more complex finding emerged in relation to age effects. The healthy participants showed an inverse relationship of FP gray volume with age, even after taking total brain volume differences into account. But this age effect was completely absent in the schizophrenia group. Moreover, all the volumetric measures in schizophrenia subjects showed substantially higher range, variance, skewness and kurtosis when compared to those of healthy subjects. These findings have implications in understanding the possible role of FP in the pathophysiology of schizophrenia.