New resting-state fMRI related studies at PubMed

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Characterization of functional brain activity and connectivity using EEG and fMRI in patients with sickle cell disease.

Wed, 01/25/2017 - 11:05
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Characterization of functional brain activity and connectivity using EEG and fMRI in patients with sickle cell disease.

Neuroimage Clin. 2017;14:1-17

Authors: Case M, Zhang H, Mundahl J, Datta Y, Nelson S, Gupta K, He B

Abstract
Sickle cell disease (SCD) is a red blood cell disorder that causes many complications including life-long pain. Treatment of pain remains challenging due to a poor understanding of the mechanisms and limitations to characterize and quantify pain. In the present study, we examined simultaneously recording functional MRI (fMRI) and electroencephalogram (EEG) to better understand neural connectivity as a consequence of chronic pain in SCD patients. We performed independent component analysis and seed-based connectivity on fMRI data. Spontaneous power and microstate analysis was performed on EEG-fMRI data. ICA analysis showed that patients lacked activity in the default mode network (DMN) and executive control network compared to controls. EEG-fMRI data revealed that the insula cortex's role in salience increases with age in patients. EEG microstate analysis showed patients had increased activity in pain processing regions. The cerebellum in patients showed a stronger connection to the periaqueductal gray matter (involved in pain inhibition), and negative connections to pain processing areas. These results suggest that patients have reduced activity of DMN and increased activity in pain processing regions during rest. The present findings suggest resting state connectivity differences between patients and controls can be used as novel biomarkers of SCD pain.

PMID: 28116239 [PubMed - in process]

Changes in functional organization and white matter integrity in the connectome in Parkinson's disease.

Wed, 01/25/2017 - 11:05
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Changes in functional organization and white matter integrity in the connectome in Parkinson's disease.

Neuroimage Clin. 2017;13:395-404

Authors: Tinaz S, Lauro PM, Ghosh P, Lungu C, Horovitz SG

Abstract
Parkinson's disease (PD) leads to dysfunction in multiple cortico-striatal circuits. The neurodegeneration has also been associated with impaired white matter integrity. This structural and functional "disconnection" in PD needs further characterization. We investigated the structural and functional organization of the PD whole brain connectome consisting of 200 nodes using diffusion tensor imaging and resting-state functional MRI, respectively. Data from 20 non-demented PD patients on dopaminergic medication and 20 matched controls were analyzed using graph theory-based methods. We focused on node strength, clustering coefficient, and local efficiency as measures of local network properties; and network modularity as a measure of information flow. PD patients showed reduced white matter connectivity in frontoparietal-striatal nodes compared to controls, but no change in modular organization of the white matter tracts. PD group also showed reduction in functional local network metrics in many nodes distributed across the connectome. There was also decreased functional modularity in the core cognitive networks including the default mode and dorsal attention networks, and sensorimotor network, as well as a lack of modular distinction in the orbitofrontal and basal ganglia nodes in the PD group compared to controls. Our results suggest that despite subtle white matter connectivity changes, the overall structural organization of the PD connectome remains robust at relatively early disease stages. However, there is a breakdown in the functional modular organization of the PD connectome.

PMID: 28116232 [PubMed - in process]

Synergetic and redundant information flow detected by unnormalized Granger causality: application to resting state fMRI.

Tue, 01/24/2017 - 16:50

Synergetic and redundant information flow detected by unnormalized Granger causality: application to resting state fMRI.

IEEE Trans Biomed Eng. 2016 Apr 28;:

Authors: Stramaglia S, Angelini L, Wu G, Cortes JM, Faes L, Marinazzo D

Abstract
OBJECTIVES: We develop a framework for the analysis of synergy and redundancy in the pattern of information flow between subsystems of a complex network.
METHODS: The presence of redundancy and/or synergy in multivariate time series data renders difficult to estimate the neat flow of information from each driver variable to a given target. We show that adopting an unnormalized definition of Granger causality one may put in evidence redundant multiplets of variables influencing the target by maximizing the total Granger causality to a given target, over all the possible partitions of the set of driving variables. Consequently we introduce a pairwise index of synergy which is zero when two independent sources additively influence the future state of the system, differently from previous definitions of synergy.
RESULTS: We report the application of the proposed approach to resting state fMRI data from the Human Connectome Project, showing that redundant pairs of regions arise mainly due to space contiguity and interhemispheric symmetry, whilst synergy occurs mainly between non-homologous pairs of regions in opposite hemispheres.
CONCLUSIONS: Redundancy and synergy, in healthy resting brains, display characteristic patterns, revealed by the proposed approach.
SIGNIFICANCE: The pairwise synergy index, here introduced, maps the informational character of the system at hand into a weighted complex network: the same approach can be applied to other complex systems whose normal state corresponds to a balance between redundant and synergetic circuits.

PMID: 28113234 [PubMed - as supplied by publisher]

Inferring Individual-level Variations in the Functional Parcellation of the Cerebral Cortex.

Tue, 01/24/2017 - 16:50

Inferring Individual-level Variations in the Functional Parcellation of the Cerebral Cortex.

IEEE Trans Biomed Eng. 2016 May 19;:

Authors: Nie L, Matthews PM, Guo Y

Abstract
OBJECTIVE: Functional parcellation of the cerebral cortex is variable across different subjects or between cognitive states. Ignoring individual - or state - dependent variations in the functional parcellation may lead to inaccurate representations of individual functional connectivity, limiting the precision of interpretations of differences in individual connectivity profiles. However, it is difficult to infer the individual-level variations due to the relatively low robustness of methods for parcellation of individual subjects.
METHODS: We propose a method called "joint K-means" to robustly parcellate the cerebral cortex using fMRI data for contrasts between two states or subjects that intended to characterize variance in individual functional parcellations. The key idea of the proposed method is to jointly infer parcellations in contrasted datasets by iterative descent, while constraining the similarity of the two pathways in searches for local minima to reduce spurious variations.
RESULTS: Parcellations of resting-state fMRI datasets from the Human Connectome Project show that the similarity of parcellations for an individual subject studied on two sessions is greater than that between different subjects. Differences in parcellations between subjects are non-uniformly distributed across the cerebral cortex, with clusters of higher variance in the prefrontal, lateral temporal and occipito-parietal cortices. This pattern is reproducible across sessions, between groups and using different numbers of parcels.
CONCLUSION: The individual-level variations inferred by the proposed method are plausible and consistent with the previously reported functional connectivity variability.
SIGNIFICANCE: The proposed method is a promising tool for investigating relationships between the cerebral functional organization and behavioral differences.

PMID: 28113213 [PubMed - as supplied by publisher]

Tinnitus distress is linked to enhanced resting-state functional connectivity from the limbic system to the auditory cortex.

Tue, 01/24/2017 - 16:50

Tinnitus distress is linked to enhanced resting-state functional connectivity from the limbic system to the auditory cortex.

Hum Brain Mapp. 2017 Jan 23;:

Authors: Chen YC, Xia W, Chen H, Feng Y, Xu JJ, Gu JP, Salvi R, Yin X

Abstract
The phantom sound of tinnitus is believed to be triggered by aberrant neural activity in the central auditory pathway, but since this debilitating condition is often associated with emotional distress and anxiety, these comorbidities likely arise from maladaptive functional connections to limbic structures such as the amygdala and hippocampus. To test this hypothesis, resting-state functional magnetic resonance imaging (fMRI) was used to identify aberrant effective connectivity of the amygdala and hippocampus in tinnitus patients and to determine the relationship with tinnitus characteristics. Chronic tinnitus patients (n = 26) and age-, sex-, and education-matched healthy controls (n = 23) were included. Both groups were comparable for hearing level. Granger causality analysis utilizing the amygdala and hippocampus as seed regions were used to investigate the directional connectivity and the relationship with tinnitus duration or distress. Relative to healthy controls, tinnitus patients demonstrated abnormal directional connectivity of the amygdala and hippocampus, including primary and association auditory cortex, and other non-auditory areas. Importantly, scores on the Tinnitus Handicap Questionnaires were positively correlated with increased connectivity from the left amygdala to left superior temporal gyrus (r = 0.570, P = 0.005), and from the right amygdala to right superior temporal gyrus (r = 0.487, P = 0.018). Moreover, enhanced effective connectivity from the right hippocampus to left transverse temporal gyrus was correlated with tinnitus duration (r = 0.452, P = 0.030). The results showed that tinnitus distress strongly correlates with enhanced effective connectivity that is directed from the amygdala to the auditory cortex. The longer the phantom sensation, the more likely acute tinnitus becomes permanently encoded by memory traces in the hippocampus. Hum Brain Mapp, 2017. © 2017 Wiley Periodicals, Inc.

PMID: 28112466 [PubMed - as supplied by publisher]

From hippocampus to whole-brain: The role of integrative processing in episodic memory retrieval.

Tue, 01/24/2017 - 16:50

From hippocampus to whole-brain: The role of integrative processing in episodic memory retrieval.

Hum Brain Mapp. 2017 Jan 23;:

Authors: Geib BR, Stanley ML, Dennis NA, Woldorff MG, Cabeza R

Abstract
Multivariate functional connectivity analyses of neuroimaging data have revealed the importance of complex, distributed interactions between disparate yet interdependent brain regions. Recent work has shown that topological properties of functional brain networks are associated with individual and group differences in cognitive performance, including in episodic memory. After constructing functional whole-brain networks derived from an event-related fMRI study of memory retrieval, we examined differences in functional brain network architecture between forgotten and remembered words. This study yielded three main findings. First, graph theory analyses showed that successfully remembering compared to forgetting was associated with significant changes in the connectivity profile of the left hippocampus and a corresponding increase in efficient communication with the rest of the brain. Second, bivariate functional connectivity analyses indicated stronger interactions between the left hippocampus and a retrieval assembly for remembered versus forgotten items. This assembly included the left precuneus, left caudate, bilateral supramarginal gyrus, and the bilateral dorsolateral superior frontal gyrus. Integrative properties of the retrieval assembly were greater for remembered than forgotten items. Third, whole-brain modularity analyses revealed that successful memory retrieval was marginally significantly associated with a less segregated modular architecture in the network. The magnitude of the decreases in modularity between remembered and forgotten conditions was related to memory performance. These findings indicate that increases in integrative properties at the nodal, retrieval assembly, and whole-brain topological levels facilitate memory retrieval, while also underscoring the potential of multivariate brain connectivity approaches for providing valuable new insights into the neural bases of memory processes. Hum Brain Mapp, 2017. © 2017 Wiley Periodicals, Inc.

PMID: 28112460 [PubMed - as supplied by publisher]

Two patterns of anterior insular cortex functional connectivity in bipolar disorder and schizophrenia.

Tue, 01/24/2017 - 16:50

Two patterns of anterior insular cortex functional connectivity in bipolar disorder and schizophrenia.

World J Biol Psychiatry. 2017 Jan 23;:1-9

Authors: Li J, Tang Y, Womer F, Fan G, Zhou Q, Sun W, Xu K, Wang F

Abstract
OBJECTIVES: Bipolar disorder (BD) and schizophrenia (SZ) share structural abnormalities in the anterior insula cortex (AIC). The AIC appears to have a crucial role in emotional processing and regulation and cognitive control in BD and SZ.
METHODS: Forty-six participants with BD, 68 with SZ and 66 healthy controls (HC) underwent functional magnetic resonance imaging scanning. Resting-state functional connectivity (rsFC) from AIC subregions (ventral and dorsal) was compared among the three groups.
RESULTS: Compared to HC group, both BD and SZ groups exhibited increased rsFC from the ventral AIC (vAIC) and dorsal AIC (dAIC) to bilateral frontal pole and thalamus, the left middle frontal gyrus and the hippocampus. Meanwhile, the BD group demonstrated increased rsFC from the vAIC to the perigenual anterior cingulate cortex, the SZ group presented increased rsFC from the vAIC and dAIC to the right caudate. Compared with the BD group, the SZ group showed significantly increased rsFC from the vAIC and dAIC to the left middle frontal gyrus.
CONCLUSIONS: The shared AIC rsFC abnormalities in both BD and SZ support the importance of the AIC in the common pathophysiology of BD and SZ. There were also disorder-specific features of AIC rsFC, which might implicate potential avenues for differentiating during the early stages.

PMID: 28112029 [PubMed - as supplied by publisher]

The Functional Integration in the Sensory-Motor System Predicts Aging in Healthy Older Adults.

Tue, 01/24/2017 - 16:50
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The Functional Integration in the Sensory-Motor System Predicts Aging in Healthy Older Adults.

Front Aging Neurosci. 2016;8:306

Authors: He H, Luo C, Chang X, Shan Y, Cao W, Gong J, Klugah-Brown B, Bobes MA, Biswal B, Yao D

Abstract
Healthy aging is typically accompanied by a decrease in the motor capacity. Although the disrupted neural representations and performance of movement have been observed in older age in previous studies, the relationship between the functional integration of sensory-motor (SM) system and aging could be further investigated. In this study, we examine the impact of healthy aging on the resting-state functional connectivity (rsFC) of the SM system, and investigate as to how aging is affecting the rsFC in SM network. The SM network was identified and evaluated in 52 healthy older adults and 51 younger adults using two common data analytic approaches: independent component analysis and seed-based functional connectivity (seed at bilateral M1 and S1). We then evaluated whether the altered rsFC of the SM network could delineate trajectories of the age of older adults using a machine learning methodology. Compared with the younger adults, the older demonstrated reduced functional integration with increasing age in the mid-posterior insula of SM network and increased rsFC among the sensorimotor cortex. Moreover, the reduction in the rsFC of mid-posterior insula is associated with the age of older adults. Critically, the analysis based on two-aspect connectivity-based prediction frameworks revealed that the age of older adults could be reliably predicted by this reduced rsFC. These findings further indicated that healthy aging has a marked influence on the SM system that would be associated with a reorganization of SM system with aging. Our findings provide further insight into changes in sensorimotor function in the aging brain.

PMID: 28111548 [PubMed - in process]

Increased sensitivity to age-related differences in brain functional connectivity during continuous multiple object tracking compared to resting-state.

Tue, 01/24/2017 - 16:50
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Increased sensitivity to age-related differences in brain functional connectivity during continuous multiple object tracking compared to resting-state.

Neuroimage. 2017 Jan 19;:

Authors: Dørum ES, Kaufmann T, Alnæs D, Andreassen OA, Richard G, Kolskår KK, Nordvik JE, Westlye LT

Abstract
Age-related differences in cognitive agility vary greatly between individuals and cognitive functions. This heterogeneity is partly mirrored in individual differences in brain network connectivity as revealed using resting-state functional magnetic resonance imaging (fMRI), suggesting potential imaging biomarkers for age-related cognitive decline. However, although convenient in its simplicity, the resting state is essentially an unconstrained paradigm with minimal experimental control. Here, based on the conception that the magnitude and characteristics of age-related differences in brain connectivity is dependent on cognitive context and effort, we tested the hypothesis that experimentally increasing cognitive load boosts the sensitivity to age and changes the discriminative network configurations. To this end, we obtained fMRI data from younger (n=25, mean age 24.16±5.11) and older (n=22, mean age 65.09±7.53) healthy adults during rest and two load levels of continuous multiple object tracking (MOT). Brain network nodes and their time-series were estimated using independent component analysis (ICA) and dual regression, and the edges in the brain networks were defined as the regularized partial temporal correlations between each of the node pairs at the individual level. Using machine learning based on a cross-validated regularized linear discriminant analysis (rLDA) we attempted to classify groups and cognitive load from the full set of edge-wise functional connectivity indices. While group classification using resting-state data was highly above chance (approx. 70% accuracy), functional connectivity (FC) obtained during MOT strongly increased classification performance, with 82% accuracy for the young and 95% accuracy for the old group at the highest load level. Further, machine learning revealed stronger differentiation between rest and task in young compared to older individuals, supporting the notion of network dedifferentiation in cognitive aging. Task-modulation in edgewise FC was primarily observed between attention- and sensorimotor networks; with decreased negative correlations between attention- and default mode networks in older adults. These results demonstrate that the magnitude and configuration of age-related differences in brain functional connectivity are partly dependent on cognitive context and load, which emphasizes the importance of assessing brain connectivity differences across a range of cognitive contexts beyond the resting-state.

PMID: 28111190 [PubMed - as supplied by publisher]

Detecting Neuroimaging Biomarkers for Depression: A Meta-analysis of Multivariate Pattern Recognition Studies.

Tue, 01/24/2017 - 16:50
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Detecting Neuroimaging Biomarkers for Depression: A Meta-analysis of Multivariate Pattern Recognition Studies.

Biol Psychiatry. 2016 Nov 09;:

Authors: Kambeitz J, Cabral C, Sacchet MD, Gotlib IH, Zahn R, Serpa MH, Walter M, Falkai P, Koutsouleris N

Abstract
BACKGROUND: Multiple studies have examined functional and structural brain alteration in patients diagnosed with major depressive disorder (MDD). The introduction of multivariate statistical methods allows investigators to utilize data concerning these brain alterations to generate diagnostic models that accurately differentiate patients with MDD from healthy control subjects (HCs). However, there is substantial heterogeneity in the reported results, the methodological approaches, and the clinical characteristics of participants in these studies.
METHODS: We conducted a meta-analysis of all studies using neuroimaging (volumetric measures derived from T1-weighted images, task-based functional magnetic resonance imaging [MRI], resting-state MRI, or diffusion tensor imaging) in combination with multivariate statistical methods to differentiate patients diagnosed with MDD from HCs.
RESULTS: Thirty-three (k = 33) samples including 912 patients with MDD and 894 HCs were included in the meta-analysis. Across all studies, patients with MDD were separated from HCs with 77% sensitivity and 78% specificity. Classification based on resting-state MRI (85% sensitivity, 83% specificity) and on diffusion tensor imaging data (88% sensitivity, 92% specificity) outperformed classifications based on structural MRI (70% sensitivity, 71% specificity) and task-based functional MRI (74% sensitivity, 77% specificity).
CONCLUSIONS: Our results demonstrate the high representational capacity of multivariate statistical methods to identify neuroimaging-based biomarkers of depression. Future studies are needed to elucidate whether multivariate neuroimaging analysis has the potential to generate clinically useful tools for the differential diagnosis of affective disorders and the prediction of both treatment response and functional outcome.

PMID: 28110823 [PubMed - as supplied by publisher]

Aberrant Resting-State Functional Connectivity Density in Patients with Hepatitis B Virus-Related Cirrhosis.

Tue, 01/24/2017 - 16:50
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Aberrant Resting-State Functional Connectivity Density in Patients with Hepatitis B Virus-Related Cirrhosis.

Biomed Res Int. 2016;2016:4168512

Authors: Lv XF, Wu HW, Tian L, Han LJ, Li J, Qiu YW, Jiang GH, Zhang XL, Zhang R, Xie CM

Abstract
There is increasing evidence that cirrhosis may affect functional connectivity among various brain regions in patients prior to onset of overt hepatic encephalopathy (HE). However, most investigators have focused mainly on alterations in functional connectivity strengths, and the changes in functional connectivity density (FCD) are largely unknown. Here, we investigated alterations in resting-state FCD in patients with hepatitis B virus-related cirrhosis (HBV-RC) without overt HE. Totally, 31 patients with HBV-RC without overt HE and 30 age- and sex-matched healthy controls underwent resting-state functional MRI examinations. FCD mapping was employed to compute local and global FCD maps. Then, short-range and long-range FCD values were calculated and voxel-based comparisons were performed between the two groups. The HBV-RC group showed significant decreases in FCD, including decreased short-range FCDs in the bilateral middle cingulum gyrus/precuneus, the bilateral cuneus, and the left lingual gyrus/inferior occipital gyrus and decreased long-range FCD in the bilateral cuneus/precuneus. In addition, the decreased long-range FCD in the bilateral cuneus/precuneus in the HBV-RC group was related to performance on the psychometric hepatic encephalopathy score (PHES) test. These findings suggest aberrant functional connectivity density in cirrhotic patients prior to overt HE onset, which may provide better insight into understanding the pathophysiological mechanisms underlying the cirrhotic-related cognitive impairment.

PMID: 27403426 [PubMed - indexed for MEDLINE]

Interventions for Neurocognitive Dysfunction.

Mon, 01/23/2017 - 16:40
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Interventions for Neurocognitive Dysfunction.

Curr HIV/AIDS Rep. 2017 Jan 21;:

Authors: Ellero J, Lubomski M, Brew B

Abstract
PURPOSE OF REVIEW: This study aimed to evaluate current barriers to HIV cure strategies and interventions for neurocognitive dysfunction with a particular focus on recent advancements over the last 3 years.
RECENT FINDINGS: Optimal anti-retroviral therapy (ART) poses challenges to minimise neurotoxicity, whilst ensuring blood-brain barrier penetration and minimising the risk of cerebrovascular disease. CSF biomarkers, BCL11B and neurofilament light chain may be implicated with a neuroinflammatory cascade leading to cognitive impairment. Diagnostic imaging with diffusion tensor imaging and resting-state fMRI show promise in future diagnosis and monitoring of HAND. The introduction of ART has resulted in a dramatic decline in HIV-associated dementia. Despite this reduction, milder forms of HIV-associated neurocognitive disorder (HAND) are still prevalent and are clinically significant. The central nervous system (CNS) has been recognised as a probable reservoir and sanctuary for HIV, representing a significant barrier to management interventions.

PMID: 28110422 [PubMed - as supplied by publisher]

Different alterations in brain functional networks according to direct and indirect topological connections in patients with schizophrenia.

Mon, 01/23/2017 - 16:40
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Different alterations in brain functional networks according to direct and indirect topological connections in patients with schizophrenia.

Schizophr Res. 2017 Jan 18;:

Authors: Park CH, Lee S, Kim T, Won WY, Lee KU

Abstract
Schizophrenia displays connectivity deficits in the brain, but the literature has shown inconsistent findings about alterations in global efficiency of brain functional networks. We supposed that such inconsistency at the whole brain level may be due to a mixture of different portions of global efficiency at sub-brain levels. Accordingly, we considered measuring portions of global efficiency in two aspects: spatial portions by considering sub-brain networks and topological portions by considering contributions to global efficiency according to direct and indirect topological connections. We proposed adjacency and indirect adjacency as new network parameters attributable to direct and indirect topological connections, respectively, and applied them to graph-theoretical analysis of brain functional networks constructed from resting state fMRI data of 22 patients with schizophrenia and 22 healthy controls. Group differences in the network parameters were observed not for whole brain and hemispheric networks, but for regional networks. Alterations in adjacency and indirect adjacency were in opposite directions, such that adjacency increased, but indirect adjacency decreased in patients with schizophrenia. Furthermore, over connections in frontal and parietal regions, increased adjacency was associated with more severe negative symptoms, while decreased adjacency was associated with more severe positive symptoms of schizophrenia. This finding indicates that connectivity deficits associated with positive and negative symptoms of schizophrenia may involve topologically different paths in the brain. In patients with schizophrenia, although changes in global efficiency may not be clearly shown, different alterations in brain functional networks according to direct and indirect topological connections could be revealed at the regional level.

PMID: 28109669 [PubMed - as supplied by publisher]

Connectivity of the Cingulate Sulcus Visual Area (CSv) in the Human Cerebral Cortex.

Sun, 01/22/2017 - 16:20
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Connectivity of the Cingulate Sulcus Visual Area (CSv) in the Human Cerebral Cortex.

Cereb Cortex. 2017 Jan 19;:

Authors: Smith AT, Beer AL, Furlan M, Mars RB

Abstract
The human cingulate sulcus visual area (CSv) responds selectively to visual and vestibular cues to self-motion. Although it is more selective for visual self-motion cues than any other brain region studied, it is not known whether CSv mediates perception of self-motion. An alternative hypothesis, based on its location, is that it provides sensory information to the motor system for use in guiding locomotion. To evaluate this hypothesis we studied the connectivity pattern of CSv, which is completely unknown, with a combination of diffusion MRI and resting-state functional MRI. Converging results from the 2 approaches suggest that visual drive is provided primarily by areas hV6, pVIP (putative intraparietal cortex) and PIC (posterior insular cortex). A strong connection with the medial portion of the somatosensory cortex, which represents the legs and feet, suggests that CSv may receive locomotion-relevant proprioceptive information as well as visual and vestibular signals. However, the dominant connections of CSv are with specific components of the motor system, in particular the cingulate motor areas and the supplementary motor area. We propose that CSv may provide a previously unknown link between perception and action that serves the online control of locomotion.

PMID: 28108496 [PubMed - as supplied by publisher]

Stimulus-Tuned Structure of Correlated fMRI Activity in Human Visual Cortex.

Sun, 01/22/2017 - 16:20
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Stimulus-Tuned Structure of Correlated fMRI Activity in Human Visual Cortex.

Cereb Cortex. 2017 Jan 19;:

Authors: Ryu J, Lee SH

Abstract
Processing units are interconnected in the visual system, where a sensory organ and downstream cortical regions communicate through hierarchical connections, and local sites within the regions communicate through horizontal connections. In such networks, neural activities at local sites are likely to influence one another in complex ways and thus are intricately correlated. Recognizing the functional importance of correlated activity in sensory representation, spontaneous activities have been studied via diverse local or global measures in various time scales. Here, measuring functional magnetic resonance imaging (fMRI) signals in human early visual cortex, we explored systematic patterns that govern the correlated activities arising spontaneously. Specifically, guided by previously identified biases in anatomical connection patterns, we characterized all possible pairs of gray matter sites in 3 relational factors: "retinotopic distance," "cortical distance," and "stimulus tuning similarity." By evaluating and comparing the unique contributions of these factors to the correlated activity, we found that tuning similarity factors overrode distance factors in accounting for the structure of correlated fMRI activity both within and between V1, V2, and V3, irrespective of the presence or degree of visual stimulation. Our findings indicate that the early human visual cortex is intrinsically organized as a network tuned to the stimulus features.

PMID: 28108488 [PubMed - as supplied by publisher]

Modulation on brain gray matter activity and white matter integrity by APOE ε4 risk gene in cognitively intact elderly: a multimodal neuroimaging study.

Sun, 01/22/2017 - 16:20
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Modulation on brain gray matter activity and white matter integrity by APOE ε4 risk gene in cognitively intact elderly: a multimodal neuroimaging study.

Behav Brain Res. 2017 Jan 17;:

Authors: Cai S, Jiang Y, Wang Y, Wu X, Ren J, Lee MS, Lee S, Huang L

Abstract
Apolipoprotein E (APOE) ε4 allele is the genetic risk factor with the most established evidence for sporadic Alzheimer's disease. Previous neuroimaging studies have demonstrated insufficiently consistent functional and structural changes among healthy APOE ε4 carriers when compared to non-carriers. Here, in a cognitively intact elderly group (a total of 110: 45 APOE ε4 carriers, 65 non-carriers), we aimed to investigate the potential role of APOE ε4 in the modulation of grey matter activity, white matter integrity, and brain morphology before the development of clinically significant symptoms and signs, by methods of: amplitude of low frequency fluctuations and regional homogeneity analysis based on resting state fMRI, and fiber tractography approach based on diffusion tensor imaging. Our results revealed that compared to non-carriers, APOE ε4 carriers showed: 1) an inconsistent pattern of activity change in the default mode network, including increased gray matter activity in anterior cingulate cortex and medial prefrontal cortex and decreased activity in precuneus; 2) lower mean diffusivity (MD) in fibers of corona radiata and corpus callosum, and lower axial diffusivity in genu of corpus callosum; and 3) significant positive correlation between the MD value of the right superior corona radiate and gross white matter volume; significant negative correlation between the MD value of the right superior corona radiate and Mini-Mental State Examination (MMSE) score. Our results suggested that APOE ε4 gene can modulate gray matter activity and white matter integrity in cognitive and memory related regions, even before any clinical or neuropsychic symtoms or signs of imminent disease.

PMID: 28108320 [PubMed - as supplied by publisher]

Continuous theta-burst stimulation may improve visuospatial neglect via modulating the attention network: a randomized controlled study.

Sun, 01/22/2017 - 16:20
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Continuous theta-burst stimulation may improve visuospatial neglect via modulating the attention network: a randomized controlled study.

Top Stroke Rehabil. 2017 Jan 20;:1-6

Authors: Fu W, Cao L, Zhang Y, Huo S, Du J, Zhu L, Song W

Abstract
BACKGROUND: Visuospatial neglect (VSN) is devastating and common after stroke, and is thought to involve functional disturbance of the attention network. Non-invasive theta-burst stimulation (TBS) may help restore the normal function of attention network, therefore facilitating recovery from VSN.
OBJECTIVE: This study investigated the effects of continuous TBS on resting-state functional connectivity (RSFC) in the attention network, and behavioral performances of patients with VSN after stroke.
METHODS: Twelve patients were randomly assigned to receive 10-day cTBS of the left posterior parietal cortex delivered at 80% (the cTBS group), or 40% (the active control group) of the resting motor threshold. Both groups received daily visual scanning training and motor function treatment. Resting-state functional MRI (fMRI) and behavioral tests including line bisection test and star cancelation test were conducted at baseline and after the treatment.
RESULTS: At baseline, the two groups showed comparable results in the resting-state fMRI experiments and behavioral tests. After treatment, the cTBS group showed lower functional connectivity between right temporoparietal junction (TPJ) and right anterior insula, and between right superior temporal sulcus and right anterior insula, as compared with the active control group; both groups showed improvement in the behavioral tests, with the cTBS group showing larger changes from baseline than the active control group.
CONCLUSION: cTBS of the left posterior parietal cortex in patients with VSN may induce changes in inter-regional RSFC in the right ventral attention network. These changes may be associated with improved recovery of behavioral deficits after behavioral training. The TPJ and superior temporal sulcus may play crucial roles in recovery from VSN.

PMID: 28107807 [PubMed - as supplied by publisher]

Strength of Structural and Functional Frontostriatal Connectivity Predicts Self-Control in the Healthy Elderly.

Sat, 01/21/2017 - 16:00
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Strength of Structural and Functional Frontostriatal Connectivity Predicts Self-Control in the Healthy Elderly.

Front Aging Neurosci. 2016;8:307

Authors: Hänggi J, Lohrey C, Drobetz R, Baetschmann H, Forstmeier S, Maercker A, Jäncke L

Abstract
Self-regulation refers to the successful use of executive functions and initiation of top-down processes to control one's thoughts, behavior, and emotions, and it is crucial to perform self-control. Self-control is needed to overcome impulses and can be assessed by delay of gratification (DoG) and delay discounting (DD) paradigms. In children/adolescents, good DoG/DD ability depends on the maturity of frontostriatal connectivity, and its decline in strength with advancing age might adversely affect self-control because prefrontal brain regions are more prone to normal age-related atrophy than other regions. Here, we aimed at highlighting the relationship between frontostriatal connectivity strength and DoG performance in advanced age. We recruited 40 healthy elderly individuals (mean age 74.0 ± 7.7 years) and assessed the DoG ability using the German version of the DoG test for adults in addition to the delay discounting (DD) paradigm. Based on diffusion-weighted and resting-state functional magnetic resonance imaging data, respectively, the structural and functional whole-brain connectome were reconstructed based on 90 different brain regions of interest in addition to a 12-node frontostriatal DoG-specific network and the resulting connectivity matrices were subjected to network-based statistics. The 90-nodes whole-brain connectome analyses revealed subnetworks significantly associated with DoG and DD with a preponderance of frontostriatal nodes involved suggesting a high specificity of the findings. Structural and functional connectivity strengths between the putamen, caudate nucleus, and nucleus accumbens on the one hand and orbitofrontal, dorsal, and ventral lateral prefrontal cortices on the other hand showed strong positive correlations with DoG and negative correlations with DD corrected for age, sex, intracranial volume, and head motion parameters. These associations cannot be explained by differences in impulsivity and executive functioning. This pattern of correlations between structural or functional frontostriatal connectivity strength and self-control suggests that, in addition to the importance of the frontostriatal nodes itself, the structural and functional properties of different connections within the frontostriatal network are crucial for self-controlled behaviors in the healthy elderly. Because high DoG/low DD is a significant predictor of willpower and wellbeing in the elderly population, interventions aiming at strengthening frontostriatal connectivity to strengthen self-controlled behavior are needed in the future.

PMID: 28105013 [PubMed - in process]

Cerebral blood flow alterations specific to auditory verbal hallucinations in schizophrenia.

Sat, 01/21/2017 - 16:00
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Cerebral blood flow alterations specific to auditory verbal hallucinations in schizophrenia.

Br J Psychiatry. 2017 Jan 19;:

Authors: Zhuo C, Zhu J, Qin W, Qu H, Ma X, Yu C

Abstract
BACKGROUND: Auditory verbal hallucinations (AVHs) have been associated with deficits in auditory and speech-related networks. However, the resting-state cerebral blood flow (CBF) alterations specific to AVHs in schizophrenia remain unknown.
AIMS: To explore AVH-related CBF alterations in individuals with schizophrenia.
METHOD: In total, 35 individuals with schizophrenia with AVHs, 41 individuals with schizophrenia without AVHs and 50 controls underwent arterial spin labelling magnetic resonance imaging. The CBF differences were voxel-wise compared across the three groups.
RESULTS: We found AVH-specific CBF increase in the right superior temporal gyrus and caudate, and AVH-specific CBF decrease in the bilateral occipital and left parietal cortices. We also observed consistent CBF changes in both schizophrenia subgroups (i.e. those with and without AVHs) including decreased CBF in the bilateral occipital regions, the left lateral prefrontal and insular cortices, and the right anterior cingulate cortex and increased CBF in the bilateral lateral temporal regions and putamen, the left middle cingulate cortex and the right thalamus.
CONCLUSIONS: The AVH-specific CBF increases in the auditory and striatal areas and CBF reductions in the visual and parietal areas suggest that there exists a CBF redistribution associated with AVHs.

PMID: 28104737 [PubMed - as supplied by publisher]

Hippocampal Atrophy Is Associated with Altered Hippocampus-Posterior Cingulate Cortex Connectivity in Mesial Temporal Lobe Epilepsy with Hippocampal Sclerosis.

Sat, 01/21/2017 - 16:00
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Hippocampal Atrophy Is Associated with Altered Hippocampus-Posterior Cingulate Cortex Connectivity in Mesial Temporal Lobe Epilepsy with Hippocampal Sclerosis.

AJNR Am J Neuroradiol. 2017 Jan 19;:

Authors: Shih YC, Tseng CE, Lin FH, Liou HH, Tseng WY

Abstract
BACKGROUND AND PURPOSE: Unilateral mesial temporal lobe epilepsy and hippocampal sclerosis have structural and functional abnormalities in the mesial temporal regions. To gain insight into the pathophysiology of the epileptic network in mesial temporal lobe epilepsy with hippocampal sclerosis, we aimed to clarify the relationships between hippocampal atrophy and the altered connection between the hippocampus and the posterior cingulate cortex in patients with mesial temporal lobe epilepsy with hippocampal sclerosis.
MATERIALS AND METHODS: Fifteen patients with left mesial temporal lobe epilepsy with hippocampal sclerosis and 15 healthy controls were included in the study. Multicontrast MR imaging, including high-resolution T1WI, diffusion spectrum imaging, and resting-state fMRI, was performed to measure the hippocampal volume, structural connectivity of the inferior cingulum bundle, and intrinsic functional connectivity between the hippocampus and the posterior cingulate cortex, respectively.
RESULTS: Compared with controls, patients had decreased left hippocampal volume (volume ratio of the hippocampus and controls, 0.366% ± 0.029%; patients, 0.277% ± 0.063%, corrected P = .002), structural connectivity of the bilateral inferior cingulum bundle (generalized fractional anisotropy, left: controls, 0.234 ± 0.020; patients, 0.193 ± 0.022, corrected P = .0001, right: controls, 0.226 ± 0.022; patients, 0.208 ± 0.017, corrected P = .047), and intrinsic functional connectivity between the left hippocampus and the left posterior cingulate cortex (averaged z-value: controls, 0.314 ± 0.152; patients, 0.166 ± 0.062). The left hippocampal volume correlated with structural connectivity positively (standardized β = 0.864, P = .001), but it had little correlation with intrinsic functional connectivity (standardized β = -0.329, P = .113). On the contralesional side, the hippocampal volume did not show any significant correlation with structural connectivity or intrinsic functional connectivity (F2,12 = 0.284, P = .757, R(2) = 0.045).
CONCLUSIONS: In left mesial temporal lobe epilepsy with hippocampal sclerosis, the left inferior cingulum bundle undergoes degeneration in tandem with the left hippocampal volume, whereas intrinsic functional connectivity seems to react by compensating the loss of connectivity. Such insight might be helpful in understanding the development of the epileptic network in left mesial temporal lobe epilepsy with hippocampal sclerosis.

PMID: 28104639 [PubMed - as supplied by publisher]

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