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Development of brain networks and relevance of environmental and genetic factors: A systematic review.

Thu, 10/19/2017 - 10:20
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Development of brain networks and relevance of environmental and genetic factors: A systematic review.

Neurosci Biobehav Rev. 2016 Dec;71:215-239

Authors: Richmond S, Johnson KA, Seal ML, Allen NB, Whittle S

Abstract
This study conducted a systematic review to synthesize findings on the development of functional and structural brain networks from the prenatal to late adolescent period. In addition, evidence for environmental and genetic influences on the development of brain networks was reviewed. Ninety two studies fulfilled the inclusion criteria. Diffusion MRI findings indicated that clustering decreases, local and global efficiency increase and modularity stabilizes or decreases with age. Structural covariance findings indicated that local efficiency, global efficiency and modularity, may stabilize in adolescence. Findings for resting-state functional MRI were mixed. Few studies have investigated genetic or environmental influences on development of structural or functional networks. For functional networks, genetic effects have been reported with few significant environmental factors. While no studies of this nature were found for structural networks, other research has provided evidence of age-related changes in heritability of white matter volume, fractional anisotropy, and cortical thickness. Further research is required to understand the development of brain networks and the relevance of environmental and genetic factors.

PMID: 27590832 [PubMed - indexed for MEDLINE]

Levodopa Effect on Basal Ganglia Motor Circuit in Parkinson's Disease.

Thu, 10/19/2017 - 10:20
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Levodopa Effect on Basal Ganglia Motor Circuit in Parkinson's Disease.

CNS Neurosci Ther. 2017 Jan;23(1):76-86

Authors: Gao LL, Zhang JR, Chan P, Wu T

Abstract
AIMS: To investigate the effects of levodopa on the basal ganglia motor circuit (BGMC) in Parkinson's disease (PD).
METHODS: Thirty PD patients with asymmetrical bradykinesia and 30 control subjects were scanned using resting-state functional MRI. Functional connectivity of the BGMC was measured and compared before and after levodopa administration in patients with PD. The correlation between improvements in bradykinesia and changes in BGMC connectivity was examined.
RESULTS: In the PD-off state (before medication), the posterior putamen and internal globus pallidus (GPi) had decreased connectivity while the subthalamic nucleus (STN) had enhanced connectivity within the BGMC relative to control subjects. Levodopa administration increased the connectivity of posterior putamen- and GPi-related networks but decreased the connectivity of STN-related networks. Improvements in bradykinesia were correlated with enhanced connectivity of the posterior putamen-cortical motor pathway and with decreased connectivity of the STN-thalamo-cortical motor pathway.
CONCLUSION: In PD patients with asymmetrical bradykinesia, levodopa can partially normalize the connectivity of the BGMC with a larger effect on the more severely affected side. Moreover, the beneficial effect of levodopa on bradykinesia is associated with normalization of the striato-thalamo-cortical motor and STN-cortical motor pathways. Our findings inform the neural mechanism of levodopa treatment in PD.

PMID: 27663605 [PubMed - indexed for MEDLINE]

Convergence and Divergence of Brain Network Dysfunction in Deficit and Non-deficit Schizophrenia.

Tue, 10/17/2017 - 14:20

Convergence and Divergence of Brain Network Dysfunction in Deficit and Non-deficit Schizophrenia.

Schizophr Bull. 2017 Jul 20;:

Authors: Yu M, Dai Z, Tang X, Wang X, Zhang X, Sha W, Yao S, Shu N, Wang X, Yang J, Zhang X, Zhang X, He Y, Zhang Z

Abstract
Deficit schizophrenia (DS), characterized by primary and enduring negative symptoms, has been considered as a pathophysiologically distinct schizophrenic subgroup. Neuroimaging characteristics of DS, especially functional brain network architecture, remain largely unknown. Resting-state functional magnetic resonance imaging and graph theory approaches were employed to investigate the topological organization of whole-brain functional networks of 114 male participants including 33 DS, 41 non-deficit schizophrenia (NDS) and 40 healthy controls (HCs). At the whole-brain level, both the NDS and DS group exhibited lower local efficiency (Eloc) than the HC group, implying the reduction of local specialization of brain information processing (reduced functional segregation). The DS, but not NDS group, exhibited enhanced parallel information transfer (enhanced functional integration) as determined by smaller characteristic path length (Lp) and higher global efficiency (Eglob). The Lp and Eglob presented significant correlations with Brief Psychiatric Rating Scale (BPRS) total score in the DS group. At the nodal level, both the NDS and DS groups showed higher functional connectivity in the inferior frontal gyrus and hippocampus, and lower connectivity in the visual areas and striatum than the controls. The DS group exhibited higher nodal connectivity in the right inferior temporal gyrus than the NDS and HC group. The diminished expression of Scale for the Assessment of Negative Symptoms (SANS) subfactors negatively correlated with nodal connectivity of right putamen, while asociality/amotivation positively correlated with right hippocampus across whole patients. We highlighted the convergence and divergence of brain functional network dysfunctions in patients with DS and NDS, which provides crucial insights into pathophysiological mechanisms of the 2 schizophrenic subtypes.

PMID: 29036672 [PubMed - as supplied by publisher]

Modeling Causal Relationships among Brain Areas in the Mesocorticolimbic System during Resting-State in Cocaine Users Utilizing a Graph Theoretic Approach.

Tue, 10/17/2017 - 14:20
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Modeling Causal Relationships among Brain Areas in the Mesocorticolimbic System during Resting-State in Cocaine Users Utilizing a Graph Theoretic Approach.

J Alcohol Drug Depend. 2017 Aug;5(4):

Authors: Ray S, Biswal BB, Aya A, Gohel S, Srinagesh A, Hanson C, Hanson SJ

Abstract
OBJECTIVE: While effective connectivity (EC, causal interaction) between brain areas has been investigated in chronic users of cocaine as they view cocaine pictures cues, no study has examined EC while they take part in a resting-state scan. This resting-state fMRI study aims to investigate the causal interaction among brain areas in the mesocorticolimbic system (MCLS), which is involved in reward and motivation, in cocaine users (vs. controls).
METHOD: Twenty cocaine users and 17 healthy controls finished a structural and a resting-state scan. Mean voxel-based time series data were obtained from brain regions of interest (ROIs) from the MCLS, and were input into a Bayesian search algorithm called IMaGES.
RESULTS: The causal interaction pattern was different between the two groups. The feed-forward pattern found in cocaine smokers, between 7 ROIs of the MCLS during resting-state [ventral tegmental area (VTA)→hippocampus (HIPP)→ventral striatum (VenStri)→orbital frontal cortex (OFC), medial frontal cortex (MFC), anterior cingulate cortex (ACC), dorsolateral prefrontal cortex (DLPFC)], was absent in controls. That is, the subcortical VenStri area had a causal influence on four cortical brain areas only in cocaine users.
CONCLUSIONS: During the resting-state scan, the VTA of cocaine smokers abstinent for at least 72 hours, but not controls, begins causal connections to limbic, midbrain, and frontal regions in the MCLS in a feed-forward manner. Following replication, further studies may assess if changes over time in EC during resting-state predict cocaine treatment efficacy and outcome.

PMID: 29034263 [PubMed]

Identification of autism spectrum disorder using deep learning and the ABIDE dataset.

Tue, 10/17/2017 - 14:20
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Identification of autism spectrum disorder using deep learning and the ABIDE dataset.

Neuroimage Clin. 2018;17:16-23

Authors: Heinsfeld AS, Franco AR, Craddock RC, Buchweitz A, Meneguzzi F

Abstract
The goal of the present study was to apply deep learning algorithms to identify autism spectrum disorder (ASD) patients from large brain imaging dataset, based solely on the patients brain activation patterns. We investigated ASD patients brain imaging data from a world-wide multi-site database known as ABIDE (Autism Brain Imaging Data Exchange). ASD is a brain-based disorder characterized by social deficits and repetitive behaviors. According to recent Centers for Disease Control data, ASD affects one in 68 children in the United States. We investigated patterns of functional connectivity that objectively identify ASD participants from functional brain imaging data, and attempted to unveil the neural patterns that emerged from the classification. The results improved the state-of-the-art by achieving 70% accuracy in identification of ASD versus control patients in the dataset. The patterns that emerged from the classification show an anticorrelation of brain function between anterior and posterior areas of the brain; the anticorrelation corroborates current empirical evidence of anterior-posterior disruption in brain connectivity in ASD. We present the results and identify the areas of the brain that contributed most to differentiating ASD from typically developing controls as per our deep learning model.

PMID: 29034163 [PubMed - in process]

Altered Local Spatiotemporal Consistency of Resting-State BOLD Signals in Patients with Generalized Tonic-Clonic Seizures.

Tue, 10/17/2017 - 14:20
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Altered Local Spatiotemporal Consistency of Resting-State BOLD Signals in Patients with Generalized Tonic-Clonic Seizures.

Front Comput Neurosci. 2017;11:90

Authors: Ma S, Jiang S, Peng R, Zhu Q, Sun H, Li J, Jia X, Goldberg I, Yu L, Luo C

Abstract
The purpose of this study was to evaluate the spatiotemporal Consistency of spontaneous activities in local brain regions in patients with generalized tonic-clonic seizures (GTCS). The resting-state fMRI data were acquired from nineteen patients with GTCS and twenty-two matched healthy subjects. FOur-dimensional (spatiotemporal) Consistency of local neural Activities (FOCA) metric was used to analyze the spontaneous activity in whole brain. The FOCA difference between two groups were detected using a two sample t-test analysis. Correlations between the FOCA values and features of seizures were analyzed. The findings of this study showed that patients had significantly increased FOCA in motor-related cortex regions, including bilateral supplementary motor area, paracentral lobule, precentral gyrus and left basal ganglia, as well as a substantial reduction of FOCA in regions of default mode network (DMN) and parietal lobe. In addition, several brain regions in DMN demonstrated more reduction with longer duration of epilepsy and later onset age, and the motor-related regions showed higher FOCA value in accompany with later onset age. These findings implicated the abnormality of motor-related cortical network in GTCS which were associated with the genesis and propagation of epileptiform activity. And the decreased FOCA in DMN might reflect the intrinsic disturbance of brain activity. Moreover, our study supported that the FOCA might be potential tool to investigate local brain spontaneous activity related with the epileptic activity, and to provide important insights into understanding the underlying pathophysiological mechanisms of GTCS.

PMID: 29033811 [PubMed]

Connectivity changes after laser ablation: Resting-state fMRI.

Tue, 10/17/2017 - 14:20
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Connectivity changes after laser ablation: Resting-state fMRI.

Epilepsy Res. 2017 Sep 28;:

Authors: Boerwinkle VL, Vedantam A, Lam S, Wilfong AA, Curry DJ

Abstract
Resting-state functional magnetic resonance imaging (rsfMRI) is emerging as a useful tool in the multimodal assessment of patients with epilepsy. In pediatric patients who cannot perform task-based fMRI, rsfMRI may present an adjunct and alternative. Although changes in brain activation during task-based fMRI have been described after surgery for epilepsy, there is limited data on the role of postoperative rsfMRI. In this short review, we discuss the role of postoperative rsfMRI after laser ablation of seizure foci. By establishing standardized anesthesia protocols and imaging parameters, we have been able to perform serial rsfMRI at postoperative follow-up. The development of in-house software that can merge rsfMRI images to surgical navigation systems has allowed us to enhance the clinical applications of this technique. Resting-state fMRI after laser ablation has the potential to identify changes in connectivity, localize new seizure foci, and guide antiepileptic therapy. In our experience, rsfMRI complements conventional MR imaging and task-based fMRI for the evaluation of patients with seizure recurrence after laser ablation, and represents a potential noninvasive biomarker for functional connectivity.

PMID: 29031866 [PubMed - as supplied by publisher]

Combined resting state functional magnetic resonance imaging and diffusion tensor imaging study in patients with idiopathic restless legs syndrome.

Tue, 10/17/2017 - 14:20
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Combined resting state functional magnetic resonance imaging and diffusion tensor imaging study in patients with idiopathic restless legs syndrome.

Sleep Med. 2017 Oct;38:96-103

Authors: Zhuo Y, Wu Y, Xu Y, Lu L, Li T, Wang X, Li K

Abstract
OBJECTIVE: Restless legs syndrome (RLS) is a common neurological disorder characterized by an urge to move the legs along with paraesthesia deep within them. In this study, we aimed to use diffusion tensor imaging (DTI) and regional homogeneity (ReHo) to investigate the changes in regional spontaneous brain activity change for RLS patients against age- and gender-matched normal control (NC) subjects.
METHODS: A total of 35 RLS patients and 27 age- and gender-matched NC subjects were recruited for group comparison research that used DTI and ReHo techniques. DTI was analysed by FSL and tract-based spatial statistics (TBSS) software to measure the values of fractional anisotropy (FA) or mean diffusivity (MD) in brain regions. Statistical Parametric Mapping 8 (SPM8) was used for data preprocessing and Data Processing Assistant for Resting-State fMRI (DPARSF) toolbox was used for ReHo calculation. For multiple comparison correction, the AlphaSim program implemented in AFNI was used to control the false-positive rate (corrected p < 0.05).
RESULTS: There was no significant difference between the iRLS and NC groups in age or gender. In the one-sample t-test, both the NC and RSL groups showed increased ReHo in the bilateral posterior cingulate/precuneus cortex compared to the groups' global means, indicating that the default mode network was at rest. The RLS group showed a smaller cluster size than the NC group. In the two-sample t-test, the RLS group showed increased ReHo in the bilateral middle frontal gyrus, anterior cingulate cortex, caudate nucleus, insula, thalamus, putamen and left posterior cingulate cortex compared to the NC group. The statistical analysis of DTI images did not show any difference between the two groups. TBSS group comparison did not reveal any difference in FA or mean diffusivity (MD) of any brain region.
CONCLUSION: RLS patients showed that greater ReHo within the striatum, thalamus and the limbic system, which implies that the emotional processing, motion control and cognition in the cortico-striatal-thalamic-cortical (CSTC) loop may be the site of dysfunction in RLS patients. This finding may provide imaging evidence to explore the pathophysiology of RLS. On the other hand, we did not see any change in the microstructure in the DTI analysis for RLS patients when compared to the NC group, which suggests a metabolic impairment.

PMID: 29031764 [PubMed - in process]

Psilocybin for treatment-resistant depression: fMRI-measured brain mechanisms.

Tue, 10/17/2017 - 14:20
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Psilocybin for treatment-resistant depression: fMRI-measured brain mechanisms.

Sci Rep. 2017 Oct 13;7(1):13187

Authors: Carhart-Harris RL, Roseman L, Bolstridge M, Demetriou L, Pannekoek JN, Wall MB, Tanner M, Kaelen M, McGonigle J, Murphy K, Leech R, Curran HV, Nutt DJ

Abstract
Psilocybin with psychological support is showing promise as a treatment model in psychiatry but its therapeutic mechanisms are poorly understood. Here, cerebral blood flow (CBF) and blood oxygen-level dependent (BOLD) resting-state functional connectivity (RSFC) were measured with functional magnetic resonance imaging (fMRI) before and after treatment with psilocybin (serotonin agonist) for treatment-resistant depression (TRD). Quality pre and post treatment fMRI data were collected from 16 of 19 patients. Decreased depressive symptoms were observed in all 19 patients at 1-week post-treatment and 47% met criteria for response at 5 weeks. Whole-brain analyses revealed post-treatment decreases in CBF in the temporal cortex, including the amygdala. Decreased amygdala CBF correlated with reduced depressive symptoms. Focusing on a priori selected circuitry for RSFC analyses, increased RSFC was observed within the default-mode network (DMN) post-treatment. Increased ventromedial prefrontal cortex-bilateral inferior lateral parietal cortex RSFC was predictive of treatment response at 5-weeks, as was decreased parahippocampal-prefrontal cortex RSFC. These data fill an important knowledge gap regarding the post-treatment brain effects of psilocybin, and are the first in depressed patients. The post-treatment brain changes are different to previously observed acute effects of psilocybin and other 'psychedelics' yet were related to clinical outcomes. A 'reset' therapeutic mechanism is proposed.

PMID: 29030624 [PubMed - in process]

Sex differences and menstrual cycle effects in cognitive and sensory resting state networks.

Tue, 10/17/2017 - 14:20
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Sex differences and menstrual cycle effects in cognitive and sensory resting state networks.

Brain Cogn. 2017 Oct 10;:

Authors: Weis S, Hodgetts S, Hausmann M

Abstract
It has not yet been established if resting state (RS) connectivity reflects stable characteristics of the brain, or if it is modulated by the psychological and/or physiological state of the participant. Based on research demonstrating sex hormonal effects in task-related brain activity, the present study aimed to investigate corresponding differences in RS networks. RS functional Magnetic Resonance Imaging (RS fMRI) was conducted in women during three different menstrual cycle phases, while men underwent three repeated RS fMRI testing sessions. Independent component analysis was used to identify the default mode network (DMN) and an auditory RS network. For the DMN, RS connectivity was stable across testing sessions in men, but varied across the menstrual cycle in women. For the auditory network (AN), retest reliable sex difference was found. Although RS activity in the DMN has been interpreted as trait characteristic of functional brain organization, these findings suggest that RS activity in networks involving frontal areas might be less stable than in sensory-based networks and can dynamically fluctuate. This also implies that some of the previously reported effects of sex hormones on task-related activity might to some extent be mediated by cycle-related fluctuations in RS activity, especially when frontal areas are involved.

PMID: 29030069 [PubMed - as supplied by publisher]

Brain sexual differentiation and effects of cross-sex hormone therapy in transpeople: A resting-state functional magnetic resonance study.

Tue, 10/17/2017 - 14:20
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Brain sexual differentiation and effects of cross-sex hormone therapy in transpeople: A resting-state functional magnetic resonance study.

Neurophysiol Clin. 2017 Oct 10;:

Authors: Nota NM, Burke SM, den Heijer M, Soleman RS, Lambalk CB, Cohen-Kettenis PT, Veltman DJ, Kreukels BP

Abstract
OBJECTIVES: It is hypothesized that transpeople show sex-atypical differentiation of the brain. Various structural neuroimaging studies provide support for this notion, but little is known about the sexual differentiation of functional resting-state networks in transpeople. In this study we therefore aimed to determine whether brain functional connectivity (FC) patterns in transpeople are sex-typical or sex-atypical, before and after the start of cross-sex hormone therapy (CHT).
METHODS: We acquired resting-state functional magnetic resonance data in 36 transpeople (22 with female sex assigned at birth), first during gonadal suppression, and again four months after start of CHT, and in 37 cisgender people (20 females), both sessions without any hormonal intervention. We used independent component analysis to identify the default mode network (DMN), salience network (SN), and left and right working memory network (WMN). These spatial maps were used for group comparisons.
RESULTS: Within the DMN, SN, and left WMN similar FC patterns were found across groups. However, within the right WMN, cisgender males showed significantly greater FC in the right caudate nucleus than cisgender females. There was no such sex difference in FC among the transgender groups and they did not differ significantly from either of the cisgender groups. CHT (in transgender participants) and circulating sex steroids (in cisgender participants) did not affect FC.
CONCLUSION: Our findings may suggest that cisgender males and females experience a dissimilar (early) differentiation of the right WMN and that such differentiation is less pronounced in transpeople.

PMID: 29029883 [PubMed - as supplied by publisher]

Disrupted small-world brain network topology in pure conduct disorder.

Tue, 10/17/2017 - 14:20
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Disrupted small-world brain network topology in pure conduct disorder.

Oncotarget. 2017 Sep 12;8(39):65506-65524

Authors: Lu FM, Zhou JS, Zhang J, Wang XP, Yuan Z

Abstract
OBJECTIVES: Conduct disorder (CD) is characterized by the violation of the rights of others or basic social rules and a repetitive, persistent pattern of antisocial and aggressive behaviors. A large number of functional and structural neuroimaging studies have identified widely abnormalities in specific brain regions in CD, but the alterations in the topological organization of functional networks among them remain largely unknown.
METHODS: Resting-state functional magnetic resonance imaging was applied to investigate the intrinsic functional connectivity in 18 pure CD patients and eighteen typically developing healthy controls. We first constructed the functional networks and then examined the CD-related alteration in topology properties using graph theoretical analysis.
RESULTS: Both the CD group and healthy controls exhibited small-world topology. However, the CD group showed decreased global and local efficiency. Changes in the nodal characteristics in CD group were found predominantly in the default-mode network, visual, and striatum regions. In addition, altered fronto-limbic-striatum network topology was found to have a relationship with clinical scores.
CONCLUSIONS: Our findings indicate the altered nodal topology of brain functional connectivity networks in CD.
SIGNIFICANCE: The results provide unequivocal evidence of a topological disruption in the brain networks that suggest some possible pathophysiological mechanisms underlying CD.

PMID: 29029449 [PubMed]

The association between stress and mood across the adult lifespan on default mode network.

Tue, 10/17/2017 - 14:20
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The association between stress and mood across the adult lifespan on default mode network.

Brain Struct Funct. 2017 Jan;222(1):101-112

Authors: Soares JM, Marques P, Magalhães R, Santos NC, Sousa N

Abstract
Aging of brain structure and function is a complex process characterized by high inter- and intra-individual variability. Such variability may arise from the interaction of multiple factors, including exposure to stressful experience and mood variation, across the lifespan. Using a multimodal neuroimaging and neurocognitive approach, we investigated the association of stress, mood and their interaction, in the structure and function of the default mode network (DMN), both during rest and task-induced deactivation, throughout the adult lifespan. Data confirmed a decreased functional connectivity (FC) and task-induced deactivation of the DMN during the aging process and in subjects with lower mood; on the contrary, an increased FC was observed in subjects with higher perceived stress. Surprisingly, the association of aging with DMN was altered by stress and mood in specific regions. An increased difficulty to deactivate the DMN was noted in older participants with lower mood, contrasting with an increased deactivation in individuals presenting high stress, independently of their mood levels, with aging. Interestingly, this constant interaction across aging was globally most significant in the combination of high stress levels with a more depressed mood state, both during resting state and task-induced deactivations. The present results contribute to characterize the spectrum of FC and deactivation patterns of the DMN, highlighting the crucial association of stress and mood levels, during the adult aging process. These combinatorial approaches may help to understand the heterogeneity of the aging process in brain structure and function and several states that may lead to neuropsychiatric disorders.

PMID: 26971253 [PubMed - indexed for MEDLINE]

Brain functional network abnormality extends beyond the sensorimotor network in brachial plexus injury patients.

Tue, 10/17/2017 - 14:20
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Brain functional network abnormality extends beyond the sensorimotor network in brachial plexus injury patients.

Brain Imaging Behav. 2016 Dec;10(4):1198-1205

Authors: Feng JT, Liu HQ, Hua XY, Gu YD, Xu JG, Xu WD

Abstract
Brachial plexus injury (BPI) is a type of severe peripheral nerve trauma that leads to central remodeling in the brain, as revealed by functional MRI analysis. However, previously reported remodeling is mostly restricted to sensorimotor areas of the brain. Whether this disturbance in the sensorimotor network leads to larger-scale functional remodeling remains unknown. We sought to explore the higher-level brain functional abnormality pattern of BPI patients from a large-scale network function connectivity dimension in 15 right-handed BPI patients. Resting-state functional MRI data were collected and analyzed using independent component analysis methods. Five components of interest were recognized and compared between patients and healthy subjects. Patients showed significantly altered brain local functional activities in the bilateral fronto-parietal network (FPN), sensorimotor network (SMN), and executive-control network (ECN) compared with healthy subjects. Moreover, functional connectivity between SMN and ECN were significantly less in patients compared with healthy subjects, and connectivity strength between ECN and SMN was negatively correlated with patients' residual function of the affected limb. Functional connectivity between SMN and right FPN were also significantly less than in controls, although connectivity between ECN and default mode network (DMN) was greater than in controls. These data suggested that brain functional disturbance in BPI patients extends beyond the sensorimotor network and cascades serial remodeling in the brain, which significantly correlates with residual hand function of the paralyzed limb. Furthermore, functional remodeling in these higher-level functional networks may lead to cognitive alterations in complex tasks.

PMID: 26630882 [PubMed - indexed for MEDLINE]

Cerebral changes and cognitive impairment after an ischemic heart disease: a multimodal MRI study.

Tue, 10/17/2017 - 14:20
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Cerebral changes and cognitive impairment after an ischemic heart disease: a multimodal MRI study.

Brain Imaging Behav. 2016 Sep;10(3):893-900

Authors: Bernard C, Catheline G, Dilharreguy B, Couffinhal T, Ledure S, Lassalle-Lagadec S, Callaert D, Allard M, Sibon I

Abstract
Three to 6 months after an acute coronary syndrome (ACS), cognitive impairment is observed in more than 30 % of the patients, mainly in executive functioning. The aim of this study was to investigate, using multimodal MRI, cerebral anatomo-functional substratum of executive dysfunction. Thirty-three patients were recruited 4 ± 1 months after a first ACS. Executive functions were evaluated with the Trail-Making-Test-B (TMTB) at baseline (ie 4 ± 1 months after ACS) and 6 months later (ie 10 ± 1 months after ACS). Using both time-points, we identified 3 groups of patients according to normative data based on age, gender and education level: 15 'cognitively normal' patients without impairment at each follow-up, 10 'transient impaired' patients with an impairment only at baseline and 8 'impairing' patients with an impairment only at follow-up. We explored, in the whole-brain, the structural integrity using Voxel-Based Morphometry and Tract-Based Spatial Statistics and the resting-state functional connectivity using Network-Based Statistics. No structural difference was observed between impaired and cognitively normal patients. At the functional level, compared to the 'cognitively normal' group, the 'transient impaired' patients presented an increased functional connectivity in a network centered on middle-orbito-frontal regions, whereas the 'impairing' patients presented only a non-significant decrease of functional connectivity. Executive dysfunction in ACS patients is associated to functional but no structural characteristics, particularly to an increased functional connectivity in cognitive networks in transient impaired patients. Further studies with larger sample size are needed to confirm these results and to determine if these patients could be at higher risk for developing permanent cognitive disorders.

PMID: 26589710 [PubMed - indexed for MEDLINE]

A lateralized top-down network for visuospatial attention and neglect.

Tue, 10/17/2017 - 14:20
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A lateralized top-down network for visuospatial attention and neglect.

Brain Imaging Behav. 2016 Dec;10(4):1029-1037

Authors: Wang J, Tian Y, Wang M, Cao L, Wu H, Zhang Y, Wang K, Jiang T

Abstract
The lateralization of visuospatial attention has been well investigated and demonstrated to be primarily resulting from unbalanced interaction between interhemispheric fronto-parietal networks in previous studies. Many recent studies of top-down attention have reported the neural signatures of its effects within visual cortex and identified its causal basis. However, the relationship between top-down networks and asymmetric visuospatial attention has not been well studied. In the current study, we aimed to explore the relationship between top-down connectivity and asymmetric visuospatial ability by using repetitive transcranial magnetic stimulation (rTMS) and resting-state functional connectivity (RSFC) analyses. We used rTMS and RSFC to model the virtual lesion to assess the behavioral performances in visuospatial attention shifting and to identify the behavior-related top-down functional connectivities, respectively. Furthermore, we also investigated the top-down connectivity in neglect patients to validate the RSFC findings. RSFC analyses in healthy subjects and neglect patients consistently revealed that asymmetric visuospatial ability and visuospatial neglect were closely related to the bias of top-down functional connectivity between posterior superior parietal lobule (SPL) and V1. Our findings indicate that stronger top-down connectivity has stronger dominance on its corresponding visual field. We argue that an asymmetric top-down network may represent a possible neurophysiological substrate for the ongoing functional asymmetry of visuospatial attention, and its interhemispheric unbalanced interaction could contribute to the clinical manifestations of visuospatial neglect.

PMID: 26508314 [PubMed - indexed for MEDLINE]

Abnormal prefrontal cortex resting state functional connectivity and severity of internet gaming disorder.

Tue, 10/17/2017 - 14:20
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Abnormal prefrontal cortex resting state functional connectivity and severity of internet gaming disorder.

Brain Imaging Behav. 2016 Sep;10(3):719-29

Authors: Jin C, Zhang T, Cai C, Bi Y, Li Y, Yu D, Zhang M, Yuan K

Abstract
Internet Gaming Disorder (IGD) among adolescents has become an important public concern and gained more and more attention internationally. Recent studies focused on IGD and revealed brain abnormalities in the IGD group, especially the prefrontal cortex (PFC). However, the role of PFC-striatal circuits in pathology of IGD remains unknown. Twenty-five adolescents with IGD and 21 age- and gender-matched healthy controls were recruited in our study. Voxel-based morphometric (VBM) and functional connectivity analysis were employed to investigate the abnormal structural and resting-state properties of several frontal regions in individuals with online gaming addiction. Relative to healthy comparison subjects, IGD subjects showed significant decreased gray matter volume in PFC regions including the bilateral dorsolateral prefrontal cortex (DLPFC), orbitofrontal cortex (OFC), anterior cingulate cortex (ACC) and the right supplementary motor area (SMA) after controlling for age and gender effects. We chose these regions as the seeding areas for the resting-state analysis and found that IGD subjects showed decreased functional connectivity between several cortical regions and our seeds, including the insula, and temporal and occipital cortices. Moreover, significant decreased functional connectivity between some important subcortical regions, i.e., dorsal striatum, pallidum, and thalamus, and our seeds were found in the IGD group and some of those changes were associated with the severity of IGD. Our results revealed the involvement of several PFC regions and related PFC-striatal circuits in the process of IGD and suggested IGD may share similar neural mechanisms with substance dependence at the circuit level.

PMID: 26311395 [PubMed - indexed for MEDLINE]

Predicting episodic and spatial memory performance from hippocampal resting-state functional connectivity: Evidence for an anterior-posterior division of function.

Sun, 10/15/2017 - 18:40

Predicting episodic and spatial memory performance from hippocampal resting-state functional connectivity: Evidence for an anterior-posterior division of function.

Hippocampus. 2017 Oct 13;:

Authors: Persson J, Stening E, Nordin K, Söderlund H

Abstract
fMRI studies have identified distinct resting-state functional connectivity (RSFC) networks associated with the anterior and posterior hippocampus. However, the functional relevance of these two networks is still largely unknown. Hippocampal lesion studies and task-related fMRI point to a role for the anterior hippocampus in non-spatial episodic memory and the posterior hippocampus in spatial memory. We used Relevance Vector Regression (RVR), a machine-learning method that enables predictions of continuous outcome measures from multivariate patterns of brain imaging data, to test the hypothesis that patterns of whole-brain RSFC associated with the anterior hippocampus predict episodic memory performance, while patterns of whole-brain RSFC associated with the posterior hippocampus predict spatial memory performance. Magnetic resonance imaging (MRI) and memory assessment took place at two separate occasions. The anterior and posterior RSFC largely corresponded with previous findings, and showed no effect of laterality. Supporting the hypothesis, RVR produced accurate predictions of episodic performance from anterior, but not posterior, RSFC, and accurate predictions of spatial performance from posterior, but not anterior, RSFC. In contrast, a univariate approach could not predict performance from resting-state connectivity. This supports a functional dissociation between the anterior and posterior hippocampus, and indicates a multivariate relationship between intrinsic functional networks and cognitive performance within specific domains, that is relatively stable over time. This article is protected by copyright. All rights reserved.

PMID: 29028135 [PubMed - as supplied by publisher]

The effects of head-cooling on brain function during passive hyperthermia: an fMRI study.

Sun, 10/15/2017 - 18:40
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The effects of head-cooling on brain function during passive hyperthermia: an fMRI study.

Int J Hyperthermia. 2017 Oct 12;:1-20

Authors: Xue Y, Li L, Qian S, Liu K, Zhou XJ, Li B, Jiang Q, Wu Z, Du L, Sun G

Abstract
PURPOSE: To investigate the effect of head-cooling on resting-state spontaneous brain activity during passive hyperthermia.
METHODS: An environmental heat exposure was simulated on 16 healthy men under a normal control condition (NC) at 25°C and two hot conditions at 50°C with (HHC) and without (HOT) keeping the head cool, respectively. Resting-state functional MRI (fMRI) data were acquired under each condition and the values of amplitude low frequency fluctuations (ALFF) and z functional connectivity (zFC) were computed to examine regional activity and functional integration, respectively. Pearson's correlation analysis between the ALFF value and subjective sensations scores were performed.
RESULTS: Brain regions with significant ALFF differences among the three conditions were found primarily in the right medial prefrontal cortex/anterior cingulate cortex (MPFC/ACC), bilateral posterior cingulate cortex/precuneus (PCC/PCu), and right fusiform gyrus. Compared to the NC or HOT condition, the HHC condition exhibited significantly increased ALFF in the bilateral PCC/PCu and decreased ALFF in the right fusiform gyrus. However, ALFF of the right MPFC/ACC showed no significant difference between the NC and HHC conditions. Positive FC between the right MPFC/ACC and bilateral PCC/PCu was significantly increased in HHC condition with respect to HOT condition. Negative FC between the right fusiform gyrus and the right MPFC/ACC, bilateral PCC/PCu was observed with a decreasing trend from the HHC condition to the HOT condition. Moreover, head-cooling also improved thermal comfort during passive hyperthermia.
CONCLUSIONS: Head-cooling could substantially reduce the negative effect of hyperthermia on human brain activity as well as thermal sensation.

PMID: 29025324 [PubMed - as supplied by publisher]

Short-range connections in the developmental connectome during typical and atypical brain maturation.

Fri, 10/13/2017 - 16:00

Short-range connections in the developmental connectome during typical and atypical brain maturation.

Neurosci Biobehav Rev. 2017 Oct 09;:

Authors: Ouyang M, Kang H, Detre JA, Roberts TPL, Huang H

Abstract
The human brain is remarkably complex with connectivity constituting its basic organizing principle. Although long-range connectivity has been focused on in most research, short-range connectivity is characterized by unique and spatiotemporally heterogeneous dynamics from infancy to adulthood. Alterations in the maturational dynamics of short-range connectivity has been associated with neuropsychiatric disorders, such as autism and schizophrenia. Recent advances in neuroimaging techniques, especially diffusion magnetic resonance imaging (dMRI), resting-state functional MRI (rs-fMRI), electroencephalography (EEG) and magnetoencephalography (MEG), have made quantification of short-range connectivity possible in pediatric populations. This review summarizes findings on the development of short-range functional and structural connections at the macroscale. These findings suggest an inverted U-shaped pattern of maturation from primary to higher-order brain regions, and possible "hyper-" and "hypo-" short-range connections in autism and schizophrenia, respectively. The precisely balanced short- and long-range connections contribute to the integration and segregation of the connectome during development. The mechanistic relationship among short-range connectivity maturation, the developmental connectome and emerging brain functions needs further investigation, including the refinement of methodological approaches.

PMID: 29024679 [PubMed - as supplied by publisher]

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