New resting-state fMRI related studies at PubMed

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Inspection of short-time resting-state electroencephalogram functional networks in Alzheimer's disease.

Tue, 06/20/2017 - 12:20
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Inspection of short-time resting-state electroencephalogram functional networks in Alzheimer's disease.

Conf Proc IEEE Eng Med Biol Soc. 2016 Aug;2016:2810-2813

Authors: Escudero J, Smith K, Azami H, Abasolo D

Abstract
Functional connectivity has proven useful to characterise electroencephalogram (EEG) activity in Alzheimer's disease (AD). However, most current functional connectivity analyses have been static, disregarding any potential variability of the connectivity with time. In this pilot study, we compute short-time resting state EEG functional connectivity based on the imaginary part of coherency for 12 AD patients and 11 controls. We derive binary unweighted graphs using the cluster-span threshold, an objective binary threshold. For each short-time binary graph, we calculate its local clustering coefficient (Cloc), degree (K), and efficiency (E). The distribution of these graph metrics for each participant is then characterised with four statistical moments: mean, variance, skewness, and kurtosis. The results show significant differences between groups in the mean of K and E, and the kurtosis of Cloc and K. Although not significant when considered alone, the skewness of Cloc is the most frequently selected feature for the discrimination of subject groups. These results suggest that the variability of EEG functional connectivity may convey useful information about AD.

PMID: 28268902 [PubMed - indexed for MEDLINE]

Incidence and impact of subclinical epileptiform activity in Alzheimer's disease.

Tue, 06/20/2017 - 12:20
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Incidence and impact of subclinical epileptiform activity in Alzheimer's disease.

Ann Neurol. 2016 Dec;80(6):858-870

Authors: Vossel KA, Ranasinghe KG, Beagle AJ, Mizuiri D, Honma SM, Dowling AF, Darwish SM, Van Berlo V, Barnes DE, Mantle M, Karydas AM, Coppola G, Roberson ED, Miller BL, Garcia PA, Kirsch HE, Mucke L, Nagarajan SS

Abstract
OBJECTIVE: Seizures are more frequent in patients with Alzheimer's disease (AD) and can hasten cognitive decline. However, the incidence of subclinical epileptiform activity in AD and its consequences are unknown. Motivated by results from animal studies, we hypothesized higher than expected rates of subclinical epileptiform activity in AD with deleterious effects on cognition.
METHODS: We prospectively enrolled 33 patients (mean age, 62 years) who met criteria for AD, but had no history of seizures, and 19 age-matched, cognitively normal controls. Subclinical epileptiform activity was assessed, blinded to diagnosis, by overnight long-term video-electroencephalography (EEG) and a 1-hour resting magnetoencephalography exam with simultaneous EEG. Patients also had comprehensive clinical and cognitive evaluations, assessed longitudinally over an average period of 3.3 years.
RESULTS: Subclinical epileptiform activity was detected in 42.4% of AD patients and 10.5% of controls (p = 0.02). At the time of monitoring, AD patients with epileptiform activity did not differ clinically from those without such activity. However, patients with subclinical epileptiform activity showed faster declines in global cognition, determined by the Mini-Mental State Examination (3.9 points/year in patients with epileptiform activity vs 1.6 points/year in patients without; p = 0.006), and in executive function (p = 0.01).
INTERPRETATION: Extended monitoring detects subclinical epileptiform activity in a substantial proportion of patients with AD. Patients with this indicator of network hyperexcitability are at risk for accelerated cognitive decline and might benefit from antiepileptic therapies. These data call for more sensitive and comprehensive neurophysiological assessments in AD patient evaluations and impending clinical trials. Ann Neurol 2016;80:858-870.

PMID: 27696483 [PubMed - indexed for MEDLINE]

Stimulus-Elicited Connectivity Influences Resting-State Connectivity Years Later in Human Development: A Prospective Study.

Tue, 06/20/2017 - 12:20
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Stimulus-Elicited Connectivity Influences Resting-State Connectivity Years Later in Human Development: A Prospective Study.

J Neurosci. 2016 Apr 27;36(17):4771-84

Authors: Gabard-Durnam LJ, Gee DG, Goff B, Flannery J, Telzer E, Humphreys KL, Lumian DS, Fareri DS, Caldera C, Tottenham N

Abstract
UNLABELLED: Although the functional architecture of the brain is indexed by resting-state connectivity networks, little is currently known about the mechanisms through which these networks assemble into stable mature patterns. The current study posits and tests the long-term phasic molding hypothesis that resting-state networks are gradually shaped by recurring stimulus-elicited connectivity across development by examining how both stimulus-elicited and resting-state functional connections of the human brain emerge over development at the systems level. Using a sequential design following 4- to 18-year-olds over a 2 year period, we examined the predictive associations between stimulus-elicited and resting-state connectivity in amygdala-cortical circuitry as an exemplar case (given this network's protracted development across these ages). Age-related changes in amygdala functional connectivity converged on the same regions of medial prefrontal cortex (mPFC) and inferior frontal gyrus when elicited by emotional stimuli and when measured at rest. Consistent with the long-term phasic molding hypothesis, prospective analyses for both connections showed that the magnitude of an individual's stimulus-elicited connectivity unidirectionally predicted resting-state functional connectivity 2 years later. For the amygdala-mPFC connection, only stimulus-elicited connectivity during childhood and the transition to adolescence shaped future resting-state connectivity, consistent with a sensitive period ending with adolescence for the amygdala-mPFC circuit. Together, these findings suggest that resting-state functional architecture may arise from phasic patterns of functional connectivity elicited by environmental stimuli over the course of development on the order of years.
SIGNIFICANCE STATEMENT: A fundamental issue in understanding the ontogeny of brain function is how resting-state (intrinsic) functional networks emerge and relate to stimulus-elicited functional connectivity. Here, we posit and test the long-term phasic molding hypothesis that resting-state network development is influenced by recurring stimulus-elicited connectivity through prospective examination of the developing human amygdala-cortical functional connections. Our results provide critical insight into how early environmental events sculpt functional network architecture across development and highlight childhood as a potential developmental period of heightened malleability for the amygdala-medial prefrontal cortex circuit. These findings have implications for how both positive and adverse experiences influence the developing brain and motivate future investigations of whether this molding mechanism reflects a general phenomenon of brain development.

PMID: 27122035 [PubMed - indexed for MEDLINE]

Abnormal asymmetry in benign epilepsy with unilateral and bilateral centrotemporal spikes: A combined fMRI and DTI study.

Sun, 06/18/2017 - 11:30

Abnormal asymmetry in benign epilepsy with unilateral and bilateral centrotemporal spikes: A combined fMRI and DTI study.

Epilepsy Res. 2017 Jun 08;135:56-63

Authors: Cao W, Zhang Y, Hou C, Yang F, Gong J, Jiang S, Huang Y, Xiao R, Luo C, Wang X, Yao D

Abstract
Benign epilepsy with centrotemporal spikes (BECTS) is the most common idiopathic focal childhood epilepsy associated with either unilateral or bilateral epileptic discharge. Asymmetry as an important characteristic of the human brain is beneficial for brain functions. However, little is known about on asymmetry of BECTS patients with different epileptic spikes pattern. In the present study, we investigated functional and structural asymmetries in unilateral spikes BECTS (U_BECTS) patients and bilateral spikes BECTS (B_BECTS) patients using resting state functional magnetic resonance images and diffusion tensor imaging. Compared with the controls, we observed a decreased voxel-mirrored interhemispheric functional connectivity (FC) in primary sensorimotor cortex (SM1) in U_BECTS and B_BECTS groups, and reduced fractional anisotropy (FA) values of the corpus callosum (CC) connecting bilateral SM1 were also observed in B_BECTS group. Further region-based FC map analysis of SM1 demonstrated increased functional asymmetry with ipsilateral hemisphere, contralateral hemisphere and the whole brain in U_BECTS and increased functional asymmetry with the contralateral hemisphere and the whole brain in B_BECTS groups. The correlation between functional asymmetry of SM1 and intelligence quotient scores was found in the U_BECTS group. The altered asymmetries of the SM1 further indicated the important role of SM1 in the pathophysiology of the BECTS. Furthermore, the B_BECTS group also showed abnormal voxel-mirrored interhemispheric FC in the temporal pole, the lobule IX of the cerebellum, the caudate and the occipital cortex relative to the controls. Altogether, our findings provide additional insight into the neuronal mechanism of BECTS with different epileptic spikes pattern and cognitive impairments with BECTS patients.

PMID: 28623837 [PubMed - as supplied by publisher]

Comparing the Intracarotid Amobarbital Test and Functional MRI for the Presurgical Evaluation of Language in Epilepsy.

Sun, 06/18/2017 - 11:30
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Comparing the Intracarotid Amobarbital Test and Functional MRI for the Presurgical Evaluation of Language in Epilepsy.

Curr Neurol Neurosci Rep. 2017 Jul;17(7):54

Authors: Massot-Tarrús A, Mousavi SR, Mirsattari SM

Abstract
Surgery is the treatment of choice for drug-resistant temporal lobe epilepsy (TLE). However, such surgery frequently causes deficits in language function, especially if performed on the dominant hemisphere. In recent years, the intracarotid amobarbital test (IAT) has been gradually replaced by functional magnetic resonance imaging (fMRI) in the preoperative identification of language areas to estimate the risk of postoperative language decline. In this paper, we review the neural substrates for language processing, how language impairment can result both from TLE itself and from surgical attempts to treat it. Subsequently, we discuss the strengths and limitations of, and current indications for fMRI and IAT during the preoperative workup, both by discussion of the studies that have evaluated them individually and through meta-analysis of data from 31 studies deemed eligible for analysis. Electrocortical stimulation mapping (ESM) is also discussed, as is the usefulness of the novel technique of resting-state fMRI. Finally, surgical techniques designed to avoid or reduce language decline in patients at risk are explored.

PMID: 28623489 [PubMed - in process]

Alzheimer's disease: The state of the art in resting-state magnetoencephalography.

Sun, 06/18/2017 - 11:30
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Alzheimer's disease: The state of the art in resting-state magnetoencephalography.

Clin Neurophysiol. 2017 May 21;128(8):1426-1437

Authors: Engels MMA, van der Flier WM, Stam CJ, Hillebrand A, Scheltens P, van Straaten ECW

Abstract
Alzheimer's disease (AD) is accompanied by functional brain changes that can be detected in imaging studies, including electromagnetic activity recorded with magnetoencephalography (MEG). Here, we systematically review the studies that have examined resting-state MEG changes in AD and identify areas that lack scientific or clinical progress. Three levels of MEG analysis will be covered: (i) single-channel signal analysis, (ii) pairwise analyses over time series, which includes the study of interdependencies between two time series and (iii) global network analyses. We discuss the findings in the light of other functional modalities, such as electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). Overall, single-channel MEG results show consistent changes in AD that are in line with EEG studies, but the full potential of the high spatial resolution of MEG and advanced functional connectivity and network analysis has yet to be fully exploited. Adding these features to the current knowledge will potentially aid in uncovering organizational patterns of brain function in AD and thereby aid the understanding of neuronal mechanisms leading to cognitive deficits.

PMID: 28622527 [PubMed - as supplied by publisher]

Brain Magnetic Resonance Imaging (MRI) as a Potential Biomarker for Parkinson's Disease (PD).

Sun, 06/18/2017 - 11:30
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Brain Magnetic Resonance Imaging (MRI) as a Potential Biomarker for Parkinson's Disease (PD).

Brain Sci. 2017 Jun 16;7(6):

Authors: Tuite P

Abstract
Magnetic resonance imaging (MRI) has the potential to serve as a biomarker for Parkinson's disease (PD). However, the type or types of biomarker it could provide remain to be determined. At this time there is not sufficient sensitivity or specificity for MRI to serve as an early diagnostic biomarker, i.e., it is unproven in its ability to determine if a single individual is normal, has mild PD, or has some other forms of degenerative parkinsonism. However there is accumulating evidence that MRI may be useful in staging and monitoring disease progression (staging biomarker), and also possibly as a means to monitor pathophysiological aspects of disease and associated response to treatments, i.e., theranostic marker. As there are increasing numbers of manuscripts that are dedicated to diffusion- and neuromelanin-based imaging methods, this review will focus on these topics cursorily and will delve into pharmacodynamic imaging as a means to get at theranostic aspects of PD.

PMID: 28621758 [PubMed]

Racial Differences in Insular Connectivity and Thickness and Related Cognitive Impairment in Hypertension.

Sun, 06/18/2017 - 11:30
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Racial Differences in Insular Connectivity and Thickness and Related Cognitive Impairment in Hypertension.

Front Aging Neurosci. 2017;9:177

Authors: Chand GB, Wu J, Qiu D, Hajjar I

Abstract
Hypertensive African-Americans have a greater risk of cognitive impairment than hypertensive Caucasian-Americans. The neural basis of this increased risk is yet unknown. Neuroimaging investigations suggest that the normal neural activity comprises complex interactions between brain networks. Recent studies consistently demonstrate that the insula, part of the salience network, provides modulation effects (information flow) over the default-mode and central-executive networks in cognitively normal subjects, and argue that the modulation effect is declined in cognitive impairment. The purpose of this study is to examine the information flow at the nodes of three networks using resting state functional magnetic resonance imaging (MRI) data in cognitively impaired hypertensive individuals with the African-Americans and the Caucasian-Americans races, and to compare the thickness of impaired node between two racial groups. Granger causality methodology was used to calculate information flow between networks using resting state functional MRI data, and FreeSurfer was used to measure cortical thickness from T1-weighted structural images. We found that negative information flow of the insula in both African-Americans and Caucasian-Americans, which was in contrast with previously reported positive information flow in this region of normal individuals. Also, significantly greater negative information flow in insula was found in African-Americans than Caucasian-Americans (Wilcoxon rank sum; Z = 2.06; p < 0.05). Significantly, lower insula thickness was found in African-Americans compared with Caucasian-Americans (median = 2.797 mm vs. 2.897 mm) (Wilcoxon rank sum; Z = 2.09; p < 0.05). Finally, the insula thickness correlated with the global cognitive testing measured by Montreal cognitive assessment (Spearman's correlation; r = 0.30; p < 0.05). These findings suggest that the insula is a potential biomarker for the racial disparity in cognitive impairment of hypertensive individuals.

PMID: 28620297 [PubMed - in process]

Shared and Specific Intrinsic Functional Connectivity Patterns in Unmedicated Bipolar Disorder and Major Depressive Disorder.

Sun, 06/18/2017 - 11:30
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Shared and Specific Intrinsic Functional Connectivity Patterns in Unmedicated Bipolar Disorder and Major Depressive Disorder.

Sci Rep. 2017 Jun 15;7(1):3570

Authors: Wang Y, Wang J, Jia Y, Zhong S, Niu M, Sun Y, Qi Z, Zhao L, Huang L, Huang R

Abstract
Identifying brain differences and similarities between bipolar disorder (BD) and major depressive disorder (MDD) is necessary for increasing our understanding of the pathophysiology and for developing more effective treatments. However, the features of whole-brain intrinsic functional connectivity underlying BD and MDD have not been directly compared. We collected resting-state fMRI data from 48 BD patients, 48 MDD patients, and 51 healthy subjects. We constructed voxel-wise whole-brain functional networks and computed regional functional connectivity strength (FCS) using graph-theory and further divided the regional FCS into long-range FCS (lFCS) and short-range FCS (sFCS). Relative to the controls, both the BD and MDD patients showed decreased sFCS in the bilateral precuneus. In addition, the BD patients showed increased and the MDD patients showed decreased lFCS and sFCS in the bilateral cerebellum. The BD patients also showed increased lFCS in the right middle temporal gyrus and increased sFCS in the bilateral thalamus compared to either the MDD patients or the controls. These findings suggest that BD and MDD may have some shared as well as a greater number of specific impairments in their functional connectivity patterns, providing new evidence for the pathophysiology of BD and MDD at the large-scale whole brain connectivity level.

PMID: 28620239 [PubMed - in process]

The large-scale functional connectivity correlates of consciousness and arousal during the healthy and pathological human sleep cycle.

Sun, 06/18/2017 - 11:30
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The large-scale functional connectivity correlates of consciousness and arousal during the healthy and pathological human sleep cycle.

Neuroimage. 2017 Jun 12;:

Authors: Tagliazucchi E, van Someren EJW

Abstract
Advances in neuroimaging have greatly improved our understanding of human sleep from a systems neuroscience perspective. However, cognition and awareness are reduced during sleep, hindering the applicability of standard task-based paradigms. Methods recently developed to study spontaneous brain activity fluctuations have proven useful to overcome this limitation. In this review, we focus on the concept of functional connectivity (FC, i.e. statistical covariance between brain activity signals) and its application to functional magnetic resonance imaging (fMRI) data acquired during sleep. We discuss how FC analyses of endogenous brain activity during sleep have contributed towards revealing the large-scale neural networks associated with arousal and conscious awareness. We argue that the neuroimaging of deep sleep can be used to evaluate the predictions of theories of consciousness; at the same time, we highlight some apparent limitations of deep sleep as an experimental model of unconsciousness. In resting state fMRI experiments, the onset of sleep can be regarded as the object of interest but also as an undesirable confound. We discuss a series of articles contributing towards the disambiguation of wakefulness from sleep on the basis of fMRI-derived dynamic FC, and then outline a plan for the development of more general and data-driven sleep classifiers. To complement our review of studies investigating the brain systems of arousal and consciousness during healthy sleep, we then turn to pathological and abnormal sleep patterns. We review the current literature on sleep deprivation studies and sleep disorders, adopting the critical stance that lack of independent vigilance monitoring during fMRI experiments is liable for false positives related to atypical sleep propensity in clinical and sleep-deprived populations. Finally, we discuss multimodal neuroimaging as a promising future direction to achieve a better understanding of the large-scale FC of the brain during sleep and its relationship to mechanisms at the cellular level.

PMID: 28619656 [PubMed - as supplied by publisher]

High-frequency brain networks undergo modular breakdown during epileptic seizures.

Sun, 06/18/2017 - 11:30
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High-frequency brain networks undergo modular breakdown during epileptic seizures.

Epilepsia. 2016 Jul;57(7):1097-108

Authors: Fuertinger S, Simonyan K, Sperling MR, Sharan AD, Hamzei-Sichani F

Abstract
OBJECTIVE: Cortical high-frequency oscillations (HFOs; 100-500 Hz) play a critical role in the pathogenesis of epilepsy; however, whether they represent a true epileptogenic process remains largely unknown. HFOs have been recorded in the human cortex but their network dynamics during the transitional period from interictal to ictal phase remain largely unknown. We sought to determine the high-frequency network dynamics of these oscillations in patients with epilepsy who were undergoing intracranial electroencephalographic recording for seizure localization.
METHODS: We applied a graph theoretical analysis framework to high-resolution intracranial electroencephalographic recordings of 24 interictal and 24 seizure periods to identify the spatiotemporal evolution of community structure of high-frequency cortical networks at rest and during multiple seizure episodes in patients with intractable epilepsy.
RESULTS: Cortical networks at all examined frequencies showed temporally stable community architecture in all 24 interictal periods. During seizure periods, high-frequency networks showed a significant breakdown of their community structure, which was characterized by the emergence of numerous small nodal communities, not limited to seizure foci and encompassing the entire recorded network. Such network disorganization was observed on average 225 s before the electrographic seizure onset and extended on average 190 s after termination of the seizure. Gamma networks were characterized by stable community dynamics during resting and seizure periods.
SIGNIFICANCE: Our findings suggest that the modular breakdown of high-frequency cortical networks represents a distinct functional pathology that underlies epileptogenesis and corresponds to a cortical state of highest propensity to generate seizures.

PMID: 27221325 [PubMed - indexed for MEDLINE]

Abnormal Spontaneous Brain Activity in Patients With Anisometropic Amblyopia Using Resting-State Functional Magnetic Resonance Imaging.

Fri, 06/16/2017 - 10:25

Abnormal Spontaneous Brain Activity in Patients With Anisometropic Amblyopia Using Resting-State Functional Magnetic Resonance Imaging.

J Pediatr Ophthalmol Strabismus. 2017 Jun 15;:1-8

Authors: Tang A, Chen T, Zhang J, Gong Q, Liu L

Abstract
PURPOSE: To explore the abnormality of spontaneous activity in patients with anisometropic amblyopia under resting-state functional magnetic resonance imaging (Rs-fMRI).
METHODS: Twenty-four participants were split into two groups. The anisometropic amblyopia group had 10 patients, all of whom had anisometropic amblyopia of the right eye, and the control group had 14 healthy subjects. All participants underwent Rs-fMRI scanning. Measurement of amplitude of low frequency fluctuations of the brain, which is a measure of the amplitudes of spontaneous brain activity, was used to investigate brain changes between the anisometropic amblyopia and control groups.
RESULTS: Compared with an age- and gender-matched control group, the anisometropic amblyopia group showed increased amplitude of low frequency fluctuations of spontaneous brain activity in the left superior temporal gyrus, the left inferior parietal lobe, the left pons, and the right inferior semi-lunar lobe. The anisometropic amblyopia group also showed decreased amplitude of low frequency fluctuations in the bilateral medial frontal gyrus.
CONCLUSIONS: This study demonstrated abnormal spontaneous brain activities in patients with anisometropic amblyopia under Rs-fMRI, and these abnormalities might contribute to the neuropathological mechanisms of anisometropic amblyopia. [J Pediatr Ophthalmol Strabismus. 200X;XX(X):XX-XX.].

PMID: 28617520 [PubMed - as supplied by publisher]

Multiparametric MRI to distinguish early onset Alzheimer's disease and behavioural variant of frontotemporal dementia.

Fri, 06/16/2017 - 10:25
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Multiparametric MRI to distinguish early onset Alzheimer's disease and behavioural variant of frontotemporal dementia.

Neuroimage Clin. 2017;15:428-438

Authors: Canu E, Agosta F, Mandic-Stojmenovic G, Stojković T, Stefanova E, Inuggi A, Imperiale F, Copetti M, Kostic VS, Filippi M

Abstract
This prospective study explored whether an approach combining structural [cortical thickness and white matter (WM) microstructure] and resting state functional MRI can aid differentiation between 62 early onset Alzheimer's disease (EOAD) and 27 behavioural variant of frontotemporal dementia (bvFTD) patients. Random forest and receiver operator characteristic curve analyses assessed the ability of MRI in classifying the two clinical syndromes. All patients showed a distributed pattern of brain alterations relative to controls. Compared to bvFTD, EOAD patients showed bilateral inferior parietal cortical thinning and decreased default mode network functional connectivity. Compared to EOAD, bvFTD patients showed bilateral orbitofrontal and temporal cortical thinning, and WM damage of the corpus callosum, bilateral uncinate fasciculus, and left superior longitudinal fasciculus. Random forest analysis revealed that left inferior parietal cortical thickness (accuracy 0.78, specificity 0.76, sensitivity 0.83) and WM integrity of the right uncinate fasciculus (accuracy 0.81, specificity 0.96, sensitivity 0.43) were the best predictors of clinical diagnosis. The combination of cortical thickness and DT MRI measures was able to distinguish patients with EOAD and bvFTD with accuracy 0.82, specificity 0.76, and sensitivity 0.96. The diagnostic ability of MRI models was confirmed in a subsample of patients with biomarker-based clinical diagnosis. Multiparametric MRI is useful to identify brain alterations which are specific to EOAD and bvFTD. A severe cortical involvement is suggestive of EOAD, while a prominent WM damage is indicative of bvFTD.

PMID: 28616383 [PubMed - in process]

Anosognosia for memory deficits in mild cognitive impairment: Insight into the neural mechanism using functional and molecular imaging.

Fri, 06/16/2017 - 10:25
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Anosognosia for memory deficits in mild cognitive impairment: Insight into the neural mechanism using functional and molecular imaging.

Neuroimage Clin. 2017;15:408-414

Authors: Vannini P, Hanseeuw B, Munro CE, Amariglio RE, Marshall GA, Rentz DM, Pascual-Leone A, Johnson KA, Sperling RA

Abstract
Anosognosia, or loss of insight of memory deficits, is a common and striking symptom in Alzheimer's disease (AD). Previous findings in AD dementia patients suggest that anosognosia is due to both functional metabolic changes within cortical midline structures involved in self-referential processes, as well as functional disconnection between these regions. The present study aims to extend these findings by investigating the neural correlates of anosognosia in the prodromal stage of AD. Here, we used regional brain metabolism (resting state 18-F fluorodeoxyglucose positron emission tomography (FDG-PET)) to unravel the metabolic correlates of anosognosia in subjects with amnestic mild cognitive impairment (aMCI) and subsequently resting state functional magnetic resonance imaging (rs-fMRI) to investigate the intrinsic connectivity disruption between brain regions. Thirty-one subjects (mean age: 74.1; Clinical Dementia Rating (CDR) global score: 0.5) with aMCI, and 251 cognitively normal (CN) older adults (mean age: 73.3; CDR: 0) were included as a reference group for behavioral and FDG data. An anosognosia index was obtained by calculating a discrepancy score between subjective and objective memory scores. All subjects underwent FDG-PET for glucose metabolism measurement, and aMCI subjects underwent additional rs-fMRI for intrinsic connectivity measurement. Voxel-wise correlations between anosognosia and neuroimaging data were conducted in the aMCI subjects. Subjects with aMCI had significantly decreased memory awareness as compared to the CN older adults. Greater anosognosia in aMCI subjects was associated with reduced glucose metabolism in the posterior cingulate (PCC) cortices and hippocampus. Intrinsic connectivity analyses revealed a significant association between anosognosia and attenuated functional connectivity between the PCC seed region and orbitofrontal cortex (OFC) as well as bilateral inferior parietal lobes (IPL). These findings provide further evidence that implicates cortical midline structures and hippocampus in the awareness of memory deficits. Investigating neuroimaging changes that co-vary with memory awareness may improve our ability to identify the cause of anosognosia and ultimately increase our chances for its treatment.

PMID: 28616381 [PubMed - in process]

Modulation of intrinsic resting-state fMRI networks in women with chronic migraine.

Fri, 06/16/2017 - 10:25
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Modulation of intrinsic resting-state fMRI networks in women with chronic migraine.

Neurology. 2017 Jun 14;:

Authors: Androulakis XM, Krebs K, Peterlin BL, Zhang T, Maleki N, Sen S, Rorden C, Herath P

Abstract
OBJECTIVE: To evaluate the intrinsic resting functional connectivity of the default mode network (DMN), salience network (SN), and central executive network (CEN) network in women with chronic migraine (CM), and whether clinical features are associated with such abnormalities.
METHODS: We analyzed resting-state connectivity in 29 women with CM as compared to age- and sex-matched controls. Relationships between clinical characteristics and changes in targeted networks connectivity were evaluated using a multivariate linear regression model.
RESULTS: All 3 major intrinsic brain networks were less coherent in CM (DMN: p = 0.030, SN: p = 0.007, CEN: p = 0.002) as compared to controls. When stratified based on medication overuse headache (MOH) status, CM without MOH (DMN: p = 0.029, SN: p = 0.023, CEN: p = 0.003) and CM with MOH (DMN: p = 0.016, SN: p = 0.016, CEN: p = 0.015) were also less coherent as compared to controls. There was no difference in CM with MOH as compared to CM without MOH (DMN: p = 0.382, SN: p = 0.408, CEN: p = 0.419). The frequency of moderate and severe headache days was associated with decreased connectivity in SN (p = 0.003) and CEN (p = 0.015), while cutaneous allodynia was associated with increased connectivity in SN (p = 0.011).
CONCLUSIONS: Our results demonstrated decreased overall resting-state functional connectivity of the 3 major intrinsic brain networks in women with CM, and these patterns were associated with frequency of moderate to severe headache and cutaneous allodynia.

PMID: 28615426 [PubMed - as supplied by publisher]

Are Movement Artifacts in Magnetic Resonance Imaging a Real Problem?-A Narrative Review.

Thu, 06/15/2017 - 16:10
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Are Movement Artifacts in Magnetic Resonance Imaging a Real Problem?-A Narrative Review.

Front Neurol. 2017;8:232

Authors: Havsteen I, Ohlhues A, Madsen KH, Nybing JD, Christensen H, Christensen A

Abstract
Movement artifacts compromise image quality and may interfere with interpretation, especially in magnetic resonance imaging (MRI) applications with low signal-to-noise ratio such as functional MRI or diffusion tensor imaging, and when imaging small lesions. High image resolution has high sensitivity to motion artifacts and often prolongs scan time that again aggravates movement artifacts. During the scan fast imaging techniques and sequences, optimal receiver coils, careful patient positioning, and instruction may minimize movement artifacts. Physiological noise sources are motion from respiration, flow and pulse coupled to cardiac cycles, from the swallowing reflex and small spontaneous head movements. Par example, in resting-state functional MRI spontaneous neuronal activity adds 1-2% of signal change, even under optimal conditions signal contributions from physiological noise remain a considerable fraction hereof. Movement tracking during imaging may allow for prospective correction or postprocessing steps separating signal and noise.

PMID: 28611728 [PubMed - in process]

Differential Functional Connectivity Alterations of Two Subdivisions within the Right dlPFC in Parkinson's Disease.

Thu, 06/15/2017 - 16:10
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Differential Functional Connectivity Alterations of Two Subdivisions within the Right dlPFC in Parkinson's Disease.

Front Hum Neurosci. 2017;11:288

Authors: Caspers J, Mathys C, Hoffstaedter F, Südmeyer M, Cieslik EC, Rubbert C, Hartmann CJ, Eickhoff CR, Reetz K, Grefkes C, Michely J, Turowski B, Schnitzler A, Eickhoff SB

Abstract
Patients suffering from Parkinson's disease (PD) often show impairments in executive function (EF) like decision-making and action control. The right dorsolateral prefrontal cortex (dlPFC) has been strongly implicated in EF in healthy subjects and has repeatedly been reported to show alterations related to EF impairment in PD. Recently, two key regions for cognitive action control have been identified within the right dlPFC by co-activation based parcellation. While the posterior region is engaged in rather basal EF like stimulus integration and working memory, the anterior region has a more abstract, supervisory function. To investigate whether these functionally distinct subdivisions of right dlPFC are differentially affected in PD, we analyzed resting-state functional connectivity (FC) in 39 PD patients and 44 age- and gender-matched healthy controls. Patients were examined both after at least 12 h withdrawal of dopaminergic drugs (OFF) and under their regular dopaminergic medication (ON). We found that only the posterior right dlPFC subdivision shows FC alterations in PD, while the anterior part remains unaffected. PD-related decreased FC with posterior right dlPFC was found in the bilateral medial posterior parietal cortex (mPPC) and left dorsal premotor region (PMd) in the OFF state. In the medical ON, FC with left PMd normalized, while decoupling with bilateral mPPC remained. Furthermore, we observed increased FC between posterior right dlPFC and the bilateral dorsomedial prefrontal cortex (dmPFC) in PD in the ON state. Our findings point to differential disturbances of right dlPFC connectivity in PD, which relate to its hierarchical organization of EF processing by stronger affecting the functionally basal posterior aspect than the hierarchically higher anterior part.

PMID: 28611616 [PubMed - in process]

Functional and Structural Network Recovery after Mild Traumatic Brain Injury: A 1-Year Longitudinal Study.

Thu, 06/15/2017 - 16:10
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Functional and Structural Network Recovery after Mild Traumatic Brain Injury: A 1-Year Longitudinal Study.

Front Hum Neurosci. 2017;11:280

Authors: Dall'Acqua P, Johannes S, Mica L, Simmen HP, Glaab R, Fandino J, Schwendinger M, Meier C, Ulbrich EJ, Müller A, Baetschmann H, Jäncke L, Hänggi J

Abstract
Brain connectivity after mild traumatic brain injury (mTBI) has not been investigated longitudinally with respect to both functional and structural networks together within the same patients, crucial to capture the multifaceted neuropathology of the injury and to comprehensively monitor the course of recovery and compensatory reorganizations at macro-level. We performed a prospective study with 49 mTBI patients at an average of 5 days and 1 year post-injury and 49 healthy controls. Neuropsychological assessments as well as resting-state functional and diffusion-weighted magnetic resonance imaging were obtained. Functional and structural connectome analyses were performed using network-based statistics. They included a cross-sectional group comparison and a longitudinal analysis with the factors group and time. The latter tracked the subnetworks altered at the early phase and, in addition, included a whole-brain group × time interaction analysis. Finally, we explored associations between the evolution of connectivity and changes in cognitive performance. The early phase of mTBI was characterized by a functional hypoconnectivity in a subnetwork with a large overlap of regions involved within the classical default mode network. In addition, structural hyperconnectivity in a subnetwork including central hub areas such as the cingulate cortex was found. The impaired functional and structural subnetworks were strongly correlated and revealed a large anatomical overlap. One year after trauma and compared to healthy controls we observed a partial normalization of both subnetworks along with a considerable compensation of functional and structural connectivity subsequent to the acute phase. Connectivity changes over time were correlated with improvements in working memory, divided attention, and verbal recall. Neuroplasticity-induced recovery or compensatory processes following mTBI differ between brain regions with respect to their time course and are not fully completed 1 year after trauma.

PMID: 28611614 [PubMed - in process]

Prenatal Manganese Exposure and Intrinsic Functional Connectivity of Emotional Brain Areas in Children.

Thu, 06/15/2017 - 16:10
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Prenatal Manganese Exposure and Intrinsic Functional Connectivity of Emotional Brain Areas in Children.

Neurotoxicology. 2017 Jun 10;:

Authors: de Water E, Proal E, Wang V, Medina SM, Schnaas L, Téllez-Rojo MM, Wright RO, Tang CY, Horton MK

Abstract
Manganese (Mn) is an essential trace metal that is neurotoxic at high levels of exposure. Disruption of brain maturation processes during the prenatal period may have lasting consequences. During this critical period, the developing human brain is uniquely vulnerable to exposure to environmental toxicants such as Mn, and prenatal Mn exposure has been associated with changes in brain areas involved in emotion processing and regulation. The goal of the present pilot study was to examine whether prenatal Mn exposure is associated with changes in the intrinsic functional connectivity (iFC) of the brain in childhood, focusing on changes in emotional brain areas. We selected 15 subjects (age 6-7 years) from an ongoing longitudinal birth cohort study to participate in a resting state functional magnetic resonance imaging (fMRI) study. Prenatal Mn exposure was determined from maternal blood collected during the 2nd and 3rd trimesters of pregnancy. We used seed-based correlation analyses and independent component analyses to examine whether prenatal Mn exposure was associated with the iFC of the brain in children. We found that the right globus pallidus showed reduced iFC with the dorsal anterior cingulate cortex and lateral prefrontal cortex in children who were exposed to higher prenatal Mn levels, after controlling for sociodemographic confounders (SES, maternal education, child sex, home environment support) and environmental confounders (prenatal lead exposure and air pollution). These findings suggest that prenatal Mn exposure is associated with reduced iFC of brain areas involved in emotion processing and regulation in children. Future studies should investigate whether this reduced iFC mediates the association between prenatal Mn exposure and emotional dysfunction in childhood.

PMID: 28610744 [PubMed - as supplied by publisher]

Spontaneous activity in the visual cortex is organized by visual streams.

Wed, 06/14/2017 - 15:45

Spontaneous activity in the visual cortex is organized by visual streams.

Hum Brain Mapp. 2017 Jun 13;:

Authors: Lu KH, Jeong JY, Wen H, Liu Z

Abstract
Large-scale functional networks have been extensively studied using resting state functional magnetic resonance imaging (fMRI). However, the pattern, organization, and function of fine-scale network activity remain largely unknown. Here, we characterized the spontaneously emerging visual cortical activity by applying independent component (IC) analysis to resting state fMRI signals exclusively within the visual cortex. In this subsystem scale, we observed about 50 spatially ICs that were reproducible within and across subjects, and analyzed their spatial patterns and temporal relationships to reveal the intrinsic parcellation and organization of the visual cortex. The resulting visual cortical parcels were aligned with the steepest gradient of cortical myelination, and were organized into functional modules segregated along the dorsal/ventral pathways and foveal/peripheral early visual areas. Cortical distance could partly explain intra-hemispherical functional connectivity, but not interhemispherical connectivity; after discounting the effect of anatomical affinity, the fine-scale functional connectivity still preserved a similar visual-stream-specific modular organization. Moreover, cortical retinotopy, folding, and cytoarchitecture impose limited constraints to the organization of resting state activity. Given these findings, we conclude that spontaneous activity patterns in the visual cortex are primarily organized by visual streams, likely reflecting feedback network interactions. Hum Brain Mapp, 2017. © 2017 Wiley Periodicals, Inc.

PMID: 28608643 [PubMed - as supplied by publisher]

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