New resting-state fMRI related studies at PubMed

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Abnormal resting-state functional network centrality in patients with high myopia: evidence from a voxel-wise degree centrality analysis.

Tue, 11/20/2018 - 17:20
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Abnormal resting-state functional network centrality in patients with high myopia: evidence from a voxel-wise degree centrality analysis.

Int J Ophthalmol. 2018;11(11):1814-1820

Authors: Hu YX, He JR, Yang B, Huang X, Li YP, Zhou FQ, Xu XX, Zhong YL, Wang J, Wu XR

Abstract
AIM: To investigate the functional networks underlying the brain-activity changes of patients with high myopia using the voxel-wise degree centrality (DC) method.
METHODS: In total, 38 patients with high myopia (HM) (17 males and 21 females), whose binocular refractive diopter were -6.00 to -7.00 D, and 38 healthy controls (17 males and 21 females), closely matched in age, sex, and education levels, participated in the study. Spontaneous brain activities were evaluated using the voxel-wise DC method. The receiver operating characteristic curve was measured to distinguish patients with HM from healthy controls. Correlation analysis was used to explore the relationship between the observed mean DC values of the different brain areas and the behavioral performance.
RESULTS: Compared with healthy controls, HM patients had significantly decreased DC values in the right inferior frontal gyrus/insula, right middle frontal gyrus, and right supramarginal/inferior parietal lobule (P<0.05). In contrast, HM patients had significantly increased DC values in the right cerebellum posterior lobe, left precentral gyrus/postcentral gyrus, and right middle cingulate gyrus (P<0.05). However, no relationship was found between the observed mean DC values of the different brain areas and the behavioral performance (P>0.05).
CONCLUSION: HM is associated with abnormalities in many brain regions, which may indicate the neural mechanisms of HM. The altered DC values may be used as a useful biomarker for the brain activity changes in HM patients.

PMID: 30450313 [PubMed]

Recursive Partitioning Analysis of Fractional Low-Frequency Fluctuations in Narcolepsy With Cataplexy.

Tue, 11/20/2018 - 17:20
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Recursive Partitioning Analysis of Fractional Low-Frequency Fluctuations in Narcolepsy With Cataplexy.

Front Neurol. 2018;9:936

Authors: Fulong X, Chao L, Dianjiang Z, Qihong Z, Wei Z, Jun Z, Fang H

Abstract
Objective: To identify narcolepsy related regional brain activity alterations compared with matched healthy controls. To determine whether these changes can be used to distinguish narcolepsy from healthy controls by recursive partitioning analysis (RPA) and receiver operating characteristic (ROC) curve analysis. Method: Fifty-one narcolepsy with cataplexy patients (26 adults and 25 juveniles) and sixty matched heathy controls (30 adults and 30 juveniles) were recruited. All subjects underwent a resting-state functional magnetic resonance imaging scan. Fractional low-frequency fluctuations (fALFF) was used to investigate narcolepsy induced regional brain activity alterations among adult and juveniles, respectively. Recursive partitioning analysis and Receiver operating curve analysis was used to seek the ability of fALFF values within brain regions in distinguishing narcolepsy from healthy controls. Results: Compared with healthy controls, both adult and juvenile narcolepsy had lower fALFF values in bilateral medial superior frontal gyrus, bilateral inferior parietal lobule and supra-marginal gyrus. Compared with healthy controls, both adult and juvenile narcolepsy had higher fALFF values in bilateral sensorimotor cortex and middle temporal gyrus. Also juvenile narcolepsy had higher fALFF in right putamen and right thalamus compared with healthy controls. Based on RPA and ROC curve analysis, in adult participants, fALFF differences in right medial superior frontal gyrus can discriminate narcolepsy from healthy controls with high degree of sensitivity (100%) and specificity (88.9%). In juvenile participants, fALFF differences in left superior frontal gyrus can discriminate narcolepsy from healthy controls with moderate degree of sensitivity (57.1%) and specificity (88.9%). Conclusion: Compared with healthy controls, both the adult and juvenile narcolepsy showed overlap brain regions in fALFF differences after case-control comparison. Furthermore, we propose that fALFF value can be a helpful imaging biomarker in distinguishing narcolepsy from healthy controls among both adults and juveniles.

PMID: 30450078 [PubMed]

Abnormal Global Brain Functional Connectivity in Primary Insomnia Patients: A Resting-State Functional MRI Study.

Tue, 11/20/2018 - 17:20
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Abnormal Global Brain Functional Connectivity in Primary Insomnia Patients: A Resting-State Functional MRI Study.

Front Neurol. 2018;9:856

Authors: Yan CQ, Wang X, Huo JW, Zhou P, Li JL, Wang ZY, Zhang J, Fu QN, Wang XR, Liu CZ, Liu QQ

Abstract
Background: Resting-state functional magnetic resonance imaging (fMRI) studies have uncovered the disruptions of functional brain networks in primary insomnia (PI) patients. However, the etiology and pathogenesis underlying this disorder remains ambiguous, and the insomnia related symptoms are influenced by a complex network organization in the brain. The purpose of this study was to explore the abnormal intrinsic functional hubs in PI patients using a voxel-wise degree centrality (DC) analysis and seed-based functional connectivity (FC) approach. Methods: A total of 26 PI patients and 28 healthy controls were enrolled, and they underwent resting-state fMRI. Degree centrality was measured across the whole brain, and group differences in DC were compared. The peak points, which significantly altered DC between the two groups, were defined as the seed regions and were further used to calculate FC of the whole brain. Later, correlation analyses were performed between the changes in brain function and clinical features. Results: Primary insomnia patients showed DC values lower than healthy controls in the left inferior frontal gyrus (IFG) and middle temporal gyrus (MTG) and showed a higher DC value in the right precuneus. The seed-based analyses demonstrated decreased FC between the left MTG and the left posterior cingulate cortex (PCC), and decreased FC was observed between the right precuneus and the right lateral occipital cortex. Reduced DC in the left IFG and decreased FC in the left PCC were positively correlated with the Pittsburgh sleep quality index and the insomnia severity index. Conclusions: This study revealed that PI patients exhibited abnormal intrinsic functional hubs in the left IFG, MTG, and the right precuneus, as well as abnormal seed-based FC in these hubs. These results contribute to better understanding of how brain function influences the symptoms of PI.

PMID: 30450072 [PubMed]

Altered Brain Fraction Amplitude of Low Frequency Fluctuation at Resting State in Patients With Early Left and Right Bell's Palsy: Do They Have Differences?

Tue, 11/20/2018 - 17:20
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Altered Brain Fraction Amplitude of Low Frequency Fluctuation at Resting State in Patients With Early Left and Right Bell's Palsy: Do They Have Differences?

Front Neurosci. 2018;12:797

Authors: Han X, Li H, Wang X, Zhu Y, Song T, Du L, Sun S, Guo R, Liu J, Shi S, Fu C, Gao W, Zhang L, Ma G

Abstract
Purpose: Bell's palsy refers to acute idiopathic unilateral facial nerve palsy. It is a common disorder of the main motor pathway to the facial muscles. This study aimed to investigate the abnormal fraction amplitude of low frequency fluctuation (fALFF) of the brain in patients with early left and right Bell's palsy. Materials and Methods: Sixty-seven patients (left 33, right 34) and 37 age- and sex-matched healthy controls underwent resting-state functional magnetic resonance imaging (R-fMRI) examination. The fALFF values were measured from all subjects and were compared among the left palsy, right palsy, and control groups. Then, correlations between the Toronto Facial Grading System (TFGS) scores of the patients and the fALFF values of abnormal brain regions were analyzed. Results: Significant group differences in fALFF values among the three groups were observed mainly in the cerebral cortical, subcortical, and deep gray matter regions. Compared with the right Bell's palsy group, the left Bell's palsy group showed significantly decreased fALFF values in the left temporal pole of the superior temporal gyrus (TPOsup), right supramarginal, left and right middle cingulate cortex (MCC), left superior frontal gyrus (SFG), and left precentral gyrus (PreCG), and increased fALFF values were observed in the right SFG and PreCG. Furthermore, altered fALFF values correlated positively with the TFGS scores in the left superior TPO, bilateral MCC, and right PreCG, and correlated negatively with the TFGS scores in the right SFG of the left Bell's palsy group. Altered fALFF values correlated positively with the TFGS scores in the bilateral MCC and right PreCG and correlated negatively with the TFGS scores in the left superior TPO and SFG of the right Bell's palsy group. Conclusion: Regulatory mechanisms seem to differ between patients with left and right early Bell's palsy. The severity of the disease is associated with these functional alterations.

PMID: 30450029 [PubMed]

Regional Prefrontal Resting-State Functional Connectivity in Posttraumatic Stress Disorder.

Tue, 11/20/2018 - 17:20
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Regional Prefrontal Resting-State Functional Connectivity in Posttraumatic Stress Disorder.

Biol Psychiatry Cogn Neurosci Neuroimaging. 2018 Oct 04;:

Authors: Olson EA, Kaiser RH, Pizzagalli DA, Rauch SL, Rosso IM

Abstract
BACKGROUND: Prefrontal subregions, including the ventromedial prefrontal cortex (PFC), dorsomedial PFC, and dorsolateral PFC (DLPFC), are differentially implicated in the pathophysiology of posttraumatic stress disorder (PTSD), though few existing studies have examined subregional differences in resting-state functional connectivity (rsFC). We hypothesized that PTSD would involve weaker positive rsFC between ventromedial PFC, dorsomedial PFC, and other default mode network regions and increased negative rsFC between DLPFC and posterior default mode network regions. Additionally, we hypothesized that prefrontal regions exhibiting group differences in rsFC would be characterized by alterations in cortical thickness.
METHODS: Participants included 36 healthy control subjects, 30 trauma-exposed control subjects, and 21 individuals with current DSM-IV PTSD resulting from community-acquired trauma. Participants completed the Clinician Administered PTSD Scale, questionnaires (Childhood Trauma Questionnaire, Adverse Childhood Events, Life Events Checklist, Beck Depression Inventory), structural neuroimaging, and resting-state functional magnetic resonance imaging. rsFC of DLPFC, ventromedial PFC, and dorsomedial PFC seeds was evaluated in SPM12 and CONN. Cortical thickness for regions with significant rsFC findings was assessed using FreeSurfer.
RESULTS: Relative to both healthy control and trauma-exposed control subjects, individuals with PTSD showed increased negative rsFC between the DLPFC and a region of precuneus. This finding was associated with increased overall symptom severity but not with trauma load or childhood trauma exposure. Greater negative DLPFC-precuneus connectivity was associated with greater bilateral precuneus thickness.
CONCLUSIONS: Given participation of precuneus subregions in the central executive network, increased anticorrelation between right DLPFC and precuneus in this sample may reflect increased opposition between anterior and posterior central executive network hubs in PTSD.

PMID: 30449518 [PubMed - as supplied by publisher]

Disturbed effective connectivity patterns in an intrinsic triple network model are associated with posttraumatic stress disorder.

Mon, 11/19/2018 - 16:00
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Disturbed effective connectivity patterns in an intrinsic triple network model are associated with posttraumatic stress disorder.

Neurol Sci. 2018 Nov 17;:

Authors: Weng Y, Qi R, Zhang L, Luo Y, Ke J, Xu Q, Zhong Y, Li J, Chen F, Cao Z, Lu G

Abstract
BACKGROUND: Disturbance of the triple network model was recently proposed to be associated with the occurrence of posttraumatic stress disorder (PTSD) symptoms. Based on resting-state dynamic causal modeling (rs-DCM) analysis, we investigated the neurobiological model at a neuronal level along with potential neuroimaging biomarkers for identifying individuals with PTSD.
METHODS: We recruited survivors of a devastating typhoon including 27 PTSD patients, 33 trauma-exposed controls (TECs), and 30 healthy controls without trauma exposure. All subjects underwent resting-state functional magnetic resonance imaging. Independent components analysis was used to identify triple networks. Detailed effective connectivity patterns were estimated by rs-DCM analysis. Spearman correlation analysis was performed on aberrant DCM parameters with clinical assessment results relevant to PTSD diagnosis. We also carried out step-wise binary logistic regression and receiver operating characteristic curve (ROC) analysis to confirm the capacity of altered effective connectivity parameters to distinguish PTSD patients.
RESULTS: Within the executive control network, enhanced positive connectivity from the left posterior parietal cortex to the left dorsolateral prefrontal cortex was correlated with intrusion symptoms and showed good performance (area under the receiver operating characteristic curve = 0.879) in detecting PTSD patients. In the salience network, we observed a decreased causal flow from the right amygdala to the right insula and a lower transit value for the right amygdala in PTSD patients relative to TECs.
CONCLUSION: Altered effective connectivity patterns in the triple network may reflect the occurrence of PTSD symptoms, providing a potential biomarker for detecting patients. Our findings shed new insight into the neural pathophysiology of PTSD.

PMID: 30448966 [PubMed - as supplied by publisher]

resting state fMRI; +18 new citations

Sun, 11/18/2018 - 14:27

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resting state fMRI

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Longitudinal decreases in suicidal ideation are associated with increases in salience network coherence in depressed adolescents.

Fri, 11/16/2018 - 12:20

Longitudinal decreases in suicidal ideation are associated with increases in salience network coherence in depressed adolescents.

J Affect Disord. 2018 Nov 03;245:545-552

Authors: Schwartz J, Ordaz SJ, Ho TC, Gotlib IH

Abstract
BACKGROUND: Suicidal ideation (SI) is an important predictor of suicide attempt, yet SI is difficult to predict. Given that SI begins in adolescence when brain networks are maturing, it is important to understand associations between network functioning and changes in severity of SI.
METHODS: Thirty-three depressed adolescents were administered the Columbia-Suicide Severity Rating Scale to assess SI and completed resting-state fMRI at baseline (T1) and 6 months later (T2). We computed coherence in the executive control (ECN), default mode (DMN), salience (SN), and non-relevant noise networks and then examined the association between changes in brain network coherence and changes in SI severity from T1 to T2.
RESULTS: A greater reduction in severity of SI was associated with a stronger increase in SN coherence from T1 to T2. There were no associations between the other networks and SI.
LIMITATIONS: We cannot generalize our findings to more psychiatrically diverse samples. More time-points are necessary to understand the trajectory of SI and SN coherence change.
CONCLUSIONS: Our finding that reductions in SI are associated with increases in SN coherence extends previous cross-sectional results documenting a negative association between SI severity and SN coherence. The SN is involved in coordinating activation of ECN and DMN in response to salient information. Given this regulatory role of the SN, the association between SN coherence and SI suggests that adolescents with reduced SN coherence might more easily engage in harmful thoughts. Thus, the SN may be particularly relevant as a target for treatment applications in depressed adolescents.

PMID: 30439679 [PubMed - as supplied by publisher]

Image-guided phenotyping of ovariectomized mice: altered functional connectivity, cognition, myelination, and dopaminergic functionality.

Fri, 11/16/2018 - 12:20

Image-guided phenotyping of ovariectomized mice: altered functional connectivity, cognition, myelination, and dopaminergic functionality.

Neurobiol Aging. 2018 Oct 17;74:77-89

Authors: Anckaerts C, van Gastel J, Leysen V, Hinz R, Azmi A, Simoens P, Shah D, Kara F, Langbeen A, Bols P, Laloux C, Prevot V, Verhoye M, Maudsley S, Van der Linden A

Abstract
A large proportion of the population suffers from endocrine disruption, e.g., menopausal women, which might result in accelerated aging and a higher risk for developing cognitive disorders. Therefore, it is crucial to fully understand the impact of such disruptions on the brain to identify potential therapeutic strategies. Here, we show using resting-state functional magnetic resonance imaging that ovariectomy and consequent hypothalamus-pituitary-gonadal disruption result in the selective dysconnectivity of 2 discrete brain regions in mice. This effect coincided with cognitive deficits and an underlying pathological molecular phenotype involving an imbalance of neurodevelopmental/neurodegenerative signaling. Furthermore, this quantitative mass spectrometry proteomics-based analysis of molecular signaling patterns further identified a strong involvement of altered dopaminergic functionality (e.g., DAT and predicted upstream regulators DRD3, NR4A2), reproductive signaling (e.g., Srd5a2), rotatin expression (rttn), cellular aging (e.g., Rxfp3, Git2), myelination, and axogenesis (e.g., Nefl, Mag). With this, we have provided an improved understanding of the impact of hypothalamus-pituitary-gonadal dysfunction and highlighted the potential of using a highly translational magnetic resonance imaging technique for monitoring these effects on the brain.

PMID: 30439596 [PubMed - as supplied by publisher]

Altered baseline activity and connectivity associated with cognitive impairment following acute cerebellar infarction: A resting-state fMRI study.

Fri, 11/16/2018 - 12:20

Altered baseline activity and connectivity associated with cognitive impairment following acute cerebellar infarction: A resting-state fMRI study.

Neurosci Lett. 2018 Nov 12;:

Authors: Fan L, Hu J, Ma W, Wang D, Yao Q, Shi J

Abstract
The aims of this study were to investigated the changes of brain function and cognitive function in patients with acute posterior cerebellar infarction using the functional magnetic resonance imaging (fMRI) tecniques: fractional amplitude of low-frequency fluctuation (fALFF) and functional connectivity (FC). Forty acute cerebellar infarction patients and 40 healthy controls were included. The differences of fALFF were compared. The regions showed significant differences were set as regions of interest (ROIs), and then the FC values between ROIs and the whole brain were analysed. Pearson correlation analysis was used to understand the correlation between FC values and cognitive function scores. The results showed significant group differences in fALFF values in the four brain regions, including the right frontal lobe, left hippocampus, right cingulate gyrus and cerebellum posterior lobe. Pearson correlation analysis suggested that abnormal alterations in the left hippocampus and right cingulate gyrus may play a core role in the cognitive impairment associated with cerebellar infarction. The changes of fALFF and FC values in related brain area from cerebellar stroke complement and enrich our understanding of cerebellar involvement in cognition involved in cognitive performance.

PMID: 30439397 [PubMed - as supplied by publisher]

Beware detrending: Optimal preprocessing pipeline for low-frequency fluctuation analysis.

Fri, 11/16/2018 - 12:20
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Beware detrending: Optimal preprocessing pipeline for low-frequency fluctuation analysis.

Hum Brain Mapp. 2018 Nov 15;:

Authors: Woletz M, Hoffmann A, Tik M, Sladky R, Lanzenberger R, Robinson S, Windischberger C

Abstract
Resting-state functional magnetic resonance imaging (rs-fMRI) offers the possibility to assess brain function independent of explicit tasks and individual performance. This absence of explicit stimuli in rs-fMRI makes analyses more susceptible to nonneural signal fluctuations than task-based fMRI. Data preprocessing is a critical procedure to minimise contamination by artefacts related to motion and physiology. We herein investigate the effects of different preprocessing strategies on the amplitude of low-frequency fluctuations (ALFFs) and its fractional counterpart, fractional ALFF (fALFF). Sixteen artefact reduction schemes based on nuisance regression are applied to data from 82 subjects acquired at 1.5 T, 30 subjects at 3 T, and 23 subjects at 7 T, respectively. In addition, we examine test-retest variance and effects of bias correction. In total, 569 data sets are included in this study. Our results show that full artefact reduction reduced test-retest variance by up to 50%. Polynomial detrending of rs-fMRI data has a positive effect on group-level t-values for ALFF but, importantly, a negative effect for fALFF. We show that the normalisation process intrinsic to fALFF calculation causes the observed reduction and introduce a novel measure for low-frequency fluctuations denoted as high-frequency ALFF (hfALFF). We demonstrate that hfALFF values are not affected by the negative detrending effects seen in fALFF data. Still, highest grey matter (GM) group-level t-values were obtained for fALFF data without detrending, even when compared to an exploratory detrending approach based on autocorrelation measures. From our results, we recommend the use of full nuisance regression including polynomial detrending in ALFF data, but to refrain from using polynomial detrending in fALFF data. Such optimised preprocessing increases GM group-level t-values by up to 60%.

PMID: 30430691 [PubMed - as supplied by publisher]

Transcranial direct current stimulation reconstructs diminished thalamocortical connectivity during prolonged resting wakefulness: a resting-state fMRI pilot study.

Fri, 11/16/2018 - 12:20
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Transcranial direct current stimulation reconstructs diminished thalamocortical connectivity during prolonged resting wakefulness: a resting-state fMRI pilot study.

Brain Imaging Behav. 2018 Nov 14;:

Authors: Dalong G, Jiyuan L, Ying Z, Lei Z, Yanhong H, Yongcong S

Abstract
Reductions in the alertness and information processing capacity of individuals due to sleep deprivation (SD) were previously thought to be related to dysfunction of the thalamocortical network. Previous studies have shown that transcranial direct current stimulation (tDCS) can restore vigilance and information processing after SD. However, the underlying neural mechanisms of this phenomenon remain unclear. The purpose of this study was to investigate the neurocognitive mechanisms of tDCS following SD, by comparing changes in the brain network, especially the thalamocortical network, after tDCS and sham stimulation following 24 h of SD. Sixteen healthy volunteers were tested in a sham-controlled, randomized crossover design experiment. Resting-state functional magnetic resonance imaging was conducted during resting wakefulness and again after either active tDCS or sham stimulation to the right dorsolateral prefrontal cortex (1.0 mA, 20 min) immediately following 24 h of SD. Seed-based correlations and graph theory analysis were used to determine functional connectivity within the brain thalamocortical network. When tDCS was used, the functional connectivity of the thalamus with the temporal lobe and left caudate was higher than that when the sham stimulation was used. Analysis using graph theory showed that compared with sham stimulation, tDCS administration was associated with a significant improvement in not only the number of connections but also the global efficiency of the thalamus itself. Our study reveals a modulation of the activity of the intrinsic thalamus networks after tDCS. The effects may help explain earlier reports of improvements in the cognitive performance after anodal-tDCS.

PMID: 30430411 [PubMed - as supplied by publisher]

Homotopic Connectivity in Early Pontine Infarction Predicts Late Motor Recovery.

Fri, 11/16/2018 - 12:20
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Homotopic Connectivity in Early Pontine Infarction Predicts Late Motor Recovery.

Front Neurol. 2018;9:907

Authors: Shan Y, Wang YS, Zhang M, Rong DD, Zhao ZL, Cao YX, Wang PP, Deng ZZ, Ma QF, Li KC, Zuo XN, Lu J

Abstract
Connectivity-based methods are essential to explore brain reorganization after a stroke and to provide meaningful predictors for late motor recovery. We aim to investigate the homotopic connectivity alterations during a 180-day follow-up of patients with pontine infarction to find an early biomarker for late motor recovery prediction. In our study, resting-state functional MRI was performed in 15 patients (11 males, 4 females, age: 57.87 ± 6.50) with unilateral pontine infarction and impaired motor function during a period of 6 months (7, 14, 30, 90, and 180 days after stroke onset). Clinical neurological assessments were performed using the Fugl-Meyer scale (FM).15 matched healthy volunteers were also recruited. Whole-brain functional homotopy in each individual scan was measured by voxel-mirrored homotopic connectivity (VMHC) values. Group-level analysis was performed between stroke patients and normal controls. A Pearson correlation was performed to evaluate correlations between early VMHC and the subsequent 4 visits for behavioral measures during day 14 to day 180. We found in early stroke (within 7 days after onset), decreased VMHC was detected in the bilateral precentral and postcentral gyrus and precuneus/posterior cingulate cortex (PCC), while increased VMHC was found in the hippocampus/amygdala and frontal pole (P < 0.01). During follow-up, VMHC in the precentral and postcentral gyrus increased to the normal level from day 90, while VMHC in the precuneus/PCC presented decreased intensity during all time points (P < 0.05). The hippocampus/amygdala and frontal pole presented a higher level of VMHC during all time points (P < 0.05). Negative correlation was found between early VMHC in the hippocampus/amygdala with FM on day 14 (r = -0.59, p = 0.021), day 30 (r = -0.643, p = 0.01), day 90 (r = -0.693, p = 0.004), and day 180 (r = -0.668, p = 0.007). Furthermore, early VMHC in the frontal pole was negatively correlated with FM scores on day 30 (r = -0.662, p = 0.013), day 90 (r = -0.606, p = 0.017), and day 180 (r = -0.552, p = 0.033). Our study demonstrated the potential utility of early homotopic connectivity for prediction of late motor recovery in pontine infarction.

PMID: 30429821 [PubMed]

Primary Disruption of the Memory-Related Subsystems of the Default Mode Network in Alzheimer's Disease: Resting-State Functional Connectivity MRI Study.

Fri, 11/16/2018 - 12:20
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Primary Disruption of the Memory-Related Subsystems of the Default Mode Network in Alzheimer's Disease: Resting-State Functional Connectivity MRI Study.

Front Aging Neurosci. 2018;10:344

Authors: Qi H, Liu H, Hu H, He H, Zhao X

Abstract
Background: Recent studies have indicated that the default mode network (DMN) comprises at least three subsystems: The medial temporal lobe (MTL) and dorsal medial prefrontal cortex (DMPFC) subsystems and a core comprising the anterior MPFC (aMPFC) and posterior cingulate cortex (PCC). Additionally, the disruption of the DMN is related to Alzheimer's disease (AD). However, little is known regarding the changes in these subsystems in AD, a progressive disease characterized by memory impairment. Here, we performed a resting-state functional connectivity (FC) analysis to test our hypothesis that the memory-related MTL subsystem was predominantly disrupted in AD. Method: To reveal specific subsystem changes, we calculated the strength and number of FCS in the DMN intra- and inter-subsystems across individuals and compared the FC of the two groups. To further examine which pairs of brain regional functional connections contributed to the subsystem alterations, correlation coefficients between any two brain regions in the DMN were compared across groups. Additionally, to identify which regions made the strongest contributions to the subsystem changes, we calculated the regional FC strength (FCS), which was compared across groups. Results: For the intra-subsystem, decreased FC number and strength occurred in the MTL subsystem of AD patients but not in the DMPFC subsystem or core. For the inter-subsystems, the AD group showed decreased FCS and number between the MTL subsystem and PCC and a decreased number between the PCC and DMPFC subsystem. Decreased inter-regional FCS were found within the MTL subsystem in AD patients relative to controls: The posterior inferior parietal lobule (pIPL) showed decreased FC with the hippocampal formation (HF), parahippocampal cortex (PHC) and ventral MPFC (vMPFC). Decreased inter-regional FCS of the inter-subsystems were also found in AD patients: The HF and/or PHC showed decreased FC with dMPFC and TPJ, located in the DMPFC subsystem, and with PCC. AD patients also showed decreased FC between the PCC and TLC of the dMPFC subsystem. Furthermore, the HF and PHC in the MTL subsystem showed decreased regional FCS. Conclusion: Decreased intrinsic FC was mainly associated with the MTL subsystem of the AD group, suggesting that the MTL subsystem is predominantly disrupted.

PMID: 30429784 [PubMed]

Rehabilitation in chronic spatial neglect strengthens resting state connectivity.

Thu, 11/15/2018 - 11:20

Rehabilitation in chronic spatial neglect strengthens resting state connectivity.

Acta Neurol Scand. 2018 Nov 14;:

Authors: Wåhlin A, Fordell H, Ekman U, Lenfeldt N, Malm J

Abstract
OBJECTIVES: Rehabilitation of patients with chronic visuospatial neglect is underexplored, and little is known about neural mechanisms that can be exploited to promote recovery. In this study, we present data on resting state functional connectivity within the dorsal attention network (DAN) in chronic neglect patients as they underwent training in a virtual reality (VR) environment that improved left-side awareness.
METHODS: The study included 13 patients with visuospatial neglect persisting more than six months after a right-sided stroke. The patients underwent resting state functional magnetic resonance imaging (fMRI). Scans were collected at baseline and after five weeks of intense training. We specifically examined resting state functional connectivity within the DAN. In addition, using spatial concordance correlation, we compared changes in the spatial topology of the DAN with that of other networks.
RESULTS: We found a longitudinal increase in interhemispheric functional connectivity between the right frontal eye field and the left intraparietal sulcus following training (pre: 0.33±0.17 [mean±SD]; post 0.45±0.13; P=0.004). The spatial concordance analyses indicated that training influenced the DAN connectivity more than any of the other networks.
CONCLUSION: Intense VR training that improved left sided awareness in chronic stroke patients also increased sporadic interhemispheric functional connectivity within the DAN. Specifically, a region responsible for saccadic eye movement to the left became more integrated with the left posterior parietal cortex. These results highlight a mechanism that should be exploited in the training of patients with chronic visuospatial neglect. This article is protected by copyright. All rights reserved.

PMID: 30427058 [PubMed - as supplied by publisher]

Altered functional connectivity strength in informant-reported subjective cognitive decline: A resting-state functional magnetic resonance imaging study.

Thu, 11/15/2018 - 11:20
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Altered functional connectivity strength in informant-reported subjective cognitive decline: A resting-state functional magnetic resonance imaging study.

Alzheimers Dement (Amst). 2018;10:688-697

Authors: Dong C, Liu T, Wen W, Kochan NA, Jiang J, Li Q, Liu H, Niu H, Zhang W, Wang Y, Brodaty H, Sachdev PS

Abstract
Introduction: Informant-reported subjective cognitive decline (iSCD) has been associated with a higher risk of conversion to dementia, but the findings of whole brain functional connectivity strength (FCS) changes in iSCD are limited.
Methods: The sample comprised 39 participants with iSCD and 39 age- and sex- matched healthy controls. The global absolute (aFCS) and relative functional connectivity strengths were estimated using weighted degree centrality and the z-scores of the weighted degree centrality respectively. FreeSurfer was used for measuring cortical thickness.
Results: The aFCS was lower in iSCD primarily in left medial superior frontal, left precuneus, left parietal, right cuneus, and bilateral calcarine; while relative functional connectivity strength was higher in posterior cingulate cortex/precuneus compared with healthy controls. No significant differences in cortical thickness were observed.
Discussion: There are detectable changes of FCS in iSCD, with the precuneus possibly playing a compensatory role. FCS could therefore have a potential role to serve as one of the earliest neuroimaging markers of neurodegenerative disease.

PMID: 30426065 [PubMed]

Functional and Structural Plasticity of Brain in Elite Karate Athletes.

Thu, 11/15/2018 - 11:20
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Functional and Structural Plasticity of Brain in Elite Karate Athletes.

J Healthc Eng. 2018;2018:8310975

Authors: Duru AD, Balcioglu TH

Abstract
The structural and functional neural differences between the elite karate athletes and control group have been investigated in the concept of this study. 13 elite karate athletes and age-gender matched 13 volunteers who have not performed regular exercises participated in the study. Magnetic resonance imaging was used to acquire the anatomical and functional maps. T1-weighted anatomical images were segmented to form gray and white matter images. Voxel-based morphometry is used to elucidate the differences between the groups. Moreover, resting state functional measurements had been done, and group independent component analysis was implemented in order to exhibit the resting state networks. Then, second-level general linear models were used to compute the statistical maps. It has been revealed that increased GM volume values of inferior/superior temporal, occipital, premotor cortex, and temporal pole superior were present for the elite athletes. Additionally, WM values were found to be increased in caudate nucleus, hypothalamus, and mammilary region for the elite karate players. Similarly, for the elite karate players, the brain regions involved in the movement planning and visual perception are found to have higher connectivity values. The differences in these findings can be thought to be originated from the advances gained through the several years of training which is required to be an elite karate athlete.

PMID: 30425820 [PubMed - in process]

Mutual Information Better Quantifies Brain Network Architecture in Children with Epilepsy.

Thu, 11/15/2018 - 11:20
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Mutual Information Better Quantifies Brain Network Architecture in Children with Epilepsy.

Comput Math Methods Med. 2018;2018:6142898

Authors: Zhang W, Muravina V, Azencott R, Chu ZD, Paldino MJ

Abstract
Purpose: Metrics of the brain network architecture derived from resting-state fMRI have been shown to provide physiologically meaningful markers of IQ in children with epilepsy. However, traditional measures of functional connectivity (FC), specifically the Pearson correlation, assume a dominant linear relationship between BOLD time courses; this assumption may not be valid. Mutual information is an alternative measure of FC which has shown promise in the study of complex networks due to its ability to flexibly capture association of diverse forms. We aimed to compare network metrics derived from mutual information-defined FC to those derived from traditional correlation in terms of their capacity to predict patient-level IQ.
Materials and Methods: Patients were retrospectively identified with the following: (1) focal epilepsy; (2) resting-state fMRI; and (3) full-scale IQ by a neuropsychologist. Brain network nodes were defined by anatomic parcellation. Parcellation was performed at the size threshold of 350 mm2, resulting in networks containing 780 nodes. Whole-brain, weighted graphs were then constructed according to the pairwise connectivity between nodes. In the traditional condition, edges (connections) between each pair of nodes were defined as the absolute value of the Pearson correlation coefficient between their BOLD time courses. In the mutual information condition, edges were defined as the mutual information between time courses. The following metrics were then calculated for each weighted graph: clustering coefficient, modularity, characteristic path length, and global efficiency. A machine learning algorithm was used to predict the IQ of each individual based on their network metrics. Prediction accuracy was assessed as the fractional variation explained for each condition.
Results: Twenty-four patients met the inclusion criteria (age: 8-18 years). All brain networks demonstrated expected small-world properties. Network metrics derived from mutual information-defined FC significantly outperformed the use of the Pearson correlation. Specifically, fractional variation explained was 49% (95% CI: 46%, 51%) for the mutual information method; the Pearson correlation demonstrated a variation of 17% (95% CI: 13%, 19%).
Conclusion: Mutual information-defined functional connectivity captures physiologically relevant features of the brain network better than correlation.
Clinical Relevance: Optimizing the capacity to predict cognitive phenotypes at the patient level is a necessary step toward the clinical utility of network-based biomarkers.

PMID: 30425750 [PubMed - in process]

Pre-treatment Resting-State Functional MR Imaging Predicts the Long-Term Clinical Outcome After Short-Term Paroxtine Treatment in Post-traumatic Stress Disorder.

Thu, 11/15/2018 - 11:20
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Pre-treatment Resting-State Functional MR Imaging Predicts the Long-Term Clinical Outcome After Short-Term Paroxtine Treatment in Post-traumatic Stress Disorder.

Front Psychiatry. 2018;9:532

Authors: Yuan M, Qiu C, Meng Y, Ren Z, Yuan C, Li Y, Gao M, Lui S, Zhu H, Gong Q, Zhang W

Abstract
Background: The chronic phase of post-traumatic stress disorder (PTSD) and the limited effectiveness of existing treatments creates the need for the development of potential biomarkers to predict response to antidepressant medication at an early stage. However, findings at present focus on acute therapeutic effect without following-up the long-term clinical outcome of PTSD. So far, studies predicting the long-term clinical outcome of short-term treatment based on both pre-treatment and post-treatment functional MRI in PTSD remains limited. Methods: Twenty-two PTSD patients were scanned using resting-state functional MRI (rs-fMRI) before and after 12 weeks of treatment with paroxetine. Twenty patients were followed up using the same psychopathological assessments 2 years after they underwent the second MRI scan. Based on clinical outcome, the follow-up patients were divided into those with remitted PTSD or persistent PTSD. Amplitude of low-frequency fluctuations (ALFF) and degree centrality (DC) derived from pre-treatment and post-treatment rs-fMRI were used as classification features in a support vector machine (SVM) classifier. Results: Prediction of long-term clinical outcome by combined ALFF and DC features derived from pre-treatment rs-fMRI yielded an accuracy rate of 72.5% (p < 0.005). The most informative voxels for outcome prediction were mainly located in the precuneus, superior temporal area, insula, dorsal medial prefrontal cortex, frontal orbital cortex, supplementary motor area, lingual gyrus, and cerebellum. Long-term outcome could not be successfully classified by post-treatment imaging features with accuracy rates <50%. Conclusions: Combined information from ALFF and DC from rs-fMRI data before treatment could predict the long-term clinical outcome of PTSD, which is critical for defining potential biomarkers to customize PTSD treatment and improve the prognosis.

PMID: 30425661 [PubMed]

Non-invasive Assessment of Systolic and Diastolic Cardiac Function During Rest and Stress Conditions Using an Integrated Image-Modeling Approach.

Thu, 11/15/2018 - 11:20
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Non-invasive Assessment of Systolic and Diastolic Cardiac Function During Rest and Stress Conditions Using an Integrated Image-Modeling Approach.

Front Physiol. 2018;9:1515

Authors: Casas B, Viola F, Cedersund G, Bolger AF, Karlsson M, Carlhäll CJ, Ebbers T

Abstract
Background: The possibility of non-invasively assessing load-independent parameters characterizing cardiac function is of high clinical value. Typically, these parameters are assessed during resting conditions. However, for diagnostic purposes, the parameter behavior across a physiologically relevant range of heart rate and loads is more relevant than the isolated measurements performed at rest. This study sought to evaluate changes in non-invasive estimations of load-independent parameters of left-ventricular contraction and relaxation patterns at rest and during dobutamine stress. Methods: We applied a previously developed approach that combines non-invasive measurements with a physiologically-based, reduced-order model of the cardiovascular system to provide subject-specific estimates of parameters characterizing left ventricular function. In this model, the contractile state of the heart at each time point along the cardiac cycle is modeled using a time-varying elastance curve. Non-invasive data, including four-dimensional magnetic resonance imaging (4D Flow MRI) measurements, were acquired in nine subjects without a known heart disease at rest and during dobutamine stress. For each of the study subjects, we constructed two personalized models corresponding to the resting and the stress state. Results: Applying the modeling framework, we identified significant increases in the left ventricular contraction rate constant [from 1.5 ± 0.3 to 2 ± 0.5 (p = 0.038)] and relaxation constant [from 37.2 ± 6.9 to 46.1 ± 12 (p = 0.028)]. In addition, we found a significant decrease in the elastance diastolic time constant from 0.4 ± 0.04 s to 0.3 ± 0.03 s (p = 0.008). Conclusions: The integrated image-modeling approach allows the assessment of cardiovascular function given as model-based parameters. The agreement between the estimated parameter values and previously reported effects of dobutamine demonstrates the potential of the approach to assess advanced metrics of pathophysiology that are otherwise difficult to obtain non-invasively in clinical practice.

PMID: 30425650 [PubMed]

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