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Opening or closing eyes at rest modulates the functional connectivity of V1 with default and salience networks.

Sat, 06/06/2020 - 22:49
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Opening or closing eyes at rest modulates the functional connectivity of V1 with default and salience networks.

Sci Rep. 2020 Jun 04;10(1):9137

Authors: Costumero V, Bueichekú E, Adrián-Ventura J, Ávila C

Abstract
Current evidence suggests that volitional opening or closing of the eyes modulates brain activity and connectivity. However, how the eye state influences the functional connectivity of the primary visual cortex has been poorly investigated. Using the same scanner, fMRI data from two groups of participants similar in age, sex and educational level were acquired. One group (n = 105) performed a resting state with eyes closed, and the other group (n = 63) performed a resting state with eyes open. Seed-based voxel-wise functional connectivity whole-brain analyses were performed to study differences in the connectivity of the primary visual cortex. This region showed higher connectivity with the default mode and sensorimotor networks in the eyes closed group, but higher connectivity with the salience network in the eyes open group. All these findings were replicated using an open source shared dataset. These results suggest that opening or closing the eyes may set brain functional connectivity in an interoceptive or exteroceptive state.

PMID: 32499585 [PubMed - in process]

Altered neural substrates within cognitive networks of postpartum women during working memory process and resting-state.

Sat, 06/06/2020 - 22:49
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Altered neural substrates within cognitive networks of postpartum women during working memory process and resting-state.

Sci Rep. 2020 Jun 04;10(1):9110

Authors: Bak Y, Nah Y, Han S, Lee SK, Shin NY

Abstract
Postpartum working memory decline has been investigated mostly with neuropsychological tests, but neural evidence is almost unknown. Here we investigated task-related neural alterations during working memory task (n-back) and intrinsic alterations during resting-state (rs) in postpartum women using functional MRI (fMRI). Behaviorally, postpartum women showed comparable working memory performances to the controls although there was a tendency of prolonged response time. fMRI analysis results showed hyper-activation in regions belong to the task positive network (TPN) during the task and hypo-rsfMRI values in the default mode network (DMN) regions during rest in postpartum women. Based on these results, we performed network connectivity analysis using nodes of the TPN and DMN. As a result, the DMN showed a tendency of decreased connectivity in postpartum women during the working memory process compared to the controls. Our results suggest that postpartum women might have functional alterations in the DMN, and that hyper-activation in the TPN during a task might be a compensatory mechanism to maintain working memory performance in postpartum women.

PMID: 32499565 [PubMed - in process]

Brain Network Disruption in Whiplash.

Sat, 06/06/2020 - 22:49
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Brain Network Disruption in Whiplash.

AJNR Am J Neuroradiol. 2020 Jun 04;:

Authors: Higgins JP, Elliott JM, Parrish TB

Abstract
BACKGROUND AND PURPOSE: Whiplash-associated disorders frequently develop following motor vehicle collisions and often involve a range of cognitive and affective symptoms, though the neural correlates of the disorder are largely unknown. In this study, a sample of participants with chronic whiplash injuries were scanned by using resting-state fMRI to assess brain network changes associated with long-term outcome metrics.
MATERIALS AND METHODS: Resting-state fMRI was collected for 23 participants and used to calculate network modularity, a quantitative measure of the functional segregation of brain region communities. This was analyzed for associations with whiplash-associated disorder outcome metrics, including scales of neck disability, traumatic distress, depression, and pain. In addition to these clinical scales, cervical muscle fat infiltration was quantified by using Dixon fat-water imaging, which has shown promise as a biomarker for assessing disorder severity and predicting recovery in chronic whiplash.
RESULTS: An association was found between brain network structure and muscle fat infiltration, wherein lower network modularity was associated with larger amounts of cervical muscle fat infiltration after controlling for age, sex, body mass index, and scan motion (t = -4.02, partial R 2  = 0.49, P < .001).
CONCLUSIONS: This work contributes to the existing whiplash literature by examining a sample of participants with whiplash-associated disorder by using resting-state fMRI. Less modular brain networks were found to be associated with greater amounts of cervical muscle fat infiltration suggesting a connection between disorder severity and neurologic changes, and a potential role for neuroimaging in understanding the pathophysiology of chronic whiplash-associated disorders.

PMID: 32499250 [PubMed - as supplied by publisher]

Multimodal data analysis of epileptic EEG and rs-fMRI via deep learning and edge computing.

Sat, 06/06/2020 - 22:49
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Multimodal data analysis of epileptic EEG and rs-fMRI via deep learning and edge computing.

Artif Intell Med. 2020 Apr;104:101813

Authors: Hosseini MP, Tran TX, Pompili D, Elisevich K, Soltanian-Zadeh H

Abstract
BACKGROUND AND OBJECTIVE: Multimodal data analysis and large-scale computational capability is entering medicine in an accelerative fashion and has begun to influence investigational work in a variety of disciplines. It is also informing us of therapeutic interventions that will come about with such development. Epilepsy is a chronic brain disorder in which functional changes may precede structural ones and which may be detectable using existing modalities.
METHODS: Functional connectivity analysis using electroencephalography (EEG) and resting state-functional magnetic resonance imaging (rs-fMRI) has provided such meaningful input in cases of epilepsy. By leveraging the potential of autonomic edge computing in epilepsy, we develop and deploy both noninvasive and invasive methods for monitoring, evaluation, and regulation of the epileptic brain. First, an autonomic edge computing framework is proposed for the processing of big data as part of a decision support system for surgical candidacy. Second, a multimodal data analysis using independently acquired EEG and rs-fMRI is presented for estimation and prediction of the epileptogenic network. Third, an unsupervised feature extraction model is developed for EEG analysis and seizure prediction based on a Convolutional deep learning (CNN) structure for distinguishing preictal (pre-seizure) state from non-preictal periods by support vector machine (SVM) classifier.
RESULTS: Experimental and simulation results from actual patient data validate the effectiveness of the proposed methods.
CONCLUSIONS: The combination of rs-fMRI and EEG/iEEG can reveal more information about dynamic functional connectivity. However, simultaneous fMRI and EEG data acquisition present challenges. We have proposed system models for leveraging and processing independently acquired fMRI and EEG data.

PMID: 32498996 [PubMed - in process]

Functional connectivity is preserved but reorganized across several anesthetic regimes.

Fri, 06/05/2020 - 22:47
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Functional connectivity is preserved but reorganized across several anesthetic regimes.

Neuroimage. 2020 Jun 01;:116945

Authors: Becq GJC, Habet T, Collomb N, Faucher M, Delon-Martin C, Coizet V, Achard S, Barbier EL

Abstract
Under anesthesia, systemic variables and CBF are modified. How does this alter the connectivity measures obtained with rs-fMRI? To tackle this question, we explored the effect of four different anesthetics on Long Evans and Wistar rats with multimodal recordings of rs-fMRI, systemic variables and CBF. After multimodal signal processing, we show that the blood-oxygen-level-dependent (BOLD) variations and functional connectivity (FC) evaluated at low frequencies (0.031-0.25 Hz) do not depend on systemic variables and are preserved across a large interval of baseline CBF values. Based on these findings, we found that most brain areas remain functionally active under any anesthetics, i.e. connected to at least one other brain area, as shown by the connectivity graphs. In addition, we quantified the influence of nodes by a measure of functional connectivity strength to show the specific areas targeted by anesthetics and compare correlation values of edges at different levels. These measures enable us to highlight the specific network alterations induced by anesthetics. Altogether, this suggests that changes in connectivity could be evaluated under anesthesia, routinely used in the control of neurological injury.

PMID: 32497787 [PubMed - as supplied by publisher]

Multiple functional connectivity networks fusion for schizophrenia diagnosis.

Fri, 06/05/2020 - 22:47
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Multiple functional connectivity networks fusion for schizophrenia diagnosis.

Med Biol Eng Comput. 2020 Jun 03;:

Authors: Zou H, Yang J

Abstract
Accurate diagnosis of schizophrenia is of great importance to patients and clinicians. Recent studies have found that different frequency bands contain complementary information for diagnosis and prognosis. However, conventional multiple frequency functional connectivity (FC) networks using Pearson's correlation coefficient (PCC) are usually based on pairwise correlations among different brain regions on single frequency band, while ignoring the interactions between regions in different frequency bands, the relationship among different networks, and the nonlinear properties of blood-oxygen-level-dependent (BOLD) signal. To take into account these relationships, we propose in this study a multiple networks fusion method for schizophrenia diagnosis. Specifically, we first construct FC networks within the same and across frequency from the resting-state functional magnetic resonance imaging (rs-fMRI) time series by using extended maximal information coefficient (eMIC) based on four frequency bands: slow-5 (0.01-0.027 Hz), slow-4 (0.027-0.073 Hz), slow-3 (0.073-0.198 Hz), and slow-2 (0.198-0.25 Hz). Then, these networks are combined nonlinearly through network fusion, which generates a unified network for each subject. Features extracted from the unified network are used for final classification. Experimental results demonstrated that the interaction between distinct brain regions across different frequency bands can significantly improve the classification performance, comparing with conventional FC analysis based on specific or entire low-frequency band. The promising results suggest that our proposed framework would be a useful tool in computer-aided diagnosis of schizophrenia. Graphical abstract The flowchart of proposed classification framework.

PMID: 32495268 [PubMed - as supplied by publisher]

A Critical, Event-Related Appraisal of Denoising in Resting-State fMRI Studies.

Fri, 06/05/2020 - 22:47
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A Critical, Event-Related Appraisal of Denoising in Resting-State fMRI Studies.

Cereb Cortex. 2020 Jun 04;:

Authors: Power JD, Lynch CJ, Adeyemo B, Petersen SE

Abstract
This article advances two parallel lines of argument about resting-state functional magnetic resonance imaging (fMRI) signals, one empirical and one conceptual. The empirical line creates a four-part organization of the text: (1) head motion and respiration commonly cause distinct, major, unwanted influences (artifacts) in fMRI signals; (2) head motion and respiratory changes are, confoundingly, both related to psychological and clinical and biological variables of interest; (3) many fMRI denoising strategies fail to identify and remove one or the other kind of artifact; and (4) unremoved artifact, due to correlations of artifacts with variables of interest, renders studies susceptible to identifying variance of noninterest as variance of interest. Arising from these empirical observations is a conceptual argument: that an event-related approach to task-free scans, targeting common behaviors during scanning, enables fundamental distinctions among the kinds of signals present in the data, information which is vital to understanding the effects of denoising procedures. This event-related perspective permits statements like "Event X is associated with signals A, B, and C, each with particular spatial, temporal, and signal decay properties". Denoising approaches can then be tailored, via performance in known events, to permit or suppress certain kinds of signals based on their desirability.

PMID: 32494823 [PubMed - as supplied by publisher]

Bipartite Functional Fractionation within the Default Network Supports Disparate Forms of Internally Oriented Cognition.

Fri, 06/05/2020 - 22:47
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Bipartite Functional Fractionation within the Default Network Supports Disparate Forms of Internally Oriented Cognition.

Cereb Cortex. 2020 Jun 04;:

Authors: Chiou R, Humphreys GF, Lambon Ralph MA

Abstract
Our understanding about the functionality of the brain's default network (DN) has significantly evolved over the past decade. Whereas traditional views define this network based on its suspension/disengagement during task-oriented behavior, contemporary accounts have characterized various situations wherein the DN actively contributes to task performance. However, it is unclear how different task-contexts drive componential regions of the DN to coalesce into a unitary network and fractionate into different subnetworks. Here we report a compendium of evidence that provides answers to these questions. Across multiple analyses, we found a striking dyadic structure within the DN in terms of the profiles of task-triggered fMRI response and effective connectivity, significantly extending beyond previous inferences based on meta-analysis and resting-state activities. In this dichotomy, one subset of DN regions prefers mental activities "interfacing with" perceptible events, while the other subset prefers activities "detached from" perceptible events. While both show a common "aversion" to sensory-motoric activities, their differential preferences manifest a subdivision that sheds light upon the taxonomy of the brain's memory systems. This dichotomy is consistent with proposals of a macroscale gradational structure spanning across the cerebrum. This gradient increases its representational complexity, from primitive sensory-motoric processing, through lexical-semantic representations, to elaborated self-generated thoughts.

PMID: 32494802 [PubMed - as supplied by publisher]

Functional connectivity of EEG is subject-specific, associated with phenotype, and different from fMRI.

Thu, 06/04/2020 - 22:46
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Functional connectivity of EEG is subject-specific, associated with phenotype, and different from fMRI.

Neuroimage. 2020 May 31;:117001

Authors: Nentwich M, Ai L, Madsen J, Telesford QK, Haufe S, Milham MP, Parra LC

Abstract
A variety of psychiatric, behavioral and cognitive phenotypes have been linked to brain ''functional connectivity'' -- the pattern of correlation observed between different brain regions. Most commonly assessed using functional magnetic resonance imaging (fMRI), here, we investigate the connectivity-phenotype associations with functional connectivity measured with electroencephalography (EEG), using phase-coupling. We analyzed data from the publicly available Healthy Brain Network Biobank. This database compiles a growing sample of children and adolescents, currently encompassing 1,657 individuals. Among a variety of assessment instruments we focus on ten phenotypic and additional demographic measures that capture most of the variance in this sample. The largest effect sizes are found for age and sex for both fMRI and EEG. We replicate previous findings of an association of Intelligence Quotient (IQ) and Attention Deficit Hyperactivity Disorder (ADHD) with the pattern of fMRI functional connectivity. We also find an association with socioeconomic status, anxiety and the Child Behavior Checklist Score. For EEG we find a significant connectivity-phenotype relationship with IQ. The actual spatial patterns of functional connectivity are quite different between fMRI and source-space EEG. However, within EEG we observe clusters of functional connectivity that are consistent across frequency bands. Additionally we analyzed reproducibility of functional connectivity. We compare connectivity obtained with different tasks, including resting state, a video and a visual flicker task. For both EEG and fMRI the variation between tasks was smaller than the variability observed between subjects. We also found an increase of reliability with increasing frequency of the EEG, and increased sampling duration. We conclude that, while the patterns of functional connectivity are distinct between fMRI and phase-coupling of EEG, they are nonetheless similar in their robustness to the task, and similar in that idiosyncratic patterns of connectivity predict individual phenotypes.

PMID: 32492509 [PubMed - as supplied by publisher]

Resting-state fMRI analysis in apathetic Alzheimer's disease.

Thu, 06/04/2020 - 22:46
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Resting-state fMRI analysis in apathetic Alzheimer's disease.

Diagn Interv Radiol. 2020 Jun 03;:

Authors: Büyükgök D, Bayraktaroğlu Z, Buker HS, Kulaksızoğlu MIB, Gurvit IH

Abstract
PURPOSE: Diagnosis of comorbid psychiatric conditions are a significant determinant for the prognosis of neurodegenerative diseases. Apathy, which is a behavioral executive dysfunction, frequently accompanies Alzheimer's disease (AD) and leads to higher daily functional loss. We assume that frontal lobe hypofunction in apathetic AD patients are more apparent than the AD patients without apathy. This study aims to address the neuroanatomical correlates of apathy in the early stage of AD using task-free functional magnetic resonance imaging (MRI).
METHODS: Patients (n=20) were recruited from the Neurology and Psychiatry Departments of İstanbul University, İstanbul School of Medicine whose first referrals were 6- to 12-month history of progressive cognitive decline. Patients with clinical dementia rating 0.5 and 1 were included in the study. The patient group was divided into two subgroups as apathetic and non-apathetic AD according to their psychiatric examination and assessment scores. A healthy control group was also included (n=10). All subjects underwent structural and functional MRI. The resting-state condition was recorded eyes open for 5 minutes.
RESULTS: The difference between the three groups came up in the pregenual anterior cingulate cortex (pgACC) at the trend level (P = 0.056). Apathetic AD group showed the most constricted activation area at pgACC.
CONCLUSION: The region in and around anterior default mode network (pgACC) seems to mediate motivation to initiate behavior, and this function appears to weaken as the apathy becomes more severe in AD.

PMID: 32490831 [PubMed - as supplied by publisher]

Correlation of language lateralization with resting state hippocampal connectivity in temporal lobe epilepsy patients.

Thu, 06/04/2020 - 22:46
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Correlation of language lateralization with resting state hippocampal connectivity in temporal lobe epilepsy patients.

Turk J Med Sci. 2020 Jun 03;:

Authors: Koç AM, Öner AY, Özer H, Güryildirim M, Tali ET, Öncü F, Uçar M, Bilir E, Çapraz I, Kurt G

Abstract
PURPOSE: The main purpose of this study is to evaluate the resting state hippocampal connectivity with language areas and to correlate them with laterality index calculations on single subject basis, hence to present hippocampal lateralization for language with rs-fMRI.
METHODS: Task based and rs-fMRI data were gathered from a total of 45 subjects in 3T scanner. Brainvoyager QX, SPM and CONN softwares were used for data analysis. LI score of each subject was calculated and converted into normalized LI score (nLI). Intrahemispheric rs-connectivity analysis was performed between hippocampus and Broca regions on both sides. Correlation between these variables was measured with SPSS software.
RESULTS: Right-TLE patients were found to have highest whereas left-TLE group were found to have lowest mean LI scores. Regarding hippocampo-lingual networks; left intrahemispheric connectivity values showed strong positive correlation with nLI values in left, right-TLE patients and healthy controls (p=0.035, 0.014, 0.047). There were no significant correlation between right intrahemispheric connectivity values and nLI scores in all groups.
CONCLUSION: This study seems to depict the existence of resting state hippocampo-lingual functional network which correlates well with lateralization of language function in the left hemisphere in both temporal lobe epilepsy patients and healthy controls.

PMID: 32490643 [PubMed - as supplied by publisher]

Stress-induced changes in modular organizations of human brain functional networks.

Thu, 06/04/2020 - 22:46
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Stress-induced changes in modular organizations of human brain functional networks.

Neurobiol Stress. 2020 Nov;13:100231

Authors: Zhang Y, Dai Z, Hu J, Qin S, Yu R, Sun Y

Abstract
Humans inevitably go through various stressful events, which initiates a chain of neuroendocrine reactions that may affect brain functions and lead to psychopathological symptoms. Previous studies have shown stress-induced changes in activation of individual brain regions or pairwise inter-regional connectivity. However, it remains unclear how large-scale brain network is reconfigured in response to stress. Using a within-subjects design, we combined the Trier Social Stress Test and graph theoretical method to characterize stress-induced topological alterations of brain functional network. Modularity analysis revealed that the brain network can be divided into frontoparietal, default mode, occipital, subcortical, and central-opercular modules under control and stress conditions, corresponding to several well-known functional systems underpinning cognitive control, self-referential mental processing, visual, salience processing, sensory and motor functions. While the frontoparietal module functioned as a connector module under stress, its within-module connectivity was weakened. The default mode module lost its connector function and its within-module connectivity was enhanced under stress. Moreover, stress altered the capacity to control over information flow in a few regions important for salience processing and self-referential metal processing. Furthermore, there was a trend of negative correlation between modularity and stress response magnitude. These findings demonstrate that acute stress prompts large-scale brain-wide reconfiguration involving multiple functional modules.

PMID: 32490057 [PubMed]

Altered intrinsic functional connectivity of the primary visual cortex in patients with retinal vein occlusion: a resting-state fMRI study.

Thu, 06/04/2020 - 22:46
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Altered intrinsic functional connectivity of the primary visual cortex in patients with retinal vein occlusion: a resting-state fMRI study.

Quant Imaging Med Surg. 2020 May;10(5):958-969

Authors: Su T, Yuan Q, Liao XL, Shi WQ, Zhou XZ, Lin Q, Min YL, Li B, Jiang N, Shao Y

Abstract
Background: To investigate the differences of spontaneous functional connectivity (FC) of the primary visual cortex (V1) between patients with retinal vein occlusion (RVO) and healthy controls (HCs) using resting-state functional magnetic resonance imaging (rs-fMRI) data.
Methods: Twenty-one patients with RVO in total (11 males, 10 females) and 21 HCs similarly analogue in age and sex background were enrolled and inspected with rs-fMRI. The difference in FC of V1 between two groups were compared using two-sample t-test. We used the receiver operating characteristic (ROC) curve to distinguish average FC values of RVO subjects from HCs. The interrelationships between FC signals of specific cerebrum regions and clinical features in RVOs were assessed with the Pearson's correlation analysis.
Results: Compared with HCs, FC in left V1 and right middle frontal gyrus increased significantly in RVO group, while FC in left V1 and right cuneus decreased significantly. Meanwhile, patients with RVO presented increased FC between the right V1 and right middle frontal gyrus, right superior frontal gyrus, but declining FC between right V1 and right cuneus. The mean FC value between the right cuneus and the right V1 as well as the left V1 were negative correlated with the foveal thickness of RVO patients. ROC curve analysis of each brain regions showed the accuracy of AUC was excellent.
Conclusions: RVO involves aberrant FC in V1 in different brain areas including visual-related and cognitive-related region, which might assist to unveil the underlying neural mechanisms of impaired visual function in RVO.

PMID: 32489920 [PubMed]

The neural correlates of falls: Alterations in large-scale resting-state networks in elderly fallers.

Wed, 06/03/2020 - 22:45
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The neural correlates of falls: Alterations in large-scale resting-state networks in elderly fallers.

Gait Posture. 2020 May 22;80:56-61

Authors: Maidan I, Droby A, Jacob Y, Giladi N, Hausdorff JM, Mirelman A

Abstract
INTRODUCTION: Falls are associated with numerous risk factors, such as motor and cognitive impairments. However, the neural correlates of falls are poorly understood.
OBJECTIVES: Here, we aimed to assess patterns of structural, and resting-state functional connectivity (FC) alterations related to falls in a group of older adults with a history of falls compared to non-fallers.
METHODS: Fourteen elderly fallers (mean age = 78.1 ± 1.5 yrs, >2 falls previous six months), and 20 healthy controls (mean age = 69.6 ± 1.3 yrs) were examined. All participants underwent a 3T MRI scan obtaining 3D T1-weighted images, and eyes-open resting-state (rs)-fMRI. Voxel-based morphometry was conducted to detect grey matter differences between the groups. Independent component analysis was conducted based on rs-fMRI and number of attention-and-motor related functional networks was identified and compared between groups using an independent-sample T-test.
RESULTS: No differences were observed in grey matter between the groups after correcting for age and gender (p > 0.01, FWEc). Compared with non-fallers, the fallers had lower FC in cerebellar, frontal and parietal cortical nodes within the sensorimotor network (SMN), lateral motor network (M1), Cerebellar network (CBL), frontal-striatal network (FSN), executive control network (ECN), and dorsal attention network (DAN). Moreover, fallers had increased FC in the basal ganglia network (BGN), Left paracentral in M1 and SMN, and right hippocampus in DAN (p < 0.01, FWEc).
CONCLUSIONS: Among fallers, reduced connectivity was observed in areas that relate to integration of information, while increased connectivity was found in areas associated with motor and sensory information processing. Together, these results provide evidence to the complex multidimensionality of the neural underpinnings of falls. Furthermore, these findings may help emphasize the importance of interventions that target both motor and cognitive aspects.

PMID: 32485425 [PubMed - as supplied by publisher]

Nonlinear ICA of fMRI reveals primitive temporal structures linked to rest, task, and behavioral traits.

Wed, 06/03/2020 - 22:45
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Nonlinear ICA of fMRI reveals primitive temporal structures linked to rest, task, and behavioral traits.

Neuroimage. 2020 May 30;:116989

Authors: Morioka H, Calhoun V, Hyvärinen A

Abstract
Accumulating evidence from whole brain functional magnetic resonance imaging (fMRI) suggests that the human brain at rest is functionally organized in a spatially and temporally constrained manner. However, because of their complexity, the fundamental mechanisms underlying time-varying functional networks are still not well understood. Here, we develop a novel nonlinear feature extraction framework called local space-contrastive learning (LSCL), which extracts distinctive nonlinear temporal structure hidden in time series, by training a deep temporal convolutional neural network in an unsupervised, data-driven manner. We demonstrate that LSCL identifies certain distinctive local temporal structures, referred to as temporal primitives, which repeatedly appear at different time points and spatial locations, reflecting dynamic resting-state networks. We also show that these temporal primitives are also present in task-evoked spatiotemporal responses. We further show that the temporal primitives capture unique aspects of behavioral traits such as fluid intelligence and working memory. These results highlight the importance of capturing transient spatiotemporal dynamics within fMRI data and suggest that such temporal primitives may capture fundamental information underlying both spontaneous and task-induced fMRI dynamics.

PMID: 32485305 [PubMed - as supplied by publisher]

Amygdala and ventral tegmental area differentially interact with hippocampus and cortical medial temporal lobe during rest in humans.

Wed, 06/03/2020 - 22:45
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Amygdala and ventral tegmental area differentially interact with hippocampus and cortical medial temporal lobe during rest in humans.

Hippocampus. 2020 Jun 02;:

Authors: Gregory DF, Ritchey M, Murty VP

Abstract
Neuromodulatory regions that detect salience, such as amygdala and ventral tegmental area (VTA), have distinct effects on memory. Yet, questions remain about how these modulatory regions target subregions across the hippocampus and medial temporal lobe (MTL) cortex. Here, we sought to characterize how VTA and amygdala subregions (i.e., basolateral amygdala and central-medial amygdala) interact with hippocampus head, body, and tail, as well as cortical MTL areas of perirhinal cortex and parahippocampal cortex in a task-free state. To quantify these interactions, we used high-resolution resting state fMRI and characterized pair-wise, partial correlations across regions-of-interest. We found that basolateral amygdala showed greater functional coupling with hippocampus head, hippocampus tail, and perirhinal cortex when compared to either VTA or central-medial amygdala. Furthermore, the VTA showed greater functional coupling with hippocampus tail when compared to central-medial amygdala. There were no significant differences in functional coupling with hippocampus body and parahippocampal cortex. These results support a framework by which neuromodulatory regions do not indiscriminately influence all MTL subregions equally, but rather bias information processing to discrete MTL targets. These findings provide a more specified model of the intrinsic properties of systems underlying MTL neuromodulation. This emphasizes the need to consider heterogeneity both across and within neuromodulatory systems to better understand affective memory.

PMID: 32485015 [PubMed - as supplied by publisher]

Altered resting-state functional connectivity density in patients with neuromyelitis optica-spectrum disorders.

Tue, 06/02/2020 - 22:44
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Altered resting-state functional connectivity density in patients with neuromyelitis optica-spectrum disorders.

Mult Scler Relat Disord. 2020 May 21;43:102187

Authors: Wang Y, Kwapong WR, Tu Y, Xia Y, Tang J, Miao H, Liu X, Lu Y, Yan Z

Abstract
BACKGROUND: Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune, demyelinating disorder, accompanied by abnormal spontaneous activity of the brain and impairment of the retina and optic nerve. Functional connectivity density (FCD) map, a graph theory method, was applied to explore the functional connectivity alterations of brian in NMOSD patients and investigate the alterations of FCD to the structural and microvascular changes around the optic nerve head (ONH).
METHODS: Nineteen NMOSD patients and 22 healthy controls (HCs) were included in our study. All participants underwent resting-state functional magnetic resonance imaging (fMRI) scans of the brain, and ophthalmological examinations included optical coherence tomographic angiography (OCT-A) imaging, visual acuity (VA), and intraocular pressure (IOP). The long- and short-range FCD was calculated by the fMRI graph theory method and two-sample t-tests were performed to compare the discrepancy of FCD between NMOSD and HCs. OCT-A imaging was used to obtain the structure (peripapillary retinal nerve fiber layer, pRNFL) and microvessels (radial peripapillary capillary, RPC) details around the ONH. The association between the long- and short-range FCD values with the structural and microvascular variation around the ONH were evaluated using Spearman's correlation.
RESULTS: Significantly decreased (corrected p < 0.05) long-range FCD was seen in the right superior parietal gyrus (SPG) in patients with NMOSD when compared to HCs. Increased long-range FCD was seen in the right fusiform gyrus (FFG), left orbital part of superior frontal orbital gyrus (ORBsup) and left anterior cingulum and paracingulate gyri (ACG) in NMOSD patients (corrected p < 0.05). The regions with reduced short-range FCD in NMOSD were the left angular gyrus (ANG) and right SPG (corrected p < 0.05). Increased short-range FCD was shown (corrected p < 0.05) in the right FFG of NMOSD. The pRNFL thickness and RPC density in all participants were negatively correlated with the long-range FCD values in the right FFG, left ORBsup, and left ACG as well as short-range FCD values in the right FFG, besides, both were positively correlated with the long-range FCD values in the right SPG and short-range FCD values in the left ANG and right SPG (p < 0.05).
CONCLUSION: Our study demonstrates that patients with NMOSD have widespread brain dysfunction after optic neuritis attacks which shows as impairment of widespread spatial distribution in long- and short-range FCD. Structural and microvascular changes around the ONH are associated with neural changes in the brain.

PMID: 32480345 [PubMed - as supplied by publisher]

Lower cortical gamma-aminobutyric acid level contributes to connectivity in sensory-motor inter-connected regions in progressive MS.

Tue, 06/02/2020 - 22:44
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Lower cortical gamma-aminobutyric acid level contributes to connectivity in sensory-motor inter-connected regions in progressive MS.

Mult Scler Relat Disord. 2020 May 25;43:102183

Authors: Droby A, Fleysher L, Petracca M, Podranski K, Xu J, Fabian M, Marjańska M, Inglese M

Abstract
BACKGROUND: Large-scale functional abnormalities and decreased synchronization between functionally connected regions within brain networks were reported in progressive multiple sclerosis (P-MS) patients. Low concentration of gamma-aminobutyric acid (GABA) was observed in the sensorimotor cortex (SMC) of these patients and was associated with reduced motor functions of limbs. Yet, the role of GABA in modulating functional connectivity (FC) has not been investigated in MS patients.
OBJECTIVES: To determine the relationship between GABA concentration in the SMC and short-term FC changes within the sensorimotor network (SMN) in P-MS patients.
METHODS: Combining magnetic resonance spectroscopy (MRS) and resting-state functional MRI (rs-fMRI), we investigated the relationship between baseline GABA concentration in the left SMC and FC within SMN in P-MS patients compared to healthy controls (HCs). Additionally, we assessed the relationship between baseline GABA concentration and FC changes over a 1-year follow-up period in the patients' group only.
RESULTS: At baseline, lower GABA levels, and decreased FC levels in regions within the SMN were observed in MS patients compared to healthy controls (HCs). Overtime, an increase in FC was observed in regions within the SMN in the MS group. This increase correlated inversely with motor performance scores.
CONCLUSIONS: We postulate that in P-MS patients, lower levels of GABA in the SMC contribute to decreased inhibition, and as a result, to a reactive increase of FC in inter-connected sensorimotor brain regions, thus minimizing clinical worsening.

PMID: 32480344 [PubMed - as supplied by publisher]

Structural and functional brain alterations in psychiatric patients with dissociative experiences: A systematic review of magnetic resonance imaging studies.

Tue, 06/02/2020 - 22:44
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Structural and functional brain alterations in psychiatric patients with dissociative experiences: A systematic review of magnetic resonance imaging studies.

J Psychiatr Res. 2020 May 13;128:5-15

Authors: Lotfinia S, Soorgi Z, Mertens Y, Daniels J

Abstract
INTRODUCTION: There is currently no general agreement on how to best conceptualize dissociative symptoms and whether they share similar neural underpinnings across dissociative disorders. Neuroimaging data could help elucidate these questions.
OBJECTIVES: The objective of this review is to summarize empirical evidence for neural aberrations observed in patients suffering from dissociative symptoms.
METHODS: A systematic literature review was conducted including patient cohorts diagnosed with primary dissociative disorders, post-traumatic stress disorder (PTSD), or borderline personality disorder.
RESULTS: Results from MRI studies reporting structural (gray matter and white matter) and functional (during resting-state and task-related activation) brain aberrations were extracted and integrated. In total, 33 articles were included of which 10 pertained to voxel-based morphology, 2 to diffusion tensor imaging, 10 to resting-state fMRI, and 11 to task-related fMRI. Overall findings indicated aberrations spread across diverse brain regions, especially in the temporal and frontal cortices. Patients with dissociative identity disorder and with dissociative PTSD showed more overlap in brain activation than each group showed with depersonalization/derealization disorder.
CONCLUSION: In conjunction, the results indicate that dissociative processing cannot be localized to a few distinctive brain regions but rather corresponds to differential neural signatures depending on the symptom constellation.

PMID: 32480060 [PubMed - as supplied by publisher]

Concurrent EEG- and fMRI-derived functional connectomes exhibit linked dynamics.

Tue, 06/02/2020 - 22:44
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Concurrent EEG- and fMRI-derived functional connectomes exhibit linked dynamics.

Neuroimage. 2020 May 29;:116998

Authors: Wirsich J, Giraud AL, Sadaghiani S

Abstract
Long-range connectivity has become the most studied feature of human functional Magnetic Resonance Imaging (fMRI), yet the spatial and temporal relationship between its whole-brain dynamics and electrophysiological connectivity remains largely unknown. FMRI-derived functional connectivity exhibits spatial reconfigurations or time-varying dynamics at infraslow (<0.1Hz) speeds. Conversely, electrophysiological connectivity is based on cross-region coupling of fast oscillations (∼1-100Hz). It is unclear whether such fast oscillation-based coupling varies at infraslow speeds, temporally coinciding with infraslow dynamics across the fMRI-based connectome. If so, does the association of fMRI-derived and electrophysiological dynamics spatially vary over the connectome across the functionally distinct electrophysiological oscillation bands? In two concurrent electroencephalography (EEG)-fMRI resting-state datasets, oscillation-based coherence in all canonical bands (delta through gamma) indeed reconfigured at infraslow speeds in tandem with fMRI-derived connectivity changes in corresponding region-pairs. Interestingly, irrespective of EEG frequency-band the cross-modal tie of connectivity dynamics comprised a large proportion of connections distributed across the entire connectome. However, there were frequency-specific differences in the relative strength of the cross-modal association. This association was strongest in visual to somatomotor connections for slower EEG-bands, and in connections involving the Default Mode Network for faster EEG-bands. Methodologically, the findings imply that neural connectivity dynamics can be reliably measured by fMRI despite heavy susceptibility to noise, and by EEG despite shortcomings of source reconstruction. Biologically, the findings provide evidence that contrast with known territories of oscillation power, oscillation coupling in all bands slowly reconfigures in a highly distributed manner across the whole-brain connectome.

PMID: 32480035 [PubMed - as supplied by publisher]