New resting-state fMRI related studies at PubMed

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Abnormal regional spontaneous neuronal activity associated with symptom severity in treatment-naive patients with obsessive-compulsive disorder revealed by resting-state functional MRI.

Sat, 01/21/2017 - 16:00
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Abnormal regional spontaneous neuronal activity associated with symptom severity in treatment-naive patients with obsessive-compulsive disorder revealed by resting-state functional MRI.

Neurosci Lett. 2017 Jan 16;:

Authors: Qiu L, Fu X, Wang S, Tang Q, Chen X, Cheng L, Zhang F, Zhou Z, Tian L

Abstract
A large number of neuroimaging studies have revealed the dysfunction of brain activities in obsessive-compulsive disorder (OCD) during various tasks. However, regional spontaneous activity abnormalities in OCD are gradually being revealed. In this current study, we aimed to investigate cerebral regions with abnormal spontaneous activity using resting-state functional magnetic resonance imaging (fMRI) and further explored the relationship between the spontaneous neuronal activity and symptom severity of patients with OCD. Thirty-one patients with OCD and 32 age-and sex-matched normal controls received the fMRI scans and fractional amplitude of low-frequency fluctuation (fALFF) approach was applied to identify the abnormal brain activity. We found that patients with OCD showed decreased fALFF not only in the cortical-striato-thalamo-cortical (CSTC) circuits like the thalamus, but also in other cerebral systems like the cerebellum, the parietal cortex and the temporal cortex. Additionally, OCD patients demonstrated significant associations between decreased fALFF and obsessive-compulsive symptom severity in the thalamus, the paracentral lobule and the cerebellum. Our results provide evidence for abnormal spontaneous neuronal activity in distributed cerebral areas and support the notion that brain areas outside the CSTC circuits may also play an important role in the pathophysiology of OCD.

PMID: 28104431 [PubMed - as supplied by publisher]

Sex-specific neural circuits of emotion regulation in the centromedial amygdala.

Sat, 01/21/2017 - 16:00
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Sex-specific neural circuits of emotion regulation in the centromedial amygdala.

Sci Rep. 2016 Mar 23;6:23112

Authors: Wu Y, Li H, Zhou Y, Yu J, Zhang Y, Song M, Qin W, Yu C, Jiang T

Abstract
Sex-related differences in emotion regulation (ER) in the frequency power distribution within the human amygdala, a brain region involved in emotion processing, have been reported. However, how sex differences in ER are manifested in the brain networks which are seeded on the amygdala subregions is unclear. The goal of this study was to investigate this issue from a brain network perspective. Utilizing resting-state functional connectivity (RSFC) analysis, we found that the sex-specific functional connectivity patterns associated with ER trait level were only seeded in the centromedial amygdala (CM). Women with a higher trait-level ER had a stronger negative RSFC between the right CM and the medial superior frontal gyrus (mSFG), and stronger positive RSFC between the right CM and the anterior insula (AI) and the superior temporal gyrus (STG). But men with a higher trait-level ER was associated with weaker negative RSFC of the right CM-mSFG and positive RSFCs of the right CM-left AI, right CM-right AI/STG, and right CM-left STG. These results provide evidence for the sex-related effects in ER based on CM and indicate that men and women may differ in the neural circuits associated with emotion representation and integration.

PMID: 27004933 [PubMed - indexed for MEDLINE]

Resting-State Functional Connectivity in Autism Spectrum Disorders: A Review.

Fri, 01/20/2017 - 15:40
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Resting-State Functional Connectivity in Autism Spectrum Disorders: A Review.

Front Psychiatry. 2016;7:205

Authors: Hull JV, Jacokes ZJ, Torgerson CM, Irimia A, Van Horn JD

Abstract
Ongoing debate exists within the resting-state functional MRI (fMRI) literature over how intrinsic connectivity is altered in the autistic brain, with reports of general over-connectivity, under-connectivity, and/or a combination of both. Classifying autism using brain connectivity is complicated by the heterogeneous nature of the condition, allowing for the possibility of widely variable connectivity patterns among individuals with the disorder. Further differences in reported results may be attributable to the age and sex of participants included, designs of the resting-state scan, and to the analysis technique used to evaluate the data. This review systematically examines the resting-state fMRI autism literature to date and compares studies in an attempt to draw overall conclusions that are presently challenging. We also propose future direction for rs-fMRI use to categorize individuals with autism spectrum disorder, serve as a possible diagnostic tool, and best utilize data-sharing initiatives.

PMID: 28101064 [PubMed - in process]

Robust Detection of Impaired Resting State Functional Connectivity Networks in Alzheimer's Disease Using Elastic Net Regularized Regression.

Fri, 01/20/2017 - 15:40
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Robust Detection of Impaired Resting State Functional Connectivity Networks in Alzheimer's Disease Using Elastic Net Regularized Regression.

Front Aging Neurosci. 2016;8:318

Authors: Teipel SJ, Grothe MJ, Metzger CD, Grimmer T, Sorg C, Ewers M, Franzmeier N, Meisenzahl E, Klöppel S, Borchardt V, Walter M, Dyrba M

Abstract
The large number of multicollinear regional features that are provided by resting state (rs) fMRI data requires robust feature selection to uncover consistent networks of functional disconnection in Alzheimer's disease (AD). Here, we compared elastic net regularized and classical stepwise logistic regression in respect to consistency of feature selection and diagnostic accuracy using rs-fMRI data from four centers of the "German resting-state initiative for diagnostic biomarkers" (psymri.org), comprising 53 AD patients and 118 age and sex matched healthy controls. Using all possible pairs of correlations between the time series of rs-fMRI signal from 84 functionally defined brain regions as the initial set of predictor variables, we calculated accuracy of group discrimination and consistency of feature selection with bootstrap cross-validation. Mean areas under the receiver operating characteristic curves as measure of diagnostic accuracy were 0.70 in unregularized and 0.80 in regularized regression. Elastic net regression was insensitive to scanner effects and recovered a consistent network of functional connectivity decline in AD that encompassed parts of the dorsal default mode as well as brain regions involved in attention, executive control, and language processing. Stepwise logistic regression found no consistent network of AD related functional connectivity decline. Regularized regression has high potential to increase diagnostic accuracy and consistency of feature selection from multicollinear functional neuroimaging data in AD. Our findings suggest an extended network of functional alterations in AD, but the diagnostic accuracy of rs-fMRI in this multicenter setting did not reach the benchmark defined for a useful biomarker of AD.

PMID: 28101051 [PubMed - in process]

Morphological and Functional Differences between Athletes and Novices in Cortical Neuronal Networks.

Fri, 01/20/2017 - 15:40
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Morphological and Functional Differences between Athletes and Novices in Cortical Neuronal Networks.

Front Hum Neurosci. 2016;10:660

Authors: Tan XY, Pi YL, Wang J, Li XP, Zhang LL, Dai W, Zhu H, Ni Z, Zhang J, Wu Y

Abstract
The cortical structural and functional differences in athletes and novices were investigated with a cross-sectional paradigm. We measured the gray matter volumes and resting-state functional connectivity in 21 basketball players and 21 novices with magnetic resonance imaging (MRI) techniques. It was found that gray matter volume in the left anterior insula (AI), inferior frontal gyrus (IFG), inferior parietal lobule (IPL) and right anterior cingulate cortex (ACC), precuneus is greater in basketball players than that in novices. These five brain regions were selected as the seed regions for testing the resting-state functional connectivity in the second experiment. We found higher functional connectivity in default mode network, salience network and executive control network in basketball players compared to novices. We conclude that the morphology and functional connectivity in cortical neuronal networks in athletes and novices are different.

PMID: 28101012 [PubMed - in process]

Towards prognostic biomarkers from BOLD fluctuations to differentiate a first epileptic seizure from new-onset epilepsy.

Thu, 01/19/2017 - 15:20
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Towards prognostic biomarkers from BOLD fluctuations to differentiate a first epileptic seizure from new-onset epilepsy.

Epilepsia. 2017 Jan 18;:

Authors: Gupta L, Janssens R, Vlooswijk MC, Rouhl RP, de Louw A, Aldenkamp AP, Ulman S, Besseling RM, Hofman PA, van Kranen-Mastenbroek VH, Hilkman DM, Jansen JF, Backes WH

Abstract
OBJECTIVE: The diagnosis of epilepsy cannot be reliably made prior to a patient's second seizure in most cases. Therefore, adequate diagnostic tools are needed to differentiate subjects with a first seizure from those with a seizure preceding the onset of epilepsy. The objective was to explore spontaneous blood oxygen level-dependent (BOLD) fluctuations in subjects with a first-ever seizure and patients with new-onset epilepsy (NOE), and to find characteristic biomarkers for seizure recurrence after the first seizure.
METHODS: We examined 17 first-seizure subjects, 19 patients with new-onset epilepsy (NOE), and 18 healthy controls. All subjects underwent clinical investigation and received electroencephalography and resting-state functional magnetic resonance imaging (MRI). The BOLD time series were analyzed in terms of regional homogeneity (ReHo) and fractional amplitude of low-frequency fluctuations (fALFFs).
RESULTS: We found significantly stronger amplitudes (higher fALFFs) in patients with NOE relative to first-seizure subjects and healthy controls. The frequency range of 73-198 mHz (slow-3 subband) appeared most useful for discriminating patients with NOE from first-seizure subjects. The ReHo measure did not show any significant differences.
SIGNIFICANCE: The fALFF appears to be a noninvasive measure that characterizes spontaneous BOLD fluctuations and shows stronger amplitudes in the slow-3 subband of patients with NOE relative first-seizure subjects and healthy controls. A larger study population with follow-up is required to determine whether fALFF holds promise as a potential biomarker for identifying subjects at increased risk to develop epilepsy.

PMID: 28098938 [PubMed - as supplied by publisher]

Noninvasive measurement of lower extremity muscle oxygen extraction fraction under cuff compression paradigm.

Thu, 01/19/2017 - 15:20
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Noninvasive measurement of lower extremity muscle oxygen extraction fraction under cuff compression paradigm.

J Magn Reson Imaging. 2016 May;43(5):1148-58

Authors: Wang C, Zhang R, Zhang X, Wang H, Zhao K, Jin L, Zhang J, Wang X, Fang J

Abstract
BACKGROUND: To demonstrate the feasibility of using a susceptibility-based MRI technique with asymmetric spin-echo (ASE) sequence to assess the lower extremity muscle oxygen extraction fraction (OEF) alternations under cuff compression paradigm.
METHODS: Approved by the local institutional human study committee, nine healthy young volunteers participated in this study. All the ASE scans were conducted using a 3 Tesla clinical MRI scanner during resting state (pre), 1-3 min (post1) and 3-5 min (post2) after a pressure of 50 mmHg above individual systolic blood pressure imposed on the thigh. Moreover, near-infrared spectroscopy (NIRS) measurements were performed on the same day under the same cuff compression protocol to verify the accuracy of this susceptibility-based method.
RESULTS: In all volunteers, the mean MRI based OEF in gastrocnemius (GAS) muscle increased significantly from 0.28 ± 0.02 (pre) to 0.31 ± 0.03 (post1, P < 0.05) and 0.31 ± 0.03 (post2, P < 0.05). In addition, mean OEF in soleus (SOL) muscle went up from 0.31 ± 0.01 (pre) to 0.33 ± 0.03 (post1, P = 0.14) and 0.37 ± 0.04 (post2, P < 0.05). For comparison, NIRS measured 1-%HbO2 (percentage of deoxyhemoglobin concentration within total hemoglobin) in GAS rose significantly from 0.29 ± 0.03 (pre) to 0.31 ± 0.04 (post1, P < 0.05) and 0.31 ± 0.04 (post2, P < 0.05), which confirmed the accuracy of the MRI-based OEF.
CONCLUSION: This susceptibility-based OEF quantification technique together with cuff compression paradigm could provide a noninvasive, quantifiable and effective tool for measuring skeletal muscle oxygenation.

PMID: 26527473 [PubMed - indexed for MEDLINE]

Apathy and intrinsic functional connectivity networks in amnestic mild cognitive impairment.

Wed, 01/18/2017 - 21:05
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Apathy and intrinsic functional connectivity networks in amnestic mild cognitive impairment.

Neuropsychiatr Dis Treat. 2017;13:61-67

Authors: Joo SH, Lee CU, Lim HK

Abstract
BACKGROUND: Although several prior works reported that apathy is associated with conversion to Alzheimer's disease in individuals with amnestic mild cognitive impairment (aMCI), effects of apathy on the functional connectivity (FC) of the brain remain unclear. In this study, we assessed the pattern of association between apathy and default mode network (DMN), salience network and central executive network (CEN) in aMCI subjects.
METHODS: Fifty subjects with aMCI and 50 controls (CONs) participated in this study. They underwent clinical assessments and magnetic resonance imaging for the structural and resting-state scan. We explored the patterns of association between apathy inventory (IA) total score and the whole-brain voxel-wise FCs of the DMN, salience network and CEN in aMCI subjects.
RESULTS: We observed that the FCs of the DMN were less and those of CEN were more in the aMCI group than the CON group. Total IA score was negatively correlated with FCs of the anterior cingulate within the DMN, and positively correlated with FCs of the middle frontal, inferior frontal, and supramarginal gyrus within the CEN in the aMCI group.
CONCLUSION: Our findings suggest that distinctive patterns of association between apathy and FCs in the DMN and CEN in the aMCI group might reflect the putative role of functional network change in the development of apathy in aMCI.

PMID: 28096673 [PubMed - in process]

Effect of Heroin Use on Changes of Brain Functions as Measured by fMRI, a Systematic Review.

Wed, 01/18/2017 - 21:05
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Effect of Heroin Use on Changes of Brain Functions as Measured by fMRI, a Systematic Review.

J Addict Dis. 2017 Jan 17;:0

Authors: Fareed A, Kim J, Ketchen B, Kwak WJ, Wang D, Shongo-Hiango H, Drexler K

Abstract
BACKGROUND AND OBJECTIVES: In this study we focus on reviewing imaging studies that used resting state functional magnetic resonance imaging (fMRI) for individuals with a history of heroin use. This review study compiled existing research addressing the effect of heroin use on decision making by reviewing available functional neuroimaging data..
METHODS: Systematic review of the literatures using the PRISMA checklist. Eligible articles were retrieved through a computer-based MEDLINE and PsycINFO search from 1960 to December 2015 using the major medical subject headings 'heroin, fMRI' (all fields). Only English language were included.
RESULTS: Thirty-seven articles were initially included in the review. Sixteen were excluded because they did not meet the inclusion criteria. We present the results of 21 articles that met all the inclusion criteria.
CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE: Based on the 21 studies included in this review, there is evidence that heroin use may have a direct and damaging effect on certain brain functions and that these changes may be associated with impulsive and unhealthy decision making. From our review of these studies, we understand that longer duration of heroin use may be associated with more damaging effects on brain functions. We also understand that these brain changes could last long after abstinence, which may increase the risk of relapse to heroin use. More research is needed to create a biomarker map for patients with heroin use disorder that can be used to guide and assess response to treatment.

PMID: 28095255 [PubMed - as supplied by publisher]

Maximum Pseudolikelihood Estimation for Model-Based Clustering of Time Series Data.

Wed, 01/18/2017 - 21:05
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Maximum Pseudolikelihood Estimation for Model-Based Clustering of Time Series Data.

Neural Comput. 2017 Jan 17;:1-31

Authors: Nguyen HD, McLachlan GJ, Orban P, Bellec P, Janke AL

Abstract
Mixture of autoregressions (MoAR) models provide a model-based approach to the clustering of time series data. The maximum likelihood (ML) estimation of MoAR models requires evaluating products of large numbers of densities of normal random variables. In practical scenarios, these products converge to zero as the length of the time series increases, and thus the ML estimation of MoAR models becomes infeasible without the use of numerical tricks. We propose a maximum pseudolikelihood (MPL) estimation approach as an alternative to the use of numerical tricks. The MPL estimator is proved to be consistent and can be computed with an EM (expectation-maximization) algorithm. Simulations are used to assess the performance of the MPL estimator against that of the ML estimator in cases where the latter was able to be calculated. An application to the clustering of time series data arising from a resting state fMRI experiment is presented as a demonstration of the methodology.

PMID: 28095191 [PubMed - as supplied by publisher]

The effect of network template from normal subjects in the detection of network impairment.

Wed, 01/18/2017 - 21:05
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The effect of network template from normal subjects in the detection of network impairment.

Acta Neurobiol Exp (Wars). 2016;76(4):294-303

Authors: Chun-Chao H, Shang-Hua L, Ching-Po L, Disease Neuroimaging Initiative TA

Abstract
This study aimed to provide a simple way to approach group differences by independent component analysis when researching functional connectivity changes of resting-state network in brain disorders. We used baseline resting state functional magnetic resonance imaging from the Alzheimer's disease neuroimaging initiative dataset and performed independent component analysis based on different kinds of subject selection, by including two downloaded templates and single-subject independent component analysis method. All conditions were used to calculate the functional connectivity of the default mode network, and to test group differences and evaluate correlation with cognitive measurements and hippocampal volume. The default mode network functional connectivity results most fitting clinical evaluations were from templates based on young healthy subjects and the worst results were from heterogeneous or more severe disease groups or single-subject independent component analysis method. Using independent component analysis network maps derived from normal young subjects to extract all individual functional connectivities provides significant correlations with clinical evaluations.

PMID: 28094820 [PubMed - in process]

Aberrant development of intrinsic brain activity in a rat model of caregiver maltreatment of offspring.

Wed, 01/18/2017 - 21:05
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Aberrant development of intrinsic brain activity in a rat model of caregiver maltreatment of offspring.

Transl Psychiatry. 2017 Jan 17;7(1):e1005

Authors: Yan CG, Rincón-Cortés M, Raineki C, Sarro E, Colcombe S, Guilfoyle DN, Yang Z, Gerum S, Biswal BB, Milham MP, Sullivan RM, Castellanos FX

Abstract
Caregiver maltreatment induces vulnerability to later-life psychopathology. Clinical and preclinical evidence suggest changes in prefrontal and limbic circuitry underlie this susceptibility. We examined this question using a rat model of maternal maltreatment and methods translated from humans, resting-state functional magnetic resonance imaging (R-fMRI). Rat pups were reared by mothers provided with insufficient or abundant bedding for nest building from postnatal (PN) days 8 to 12 and underwent behavioral assessments of affect-related behaviors (forced swim, sucrose preference and social interaction) in adolescence (PN45) and early adulthood (PN60). R-fMRI sessions were conducted under light anesthesia at both ages. Offspring reared with insufficient bedding (that is, maltreated) displayed enduring negative affective behaviors. Amygdala-prefrontal cortex (PFC) functional connectivity increased significantly from adolescence to adulthood in controls, but not in maltreated animals. We computed the fractional amplitude of low-frequency fluctuations (fALFF), an index of intrinsic brain activity, and found that fALFF in medial prefrontal cortex and anterior cingulate cortex (MPFC/ACC) increased significantly with age in controls but remained unchanged in maltreated animals during adolescence and adulthood. We used a seed-based analysis to explore changes in functional connectivity between this region and the whole brain. Compared with controls, maltreated animals demonstrated reduced functional connectivity between MPFC/ACC and left caudate/putamen across both ages. Functional connectivity between MPFC/ACC and right caudate/putamen showed a group by age interaction: decreased in controls but increased in maltreated animals. These data suggest that maltreatment induces vulnerability to psychopathology and is associated with differential developmental trajectories of prefrontal and subcortical circuits underlying affect regulation.

PMID: 28094810 [PubMed - in process]

Test-retest reliability of functional connectivity networks during naturalistic fMRI paradigms.

Wed, 01/18/2017 - 21:05
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Test-retest reliability of functional connectivity networks during naturalistic fMRI paradigms.

Hum Brain Mapp. 2017 Jan 17;:

Authors: Wang J, Ren Y, Hu X, Nguyen VT, Guo L, Han J, Guo CC

Abstract
Functional connectivity analysis has become a powerful tool for probing the human brain function and its breakdown in neuropsychiatry disorders. So far, most studies adopted resting-state paradigm to examine functional connectivity networks in the brain, thanks to its low demand and high tolerance that are essential for clinical studies. However, the test-retest reliability of resting-state connectivity measures is moderate, potentially due to its low behavioral constraint. On the other hand, naturalistic neuroimaging paradigms, an emerging approach for cognitive neuroscience with high ecological validity, could potentially improve the reliability of functional connectivity measures. To test this hypothesis, we characterized the test-retest reliability of functional connectivity measures during a natural viewing condition, and benchmarked it against resting-state connectivity measures acquired within the same functional magnetic resonance imaging (fMRI) session. We found that the reliability of connectivity and graph theoretical measures of brain networks is significantly improved during natural viewing conditions over resting-state conditions, with an average increase of almost 50% across various connectivity measures. Not only sensory networks for audio-visual processing become more reliable, higher order brain networks, such as default mode and attention networks, but also appear to show higher reliability during natural viewing. Our results support the use of natural viewing paradigms in estimating functional connectivity of brain networks, and have important implications for clinical application of fMRI. Hum Brain Mapp, 2017. © 2017 Wiley Periodicals, Inc.

PMID: 28094464 [PubMed - as supplied by publisher]

Evidence for Accelerated Decline of Functional Brain Network Efficiency in Schizophrenia.

Wed, 01/18/2017 - 21:05
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Evidence for Accelerated Decline of Functional Brain Network Efficiency in Schizophrenia.

Schizophr Bull. 2016 May;42(3):753-61

Authors: Sheffield JM, Repovs G, Harms MP, Carter CS, Gold JM, MacDonald AW, Ragland JD, Silverstein SM, Godwin D, Barch DM

Abstract
Previous work suggests that individuals with schizophrenia display accelerated aging of white matter integrity, however, it is still unknown whether functional brain networks also decline at an elevated rate in schizophrenia. Given the known degradation of functional connectivity and the normal decline in cognitive functioning throughout healthy aging, we aimed to test the hypothesis that efficiency of large-scale functional brain networks supporting overall cognition, as well as integrity of hub nodes within those networks, show evidence of accelerated aging in schizophrenia. Using pseudo-resting state data in 54 healthy controls and 46 schizophrenia patients, in which task-dependent signal from 3 tasks was regressed out to approximate resting-state data, we observed a significant diagnosis by age interaction in the prediction of both global and local efficiency of the cingulo-opercular network, and of the local efficiency of the fronto-parietal network, but no interaction when predicting both default mode network and whole brain efficiency. We also observed a significant diagnosis by age interaction for the node degree of the right anterior insula, left dorsolateral prefrontal cortex, and dorsal anterior cingulate cortex. All interactions were driven by stronger negative associations between age and network metrics in the schizophrenia group than the healthy controls. These data provide evidence that is consistent with accelerated aging of large-scale functional brain networks in schizophrenia that support higher-order cognitive ability.

PMID: 26472685 [PubMed - indexed for MEDLINE]

Aberrant spontaneous neural activity and correlation with evoked-brain potentials in first-episode, treatment-naïve patients with deficit and non-deficit schizophrenia.

Tue, 01/17/2017 - 14:45

Aberrant spontaneous neural activity and correlation with evoked-brain potentials in first-episode, treatment-naïve patients with deficit and non-deficit schizophrenia.

Psychiatry Res. 2017 Jan 05;261:9-19

Authors: Li Z, Lei W, Deng W, Zheng Z, Li M, Ma X, Wang Q, Huang C, Li N, Collier DA, Gong Q, Li T

Abstract
The goals of the study were to analyze spontaneous neural activity between deficit and non-deficit schizophrenia (DS, NDS) using resting-state fMRI, and to investigate the correlation of fMRI with clinical features and evoked brain potentials. The amplitude of low frequency fluctuation (ALFF) was measured in 41 DS participants, 42 NDS participants, and 42 healthy controls. ALFF in the bilateral cerebellum posterior lobe was significantly decreased in patients, while ALFF in the right fusiform gyrus and the bilateral putamen was significantly increased. In schizophrenia patients, ALFF in the right putamen positively correlated with excited/activation on Positive and Negative Syndrome Scale (PANSS-EXC/ACT). In DS patients, ALFF in the right insula was significantly increased than in controls and positively correlated with S2-P50 amplitude of sensory gating P50. ALFF in the left cerebellum posterior lobe negatively correlated with negative symptoms and withdrawn on PANSS (PANSS-NS, PANSS-WIT), ALFF in the right putamen positively correlated with PANSS-WIT. In NDS patients, ALFF in the middle temporal gyrus decreased than in controls and negatively correlated with P3b subcomponent of P300 latency. ALFF in the left cerebellum posterior lobe negatively correlated with PANSS-EXC/ACT. The middle temporal gyrus in NDS or the right insula in DS may show spatiotemporal defects.

PMID: 28092779 [PubMed - as supplied by publisher]

Dexmedetomidine Disrupts the Local and Global Efficiencies of Large-scale Brain Networks.

Tue, 01/17/2017 - 14:45

Dexmedetomidine Disrupts the Local and Global Efficiencies of Large-scale Brain Networks.

Anesthesiology. 2017 Jan 16;:

Authors: Hashmi JA, Loggia ML, Khan S, Gao L, Kim J, Napadow V, Brown EN, Akeju O

Abstract
BACKGROUND: A clear understanding of the neural basis of consciousness is fundamental to research in clinical and basic neuroscience disciplines and anesthesia. Recently, decreased efficiency of information integration was suggested as a core network feature of propofol-induced unconsciousness. However, it is unclear whether this finding can be generalized to dexmedetomidine, which has a different molecular target.
METHODS: Dexmedetomidine was administered as a 1-μg/kg bolus over 10 min, followed by a 0.7-μg · kg · h infusion to healthy human volunteers (age range, 18 to 36 yr; n = 15). Resting-state functional magnetic resonance imaging data were acquired during baseline, dexmedetomidine-induced altered arousal, and recovery states. Zero-lag correlations between resting-state functional magnetic resonance imaging signals extracted from 131 brain parcellations were used to construct weighted brain networks. Network efficiency, degree distribution, and node strength were computed using graph analysis. Parcellated brain regions were also mapped to known resting-state networks to study functional connectivity changes.
RESULTS: Dexmedetomidine significantly reduced the local and global efficiencies of graph theory-derived networks. Dexmedetomidine also reduced the average brain connectivity strength without impairing the degree distribution. Functional connectivity within and between all resting-state networks was modulated by dexmedetomidine.
CONCLUSIONS: Dexmedetomidine is associated with a significant drop in the capacity for efficient information transmission at both the local and global levels. These changes result from reductions in the strength of connectivity and also manifest as reduced within and between resting-state network connectivity. These findings strengthen the hypothesis that conscious processing relies on an efficient system of information transfer in the brain.

PMID: 28092321 [PubMed - as supplied by publisher]

The effects of flavanone-rich citrus juice on cognitive function and cerebral blood flow: an acute, randomised, placebo-controlled cross-over trial in healthy, young adults.

Tue, 01/17/2017 - 14:45

The effects of flavanone-rich citrus juice on cognitive function and cerebral blood flow: an acute, randomised, placebo-controlled cross-over trial in healthy, young adults.

Br J Nutr. 2017 Jan 16;:1-9

Authors: Lamport DJ, Pal D, Macready AL, Barbosa-Boucas S, Fletcher JM, Williams CM, Spencer JP, Butler LT

Abstract
A plausible mechanism underlying flavonoid-associated cognitive effects is increased cerebral blood flow (CBF). However, behavioural and CBF effects following flavanone-rich juice consumption have not been explored. The aim of this study was to investigate whether consumption of flavanone-rich juice is associated with acute cognitive benefits and increased regional CBF in healthy, young adults. An acute, single-blind, randomised, cross-over design was applied with two 500-ml drink conditions - high-flavanone (HF; 70·5 mg) drink and an energy-, and vitamin C- matched, zero-flavanone control. A total of twenty-four healthy young adults aged 18-30 years underwent cognitive testing at baseline and 2-h after drink consumption. A further sixteen, healthy, young adults were recruited for functional MRI assessment, whereby CBF was measured with arterial spin labelling during conscious resting state at baseline as well as 2 and 5 h after drink consumption. The HF drink was associated with significantly increased regional perfusion in the inferior and middle right frontal gyrus at 2 h relative to baseline and the control drink. In addition, the HF drink was associated with significantly improved performance on the Digit Symbol Substitution Test at 2 h relative to baseline and the control drink, but no effects were observed on any other behavioural cognitive tests. These results demonstrate that consumption of flavanone-rich citrus juice in quantities commonly consumed can acutely enhance blood flow to the brain in healthy, young adults. However, further studies are required to establish a direct causal link between increased CBF and enhanced behavioural outcomes following citrus juice ingestion.

PMID: 28091350 [PubMed - as supplied by publisher]

Global Signal Regression Acts as a Temporal Downweighting Process in Resting-State fMRI.

Tue, 01/17/2017 - 14:45
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Global Signal Regression Acts as a Temporal Downweighting Process in Resting-State fMRI.

Neuroimage. 2017 Jan 09;:

Authors: Nalci A, Rao BD, Liu TT

Abstract
In resting-state functional MRI (rsfMRI), the correlation between blood oxygenation level dependent (BOLD) signals across different brain regions is used to estimate the functional connectivity of the brain. This approach has led to the identification of a number of resting-state networks, including the default mode network (DMN) and the task positive network (TPN). Global signal regression (GSR) is a widely used pre-processing step in rsfMRI that has been shown to improve the spatial specificity of the estimated resting-state networks. In GSR, a whole brain average time series, known as the global signal (GS), is regressed out of each voxel time series prior to the computation of the correlations. However, the use of GSR is controversial because it can introduce artifactual negative correlations. For example, it has been argued that anticorrelations observed between the DMN and TPN are primarily an artifact of GSR. Despite the concerns about GSR, there is currently no consensus regarding its use. In this paper, we introduce a new framework for understanding the effects of GSR. In particular, we show that the main effects of GSR can be well approximated as a temporal downweighting process in which the data from time points with relatively large GS magnitudes are greatly attenuated while data from time points with relatively small GS magnitudes are largely unaffected. Furthermore, we show that a limiting case of this downweighting process in which data from time points with large GS magnitudes are censored can also approximate the effects of GSR. In other words, the correlation maps obtained after GSR show a high degree of spatial similarity (including the presence of anticorrelations between the DMN and TPN) with maps obtained using only the uncensored (i.e. retained) time points. Since the data from these retained time points are unaffected by the censoring process, this finding suggests that the observed anticorrelations inherently exist in the data from time points with small GS magnitudes and are not simply an artifact of GSR.

PMID: 28089677 [PubMed - as supplied by publisher]

Multimodal evaluation of the amygdala's functional connectivity.

Tue, 01/17/2017 - 14:45
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Multimodal evaluation of the amygdala's functional connectivity.

Neuroimage. 2017 Jan 09;:

Authors: Kerestes R, Chase HW, Phillips ML, Ladouceur CD, Eickhoff SB

Abstract
The amygdala is one of the most extensively studied human brain regions and undisputedly plays a central role in many psychiatric disorders. However, an outstanding question is whether connectivity of amygdala subregions, specifically the centromedial (CM), laterobasal (LB) and superficial (SF) nuclei, are modulated by brain state (i.e., task vs. rest). Here, using a multimodal approach, we directly compared meta-analytic connectivity modeling (MACM) and specific co-activation likelihood estimation (SCALE)-derived estimates of CM, LB and SF task-based co-activation to the functional connectivity of these nuclei as assessed by resting state fmri (rs-fmri). Finally, using a preexisting resting state functional connectivity-derived cortical parcellation, we examined both MACM and rs-fmri amygdala subregion connectivity with 17 large-scale networks, to explicitly address how the amygdala interacts with other large-scale neural networks. Analyses revealed strong differentiation of CM, LB and SF connectivity patterns with other brain regions, both in task-dependent and task-independent contexts. All three regions, however, showed convergent connectivity with the right ventrolateral prefrontal cortex (VLPFC) that was not driven by high base rate levels of activation. Similar patterns of connectivity across rs-fmri and MACM were observed for each subregion, suggesting a similar network architecture of amygdala connectivity with the rest of the brain across tasks and resting state for each subregion, that may be modified in the context of specific task demands. These findings support animal models that posit a parallel model of amygdala functioning, but importantly, also modify this position to suggest integrative processing in the amygdala.

PMID: 28089676 [PubMed - as supplied by publisher]

Functional Connectivity of Vim Nucleus in Tremor- and Akinetic-/Rigid-Dominant Parkinson's Disease.

Tue, 01/17/2017 - 14:45
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Functional Connectivity of Vim Nucleus in Tremor- and Akinetic-/Rigid-Dominant Parkinson's Disease.

CNS Neurosci Ther. 2016 May;22(5):378-86

Authors: Zhang JR, Feng T, Hou YN, Chan P, Wu T

Abstract
AIMS: The aim of this study was to investigate the involvement of the ventral intermediate nucleus of thalamus (Vim) in the tremor- and akinetic-/rigid-related networks in Parkinson's disease (PD).
METHODS: Tremor-dominant (TD) and akinetic-/rigid-dominant (ARD) PD patients were recruited and scanned by resting-state functional MRI. Functional connectivity from the Vim nucleus was analyzed.
RESULTS: In the TD patients, the Vim nucleus exhibited increased connectivity with the cerebellum/dentate nucleus, primary motor cortex (M1), supplementary motor area (SMA), premotor cortex, thalamus, globus pallidus, putamen, and parietal cortex compared with the controls, while the connections between the Vim nucleus and M1 and cerebellum/dentate nucleus had positive correlations with the tremor scores. In the ARD patients, the Vim nucleus only showed enhanced connectivity with the globus pallidus and limbic lobe compared with the controls, and no connectivity showed correlation against the akinetic-rigidity scores. TD patients had increased connectivity with the Vim nucleus in the cerebellum, M1, SMA, thalamus, globus pallidus, putamen, and parietal cortex compared with ARD patients.
CONCLUSIONS: This study demonstrates that the Vim nucleus has an important role in the tremor-related network, but not in the akinetic-/rigid-related network. Our finding is helpful to explain the selective effect of Vim deep brain stimulation in PD.

PMID: 26849713 [PubMed - indexed for MEDLINE]

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