New resting-state fMRI related studies at PubMed

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Disrupted global metastability and static and dynamic brain connectivity across individuals in the Alzheimer's disease continuum.

Thu, 01/12/2017 - 13:15
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Disrupted global metastability and static and dynamic brain connectivity across individuals in the Alzheimer's disease continuum.

Sci Rep. 2017 Jan 11;7:40268

Authors: Córdova-Palomera A, Kaufmann T, Persson K, Alnæs D, Doan NT, Moberget T, Lund MJ, Barca ML, Engvig A, Brækhus A, Engedal K, Andreassen OA, Selbæk G, Westlye LT

Abstract
As findings on the neuropathological and behavioral components of Alzheimer's disease (AD) continue to accrue, converging evidence suggests that macroscale brain functional disruptions may mediate their association. Recent developments on theoretical neuroscience indicate that instantaneous patterns of brain connectivity and metastability may be a key mechanism in neural communication underlying cognitive performance. However, the potential significance of these patterns across the AD spectrum remains virtually unexplored. We assessed the clinical sensitivity of static and dynamic functional brain disruptions across the AD spectrum using resting-state fMRI in a sample consisting of AD patients (n = 80) and subjects with either mild (n = 44) or subjective (n = 26) cognitive impairment (MCI, SCI). Spatial maps constituting the nodes in the functional brain network and their associated time-series were estimated using spatial group independent component analysis and dual regression, and whole-brain oscillatory activity was analyzed both globally (metastability) and locally (static and dynamic connectivity). Instantaneous phase metrics showed functional coupling alterations in AD compared to MCI and SCI, both static (putamen, dorsal and default-mode) and dynamic (temporal, frontal-superior and default-mode), along with decreased global metastability. The results suggest that brains of AD patients display altered oscillatory patterns, in agreement with theoretical premises on cognitive dynamics.

PMID: 28074926 [PubMed - in process]

Confirmation of resting-state BOLD fluctuations in the human brainstem and spinal cord after identification and removal of physiological noise.

Thu, 01/12/2017 - 13:15
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Confirmation of resting-state BOLD fluctuations in the human brainstem and spinal cord after identification and removal of physiological noise.

Magn Reson Med. 2017 Jan 11;:

Authors: Harita S, Stroman PW

Abstract
PURPOSE: Resting-state functional MRI (rs-fMRI) has been used to investigate networks within the cortex, but its use in the brainstem (BS) and spinal cord (SC) has been limited. This region presents challenges for fMRI, partly because of sources of physiological noise. This study aims to quantify noise contributions to rs-fMRI, and to obtain evidence of resting-state blood oxygenation level-dependent (BOLD) fluctuations.
METHODS: Resting-state-fMRI data were obtained from the BS/SC in 16 participants, at 3 Tesla, with T2 -weighted single-shot fast spin-echo imaging. The peripheral pulse, respiration, and expired CO2 were recorded continuously. Physiological noise was modeled from these recordings, movement parameters, and white matter regions. Model fits were then subtracted from the data. BOLD contributions were then investigated through connectivity.
RESULTS: Bulk motion was the largest contributor to the signal variance (19% of the total), followed by cardiac-related motion (14%), nonspecific signal variations detected in white matter (10%), respiratory-related motion (2.6%), and end-tidal CO2 variations (0.7%). After noise was removed, significant left-right connectivity was detected in the SC dorsal horns and ventral horns.
CONCLUSIONS: Resting-state BOLD fluctuations are demonstrated in the SC, as are the dominant noise contributions. These findings are an essential step toward establishing rs-fMRI in the BS/SC. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine.

PMID: 28074492 [PubMed - as supplied by publisher]

Dopamine controls Parkinson's tremor by inhibiting the cerebellar thalamus.

Thu, 01/12/2017 - 13:15
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Dopamine controls Parkinson's tremor by inhibiting the cerebellar thalamus.

Brain. 2017 Jan 09;:

Authors: Dirkx MF, den Ouden HE, Aarts E, Timmer MH, Bloem BR, Toni I, Helmich RC

Abstract
Parkinson's resting tremor is related to altered cerebral activity in the basal ganglia and the cerebello-thalamo-cortical circuit. Although Parkinson's disease is characterized by dopamine depletion in the basal ganglia, the dopaminergic basis of resting tremor remains unclear: dopaminergic medication reduces tremor in some patients, but many patients have a dopamine-resistant tremor. Using pharmacological functional magnetic resonance imaging, we test how a dopaminergic intervention influences the cerebral circuit involved in Parkinson's tremor. From a sample of 40 patients with Parkinson's disease, we selected 15 patients with a clearly tremor-dominant phenotype. We compared tremor-related activity and effective connectivity (using combined electromyography-functional magnetic resonance imaging) on two occasions: ON and OFF dopaminergic medication. Building on a recently developed cerebral model of Parkinson's tremor, we tested the effect of dopamine on cerebral activity associated with the onset of tremor episodes (in the basal ganglia) and with tremor amplitude (in the cerebello-thalamo-cortical circuit). Dopaminergic medication reduced clinical resting tremor scores (mean 28%, range -12 to 68%). Furthermore, dopaminergic medication reduced tremor onset-related activity in the globus pallidus and tremor amplitude-related activity in the thalamic ventral intermediate nucleus. Network analyses using dynamic causal modelling showed that dopamine directly increased self-inhibition of the ventral intermediate nucleus, rather than indirectly influencing the cerebello-thalamo-cortical circuit through the basal ganglia. Crucially, the magnitude of thalamic self-inhibition predicted the clinical dopamine response of tremor. Dopamine reduces resting tremor by potentiating inhibitory mechanisms in a cerebellar nucleus of the thalamus (ventral intermediate nucleus). This suggests that altered dopaminergic projections to the cerebello-thalamo-cortical circuit have a role in Parkinson's tremor.

PMID: 28073788 [PubMed - as supplied by publisher]

Role of testosterone and Y chromosome genes for the masculinization of the human brain.

Thu, 01/12/2017 - 01:05
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Role of testosterone and Y chromosome genes for the masculinization of the human brain.

Hum Brain Mapp. 2017 Jan 10;:

Authors: Savic I, Frisen L, Manzouri A, Nordenstrom A, Lindén Hirschberg A

Abstract
Women with complete androgen insensitivity syndrome (CAIS) have a male (46,XY) karyotype but no functional androgen receptors. Their condition, therefore, offers a unique model for studying testosterone effects on cerebral sex dimorphism. We present MRI data from 16 women with CAIS and 32 male (46,XY) and 32 female (46,XX) controls.
METHODS: FreeSurfer software was employed to measure cortical thickness and subcortical structural volumes. Axonal connections, indexed by fractional anisotropy, (FA) were measured with diffusion tensor imaging, and functional connectivity with resting state fMRI.
RESULTS: Compared to men, CAIS women displayed a "female" pattern by having thicker parietal and occipital cortices, lower FA values in the right corticospinal, superior and inferior longitudinal tracts, and corpus callosum. Their functional connectivity from the amygdala to the medial prefrontal cortex, was stronger and amygdala-connections to the motor cortex weaker than in control men. CAIS and control women also showed stronger posterior cingulate and precuneus connections in the default mode network. Thickness of the motor cortex, the caudate volume, and the FA in the callosal body followed, however, a "male" pattern.
CONCLUSION: Altogether, these data suggest that testosterone modulates the microstructure of somatosensory and visual cortices and their axonal connections to the frontal cortex. Testosterone also influenced functional connections from the amygdala, whereas the motor cortex could, in agreement with our previous reports, be moderated by processes linked to X-chromosome gene dosage. These data raise the question about other genetic factors masculinizing the human brain than the SRY gene and testosterone. Hum Brain Mapp, 2016. © 2016 Wiley Periodicals, Inc.

PMID: 28070912 [PubMed - as supplied by publisher]

Cerebellar tDCS modulates neural circuits during semantic prediction: A combined tDCS-fMRI study.

Thu, 01/12/2017 - 01:05
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Cerebellar tDCS modulates neural circuits during semantic prediction: A combined tDCS-fMRI study.

J Neurosci. 2017 Jan 09;:

Authors: D'Mello AM, Turkeltaub PE, Stoodley CJ

Abstract
It has been proposed that the cerebellum acquires internal models of mental processes that enable prediction, allowing for the optimization of behavior. In language, semantic prediction speeds speech production and comprehension. Right cerebellar lobules VI and VII (including Crus I/II) are engaged during a variety of language processes and are functionally connected with cerebral cortical language networks. Further, right posterolateral cerebellar neuromodulation modifies behavior during predictive language processing. These data are consistent with a role for the cerebellum in semantic processing and semantic prediction. We combined transcranial direct current stimulation (tDCS) and functional magnetic resonance imaging (fMRI) to assess the behavioral and neural consequences of cerebellar tDCS during a sentence completion task. Task-based and resting-state fMRI data were acquired in healthy human adults (n=32; μ=23.1 years) both before and after 20min of 1.5 mA anodal (n=18) or sham (n=14) tDCS applied to the right posterolateral cerebellum. In the sentence completion task, the first four words of the sentence modulated the predictability of the final target word. In some sentences, the preceding context strongly predicted the target word, while other sentences were non-predictive. Completion of predictive sentences increased activation in right Crus I/II of the cerebellum. Relative to sham tDCS, anodal tDCS increased activation in right Crus I/II during semantic prediction and enhanced resting-state functional connectivity between hubs of the reading/language networks. These results are consistent with a role for the right posterolateral cerebellum beyond motor aspects of language, and suggest that cerebellar internal models of linguistic stimuli support semantic prediction.
SIGNIFICANCE STATEMENT: Cerebellar involvement in language tasks and language networks is now well-established, yet the specific cerebellar contribution to language processing remains unclear. It is thought that the cerebellum acquires internal models of mental processes that enable prediction, allowing for the optimization of behavior. Here we combined neuroimaging and neuromodulation to provide evidence that the cerebellum is specifically involved in semantic prediction during sentence processing. We found that activation within right Crus I/II was enhanced when semantic predictions were made, and show that modulation of this region with transcranial direct current stimulation alters both activation patterns and functional connectivity within whole-brain language networks. For the first time, these data show that cerebellar neuromodulation impacts activation patterns specifically during predictive language processing.

PMID: 28069925 [PubMed - as supplied by publisher]

Dopamine modulates the functional organization of the orbitofrontal cortex.

Thu, 01/12/2017 - 01:05
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Dopamine modulates the functional organization of the orbitofrontal cortex.

J Neurosci. 2017 Jan 09;:

Authors: Kahnt T, Tobler PN

Abstract
Neuromodulators such as dopamine can alter the intrinsic firing properties of neurons, and may thereby change the configuration of larger functional circuits. The primate orbitofrontal cortex (OFC) receives dopaminergic input from midbrain nuclei, but the role of dopamine in the OFC is still unclear. Here we tested the idea that dopaminergic activity changes the pattern of connectivity between the OFC and the rest of the brain, and thereby reconfigures functional networks in the OFC. To this end, we combined double-blind, placebo-controlled pharmacology (D2 receptor [D2R] antagonist amisulpride) in humans with resting-state functional magnetic resonance imaging (fMRI) and clustering methods. In the placebo group, we replicated previously observed parcellations of the OFC into two and six subregions based on connectivity patterns with the rest of the brain. Most importantly, while the 2-fold clustering did not differ significantly between groups, blocking D2R receptors significantly changed the composition of the 6-fold parcellation, suggesting a dopamine-dependent reconfiguration of functional OFC subregions. Moreover, multivariate decoding analyses revealed that amisulpride changed the whole-brain connectivity patterns of individual OFC-subregions. In particular, D2R blockade shifted the balance of OFC connectivity from associative areas in the temporal and parietal lobe toward functional connectivity with the frontal cortex. In summary, our results suggest that dopamine alters the composition of functional OFC circuits, possibly indicating a broader role for neuromodulators in the dynamic reconfiguration of functional brain networks.
SIGNIFICANCE STATEMENT: A key role of any neuromodulator may be the reconfiguration of functional brain circuits. Here we test this idea with regard to dopamine and the organization of functional networks in the OFC. We show that blockade of dopamine D2-receptors has profound effects on the functional connectivity patterns of the OFC, yielding in altered connectivity-based subdivisions of this region. Our results suggest that dopamine changes the connectional configuration of the OFC, possibly leading to transitions between different operating modes that favor either sensory input or recurrent processing in the prefrontal cortex. More generally, our findings support a broader role for neuromodulators in the dynamic reconfiguration of functional brain networks and may have clinical implications for understanding the actions of antipsychotics.

PMID: 28069917 [PubMed - as supplied by publisher]

Brain connectomics predict response to treatment in social anxiety disorder.

Thu, 01/12/2017 - 01:05
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Brain connectomics predict response to treatment in social anxiety disorder.

Mol Psychiatry. 2016 May;21(5):680-5

Authors: Whitfield-Gabrieli S, Ghosh SS, Nieto-Castanon A, Saygin Z, Doehrmann O, Chai XJ, Reynolds GO, Hofmann SG, Pollack MH, Gabrieli JD

Abstract
We asked whether brain connectomics can predict response to treatment for a neuropsychiatric disorder better than conventional clinical measures. Pre-treatment resting-state brain functional connectivity and diffusion-weighted structural connectivity were measured in 38 patients with social anxiety disorder (SAD) to predict subsequent treatment response to cognitive behavioral therapy (CBT). We used a priori bilateral anatomical amygdala seed-driven resting connectivity and probabilistic tractography of the right inferior longitudinal fasciculus together with a data-driven multivoxel pattern analysis of whole-brain resting-state connectivity before treatment to predict improvement in social anxiety after CBT. Each connectomic measure improved the prediction of individuals' treatment outcomes significantly better than a clinical measure of initial severity, and combining the multimodal connectomics yielded a fivefold improvement in predicting treatment response. Generalization of the findings was supported by leave-one-out cross-validation. After dividing patients into better or worse responders, logistic regression of connectomic predictors and initial severity combined with leave-one-out cross-validation yielded a categorical prediction of clinical improvement with 81% accuracy, 84% sensitivity and 78% specificity. Connectomics of the human brain, measured by widely available imaging methods, may provide brain-based biomarkers (neuromarkers) supporting precision medicine that better guide patients with neuropsychiatric diseases to optimal available treatments, and thus translate basic neuroimaging into medical practice.

PMID: 26260493 [PubMed - indexed for MEDLINE]

Characterization of brain blood flow and the amplitude of low-frequency fluctuations in major depressive disorder: A multimodal meta-analysis.

Tue, 01/10/2017 - 12:40

Characterization of brain blood flow and the amplitude of low-frequency fluctuations in major depressive disorder: A multimodal meta-analysis.

J Affect Disord. 2016 Dec 23;210:303-311

Authors: Li W, Chen Z, Wu M, Zhu H, Gu L, Zhao Y, Kuang W, Bi F, Kemp GJ, Gong Q

Abstract
BACKGROUND: In healthy subjects, there is an association between amplitude of low-frequency fluctuations (ALFF) and regional cerebral blood flow (rCBF). To date, no published meta-analysis has investigated changes in the regional ALFF in medication-free depressed patients.
METHODS: In this study, we aimed to explore whether resting-state rCBF and ALFF changes co-occur in the depressed brain without the potential confound of medication. Using signed differential mapping (SDM), we conducted two meta-analyses, one of rCBF studies and one of ALFF studies, involving medication-free patients with major depressive disorder (MDD). In addition, we conducted a multimodal meta-analysis to identify brain regions that showed abnormalities in both rCBF and ALFF.
RESULTS: A total of 16 studies were included in this series. We identified abnormalities in resting-state rCBF and ALFF in the left insula in medication-free MDD patients compared with healthy controls (HC). In addition, we observed altered resting-state rCBF in the limbic-subcortical-cortical circuit and altered ALFF in the default mode network (DMN) and some motor-related brain regions.
LIMITATIONS: The analysis techniques, patient characteristics and clinical variables of the included studies were heterogeneous.
CONCLUSIONS: The conjoint alterations in ALFF and rCBF in the left insula may represent core neuropathological changes in medication-free patients with MDD and merit further studying.

PMID: 28068619 [PubMed - as supplied by publisher]

Weak functional connectivity in the human fetal brain prior to preterm birth.

Tue, 01/10/2017 - 12:40

Weak functional connectivity in the human fetal brain prior to preterm birth.

Sci Rep. 2017 Jan 09;7:39286

Authors: Thomason ME, Scheinost D, Manning JH, Grove LE, Hect J, Marshall N, Hernandez-Andrade E, Berman S, Pappas A, Yeo L, Hassan SS, Constable RT, Ment LR, Romero R

Abstract
It has been suggested that neurological problems more frequent in those born preterm are expressed prior to birth, but owing to technical limitations, this has been difficult to test in humans. We applied novel fetal resting-state functional MRI to measure brain function in 32 human fetuses in utero and found that systems-level neural functional connectivity was diminished in fetuses that would subsequently be born preterm. Neural connectivity was reduced in a left-hemisphere pre-language region, and the degree to which connectivity of this left language region extended to right-hemisphere homologs was positively associated with the time elapsed between fMRI assessment and delivery. These results provide the first evidence that altered functional connectivity in the preterm brain is identifiable before birth. They suggest that neurodevelopmental disorders associated with preterm birth may result from neurological insults that begin in utero.

PMID: 28067865 [PubMed - in process]

Segregation between the parietal memory network and the default mode network: effects of spatial smoothing and model order in ICA.

Tue, 01/10/2017 - 12:40
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Segregation between the parietal memory network and the default mode network: effects of spatial smoothing and model order in ICA.

Sci Bull (Beijing). 2016;61(24):1844-1854

Authors: Hu Y, Wang J, Li C, Wang YS, Yang Z, Zuo XN

Abstract
A brain network consisting of two key parietal nodes, the precuneus and the posterior cingulate cortex, has emerged from recent fMRI studies. Though it is anatomically adjacent to and spatially overlaps with the default mode network (DMN), its function has been associated with memory processing, and it has been referred to as the parietal memory network (PMN). Independent component analysis (ICA) is the most common data-driven method used to extract PMN and DMN simultaneously. However, the effects of data preprocessing and parameter determination in ICA on PMN-DMN segregation are completely unknown. Here, we employ three typical algorithms of group ICA to assess how spatial smoothing and model order influence the degree of PMN-DMN segregation. Our findings indicate that PMN and DMN can only be stably separated using a combination of low-level spatial smoothing and high model order across the three ICA algorithms. We thus argue for more considerations on parametric settings for interpreting DMN data.

PMID: 28066681 [PubMed - in process]

Diurnal Variations in Neural Activity of Healthy Human Brain Decoded with Resting-State Blood Oxygen Level Dependent fMRI.

Tue, 01/10/2017 - 12:40
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Diurnal Variations in Neural Activity of Healthy Human Brain Decoded with Resting-State Blood Oxygen Level Dependent fMRI.

Front Hum Neurosci. 2016;10:634

Authors: Jiang C, Yi L, Su S, Shi C, Long X, Xie G, Zhang L

Abstract
It remains an ongoing investigation about how the neural activity alters with the diurnal rhythms in human brain. Resting-state functional magnetic resonance imaging (RS-fMRI) reflects spontaneous activities and/or the endogenous neurophysiological process of the human brain. In the present study, we applied the ReHo (regional homogeneity) and ALFF (amplitude of low frequency fluctuation) based on RS-fMRI to explore the regional differences in the spontaneous cerebral activities throughout the entire brain between the morning and evening sessions within a 24-h time cycle. Wide spread brain areas were found to exhibit diurnal variations, which may be attributed to the internal molecular systems regulated by clock genes, and the environmental factors including light-dark cycle, daily activities and homeostatic sleep drive. Notably, the diurnal variation of default mode network (DMN) suggests that there is an adaptation or compensation response within the subregions of DMN, implying a balance or a decoupling of regulation between these regions.

PMID: 28066207 [PubMed - in process]

Interplay between Heightened Temporal Variability of Spontaneous Brain Activity and Task-Evoked Hyperactivation in the Blind.

Tue, 01/10/2017 - 12:40
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Interplay between Heightened Temporal Variability of Spontaneous Brain Activity and Task-Evoked Hyperactivation in the Blind.

Front Hum Neurosci. 2016;10:632

Authors: Dai R, Huang Z, Tu H, Wang L, Tanabe S, Weng X, He S, Li D

Abstract
The brain's functional organization can be altered by visual deprivation. This is observed by comparing blind and sighted people's activation response to tactile discrimination tasks, like braille reading. Where, the blind have higher activation than the sighted upon tactile discrimination tasks, especially high activation difference is seen in ventral occipitotemporal (vOT) cortex. However, it remains unknown, whether this vOT hyperactivation is related to alteration of spontaneous activity. To address this question, we examined 16 blind subjects, 19 low-vision individuals, and 21 normally sighted controls using functional magnetic resonance imaging (fMRI). Subjects were scanned in resting-state and discrimination tactile task. In spontaneous activity, when compared to sighted subjects, we found both blind and low vision subjects had increased local signal synchronization and increased temporal variability. During tactile tasks, compared to sighted subjects, blind and low-vision subject's vOT had stronger tactile task-induced activation. Furthermore, through inter-subject partial correlation analysis, we found temporal variability is more related to tactile-task activation, than local signal synchronization's relation to tactile-induced activation. Our results further support that vision impairment induces vOT cortical reorganization. The hyperactivation in the vOT during tactile stimulus processing in the blind may be related to their greater dynamic range of spontaneous activity.

PMID: 28066206 [PubMed - in process]

Deep Grey Matter Iron Accumulation in Alcohol Use Disorder.

Tue, 01/10/2017 - 12:40
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Deep Grey Matter Iron Accumulation in Alcohol Use Disorder.

Neuroimage. 2017 Jan 05;:

Authors: Juhás M, Sun H, Brown MR, MacKay MB, Mann KF, Sommer WH, Wilman AH, Dursun SM, Greenshaw AJ

Abstract
PURPOSE: Evaluate brain iron accumulation in alcohol use disorder (AUD) patients compared to controls using quantitative susceptibility mapping (QSM).
METHODS: QSM was performed retrospectively by using phase images from resting state functional magnetic resonance imaging (fMRI). 20 male AUD patients and 15 matched healthy controls were examined. Susceptibility values were manually traced in deep grey matter regions including caudate nucleus, combined putamen and globus pallidus, combined substantia nigra and red nucleus, dentate nucleus, and a reference white matter region in the internal capsule. Average susceptibility values from each region were compared between the patients and controls. The relationship between age and susceptibility was also explored.
RESULTS: The AUD group exhibited increased susceptibility in caudate nucleus (+8.5%, p=0.034), combined putamen and globus pallidus (+10.8%, p=0.006), and dentate nucleus (+14.9%, p=0.022). Susceptibility increased with age in two of the four measured regions - combined putamen and globus pallidus (p=0.013) and combined substantia nigra and red nucleus (p=0.041). AUD did not significantly modulate the rate of susceptibility increase with age in our data.
CONCLUSION: Retrospective QSM computed from standard fMRI datasets provides new opportunities for brain iron studies in psychiatry. Substantially elevated brain iron was found in AUD subjects in the basal ganglia and dentate nucleus. This was the first human AUD brain iron study and the first retrospective clinical fMRI QSM study.

PMID: 28065850 [PubMed - as supplied by publisher]

Learning Effective Connectivity from fMRI using Autoregressive hidden Markov model with missing data.

Tue, 01/10/2017 - 12:40
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Learning Effective Connectivity from fMRI using Autoregressive hidden Markov model with missing data.

J Neurosci Methods. 2017 Jan 05;:

Authors: Dang S, Chaudhury S, Lall B, Roy PK

Abstract
BACKGROUND: Effective connectivity (EC) analysis of neuronal groups using fMRI delivers insights about functional-integration. However, fMRI signal has low-temporal resolution due to down-sampling and indirectly measures underlying neuronal activity.
NEW METHOD: The aim is to address above issues for more reliable EC estimates. This paper proposes use of autoregressive hidden Markov model with missing data (AR-HMM-md) in dynamically multi-linked (DML) framework for learning EC using multiple fMRI time series. In our recent work (Dang et al., 2016), we have shown how AR-HMM-md for modelling single fMRI time series outperforms the existing methods. AR-HMM-md models unobserved neuronal activity and lost data over time as variables and estimates their values by joint optimization given fMRI observation sequence.
RESULTS: The effectiveness in learning EC is shown using simulated experiments. Also the effects of sampling and noise are studied on EC. Moreover, classification-experiments are performed for Attention-Deficit/Hyperactivity Disorder subjects and age-matched controls for performance evaluation of real data. Using Bayesian model selection, we see that the proposed model converged to higher log-likelihood and demonstrated that group-classification can be performed with higher cross-validation accuracy of above 94% using distinctive network EC which characterizes patients vs.
CONTROLS: The full data EC obtained from DML-AR-HMM-md is more consistent with previous literature than the classical multivariate Granger causality method.
COMPARISON: The proposed architecture leads to reliable estimates of EC than the existing latent models.
CONCLUSIONS: This framework overcomes the disadvantage of low-temporal resolution and improves cross-validation accuracy significantly due to presence of missing data variables and autoregressive process.

PMID: 28065836 [PubMed - as supplied by publisher]

White matter lesions relate to tract-specific reductions in functional connectivity.

Mon, 01/09/2017 - 00:20

White matter lesions relate to tract-specific reductions in functional connectivity.

Neurobiol Aging. 2016 Dec 14;51:97-103

Authors: Langen CD, Zonneveld HI, White T, Huizinga W, Cremers LG, de Groot M, Ikram MA, Niessen WJ, Vernooij MW

Abstract
White matter lesions play a role in cognitive decline and dementia. One presumed pathway is through disconnection of functional networks. Little is known about location-specific effects of lesions on functional connectivity. This study examined location-specific effects within anatomically-defined white matter tracts in 1584 participants of the Rotterdam Study, aged 50-95. Tracts were delineated from diffusion magnetic resonance images using probabilistic tractography. Lesions were segmented on fluid-attenuated inversion recovery images. Functional connectivity was defined across each tract on resting-state functional magnetic resonance images by using gray matter parcellations corresponding to the tract ends and calculating the correlation of the mean functional activity between the gray matter regions. A significant relationship between both local and brain-wide lesion load and tract-specific functional connectivity was found in several tracts using linear regressions, also after Bonferroni correction. Indirect connectivity analyses revealed that tract-specific functional connectivity is affected by lesions in several tracts simultaneously. These results suggest that local white matter lesions can decrease tract-specific functional connectivity, both in direct and indirect connections.

PMID: 28063366 [PubMed - as supplied by publisher]

Role of altered cerebello-thalamo-cortical network in the neurobiology of essential tremor.

Mon, 01/09/2017 - 00:20
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Role of altered cerebello-thalamo-cortical network in the neurobiology of essential tremor.

Neuroradiology. 2017 Jan 06;:

Authors: Lenka A, Bhalsing KS, Panda R, Jhunjhunwala K, Naduthota RM, Saini J, Bharath RD, Yadav R, Pal PK

Abstract
INTRODUCTION: Essential tremor (ET) is the most common movement disorder among adults. Although ET has been recognized as a mono-symptomatic benign illness, reports of non-motor symptoms and non-tremor motor symptoms have increased its clinical heterogeneity. The neural correlates of ET are not clearly understood. The aim of this study was to understand the neurobiology of ET using resting state fMRI.
METHODS: Resting state functional MR images of 30 patients with ET and 30 age- and gender-matched healthy controls were obtained. The functional connectivity of the two groups was compared using whole-brain seed-to-voxel-based analysis.
RESULTS: The ET group had decreased connectivity of several cortical regions especially of the primary motor cortex and the primary somatosensory cortex with several right cerebellar lobules compared to the controls. The thalamus on both hemispheres had increased connectivity with multiple posterior cerebellar lobules and vermis. Connectivity of several right cerebellar seeds with the cortical and thalamic seeds had significant correlation with an overall score of Fahn-Tolosa-Marin tremor rating scale (FTM-TRS) as well as the subscores for head tremor and limb tremor.
CONCLUSION: Seed-to-voxel resting state connectivity analysis revealed significant alterations in the cerebello-thalamo-cortical network in patients with ET. These alterations correlated with the overall FTM scores as well as the subscores for limb tremor and head tremor in patients with ET. These results further support the previous evidence of cerebellar pathology in ET.

PMID: 28062908 [PubMed - as supplied by publisher]

Microstructure of the Default Mode Network in Preterm Infants.

Sat, 01/07/2017 - 11:55

Microstructure of the Default Mode Network in Preterm Infants.

AJNR Am J Neuroradiol. 2016 Nov 10;:

Authors: Cui J, Tymofiyeva O, Desikan R, Flynn T, Kim H, Gano D, Hess CP, Ferriero DM, Barkovich AJ, Xu D

Abstract
BACKGROUND AND PURPOSE: Diffusion and fMRI has been providing insights to brain development in addition to anatomic imaging. This study aimed to evaluate the microstructure of white matter tracts underlying the default mode network in premature infants by using resting-state functional MR imaging in conjunction with diffusion tensor imaging-based tractography.
MATERIALS AND METHODS: A cohort of 44 preterm infants underwent structural T1-weighted imaging, resting-state fMRI, and DTI at 3T, including 21 infants with brain injuries and 23 infants with normal-appearing structural imaging as controls. Neurodevelopment was evaluated with the Bayley Scales of Infant Development at 12 months' adjusted age. Probabilistic independent component analysis was applied to resting-state fMRI data to explore resting-state networks. The localized clusters of the default mode network were used as seeding for probabilistic tractography. The DTI metrics (fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity) of the reconstructed primary tracts within the default mode network-cingula were measured.
RESULTS: Results revealed decreased fractional anisotropy (0.20 ± 0.03) and elevated radial diffusivity values (1.24 ± 0.16) of the cingula in the preterm infants with brain injuries compared with controls (fractional anisotropy, 0.25 ± 0.03; P < .001; radial diffusivity, 1.06 ± 0.16; P = .001). The Bayley Scales of Infant Development cognitive scores were significantly associated with cingulate fractional anisotropy (P = .004) and radial diffusivity (P = .021); this association suggests that the microstructural properties of interconnecting axonal pathways within the default mode network are of critical importance in the early neurocognitive development of infants.
CONCLUSIONS: This study of combined resting-state fMRI and DTI at rest suggests that such studies may allow the investigation of key functional brain circuits in premature infants, which could function not only as diagnostic tools but also as biomarkers for long-term neurodevelopmental outcomes.

PMID: 28059709 [PubMed - as supplied by publisher]

The OPRM1 A118G polymorphism modulates the descending pain modulatory system for individual pain experience in young women with primary dysmenorrhea.

Sat, 01/07/2017 - 11:55
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The OPRM1 A118G polymorphism modulates the descending pain modulatory system for individual pain experience in young women with primary dysmenorrhea.

Sci Rep. 2017 Jan 06;7:39906

Authors: Wei SY, Chen LF, Lin MW, Li WC, Low I, Yang CJ, Chao HT, Hsieh JC

Abstract
The mu-opioid receptor (OPRM1) A118G polymorphism underpins different pain sensitivity and opioid-analgesic outcome with unclear effect on the descending pain modulatory system (DPMS). Primary dysmenorrhea (PDM), the most prevalent gynecological problem with clear painful and pain free conditions, serves as a good clinical model of spontaneous pain. The objective of this imaging genetics study was therefore to explore if differences in functional connectivity (FC) of the DPMS between the OPRM1 A118G polymorphisms could provide a possible explanation for the differences in pain experience. Sixty-one subjects with PDM and 65 controls participated in the current study of resting-state functional magnetic resonance imaging (fMRI) during the menstruation and peri-ovulatory phases; blood samples were taken for genotyping. We studied 3 aspects of pain experience, namely, mnemonic pain (recalled overall menstrual pain), present pain (spontaneous menstrual pain), and experimental pain (thermal pain) intensities. We report that G allele carriers, in comparison to AA homozygotes, exhibited functional hypo-connectivity between the anterior cingulate cortex (ACC) and periaqueductal gray (PAG). Furthermore, G allele carriers lost the correlation with spontaneous pain experience and exhibited dysfunctional DPMS by means of PAG-seeded FC dynamics. This OPRM1 A118G-DPMS interaction is one plausible neurological mechanism underlying the individual differences in pain experience.

PMID: 28057931 [PubMed - in process]

Resting state brain connectivity patterns before eventual relapse into cocaine abuse.

Sat, 01/07/2017 - 11:55
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Resting state brain connectivity patterns before eventual relapse into cocaine abuse.

Behav Brain Res. 2017 Jan 02;:

Authors: Berlingeri M, Losasso D, Girolo A, Cozzolino E, Masullo T, Scotto M, Sberna M, Bottini G, Paulesu E

Abstract
According to recent theories, drug addicted patients suffer of an impaired response inhibition and salience attribution (I-RISA) together with a perturbed connectivity between the nuclei accumbens (NAcs) and the orbito-prefrontal (oPFC) and dorsal prefrontal (dPFC) cortices, brain regions associated with motivation and cognitive control. To empirically test these assumptions, we evaluated the (neuro)psychological trait and the functional organization of the resting state brain networks associated with the NAcs in 18 former cocaine abusers (FCAs), while being in drug abstinence since 5 months. The psychological data were grouped into three empirical variables related with emotion regulation, emotion awareness and strategic and controlled behaviour. Comparison of the resting state patterns between the entire sample of FCAs and 19 controls revealed a reduction of functional connectivity between the NAcs and the dPFC and enhanced connectivity between the NAcs and the dorsal-striatum. In the 8 FCAs who relapsed into cocaine use after 3 months, the level of functional connectivity between the NAcs and dPFC was lower than the functional connectivity estimated in the group of patients that did not relapsed. Finally, in the entire sample of FCAs, the higher the connectivity between the NAc and the oPFC the lower was the level of strategic and controlled behaviour. Taken together, these results are compatible with models of the interactions between the NAcs, the dorsal striatum and frontal cortices in the I-RISA syndrome, showing that such interactions are particularly perturbed in patients at greater risk of relapse into cocaine abuse.

PMID: 28057531 [PubMed - as supplied by publisher]

[Resting-state functional magnetic resonance study of brain function changes after TIPS operation in patients with liver cirrhosis].

Sat, 01/07/2017 - 11:55
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[Resting-state functional magnetic resonance study of brain function changes after TIPS operation in patients with liver cirrhosis].

Zhonghua Yi Xue Za Zhi. 2016 Dec 20;96(47):3787-3792

Authors: Liu C, Wang HB, Yu YQ, Wang MQ, Zhang GB, Xu LY, Wu JM

Abstract
Objective: To investigate the brain function changes in cirrhosis patients after transjugular intrahepatic portosystemic shunt (TIPS), resting-state functional MRI (rs-fMRI) performed and fractional amplitude of low frequency fluctuation (fALFF) was analyzed. Methods: From January 2014 to February 2016, a total of 96 cirrhotic patients from invasive technology department and infection department in the First Affiliated Hospital of Anhui Medical University were selected , the blood ammonia data of 96 cirrhotic patients with TIPS operation in four groups were collected after 1, 3, 6 and 12 month, and all subjects performed rs-fMRI scans. The rs-fMRI data processed with DPARSF and SPM12 softwares, whole-brain fALFF values were calculated, and One-Way analysis of variance , multiple comparison analysis and correlation analysis were performed. Results: There were brain regions with significant function changes in four groups patients with TIPS operation after 1, 3, 6 and 12 month, including bilateral superior temporal gyrus, right middle temportal gyrus , right hippocampus, right island of inferior frontal gyrus, left fusiform gyrus, left olfactory cortex, left orbital superior frontal gyrus (all P<0.005). Multiple comparison analysis showed that compared with patients in the 1-month follow-up, patients in the 3-month follow-up showed that brain function areas increased in left olfactory cortex, left inferior temporal gyrus, left fusiform gyrus, left orbital middle frontal gyrus, left putamen, left cerebelum, and decreased in left lingual gyrus; patients in the 6-month follow-up showed that brain function areas increased in left middle temportal gyrus, right supramarginal gyrus, right temporal pole, right central operculum, and decreased in left top edge of angular gyrus, left postcentral gyrus; patients in the 12-month follow-up showed that brain function areas increased in right hippocampus, right middle cingulate gyrus, and decreased in right middle temportal gyrus.Compared with patients in the 3-month follow-up, patients in the 6-month follow-up showed that brain function areas increased in left superior temporal gyrus, left middle temporal gyrus, right temporal pole, right island of inferior frontal gyrus, and decreased in left cerebelum, left orbital inferior frontal gyrus; patients in the 12-month follow-up showed that there were no obvious increase and decrease brain function areas.Compared with patients in the 6-month follow-up, patients in the 12-month follow-up showed that there were no obvious increase brain function areas , but brain function areas decreased in bilateral middle temportal gyrus(P<0.001). Brain regions were positively related to blood ammonia in right middle cingulate gyrus, right central operculum, left parahippocampal gyrus, while as brain regions were negatively related to blood ammonia in bilateral medial prefrontal lobe, anterior cingulate and paracingulate gyrus, right top edge of angular gyrus, right middle temportal gyrus, left anterior central gyrus, left posterior central gyrus (all P<0.005). Conclusion: The resting state brain function increased or decreased with course of disease in cirrhosis patients after TIPS operation. The brain activity of limbic system and sensorimotor system all had significant correlation with blood ammonia levels. The blood ammonia level and the function of relative brain regions after 6-month with TIPS operation can be gradually improved.

PMID: 28057091 [PubMed - in process]

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