Most recent paper

NMDA receptor antagonists traxoprodil and lanicemine improve hippocampal-prefrontal coupling and reward-related networks in rats.

Psychopharmacology (Berl). 2019 Jul 02;:

Authors: Becker R, Gass N, Kußmaul L, Schmid B, Scheuerer S, Schnell D, Dorner-Ciossek C, Weber-Fahr W, Sartorius A

Abstract
RATIONALE: The N-methyl-D-aspartate receptor (NMDAR) antagonist ketamine is known to have not only a rapid antidepressant effect but also dissociative side effects. Traxoprodil and lanicemine, also NMDA antagonists, are candidate antidepressant drugs with fewer side effects.
OBJECTIVES: In order to understand their mechanism of action, we investigated the acute effects of traxoprodil and lanicemine on brain connectivity using resting-state functional magnetic resonance imaging (rs-fMRI).
METHODS: Functional connectivity (FC) alterations were examined using interregional correlation networks. Graph theoretical methods were used for whole brain network analysis. As interest in NMDAR antagonists as potential antidepressants was triggered by the antidepressant effect of ketamine, results were compared to previous findings from our ketamine studies.
RESULTS: Similar to ketamine but to a smaller extent, traxoprodil increased hippocampal-prefrontal (Hc-PFC) coupling. Unlike ketamine, traxoprodil decreased connectivity within the PFC. Lanicemine had no effect on these properties. The improvement of Hc-PFC coupling corresponds well to clinical result, showing ketamine to have a greater antidepressant effect than traxoprodil, while lanicemine has a weak and transient effect. Connectivity changes overlapping between the drugs as well as alterations of local network properties occurred mostly in reward-related regions.
CONCLUSION: The antidepressant effect of NMDA antagonists appears to be associated with enhanced Hc-PFC coupling. The effects on local network properties and regional connectivity suggest that improvement of reward processing might also be important for understanding the mechanisms underlying the antidepressant effects of these drugs.

PMID: 31267156 [PubMed - as supplied by publisher]

Multimodal Sparse Classifier for Adolescent Brain Age Prediction.

IEEE J Biomed Health Inform. 2019 Jun 28;:

Authors: Hosseinzadeh Kassani P, Gossmann A, Wang YP

Abstract
The study of healthy brain development helps to better understand both brain transformation and connectivity patterns, which happen during childhood to adulthood. This study presents a sparse machine learning solution across whole-brain functional connectivity (FC) measures of three data sets, derived from resting state functional magnetic resonance imaging (rs-fMRI) and two task fMRI data including a working memory n-back task (nb-fMRI) and an emotion identification task (em-fMRI). The fMRI data are collected from the Philadelphia Neurodevelopmental Cohort (PNC) for the prediction of brain age in adolescents. Due to extremely large variable-to-instance ratio of PNC data, a high dimensional matrix with several irrelevant and highly correlated features is generated, and hence a sparse learning approach is necessary to extract effective features from fMRI data. We propose a sparse learner based on the residual errors along the estimation of an inverse problem for extreme learning machine (ELM). Our proposed method is able to overcome the overlearning problem by pruning several redundant features and their corresponding output weights. The proposed multimodal sparse ELM classifier based on residual errors (RES-ELM) is highly competitive in terms of classification accuracy compared to its counterparts such as conventional ELM, and sparse Bayesian learning ELM.

PMID: 31265424 [PubMed - as supplied by publisher]

Striatal functional connectivity in chronic ketamine users: a pilot study.

Am J Drug Alcohol Abuse. 2019 Jul 02;:1-13

Authors: Hung CC, Zhang S, Chen CM, Duann JR, Lin CP, Lee TS, Li CR

Abstract
Background: The striatum supports motivated behavior and impulse control. Altered striatal activation and connectivity has been observed in link with impulse control dysfunction in individuals with drug addiction. Objectives: We examined how resting state functional connectivity (rsFC) of the striatum is altered as a result of chronic ketamine misuse. Methods: Thirty-six ketamine users (10 women) and 20 healthy controls (9 women) completed an assessment with the Barratt Impulsiveness Scale (BIS-11) and magnetic resonance imaging. In SPM we examined voxel-wise connectivities of the caudate, pallidum, putamen, and ventral striatum in ketamine users (versus healthy controls) and in association with BIS-11 score and duration of use, all at a corrected threshold. Results: Compared to controls, ketamine users showed higher connectivity between caudate and dorsal anterior cingulate cortex and between pallidum and bilateral cerebellum. In ketamine users, putamen showed higher connectivity with the left orbitofrontal cortex (OFC) in association with both BIS-11 score and months of ketamine use. Mediation analyses suggest that the connectivity z score mediated the relationship between impulsivity and duration of use. Conclusions: These preliminary findings highlighted altered striatal connectivity in chronic ketamine users, and the potential role of putamen OFC connectivity in supporting the correlation between impulsivity and duration of ketamine use. If replicated in a larger sample, these findings may represent neural markers of ketamine misuse.

PMID: 31264888 [PubMed - as supplied by publisher]

Microstates as Disease and Progression Markers in Patients With Mild Cognitive Impairment.

Front Neurosci. 2019;13:563

Authors: Musaeus CS, Nielsen MS, Høgh P

Abstract
Network dysfunction is well established in patients with Alzheimer's disease (AD) and has been shown to be present early in the disease. This is especially interesting in patients with mild cognitive impairment (MCI) since they are more likely to develop AD. In EEG, one type of network analysis is microstates where the EEG is divided into quasi-stable states and these microstates have been linked to networks found with resting state functional MRI. In the current exploratory study, we therefore wanted to explore the changes in microstates in MCI, and AD compared to healthy controls (HC) and whether microstates were able to separate patients with MCI who progressed (pMCI) and those who remained stable (sMCI). EEGs were recorded at baseline for 17 patients with AD, 27 patients with MCI, and 38 older HC and the patients were followed for 3 years. To investigate whole-brain dynamics we extracted different microstate parameters. We found that patients with MCI, and AD had significantly higher occurrence (p-value = 0.028), and coverage (p-value = 0.010) for microstate A compared to HC. However, we did not find any significant systematic deviation of the transition probabilities from randomness for any of the groups. No significant differences were found between pMCI and sMCI but the largest difference in duration was found for microstate D. Microstate A has been linked to the temporal lobes in studies combining EEG and fMRI and the temporal lobes are the most affected by AD pathology in the early stages of the disease. This supports our idea that microstate A may be the first affected microstate in early AD. Even though not significant between pMCI and sMCI, Microstate D has previously been shown to be associated with both frontal and parietal areas as measured with fMRI and may correspond to underlying pathological changes in the progression of MCI to AD. However, larger studies are needed to confirm these findings.

PMID: 31263397 [PubMed]

Sex differences in cognitive flexibility and resting brain networks in middle-aged marmosets.

eNeuro. 2019 Jul 01;:

Authors: LaClair M, Febo M, Nephew B, Gervais NJ, Poirier G, Workman K, Chumachenko S, Payne L, Moore MC, King JA, Lacreuse A

Abstract
Sex differences in human cognitive performance are well characterized. However, the neural correlates of these differences remain elusive. This issue may be clarified using nonhuman primates, for which sociocultural influences are minimized. We used the marmoset (Callithrix jacchus) to investigate sex differences in two aspects of executive function: Reversal Learning and Intradimensional/Extradimensional (ID/ED) set shifting. Stress reactivity and motor function were also assessed. In agreement with human literature, females needed more trials than males to acquire the reversals. No sex differences in ED set shifting or motivational measures were observed. The findings suggest enhanced habit formation in females, perhaps due to striatal estrogenic effects. Both sexes showed increased urinary cortisol during social separation stressor, but females showed an earlier increase in cortisol and a greater increase in agitated locomotion, possibly indicating enhanced stress reactivity. Independent of sex, basal cortisol predicted cognitive performance. No sex differences were found in motor performance. Associations between brain networks and reversal learning performance were investigated using resting state fMRI. Resting state functional connectivity analyses revealed sex differences in cognitive networks, with differences in overall neural network metrics and specific regions, including the prefrontal cortex, caudate, putamen, and nucleus accumbens. Correlations between cognitive flexibility and neural connectivity indicate that sex differences in cognitive flexibility are related to sex-dependent patterns of resting brain networks. Overall, our findings reveal sex differences in reversal learning, brain networks, and their relationship in the marmoset, positioning this species as an excellent model to investigate the biological basis of cognitive sex differences.SIGNIFICANCE STATEMENT We examined sex differences in multiple outcomes (cognition, motor function, stress reactivity and resting state functional connectivity) in middle-aged marmosets. We found that female marmosets had poorer reversal learning relative to males. Resting state functional connectivity analyses revealed substantial sex differences in cognitive networks, with differences in both overall neural network metrics and specific regions, including the prefrontal cortex, caudate, putamen, and nucleus accumbens. Sex-dependent correlations between reversal learning and neural connectivity measures indicate that the sex difference in cognitive performance is related to sex-dependent patterns of resting brain networks. Although these data are correlational and cannot determine causal effects, they are consistent with human resting state data, supporting the idea that cognitive sex differences have identifiable intrinsic neural correlates.

PMID: 31262949 [PubMed - as supplied by publisher]

Identifying individuals using fNIRS-based cortical connectomes.

Biomed Opt Express. 2019 Jun 01;10(6):2889-2897

Authors: de Souza Rodrigues J, Ribeiro FL, Sato JR, Mesquita RC, Júnior CEB

Abstract
The fMRI-based functional connectome was shown to be sufficiently unique to allow individual identification (fingerprinting). We aimed to test whether a fNIRS-based connectome could also be used to identify individuals. Forty-four participants performed experimental protocols that consisted of two periods of resting-state interleaved by a cognitive task period. Connectome identification was performed for all possible pairwise combinations of the three periods. The influence of hemodynamic global variation was tested using global signal regression and principal component analysis. High identification accuracies well-above chance level (2.3%) were observed overall, being particularly high (93%) to the oxyhemoglobin signal between resting conditions. Our results suggest that fNIRS is a suitable technique to assess connectome fingerprints.

PMID: 31259059 [PubMed]

Altered spontaneous brain activity patterns in patients with corneal ulcer using amplitude of low-frequency fluctuation: An fMRI study.

Exp Ther Med. 2019 Jul;18(1):125-132

Authors: Shi WQ, Wu W, Ye L, Jiang N, Liu WF, Shu YQ, Su T, Lin Q, Min YL, Li B, Zhu PW, Shao Y

Abstract
The aim of the present study was to investigate the altered spontaneous brain activity in patients with corneal ulcer (CU) through the amplitude of low-frequency fluctuation (ALFF) technique and the association with their visual performance. A total of 40 patients with CU and 40 healthy controls (HCs) matched for sex, age and educational level were enrolled. Resting-state functional magnetic resonance imaging (rs-fMRI) was performed to examine the probands. Spontaneous cerebral activity variations were investigated using the ALFF technique. The average ALFF values of the CU patients and the HCs were classified by utilizing receiver operating characteristic (ROC) curves. Contrary to HCs, the CU patients had significantly lower ALFF values in the left cerebellar anterior lobe, right middle frontal gyrus and left middle frontal gyrus, but higher ALFF values in the right cerebellar inferior lobe, left cerebellar inferior lobe, left inferior temporal gyrus, right fusiform gyrus, left superior frontal gyrus, right angular gyrus and bilateral superior frontal gyrus. ROC curve analysis of each brain region indicated that the accuracy of ALFF value specificity between the CU and HCs of the area under the curve was perfect. In conclusion, abnormal spontaneous activities were detected in numerous brain regions of CU patients, which may provide useful information for understanding the dysfunction of CU. These activity changes in brain regions may be used as effective clinical indicators for CU.

PMID: 31258645 [PubMed]

L-Dopa Modulation of Brain Connectivity in Parkinson's Disease Patients: A Pilot EEG-fMRI Study.

Front Neurosci. 2019;13:611

Authors: Evangelisti S, Pittau F, Testa C, Rizzo G, Gramegna LL, Ferri L, Coito A, Cortelli P, Calandra-Buonaura G, Bisquoli F, Bianchini C, Manners DN, Talozzi L, Tonon C, Lodi R, Tinuper P

Abstract
Studies of functional neurosurgery and electroencephalography in Parkinson's disease have demonstrated abnormally synchronous activity between basal ganglia and motor cortex. Functional neuroimaging studies investigated brain dysfunction during motor task or resting state and primarily have shown altered patterns of activation and connectivity for motor areas. L-dopa administration relatively normalized these functional alterations. The aim of this pilot study was to examine the effects of L-dopa administration on functional connectivity in early-stage PD, as revealed by simultaneous recording of functional magnetic resonance imaging (fMRI) and electroencephalographic (EEG) data. Six patients with diagnosis of probable PD underwent EEG-fMRI acquisitions (1.5 T MR scanner and 64-channel cap) before and immediately after the intake of L-dopa. Regions of interest in the primary motor and sensorimotor regions were used for resting state fMRI analysis. From the EEG data, weighted partial directed coherence was computed in the inverse space after the removal of gradient and cardioballistic artifacts. fMRI results showed that the intake of L-dopa increased functional connectivity within the sensorimotor network, and between motor areas and both attention and default mode networks. EEG connectivity among regions of the motor network did not change significantly, while regions of the default mode network showed a strong tendency to increase their outflow toward the rest of the brain. This pilot study provided a first insight into the potentiality of simultaneous EEG-fMRI acquisitions in PD patients, showing for both techniques the analogous direction of increased connectivity after L-dopa intake, mainly involving motor, dorsal attention and default mode networks.

PMID: 31258465 [PubMed]

Naturalistic Stimuli in Neuroscience: Critically Acclaimed.

Trends Cogn Sci. 2019 Jun 27;:

Authors: Sonkusare S, Breakspear M, Guo C

Abstract
Cognitive neuroscience has traditionally focused on simple tasks, presented sparsely and using abstract stimuli. While this approach has yielded fundamental insights into functional specialisation in the brain, its ecological validity remains uncertain. Do these tasks capture how brains function 'in the wild', where stimuli are dynamic, multimodal, and crowded? Ecologically valid paradigms that approximate real life scenarios, using stimuli such as films, spoken narratives, music, and multiperson games emerged in response to these concerns over a decade ago. We critically appraise whether this approach has delivered on its promise to deliver new insights into brain function. We highlight the challenges, technological innovations, and clinical opportunities that are required should this field meet its full potential.

PMID: 31257145 [PubMed - as supplied by publisher]

Influence of muscarinic M1 receptor antagonism on brain choline levels and functional connectivity in medication-free subjects with psychosis: A placebo controlled, cross-over study.

Psychiatry Res Neuroimaging. 2019 Jun 23;290:5-13

Authors: Vingerhoets C, Bakker G, Schrantee A, van der Pluijm M, Bloemen OJN, Reneman L, Caan M, Booij J, van Amelsvoort TAMJ

Abstract
An increasing number of studies implicate the muscarinic cholinergic system in cognitive dysfunction associated with psychosis. This study examined the effect of muscarinic M1 receptor modulation on anterior cingulate cortex (ACC) and striatal choline concentrations and the relation with cognitive performance, as well as functional connectivity of cognitive networks. Thirty medication-free subjects with a psychosis spectrum disorder and 30 gender, age and IQ-matched healthy control subjects underwent 1H-proton magnetic resonance spectroscopy (1H-MRS) twice, once after placebo and once after a single dose of biperiden (M1 receptor antagonist, 4 mg). A subset of 19 psychotic subjects and 28 controls underwent resting-state functional magnetic resonance imaging (rs-fMRI) as well. No significant differences were found in ACC and striatal choline levels, nor in functional connectivity, between the two groups after placebo. Moreover, M1 antagonism did not significantly affect choline levels or functional connectivity. No correlations were found between choline levels and cognition as well as psychotic symptoms. Our findings do not support an association between the cholinergic system and cognition and psychotic symptoms. However, the lack of group differences in choline concentrations and functional connectivity, both after biperiden and placebo, may indicate that there were no severe cholinergic abnormalities present in our sample.

PMID: 31252222 [PubMed - as supplied by publisher]

Detailed mapping of human habenula resting-state functional connectivity.

Neuroimage. 2019 Jun 25;:

Authors: Ely BA, Stern ER, Kim JW, Gabbay V, Xu J

Abstract
The habenula (Hb) inhibits dopaminergic reward signaling in response to negative outcomes and has been linked to numerous functional domains relevant to mental health, including reward prediction, motivation, and aversion processing. Despite its important neuroscientific and clinical implications, however, the human Hb remains poorly understood due to its small size and the associated technical hurdles to in vivo functional magnetic resonance imaging (fMRI) investigation. Using high-resolution 3T fMRI data from 68 healthy young adults acquired through the Human Connectome Project, we developed a rigorous approach for mapping the whole-brain resting-state functional connectivity of the human Hb. Our study combined an optimized strategy for defining subject-level connectivity seeds to maximize Hb BOLD sensitivity with high-quality surface-based alignment for robust functional localization and cortical sensitivity. We identified significant positive Hb connectivity with: (i) conserved brainstem targets, including the dopaminergic ventral tegmental area, serotonergic raphe nuclei, and periaqueductal gray; (ii) subcortical structures related to reward and motor function, including the nucleus accumbens, dorsal striatum, pallidum, thalamus, and cerebellum; and (iii) cortical areas associated with the Salience Network and early sensory processing, including the dorsal anterior cingulate, anterior insula, and primary visual and auditory cortices. Hb connectivity was strongly biased towards task-positive brain regions, with weak or negative connectivity observed throughout the task-negative Default Mode Network. Our study provides a detailed characterization of Hb resting-state functional connectivity in healthy young adults, demonstrating both the feasibility and clinical potential of studying the human Hb using high-resolution 3T fMRI.

PMID: 31252057 [PubMed - as supplied by publisher]

Latent resting-state network dynamics in boys and girls with attention-deficit/hyperactivity disorder.

PLoS One. 2019;14(6):e0218891

Authors: Scofield JE, Johnson JD, Wood PK, Geary DC

Abstract
Neuroimaging studies of subjects with ADHD typically show altered functional connectivity in prefrontal, striatal, and several temporal brain regions. While the majority of studies have focused on connectivity that is averaged over time, we investigated the temporal dynamics of brain network changes in resting-state fMRI. Using the ADHD-200 consortium, we characterized the time course of latent state changes using Hidden Markov Modeling, and compared state changes between boys and girls with ADHD along with typically developing controls. Sex differences were found in latent state switching, with boys dwelling longer in a given state than girls, and concurrently having fewer overall state transitions. These sex differences were found in children with ADHD and in typically developing controls. Children with ADHD were also found to be more variable in terms of state transitions than controls. These findings add to the growing literature on neural sex differences and may be related to the sex difference in focal versus diffuse attention.

PMID: 31251765 [PubMed - in process]

Coupling of cerebral blood flow and functional connectivity is decreased in healthy aging.

Brain Imaging Behav. 2019 Jun 27;:

Authors: Galiano A, Mengual E, García de Eulate R, Galdeano I, Vidorreta M, Recio M, Riverol M, Zubieta JL, Fernández-Seara MA

Abstract
Aging leads to cerebral perfusion and functional connectivity changes that have been assessed using various neuroimaging techniques. In addition, a link between these two parameters has been demonstrated in healthy young adults. In this work, we employed arterial spin labeling (ASL) fMRI to measure global and voxel-wise differences in cerebral blood flow (CBF) and intrinsic connectivity contrast (ICC) in the resting state in a group of cognitively normal elderly subjects and a group of cognitively normal young subjects, in order to assess the effects of aging on CBF-ICC coupling, which had not been previously evaluated. Our results showed age-related global and regional CBF decreases in prefrontal mesial areas, lateral frontal regions, insular cortex, lateral parietal areas, precuneus and occipital regions. Subcortically, perfusion was reduced in the medial thalamus and caudate nucleus. ICC was also found reduced with age in prefrontal cortical areas and insular cortex, affecting key nodes of the default mode and salience networks. Areas of ICC and CBF decrease partially overlapped, however, the CBF reduction was more extensive and encompassed more areas. This dissociation was accompanied by a decrease in CBF-ICC coupling. These results suggest that aging leads to a disruption in the relationship between CBF and intrinsic functional connectivity that could be due to neurovascular dysregulation.

PMID: 31250268 [PubMed - as supplied by publisher]

Association of LHPP genetic variation (rs35936514) with structural and functional connectivity of hippocampal-corticolimbic neural circuitry.

Brain Imaging Behav. 2019 Jun 27;:

Authors: Cui L, Gong X, Chang M, Yin Z, Geng H, Song Y, Lv J, Feng R, Wang F, Tang Y, Xu K

Abstract
A single nucleotide polymorphism at the LHPP gene (rs35936514) has been reported to be associated with major depressive disorder (MDD) in genome-wide association studies. We conducted a neuroimaging analysis to explore whether and which brain neural systems are affected by LHPP variation. Since LHPP variants seem to be associated with the hippocampus, we assessed the relationship between rs35936514 variation and structural-functional connectivity within a hippocampal-corticolimbic neural system implicated in MDD. A total of 122 Chinese subjects were divided into a CC homozygous group (CC genotype, n = 60) and a T allele-carrier group (CT/TT genotypes, n = 62). All subjects participated in resting-state functional magnetic resonance imaging (rs-fMRI) and diffusion tensor imaging (DTI) scans. Structural and functional connectivity data analyses were then performed. Compared to the CC group, the T allele-carrier group showed significantly higher fractional anisotropy (FA) values in the fornix as well as increased functional connectivity from the hippocampus to the rostral part of the anterior cingulate cortex (rACC). Moreover, a significant negative correlation between fornix FA value and hippocampus-rACC functional connectivity was identified (P < 0.05). These findings suggest that there is a relationship between rs35936514 variation and both structural and functional hippocampal-corticolimbic neural system involvement in MDD. LHPP may play an important role in the neuropathophysiology of MDD.

PMID: 31250265 [PubMed - as supplied by publisher]

Intrinsic functional connectivity of medial prefrontal cortex predicts the individual moral bias in economic valuation partially through the moral sensitivity trait.

Brain Imaging Behav. 2019 Jun 27;:

Authors: Liu J, Yuan B, Luo YJ, Cui F

Abstract
An individual's economic valuation of a given object is biased by the moral status of the persons to whom the object is attached. The neural basis for how such "moral bias" occurs, especially how it is maintained in the resting state, are largely unknown. In the current study, we explored this question by correlating the functional connectivity with participants' behavioral performance measured in a novel task which captured how the economic valuation was influenced by given moral information. Seed-based FC analysis showed that the functional connectivity between the mPFC and the orbital mPFC (omPFC), the mPFC and the precuneus, the mPFC and the left anterior cingulum, were significantly associated with the behavioral index of morality effect on economic valuation. Multivariate machine learning-based regression analysis showed that connections in the mPFC network, as well as in the putamen network could well predict the behavior performance, indicating that this mPFC network and the putamen network were crucial for this moral bias. Our results further revealed that the individuals' personal trait of moral sensitivity served as a mediator between the rsFC of mPFC network and the behavioral index of morality effect on economic valuation.

PMID: 31250264 [PubMed - as supplied by publisher]

Reduced Interhemispheric Functional Connectivity in Obsessive-Compulsive Disorder Patients.

Front Psychiatry. 2019;10:418

Authors: Deng K, Qi T, Xu J, Jiang L, Zhang F, Dai N, Cheng Y, Xu X

Abstract
Background: Neuroimaging studies have shown that the high synchrony of spontaneous neural activity in the homotopic regions between hemispheres is an important functional structural feature of normal human brains, and this feature is abnormal in the patients with various mental disorders. However, little is known about this feature in obsessive-compulsive disorder (OCD). This study aimed to further analyze the underlying neural mechanisms of OCD and to explore whether clinical characteristics are correlated with the alerted homotopic connectivity in patients with OCD. Methods: Using voxel-mirrored homotopic connectivity (VMHC) during resting state, we compared 46 OCD patients and 46 healthy controls (HCs) matched for age, gender, and education level. A partial correlation analysis was used to investigate the relationship between altered VMHC and clinical characteristics in patients with OCD. Results: Patients with OCD showed lower VMHC than HCs in fusiform gyrus/inferior occipital gyrus, lingual gyrus, postcentral gyrus/precentral gyrus, putamen, and orbital frontal gyrus. A significant positive correlation was observed between altered VMHC in the angular gyrus/middle occipital gyrus and illness duration in patients. Conclusions: Interhemispheric functional imbalance may be an essential aspect of the pathophysiological mechanism of OCD, which is reflected not only in the cortico-striato-thalamo-cortical (CSTC) loop but also elsewhere in the brain.

PMID: 31249539 [PubMed]

Localized Connectivity in Obsessive-Compulsive Disorder: An Investigation Combining Univariate and Multivariate Pattern Analyses.

Front Behav Neurosci. 2019;13:122

Authors: Hu X, Zhang L, Bu X, Li H, Li B, Tang W, Lu L, Hu X, Tang S, Gao Y, Yang Y, Roberts N, Gong Q, Huang X

Abstract
Recent developments in psychoradiological researches have highlighted the disrupted organization of large-scale functional brain networks in obsessive-compulsive disorder (OCD). However, whether abnormal activation of localized brain areas would affect network dysfunction remains to be fully characterized. We applied both univariate analysis and multivariate pattern analysis (MVPA) approaches to investigate the abnormalities of regional homogeneity (ReHo), an index to measure the localized connectivity, in 88 medication-free patients with OCD and 88 healthy control subjects (HCS). Resting-state functional magnetic resonance imaging (RS-fMRI) data of all the participants were acquired in a 3.0-T scanner. First, we adopted a traditional univariate analysis to explore ReHo alterations between the patient group and the control group. Subsequently, we utilized a support vector machine (SVM) to examine whether ReHo could be further used to differentiate patients with OCD from HCS at the individual level. Relative to HCS, OCD patients showed lower ReHo in the bilateral cerebellum and higher ReHo in the bilateral superior frontal gyri (SFG), right inferior parietal gyrus (IPG), and precuneus [P < 0.05, family-wise error (FWE) correction]. ReHo value in the left SFG positively correlated with Yale-Brown Obsessive Compulsive Scale (Y-BOCS) total score (r = 0 0.241, P = 0.024) and obsessive subscale (r = 0.224, P = 0.036). The SVM classification regarding ReHo yielded an accuracy of 78.98% (sensitivity = 78.41%, specificity = 79.55%) with P < 0.001 after permutation testing. The most discriminative regions contributing to the SVM classification were mainly located in the frontal, temporal, and parietal regions as well as in the cerebellum while the right orbital frontal cortex was identified with the highest discriminative power. Our findings not only suggested that the localized activation disequilibrium between the prefrontal cortex (PFC) and the cerebellum appeared to be associated with the pathophysiology of OCD but also indicated the translational role of the localized connectivity as a potential discriminative pattern to detect OCD at the individual level.

PMID: 31249515 [PubMed]

Application of Graph Theory for Identifying Connectivity Patterns in Human Brain Networks: A Systematic Review.

Front Neurosci. 2019;13:585

Authors: Farahani FV, Karwowski W, Lighthall NR

Abstract
Background: Analysis of the human connectome using functional magnetic resonance imaging (fMRI) started in the mid-1990s and attracted increasing attention in attempts to discover the neural underpinnings of human cognition and neurological disorders. In general, brain connectivity patterns from fMRI data are classified as statistical dependencies (functional connectivity) or causal interactions (effective connectivity) among various neural units. Computational methods, especially graph theory-based methods, have recently played a significant role in understanding brain connectivity architecture. Objectives: Thanks to the emergence of graph theoretical analysis, the main purpose of the current paper is to systematically review how brain properties can emerge through the interactions of distinct neuronal units in various cognitive and neurological applications using fMRI. Moreover, this article provides an overview of the existing functional and effective connectivity methods used to construct the brain network, along with their advantages and pitfalls. Methods: In this systematic review, the databases Science Direct, Scopus, arXiv, Google Scholar, IEEE Xplore, PsycINFO, PubMed, and SpringerLink are employed for exploring the evolution of computational methods in human brain connectivity from 1990 to the present, focusing on graph theory. The Cochrane Collaboration's tool was used to assess the risk of bias in individual studies. Results: Our results show that graph theory and its implications in cognitive neuroscience have attracted the attention of researchers since 2009 (as the Human Connectome Project launched), because of their prominent capability in characterizing the behavior of complex brain systems. Although graph theoretical approach can be generally applied to either functional or effective connectivity patterns during rest or task performance, to date, most articles have focused on the resting-state functional connectivity. Conclusions: This review provides an insight into how to utilize graph theoretical measures to make neurobiological inferences regarding the mechanisms underlying human cognition and behavior as well as different brain disorders.

PMID: 31249501 [PubMed]

Sequential replay of nonspatial task states in the human hippocampus.

Science. 2019 06 28;364(6447):

Authors: Schuck NW, Niv Y

Abstract
Sequential neural activity patterns related to spatial experiences are "replayed" in the hippocampus of rodents during rest. We investigated whether replay of nonspatial sequences can be detected noninvasively in the human hippocampus. Participants underwent functional magnetic resonance imaging (fMRI) while resting after performing a decision-making task with sequential structure. Hippocampal fMRI patterns recorded at rest reflected sequentiality of previously experienced task states, with consecutive patterns corresponding to nearby states. Hippocampal sequentiality correlated with the fidelity of task representations recorded in the orbitofrontal cortex during decision-making, which were themselves related to better task performance. Our findings suggest that hippocampal replay may be important for building representations of complex, abstract tasks elsewhere in the brain and establish feasibility of investigating fast replay signals with fMRI.

PMID: 31249030 [PubMed - in process]

Aberrant topological organization of the default mode network in temporal lobe epilepsy revealed by graph-theoretical analysis.

Neurosci Lett. 2019 Jun 24;:134351

Authors: Zhou X, Zhang Z, Liu J, Qin L, Zheng J

Abstract
Numerous neuroimaging studies have reported aberrant functional activities of the default mode network (DMN) in temporal lobe epilepsy (TLE). However, the alteration on topological organization within the DMN has not been clearly illuminated. In this study, we aimed to investigate the topological abnormalities within the DMN from a larger-scale perspective. Twenty three patients with TLE and 23 age, gender, and education matched healthy controls (HCs) were recruited in this study. All participants underwent a resting-state functional magnetic resonance imaging (rs-fMRI) scanning and completed the Attention Network Test (ANT) for executive function assessment. Specific subregions in the DMN were extracted for network construction according to the automated anatomical labelling atlas. Network properties, including global properties, nodal properties and edge analyses, were assessed using graph theory. Correlation analyses were performed between significantly different topological properties and clinical factors in patients. The ANT tests showed that executive function was impaired in the patients with TLE compared with the HCs. Furthermore, the TLE group showed decreased nodal strength in the left medial orbital superior frontal gyrus and increased nodal strength in the right inferior parietal gyrus in the DMN. Significantly increased functional connectivities between subregions in the DMN were primarily located in the bilateral superior frontal gyrus, inferior parietal gyrus, precuneus, and posterior cingulate gyrus. Moreover, the degree centrality of the right inferior parietal gyrus was positively correlated with disease duration. In conclusion, this study indicated that there existed a disrupted topological reorganization within the DMN in patients with TLE, which may further contribute to executive deficits and, to some extent, play a compensatory role.

PMID: 31247225 [PubMed - as supplied by publisher]