New resting-state fMRI related studies at PubMed

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Updated: 1 hour 35 min ago

Modeling regional dynamics in low-frequency fluctuation and its application to Autism spectrum disorder diagnosis.

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Modeling regional dynamics in low-frequency fluctuation and its application to Autism spectrum disorder diagnosis.

Neuroimage. 2018 Sep 21;:

Authors: Jun E, Kang E, Choi J, Suk HI

Abstract
With the advent of neuroimaging techniques, many studies in the literature have validated the use of resting-state fMRI (rs-fMRI) for understanding functional mechanisms of the brain, as well as for identifying brain disorders or diseases. One of the main streams in recent studies of modeling and analyzing rs-fMRI data is to account for the dynamic characteristics of a brain. In this study, we propose a novel method that directly models the regional temporal BOLD fluctuations in a stochastic manner and estimates the dynamic characteristics in the form of likelihoods. Specifically, we modeled temporal BOLD fluctuation of individual Regions Of Interest (ROIs) by means of Hidden Markov Models (HMMs), and then estimated the 'goodness-of-fit' of each ROI's BOLD signals to the corresponding trained HMM in terms of a likelihood. Using estimated likelihoods of the ROIs over the whole brain as features, we built a classifier that can discriminate subjects with Autism Spectrum Disorder (ASD) from Typically Developing (TD) controls at an individual level. In order to interpret the trained HMMs and a classifier from a neuroscience perspective, we also conducted model analysis. First, we investigated the learned weight coefficients of a classifier by transforming them into activation patterns, from which we could identify the ROIs that are highly associated with ASD and TD groups. Second, we explored the characteristics of temporal BOLD signals in terms of functional networks by clustering them based on sequences of the hidden states decoded with the trained HMMs. We validated the effectiveness of the proposed method by achieving the state-of-the-art performance on the ABIDE dataset and observed insightful patterns related to ASD.

PMID: 30248456 [PubMed - as supplied by publisher]

The impact of motor impairment on the processing of sensory information.

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The impact of motor impairment on the processing of sensory information.

Behav Brain Res. 2018 Sep 21;:

Authors: Klingner CM, Brodoehl S, Witte OW, Guntinas-Lichius O, Volk GF

Abstract
Sensorimotor adaptation is driven by mismatch errors between desired movements and actual movement outcomes. A mismatch error can be minimized by adjusting movements or by altering the interpretation of sensory information. While the effect of mismatch errors on the motor system has received much attention, the contribution of somatosensory feedback, particularly the sensory-motor interplay in the process of adaptation, remains poorly understood. Our study analyzes the impact of peripheral deefferentation on the plasticity of the brain networks responsible for sensory-motor adaptation, focusing particularly on changes in the processing of somatosensory information. For this aim, task-based and resting-state functional MRI was performed on 24 patients in the acute state of a left-sided idiopathic peripheral facial nerve palsy. The functional connectivity of cortical and subcortical networks was analyzed and compared to a healthy control group. We found a strong involvement of the somatosensory system and the thalamus in the adaptation process following an acute peripheral deefferentation. The investigated network shows the principal pattern of a reduced connectivity between cortical areas, while the connectivity to subcortical areas (the basal ganglia and the thalamus) is increased. We suggest that the increased connectivity between the subcortical and cortical structures indicates an active sensory-motor adaptation process. We further hypothesize that the decreased functional connectivity at the cortical level reflects an unsuccessful sensorimotor adaptation process due to the inability to solve the somatosensory-motor mismatch. These results extend our understanding of the somatosensory-motor interaction in response to a mismatch signal and highlight the importance of the thalamus in this process.

PMID: 30248364 [PubMed - as supplied by publisher]

Resting-state Functional Magnetic Resonance Imaging Identifies Cerebrovascular Reactivity Impairment in Patients With Arterial Occlusive Diseases: A Pilot Study.

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Resting-state Functional Magnetic Resonance Imaging Identifies Cerebrovascular Reactivity Impairment in Patients With Arterial Occlusive Diseases: A Pilot Study.

Neurosurgery. 2018 Sep 20;:

Authors: Nishida S, Aso T, Takaya S, Takahashi Y, Kikuchi T, Funaki T, Yoshida K, Okada T, Kunieda T, Togashi K, Fukuyama H, Miyamoto S

Abstract
BACKGROUND: The development of noninvasive approaches for identifying hypoperfused brain tissue at risk is of major interest. Recently, the temporal-shift (TS) maps estimated from resting-state blood oxygenation level-dependent (BOLD) signals have been proposed for determining hemodynamic state.
OBJECTIVE: To examine the equivalency of the TS map and the cerebrovascular reactivity (CVR) map derived from acetazolamide-challenged single-photon emission computed tomography (SPECT) in identifying hemodynamic impairment in patients with arterial occlusive diseases.
METHODS: Twenty-three patients with arterial occlusive diseases who underwent SPECT were studied. With a recursive TS analysis of low-frequency fluctuation of the BOLD signal, a TS map relative to the global signal was created for each patient. The voxel-by-voxel correlation coefficient was calculated to examine the image similarity between TS and SPECT-based cerebral blood flow (CBF) or CVR maps in each patient. Furthermore, simple linear regression analyses were performed to examine the quantitative relationship between the TS of BOLD signals and CVR in each cerebrovascular territory.
RESULTS: The within-patient, voxel-by-voxel comparison revealed that the TS map was more closely correlated with SPECT-CVR map ([Z(r)] = 0.42 ± 0.18) than SPECT-CBF map ([Z(r)] = 0.058 ± 0.11; P < .001, paired t-test). The regression analysis showed a significant linear association between the TS of BOLD signals and CVR in the anterior circulation where the reduction of CVR was evident in the patient group.
CONCLUSION: BOLD TS analysis has potential as a noninvasive alternative to current methods based on CVR for identification of tissue at risk of ischemic stroke.

PMID: 30247676 [PubMed - as supplied by publisher]

Anterior cingulate cortex connectivity is associated with suppression of behaviour in a rat model of chronic pain.

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Anterior cingulate cortex connectivity is associated with suppression of behaviour in a rat model of chronic pain.

Brain Neurosci Adv. 2018;2:2398212818779646

Authors: Morris LS, Sprenger C, Koda K, de la Mora DM, Yamada T, Mano H, Kashiwagi Y, Yoshioka Y, Morioka Y, Seymour B

Abstract
A cardinal feature of persistent pain that follows injury is a general suppression of behaviour, in which motivation is inhibited in a way that promotes energy conservation and recuperation. Across species, the anterior cingulate cortex is associated with the motivational aspects of phasic pain, but whether it mediates motivational functions in persistent pain is less clear. Using burrowing behaviour as an marker of non-specific motivated behaviour in rodents, we studied the suppression of burrowing following painful confirmatory factor analysis or control injection into the right knee joint of 30 rats (14 with pain) and examined associated neural connectivity with ultra-high-field resting state functional magnetic resonance imaging. We found that connectivity between anterior cingulate cortex and subcortical structures including hypothalamic/preoptic nuclei and the bed nucleus of the stria terminalis correlated with the reduction in burrowing behaviour observed following the pain manipulation. In summary, the findings implicate anterior cingulate cortex connectivity as a correlate of the motivational aspect of persistent pain in rodents.

PMID: 30246156 [PubMed]

Group analysis data representing the effects of frontopolar transcranial direct current stimulation on the default mode network.

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Group analysis data representing the effects of frontopolar transcranial direct current stimulation on the default mode network.

Data Brief. 2018 Oct;20:1309-1313

Authors: Ahn J, Lee J, Han JH, Kang MS, Han S

Abstract
The current data provide information about altered activities of the default mode network (DMN) after applying transcranial direct current stimulation (tDCS) over the frontopolar prefrontal cortex. To explore whether frontopolar tDCS with a small current intensity and small electrodes can induce changes in the DMN, resting-state functional magnetic resonance imaging (fMRI) data were collected before and after the application of tDCS. The results of independent component analysis using the resting-state fMRI data are reported in this article.

PMID: 30246109 [PubMed]

Predicting conversion from MCI to AD by integrating rs-fMRI and structural MRI.

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Predicting conversion from MCI to AD by integrating rs-fMRI and structural MRI.

Comput Biol Med. 2018 Sep 15;102:30-39

Authors: Hojjati SH, Ebrahimzadeh A, Khazaee A, Babajani-Feremi A, Alzheimer's Disease Neuroimaging Initiative

Abstract
Structural MRI (sMRI) and resting-state functional MRI (rs-fMRI) have provided promising results in the diagnosis of Alzheimer's disease (AD), though the utility of integrating sMRI with rs-fMRI has not been explored thoroughly. We investigated the performances of rs-fMRI and sMRI in single modality and multi-modality approaches for classifying patients with mild cognitive impairment (MCI) who progress to probable AD-MCI converter (MCI-C) from those with MCI who do not progress to probable AD-MCI non-converter (MCI-NC). The cortical and subcortical measurements, e.g. cortical thickness, extracted from sMRI and graph measures extracted from rs-fMRI functional connectivity were used as features in our algorithm. We trained and tested a support vector machine to classify MCI-C from MCI-NC using rs-fMRI and sMRI features. Our algorithm for classifying MCI-C and MCI-NC utilized a small number of optimal features and achieved accuracies of 89% for sMRI, 93% for rs-fMRI, and 97% for the combination of sMRI with rs-fMRI. To our knowledge, this is the first study that investigated integration of rs-fMRI and sMRI for identification of the early stage of AD. Our findings shed light on integration of sMRI with rs-fMRI for identification of the early stages of AD.

PMID: 30245275 [PubMed - as supplied by publisher]

Patterns of striatal and cerebellar functional connectivity in early-stage drug-naïve patients with Parkinson's disease subtypes.

Mon, 09/24/2018 - 15:20
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Patterns of striatal and cerebellar functional connectivity in early-stage drug-naïve patients with Parkinson's disease subtypes.

Neuroradiology. 2018 Sep 22;:

Authors: Hou Y, Ou R, Yang J, Song W, Gong Q, Shang H

Abstract
PURPOSE: Both the striatal-thalamo-cortical (STC) circuit and cerebello-thalamo-cortical (CTC) circuit play a critical role in Parkinson's disease (PD).
METHODS: Resting-state functional MRI was used to assess functional connectivity (FC) focusing on the basal ganglia (BG) and cerebellum among early-stage drug-naïve PD patients with tremor-dominant (TD) PD patients with postural instability and gait dysfunction (PIGD) and healthy controls (HCs).
RESULTS: Compared to HCs, both PD subgroups had higher FC between the cerebellum and paracentral lobule, sensorimotor areas; lower FC between the BG and superior frontal gyrus, and within the BG circuit; PD-TD patients showed higher FC between the BG and fusiform, paracentral lobule, cerebellum Lobule VI, and between the cerebellum and supplementary motor areas (SMA), insula; lower FC between the BG and rectus, sensorimotor areas, and within the cerebellum circuit; PD-PIGD patients showed higher FC between the cerebellum and middle frontal gyrus, precuneus; lower FC between the BG and cerebellum Crus II. Besides, compared to PD-PIGD patients and HCs, PD-TD patients had higher FC between the BG and calcarine region. In all PD patients, FC in paracentral lobule, SMA, and cerebellum Lobule VI positively correlated with tremor scores, and FC in calcarine area positively correlated with tremor scores, but negatively correlated with PIGD scores.
CONCLUSION: Our findings mainly suggested that the BG and cerebellum had hyper-connectivity with the cortical motor cortex, and the BG had prominent hyper-connectivity with the visual cortex in early-stage PD-TD patients. These findings may be helpful for facilitating the further understanding of potential mechanisms in the early-stage PD-TD. However, our results are preliminary, and further investigations are needed.

PMID: 30244415 [PubMed - as supplied by publisher]

Altered temporal variance and functional connectivity of BOLD signal is associated with state anxiety during acute systemic inflammation.

Mon, 09/24/2018 - 15:20
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Altered temporal variance and functional connectivity of BOLD signal is associated with state anxiety during acute systemic inflammation.

Neuroimage. 2018 Sep 20;:

Authors: Labrenz F, Ferri F, Wrede K, Forsting M, Schedlowski M, Engler H, Elsenbruch S, Benson S, Costantini M

Abstract
Systemic inflammation is accompanied by complex behavioral changes and disturbed emotion regulation that have been related to the pathophysiology of mood disorders including depression and anxiety. However, the causal role of systemic inflammation on mood disorders is still unclear. We herein investigated neural resting state patterns of temporal variance of the amygdala and functional connectivity within the salience network underlying changes in state anxiety during experimentally-induced systemic inflammation. In this randomized, double-blind study, N = 43 healthy men received an intravenous injection of either low-dose lipopolysaccharide (LPS, 0.4 ng/kg body weight) or saline. Resting state functional magnetic resonance imaging was assessed before and 3.5 h after injection. State anxiety, assessed with a standardized questionnaire, and plasma cytokine concentrations were repeatedly measured. LPS administration induced a transient systemic inflammatory response reflected in increases in plasma Interleukin (IL)-6 and Tumor Necrosis Factor (TNF)-α concentration. Compared to placebo, state anxiety and temporal variance in the amygdala significantly increased while functional connectivity in the salience network decreased during LPS-induced systemic inflammation. Together, these data indicate that acute systemic inflammation alters temporal variance of the BOLD signal as well as functional connectivity in brain regions and networks implicated in emotion processing and regulation. These results are of translational importance to encourage further research on the role of inflammatory pathways in the pathophysiology of neuropsychiatric conditions including anxiety disorders.

PMID: 30243957 [PubMed - as supplied by publisher]

Intranasal Oxytocin and OXTR Genotype Effects on Resting State Functional Connectivity: A Systematic Review.

Mon, 09/24/2018 - 15:20
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Intranasal Oxytocin and OXTR Genotype Effects on Resting State Functional Connectivity: A Systematic Review.

Neurosci Biobehav Rev. 2018 Sep 19;:

Authors: Seeley SH, Chou YH, O'Connor MF

Abstract
OBJECTIVE: Evaluate effects of intranasal oxytocin (IN-OT) and OXTR genotype on resting state functional connectivity in the human brain.
METHODS: We searched research databases for peer-reviewed empirical studies. Of 71 unique citations, 18 articles (13 IN-OT, five OXTR) met full inclusion criteria.
RESULTS: Two studies examined effects on large-scale networks; most examined acute effects on amygdala connectivity with other social and affective regions. OXTR studies identified three polymorphisms (rs2254298, rs2268498, rs53576) having allele- and sex-dependent effects on prefrontal functional connectivity, and additive effects of OXTR risk alleles on reward circuitry. Age, sex, early life stress, and psychopathology emerged as potential moderators of both IN-OT and OXTR effects.
DISCUSSION: IN-OT appears to modulate resting state functional connectivity in a manner similar to its effects on task fMRI, consistent with hypothesized models of IN-OT. However, conclusions are limited by the narrow range of neuroanatomical seed regions, and methodological and experimental design heterogeneity. Future studies should take into account individual differences. Findings may provide insight into mechanisms through which IN-OT impacts human behavior.

PMID: 30243577 [PubMed - as supplied by publisher]

Altered attention networks and DMN in refractory epilepsy: A resting-state functional and causal connectivity study.

Sun, 09/23/2018 - 14:00
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Altered attention networks and DMN in refractory epilepsy: A resting-state functional and causal connectivity study.

Epilepsy Behav. 2018 Sep 19;88:81-86

Authors: Jiang LW, Qian RB, Fu XM, Zhang D, Peng N, Niu CS, Wang YH

Abstract
PURPOSE: Epilepsy is considered a disorder of neural networks. Patients diagnosed with refractory epilepsy frequently experience attention impairments. Seizure activity in epilepsy may disturb brain networks and damage the brain function of attention. The aims of this study were to assess functional and causal connectivities of the attention networks and default mode network using resting-state functional magnetic resonance imaging (fMRI).
METHOD: Resting-state fMRI data were gathered from 19 patients with refractory epilepsy (mixed localization and aetiologies) and 21 healthy people. The fMRI data were analyzed by group independent component analysis (ICA) fMRI toolbox to extract dorsal attention network (DAN), ventral attention network (VAN), and default mode network (DMN). The components of the selected networks were compared between patients and healthy controls to explore the change in functional connectivity (FC). Granger causality analysis was performed by taking the aforementioned significant brain areas as regions of interest (ROIs) to calculate autoregression coefficients of each pair of ROIs. Comparisons were done to find the significantly different causal connectivity when FC was changed between patients and healthy controls.
RESULTS: In DAN, the FC values of the bilateral frontal eye field (FEF) and left intraparietal sulcus (IPS) were decreased. In VAN, the FC values of the double-side ventral prefrontal cortex (vPFC) and the temporoparietal junction (TPJ) were reduced. As for DMN, the FC values of the bilateral medial prefrontal cortices (mPFC) were decreased whereas those for the bilateral precuneus (PCUN) were increased. Granger causal connectivity values were correlated: causal influence was decreased significantly from the left IPS (in DAN) to the double side of the vPFC but remained the same for the right FEF (in DAN) to the right TPJ. The value was decreased from the left PCUN (in DMN) to the right TPJ and FEF, and the causal flow from the right PCUN to the right TPJ and bilateral vPFC was also significantly inhibited (p < 0.05).
CONCLUSION: Frequent seizures in patients with refractory epilepsy may damage the cortex and disturb DAN, VAN, and DMN, leading to functional and causal connectivity alteration. In addition, epileptic activity may disrupt network interactions and further influence information communication.

PMID: 30243110 [PubMed - as supplied by publisher]

Abnormal changes in functional connectivity between the amygdala and frontal regions are associated with depression in Alzheimer's disease.

Sun, 09/23/2018 - 14:00
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Abnormal changes in functional connectivity between the amygdala and frontal regions are associated with depression in Alzheimer's disease.

Neuroradiology. 2018 Sep 21;:

Authors: Guo Z, Liu X, Xu S, Hou H, Chen X, Zhang Z, Chen W

Abstract
PURPOSE: The aim of the present study was to investigate the functional connectivity (FC) of Alzheimer's disease patients with depression (D-AD) based on an amygdalar seed using resting-state functional magnetic resonance imaging (rs-fMRI).
METHODS: Twenty-one non-depressed AD (nD-AD) patients and 21 D-AD patients underwent rs-fMRI. The Hamilton Depression Rating Scale and Neuropsychiatric Inventory were used to evaluate the severity of depression. The amygdala was used as the seed for FC analysis. The FC differences between the two groups were evaluated by two-sample t tests, and the correlation of FC changes with depressive severity was analyzed by Pearson correlational analysis.
RESULTS: Compared with the nD-AD patients, D-AD patients had increased FC values between the amygdala and orbitofrontal cortex and decreased FC values among the amygdala, medial prefrontal cortex, and inferior frontal gyrus.
CONCLUSION: These data suggest that abnormal amygdala-prefrontal FC may be an important characteristic of AD patients with depression.

PMID: 30242429 [PubMed - as supplied by publisher]

Disrupted asymmetry of inter- and intra-hemispheric functional connectivity in patients with drug-naive, first-episode schizophrenia and their unaffected siblings.

Sun, 09/23/2018 - 14:00
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Disrupted asymmetry of inter- and intra-hemispheric functional connectivity in patients with drug-naive, first-episode schizophrenia and their unaffected siblings.

EBioMedicine. 2018 Sep 18;:

Authors: Zhu F, Liu F, Guo W, Chen J, Su Q, Zhang Z, Li H, Fan X, Zhao J

Abstract
BACKGROUND: Lack of normal asymmetry in the brain has been reported in patients with schizophrenia. However, it remains unclear whether disrupted asymmetry originates from inter-hemispheric functional connectivity (FC) and/or intra-hemispheric FC in this patient population.
METHODS: Forty-four patients with drug-naive, first-episode schizophrenia, 42 unaffected siblings, and 44 healthy controls underwent resting-state functional magnetic resonance imaging (fMRI) scan. The parameter of asymmetry (PAS) and support vector machine (SVM) were used to analyze the data. Patients were treated with olanzapine for 8 weeks.
FINDINGS: Compared with healthy controls, patients showed lower PAS scores in the left middle temporal gyrus (MTG)/inferior temporal gyrus (ITG), left posterior cingulate cortex (PCC)/precuneus and left angular gyrus, and higher PAS scores in the left precentral gyrus/postcentral gyrus. Unaffected siblings also showed lower PAS scores in the left MTG/ITG and left PCC/precuneus relative to healthy controls. Further, SVM analysis showed that a combination of the PAS scores in these two clusters in patients at baseline was able to predict clinical response after 8 weeks of olanzapine treatment with 77.27% sensitivity, 72.73% specificity, and 75.00% accuracy.
INTERPRETATION: The present study suggests disrupted asymmetry of inter- and intra-hemispheric FC in drug-naive, first-episode schizophrenia; in addition, a reduced asymmetry of inter-hemispheric FC in the left MTG/ITG and left PCC/precuneus may serve as an endophenotype for schizophrenia, and may have clinical utility to predict response to olanzapine treatment. FUND: The National Key R&D Program of China and the National Natural Science Foundation of China.

PMID: 30241918 [PubMed - as supplied by publisher]

Improved Detection of Pelvic Organ Prolapse: Comparative Utility of Defecography Phase Sequence to Nondefecography Valsalva Maneuvers in Dynamic Pelvic Floor Magnetic Resonance Imaging.

Sun, 09/23/2018 - 14:00
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Improved Detection of Pelvic Organ Prolapse: Comparative Utility of Defecography Phase Sequence to Nondefecography Valsalva Maneuvers in Dynamic Pelvic Floor Magnetic Resonance Imaging.

Curr Probl Diagn Radiol. 2018 Aug 23;:

Authors: Arif-Tiwari H, Twiss CO, Lin FC, Funk JT, Vedantham S, Martin DR, Kalb BT

Abstract
PURPOSE: To evaluate the utility of a defecography phase (DP) sequence in dynamic pelvic floor MRI (DPMRI), in comparison to DPMRI utilizing only non-defecography Valsalva maneuvers (VM).
MATERIALS AND METHODS: Inclusion criteria identified 237 female patients with symptoms and/or physical exam findings of pelvic floor prolapse. All DPMRI exams were obtained following insertion of ultrasound gel into the rectum and vagina. Steady-state free-precession sequences in sagittal plane were acquired in the resting state, followed by dynamic cine acquisitions during VM and DP. In all phases, two experienced radiologists performed blinded review using the H-line, M-line, Organ prolapse (HMO) system. The presence of a rectocele, enterocele and inferior descent of the anorectal junction, bladder base, and vaginal vault were recorded in all patients using the pubococcygeal line as a fixed landmark.
RESULTS: DPMRI with DP detected significantly more number of patients than VM (p<0.0001) with vaginal prolapse (231/237, 97.5% vs. 177/237, 74.7%), anorectal prolapse (227/237, 95.8% vs. 197/237, 83.1%), cystocele (197/237, 83.1% vs. 108/237, 45.6%), and rectocele (154/237, 65% vs. 93/237, 39.2%). The median cycstocele (3.2cm vs. 1cm), vaginal prolapse (3cm vs. 1.5cm), anorectal prolapse (5.4cm vs. 4.2cm), H-line (8cm vs. 7.2cm) and M-line (5.3cm vs. 3.9cm) were significantly higher with DP than VM (p<0.0001).
CONCLUSIONS: Addition of DP to DPMRI demonstrates a greater degree of pelvic floor instability as compared to imaging performed during VM alone. Pelvic floor structures may show mild descent or appear normal during VM, with marked prolapse on subsequent DP images.

PMID: 30241870 [PubMed - as supplied by publisher]

Education, and the balance between dynamic and stationary functional connectivity jointly support executive functions in relapsing-remitting multiple sclerosis.

Sat, 09/22/2018 - 19:20
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Education, and the balance between dynamic and stationary functional connectivity jointly support executive functions in relapsing-remitting multiple sclerosis.

Hum Brain Mapp. 2018 Sep 21;:

Authors: Lin SJ, Vavasour I, Kosaka B, Li DKB, Traboulsee A, MacKay A, McKeown MJ

Abstract
Graphical network characteristics and nonstationary functional connectivity features, both derived from resting-state functional magnetic resonance imaging (rsfMRI) data, have been associated with cognitive performance in healthy subjects. How these features jointly relate to cognition in diseased states has not been investigated. In this study, 46 relapsing-remitting multiple sclerosis subjects underwent rsfMRI scans and a focused cognitive battery. With a sliding window approach, we examined six dynamic network features that indicated how connectivity changed over time as well as six measures derived from graph theory to reflect static network characteristics. Multiset canonical correlation analysis (MCCA) was then carried out to investigate the relations between dynamic network features, stationary network characteristics, cognitive testing, demographic, disease severity, and mood. Multiple sclerosis (MS) subjects demonstrated weaker connectivity strength, decreased network density, reduced global changes, but increased changes in interhemispheric connectivity compared to controls. The MCCA model determined that executive functions and processing speed ability measured by Wechsler Adult Intelligence Scale IV (WAIS-IV) Working Memory Index, WAIS-IV Processing Speed Index, and the Verbal Fluency Test were positively correlated with education, dynamic connectivity, and static connectivity strength; while poor task switching was correlated with disease severity, psychiatric comorbidities such as depression, anxiety, and fatigue, and static network density. Taken together, our results suggest that better executive functioning in MS requires maintenance of a continued coordination between stationary and dynamic functional connectivity as well as the support of education, and dynamic functional connectivity may provide an additional cognitive biomarker of disease severity in the MS population.

PMID: 30240533 [PubMed - as supplied by publisher]

Functional plasticity of the dorsomedial prefrontal cortex in depression reorganized by electroconvulsive therapy: Validation in two independent samples.

Sat, 09/22/2018 - 19:20
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Functional plasticity of the dorsomedial prefrontal cortex in depression reorganized by electroconvulsive therapy: Validation in two independent samples.

Hum Brain Mapp. 2018 Sep 21;:

Authors: Bai T, Wei Q, Zu M, Xie W, Wang J, Gong-Jun J, Yu F, Tian Y, Wang K

Abstract
Previous studies have implied a key role for the prefrontal cortex in the antidepressive effect of electroconvulsive therapy (ECT). However, there is still ubiquitous inconsistency across these studies, partly due to several confounding effects induced by the use of different samples. Studies with independent samples are necessary for validations to minimize confounding effects. In the current study, resting-state magnetic resonance imaging of 84 participants was collected using two scanners and two types of scanning parameters. One sample consisted of 28 patients and 23 healthy controls, and the other sample consisted of 33 patients. The local activity (indexed by the amplitude of low-frequency fluctuations) and functional connectivity were used to examine functional plasticity in the two independent samples before and after ECT. Both samples showed increased local activity of the dorsomedial prefrontal cortex (DMPFC) and enhanced connectivity of the DMPFC with the posterior cingulate cortex (PCC) following ECT. The enhanced connectivity between the DMPFC and PCC was positively associated with clinical improvement for both samples. These findings provide relatively strong evidence to support the functional plasticity of the dorsomedial prefrontal cortex and reorganization by ECT. The functional plasticity of the DMPFC-PCC may underlie the antidepressive effect of ECT.

PMID: 30240504 [PubMed - as supplied by publisher]

Frequency-specific age-related decreased brain network diversity in cognitively healthy elderly: A whole-brain data-driven analysis.

Sat, 09/22/2018 - 19:20
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Frequency-specific age-related decreased brain network diversity in cognitively healthy elderly: A whole-brain data-driven analysis.

Hum Brain Mapp. 2018 Sep 21;:

Authors: Lou W, Wang D, Wong A, Chu WCW, Mok VCT, Shi L

Abstract
Age-related changes in functional brain network have been well documented. However, recent studies have suggested the nonstationary properties of the functional connectivity of the brain, and little is known about the changes of functional connectivity dynamics during aging. In this study, a two-step singular value decomposition was introduced to capture the dynamic patterns of the time-varying functional connectivity in different frequency intervals, and the whole-brain and regional brain diversity were quantified by using Shannon entropy. The relationships between age and functional connectivity dynamics were investigated in a relatively large sample cohort of cognitively healthy elderly (N = 188, ages 65-80). The results showed an age-related decreased diversity in the whole brain as well as in the right inferior frontal gyrus, right amygdala, right hippocampus, left parahippocampal, and left inferior parietal gyrus in the frequency interval of 0.06-0.12 Hz. In addition, the whole-brain diversity during resting state could also reflect the general mental flexibility. This study provided the first evidence of frequency-specific age effects on the functional connectivity dynamics in cognitively healthy elderly, and may shed new light on the dynamic functional connectivity analysis of aging and neurodegenerative diseases.

PMID: 30240493 [PubMed - as supplied by publisher]

Characterization of relapsing-remitting multiple sclerosis patients using support vector machine classifications of functional and diffusion MRI data.

Sat, 09/22/2018 - 19:20
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Characterization of relapsing-remitting multiple sclerosis patients using support vector machine classifications of functional and diffusion MRI data.

Neuroimage Clin. 2018 Sep 04;20:724-730

Authors: Zurita M, Montalba C, Labbé T, Cruz JP, Dalboni da Rocha J, Tejos C, Ciampi E, Cárcamo C, Sitaram R, Uribe S

Abstract
Multiple Sclerosis patients' clinical symptoms do not correlate strongly with structural assessment done with traditional magnetic resonance images. However, its diagnosis and evaluation of the disease's progression are based on a combination of this imaging analysis complemented with clinical examination. Therefore, other biomarkers are necessary to better understand the disease. In this paper, we capitalize on machine learning techniques to classify relapsing-remitting multiple sclerosis patients and healthy volunteers based on machine learning techniques, and to identify relevant brain areas and connectivity measures for characterizing patients. To this end, we acquired magnetic resonance imaging data from relapsing-remitting multiple sclerosis patients and healthy subjects. Fractional anisotropy maps, structural and functional connectivity were extracted from the scans. Each of them were used as separate input features to construct support vector machine classifiers. A fourth input feature was created by combining structural and functional connectivity. Patients were divided in two groups according to their degree of disability and, together with the control group, three group pairs were formed for comparison. Twelve separate classifiers were built from the combination of these four input features and three group pairs. The classifiers were able to distinguish between patients and healthy subjects, reaching accuracy levels as high as 89% ± 2%. In contrast, the performance was noticeably lower when comparing the two groups of patients with different levels of disability, reaching levels below 63% ± 5%. The brain regions that contributed the most to the classification were the right occipital, left frontal orbital, medial frontal cortices and lingual gyrus. The developed classifiers based on MRI data were able to distinguish multiple sclerosis patients and healthy subjects reliably. Moreover, the resulting classification models identified brain regions, and functional and structural connections relevant for better understanding of the disease.

PMID: 30238916 [PubMed - as supplied by publisher]

Ketamine influences the locus coeruleus norepinephrine network, with a dependency on norepinephrine transporter genotype - a placebo controlled fMRI study.

Sat, 09/22/2018 - 19:20
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Ketamine influences the locus coeruleus norepinephrine network, with a dependency on norepinephrine transporter genotype - a placebo controlled fMRI study.

Neuroimage Clin. 2018 Sep 04;20:715-723

Authors: Liebe T, Li M, Colic L, Munk MHJ, Sweeney-Reed CM, Woelfer M, Kretzschmar MA, Steiner J, von Düring F, Behnisch G, Schott BH, Walter M

Abstract
BACKGROUND: Ketamine is receiving increasing attention as a rapid-onset antidepressant in patients suffering from major depressive disorder (MDD) with treatment resistance or severe suicidal ideation. Ketamine modulates several neurotransmitter systems, including norepinephrine via the norepinephrine transporter (NET), both peripherally and centrally. The locus coeruleus (LC), which has high NET concentration, has been attributed to brain networks involved in depression. Thus we investigated the effects of single-dose of racemic ketamine on the LC using resting state functional MRI.
METHODS: Fifty-nine healthy participants (mean age 25.57 ± 4.72) were examined in a double-blind, randomized, placebo-controlled study with 7 Tesla MRI. We investigated the resting state functional connectivity (rs-fc) of the LC before and one hour after subanesthetic ketamine injection (0.5 mg/kg), as well as associations between its rs-fc and a common polymorphism in the NET gene (rs28386840).
RESULTS: A significant interaction of drug and time was revealed, and post hoc testing showed decreased rs-fc between LC and the thalamus after ketamine administration compared with baseline levels, including the mediodorsal, ventral anterior, ventral lateral, ventral posterolateral and centromedian nuclei. The rs-fc reduction was more pronounced in NET rs28386840 [AA] homozygous subjects than in [T] carriers.
CONCLUSIONS: We demonstrated acute rs-fc changes after ketamine administration in the central node of the norepinephrine pathway. These findings may contribute to understanding the antidepressant effect of ketamine at the system level, supporting modes of action on networks subserving aberrant arousal regulation in depression.

PMID: 30238915 [PubMed - as supplied by publisher]

Resting-State fMRI Dynamics and Null Models: Perspectives, Sampling Variability, and Simulations.

Sat, 09/22/2018 - 19:20
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Resting-State fMRI Dynamics and Null Models: Perspectives, Sampling Variability, and Simulations.

Front Neurosci. 2018;12:551

Authors: Miller RL, Abrol A, Adali T, Levin-Schwarz Y, Calhoun VD

Abstract
Studies of resting state functional MRI (rs-fRMI) are increasingly focused on "dynamics", or on those properties of brain activation that manifest and vary on timescales shorter than the scan's full duration. This shift in focus has led to a flurry of interest in developing hypothesis testing frameworks and null models applicable to the dynamical setting. Thus far however, these efforts have been weakened by a number of crucial shortcomings that are outlined and discussed in this article. We focus here on aspects of recently proposed null models that, we argue, are poorly formulated relative to the hypotheses they are designed to test, i.e., their potential role in separating functionally relevant BOLD signal dynamics from noise or intermittent background and maintenance type processes is limited by factors that are fundamental rather than merely quantitative or parametric. In this short position paper, we emphasize that (1) serious care must be exercised in building null models for rs-fMRI dynamics from distributionally stationary univariate or multivariate timeseries, i.e., timeseries whose values are each independently drawn from one pre-specified probability distribution; and (2) measures such as kurtosis that quantify over-concentration of observed values in the far tails of some reference distribution may not be particularly suitable for capturing signal features most plausibly contributing to functionally relevant brain dynamics. Other metrics targeted, for example, at capturing the type of epochal signal variation that is often viewed as a signature of brain responsiveness to stimuli or experimental tasks, could play a more scientifically clarifying role. As we learn more about the phenomenon of functionally relevant brain dynamics and its imaging correlates, scientifically meaningful null hypotheses and well-tuned null models will naturally emerge. We also revisit the important concept of distributional stationarity, discuss how it manifests within realizations vs. across multiple realizations, and provide guidance on the benefits and limitations of employing this type of stationarity in modeling the absence of functionally relevant temporal dynamics in resting state fMRI. We hope that the discussions herein are useful, and promote thoughtful consideration of these important issues.

PMID: 30237758 [PubMed]

In vivo mapping of brainstem nuclei functional connectivity disruption in Alzheimer's disease.

Sat, 09/22/2018 - 19:20
Related Articles

In vivo mapping of brainstem nuclei functional connectivity disruption in Alzheimer's disease.

Neurobiol Aging. 2018 Aug 23;72:72-82

Authors: Serra L, D'Amelio M, Di Domenico C, Dipasquale O, Marra C, Mercuri NB, Caltagirone C, Cercignani M, Bozzali M

Abstract
We assessed here functional connectivity changes in the locus coeruleus (LC) and ventral tegmental area (VTA) of patients with Alzheimer's disease (AD). We recruited 169 patients with either AD or amnestic mild cognitive impairment due to AD and 37 elderly controls who underwent cognitive and neuropsychiatric assessments and resting-state functional magnetic resonance imaging at 3T. Connectivity was assessed between LC and VTA and the rest of the brain. In amnestic mild cognitive impairment patients, VTA disconnection was predominant with parietal regions, while in AD patients, it involved the posterior nodes of the default-mode network. We also looked at the association between neuropsychiatric symptoms (assessed by the neuropsychiatric inventory) and VTA connectivity. Symptoms such as agitation, irritability, and disinhibition were associated with VTA connectivity with the parahippocampal gyrus and cerebellar vermis, while sleep and eating disorders were associated with VTA connectivity to the striatum and the insular cortex. This suggests a contribution of VTA degeneration to AD pathophysiology and to the occurrence of neuropsychiatric symptoms. We did not find evidence of LC disconnection, but this could be explained by the size of this nucleus, which makes it difficult to isolate. These results are consistent with animal findings and have potential implications for AD prognosis and therapies.

PMID: 30237073 [PubMed - as supplied by publisher]

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