Increased functional connectivity in intrinsic neural networks in individuals with aniridia.
Front Hum Neurosci. 2014;8:1013
Authors: Pierce JE, Krafft CE, Rodrigue AL, Bobilev AM, Lauderdale JD, McDowell JE
Mutations affecting the PAX6 gene result in aniridia, a condition characterized by the lack of an iris and other panocular defects. Among humans with aniridia, structural abnormalities also have been reported within the brain. The current study examined the functional implications of these deficits through "resting state" or task-free functional magnetic resonance imaging (fMRI) in 12 individuals with aniridia and 12 healthy age- and gender-matched controls. Using independent components analysis (ICA) and dual regression, individual patterns of functional connectivity associated with three intrinsic connectivity networks (ICNs; executive control, primary visual, and default mode) were compared across groups. In all three analyses, the aniridia group exhibited regions of greater connectivity correlated with the network, while the controls did not show any such regions. These differences suggest that individuals with aniridia recruit additional neural regions to supplement function in critical intrinsic networks, possibly due to inherent structural or sensory abnormalities related to the disorder.
PMID: 25566032 [PubMed - as supplied by publisher]
Spin-glass model predicts metastable brain states that diminish in anesthesia.
Front Syst Neurosci. 2014;8:234
Authors: Hudetz AG, Humphries CJ, Binder JR
Patterns of resting state connectivity change dynamically and may represent modes of cognitive information processing. The diversity of connectivity patterns (global brain states) reflects the information capacity of the brain and determines the state of consciousness. In this work, computer simulation was used to explore the repertoire of global brain states as a function of cortical activation level. We implemented a modified spin glass model to describe UP/DOWN state transitions of neuronal populations at a mesoscopic scale based on resting state BOLD fMRI data. Resting state fMRI was recorded in 20 participants and mapped to 10,000 cortical regions (sites) defined on a group-aligned cortical surface map. Each site represented the population activity of a ~20 mm(2) area of the cortex. Cross-correlation matrices of the mapped BOLD time courses of the set of sites were calculated and averaged across subjects. In the model, each cortical site was allowed to interact with the 16 other sites that had the highest pair-wise correlation values. All sites stochastically transitioned between UP and DOWN states under the net influence of their 16 pairs. The probability of local state transitions was controlled by a single parameter T corresponding to the level of global cortical activation. To estimate the number of distinct global states, first we ran 10,000 simulations at T = 0. Simulations were started from random configurations that converged to one of several distinct patterns. Using hierarchical clustering, at 99% similarity, close to 300 distinct states were found. At intermediate T, metastable state configurations were formed suggesting critical behavior with a sharp increase in the number of metastable states at an optimal T. Both reduced activation (anesthesia, sleep) and increased activation (hyper-activation) moved the system away from equilibrium, presumably incompatible with conscious mentation. During equilibrium, the diversity of large-scale brain states was maximum, compatible with maximum information capacity-a presumed condition of consciousness.
PMID: 25565989 [PubMed - as supplied by publisher]
Detection of abnormal resting-state networks in individual patients suffering from focal epilepsy: an initial step toward individual connectivity assessment.
Front Neurosci. 2014;8:419
Authors: Dansereau CL, Bellec P, Lee K, Pittau F, Gotman J, Grova C
The spatial coherence of spontaneous slow fluctuations in the blood-oxygen-level dependent (BOLD) signal at rest is routinely used to characterize the underlying resting-state networks (RSNs). Studies have demonstrated that these patterns are organized in space and highly reproducible from subject to subject. Moreover, RSNs reorganizations have been suggested in pathological conditions. Comparisons of RSNs organization have been performed between groups of subjects but have rarely been applied at the individual level, a step required for clinical application. Defining the notion of modularity as the organization of brain activity in stable networks, we propose Detection of Abnormal Networks in Individuals (DANI) to identify modularity changes at the individual level. The stability of each RSN was estimated using a spatial clustering method: Bootstrap Analysis of Stable Clusters (BASC) (Bellec et al., 2010). Our contributions consisted in (i) providing functional maps of the most stable cores of each networks and (ii) in detecting "abnormal" individual changes in networks organization when compared to a population of healthy controls. DANI was first evaluated using realistic simulated data, showing that focussing on a conservative core size (50% most stable regions) improved the sensitivity to detect modularity changes. DANI was then applied to resting state fMRI data of six patients with focal epilepsy who underwent multimodal assessment using simultaneous EEG/fMRI acquisition followed by surgery. Only patient with a seizure free outcome were selected and the resected area was identified using a post-operative MRI. DANI automatically detected abnormal changes in 5 out of 6 patients, with excellent sensitivity, showing for each of them at least one "abnormal" lateralized network closely related to the epileptic focus. For each patient, we also detected some distant networks as abnormal, suggesting some remote reorganization in the epileptic brain.
PMID: 25565949 [PubMed - as supplied by publisher]
Functional network alterations and their structural substrate in drug-resistant epilepsy.
Front Neurosci. 2014;8:411
Authors: Caciagli L, Bernhardt BC, Hong S, Bernasconi A, Bernasconi N
The advent of MRI has revolutionized the evaluation and management of drug-resistant epilepsy by allowing the detection of the lesion associated with the region that gives rise to seizures. Recent evidence indicates marked chronic alterations in the functional organization of lesional tissue and large-scale cortico-subcortical networks. In this review, we focus on recent methodological developments in functional MRI (fMRI) analysis techniques and their application to the two most common drug-resistant focal epilepsies, i.e., temporal lobe epilepsy related to mesial temporal sclerosis and extra-temporal lobe epilepsy related to focal cortical dysplasia. We put particular emphasis on methodological developments in the analysis of task-free or "resting-state" fMRI to probe the integrity of intrinsic networks on a regional, inter-regional, and connectome-wide level. In temporal lobe epilepsy, these techniques have revealed disrupted connectivity of the ipsilateral mesiotemporal lobe, together with contralateral compensatory reorganization and striking reconfigurations of large-scale networks. In cortical dysplasia, initial observations indicate functional alterations in lesional, peri-lesional, and remote neocortical regions. While future research is needed to critically evaluate the reliability, sensitivity, and specificity, fMRI mapping promises to lend distinct biomarkers for diagnosis, presurgical planning, and outcome prediction.
PMID: 25565942 [PubMed - as supplied by publisher]
The relationship between glucose metabolism, resting-state fMRI BOLD signal, and GABAA-binding potential: a preliminary study in healthy subjects and those with temporal lobe epilepsy.
J Cereb Blood Flow Metab. 2015 Jan 7;
Authors: Nugent AC, Martinez A, D'Alfonso A, Zarate CA, Theodore WH
Glucose metabolism has been associated with magnitude of blood oxygen level-dependent (BOLD) signal and connectivity across subjects within the default mode and dorsal attention networks. Similar correlations within subjects across the entire brain remain unexplored. [(18)F]-fluorodeoxyglucose positron emission tomography ([(18)F]-FDG PET), [(11)C]-flumazenil PET, and resting-state functional magnetic resonance imaging (fMRI) scans were acquired in eight healthy individuals and nine with temporal lobe epilepsy (TLE). Regional metabolic rate of glucose (rMRGlu) was correlated with amplitude of low frequency fluctuations (ALFFs) in the fMRI signal, global fMRI connectivity (GC), regional homogeneity (ReHo), and gamma-aminobutyric acid A-binding potential (GABAA BPND) across the brain. Partial correlations for ALFFs, GC, and ReHo with GABAA BPND were calculated, controlling for rMRGlu. In healthy subjects, significant positive correlations were observed across the brain between rMRGlu and ALFF, ReHo and GABAA BPND, and between ALFFs and GABAA BPND, controlling for rMRGlu. Brain-wide correlations between rMRGlu and ALFFs were significantly lower in TLE patients, and correlations between rMRGlu and GC were significantly greater in TLE than healthy subjects. These results indicate that the glutamatergic and GABAergic systems are coupled across the healthy human brain, and that ALFF is related to glutamate use throughout the healthy human brain. TLE may be a disorder of altered long-range connectivity in association with glutamate function.Journal of Cerebral Blood Flow & Metabolism advance online publication, 7 January 2015; doi:10.1038/jcbfm.2014.228.
PMID: 25564232 [PubMed - as supplied by publisher]
Errors on interrupter tasks presented during spatial and verbal working memory performance are linearly linked to large-scale functional network connectivity in high temporal resolution resting state fMRI.
Brain Imaging Behav. 2015 Jan 7;
Authors: Magnuson ME, Thompson GJ, Schwarb H, Pan W, McKinley A, Schumacher EH, Keilholz SD
The brain is organized into networks composed of spatially separated anatomical regions exhibiting coherent functional activity over time. Two of these networks (the default mode network, DMN, and the task positive network, TPN) have been implicated in the performance of a number of cognitive tasks. To directly examine the stable relationship between network connectivity and behavioral performance, high temporal resolution functional magnetic resonance imaging (fMRI) data were collected during the resting state, and behavioral data were collected from 15 subjects on different days, exploring verbal working memory, spatial working memory, and fluid intelligence. Sustained attention performance was also evaluated in a task interleaved between resting state scans. Functional connectivity within and between the DMN and TPN was related to performance on these tasks. Decreased TPN resting state connectivity was found to significantly correlate with fewer errors on an interrupter task presented during a spatial working memory paradigm and decreased DMN/TPN anti-correlation was significantly correlated with fewer errors on an interrupter task presented during a verbal working memory paradigm. A trend for increased DMN resting state connectivity to correlate to measures of fluid intelligence was also observed. These results provide additional evidence of the relationship between resting state networks and behavioral performance, and show that such results can be observed with high temporal resolution fMRI. Because cognitive scores and functional connectivity were collected on nonconsecutive days, these results highlight the stability of functional connectivity/cognitive performance coupling.
PMID: 25563228 [PubMed - as supplied by publisher]
Normalisation of brain connectivity through compensatory behaviour, despite congenital hand absence.
Authors: Hahamy A, Sotiropoulos SN, Henderson Slater D, Malach R, Johansen-Berg H, Makin TR
Previously we showed, using task-evoked fMRI, that compensatory intact hand usage after amputation facilitates remapping of limb representations in the cortical territory of the missing hand (Makin et al., 2013a). Here we show that compensatory arm usage in individuals born without a hand (one-handers) reflects functional connectivity of spontaneous brain activity in the cortical hand region. Compared with two-handed controls, one-handers showed reduced symmetry of hand region inter-hemispheric resting-state functional connectivity and corticospinal white matter microstructure. Nevertheless, those one-handers who more frequently use their residual (handless) arm for typically bimanual daily tasks also showed more symmetrical functional connectivity of the hand region, demonstrating that adaptive behaviour drives long-range brain organisation. We therefore suggest that compensatory arm usage maintains symmetrical sensorimotor functional connectivity in one-handers. Since variability in spontaneous functional connectivity in our study reflects ecological behaviour, we propose that inter-hemispheric symmetry, typically observed in resting sensorimotor networks, depends on coordinated motor behaviour in daily life.
PMID: 25562885 [PubMed - as supplied by publisher]
Resting-state anticorrelations between medial and lateral prefrontal cortex: Association with working memory, aging, and individual differences.
Cortex. 2014 Dec 13;64C:271-280
Authors: Keller JB, Hedden T, Thompson TW, Anteraper SA, Gabrieli JD, Whitfield-Gabrieli S
We examined how variation in working memory (WM) capacity due to aging or individual differences among young adults is associated with intrinsic or resting-state anticorrelations, particularly between (1) the medial prefrontal cortex (MPFC), a component of the default-mode network (DMN) that typically decreases in activation during external, attention-demanding tasks, and (2) the dorsolateral prefrontal cortex (DLPFC), a component of the fronto-parietal control network that supports executive functions and WM and typically increases in activation during attention-demanding tasks. We compared the magnitudes of MPFC-DLPFC anticorrelations between healthy younger and older participants (Experiment 1) and related the magnitudes of these anticorrelations to individual differences on two behavioral measures of WM capacity in two independent groups of young adults (Experiments 1 and 2). Relative to younger adults, older adults exhibited reductions in WM capacity and in MPFC-DLPFC anticorrelations. Within younger adults, greater MPFC-DLPFC anticorrelation at rest correlated with greater WM capacity. These findings show that variation in MPFC-DLPFC anticorrelations, whether related to aging or to individual differences, may reflect an intrinsic functional brain architecture supportive of WM capacity.
PMID: 25562175 [PubMed - as supplied by publisher]
Precuneal and amygdala spontaneous activity and functional connectivity in war-zone-related PTSD.
Psychiatry Res. 2014 Dec 13;
Authors: Yan X, Lazar M, Shalev AY, Neylan TC, Wolkowitz OM, Brown AD, Henn-Haase C, Yehuda R, Flory JD, Abu-Amara D, Sodickson DK, Marmar CR
Abnormality in the "fear circuitry" has been known as a major neural characteristic of posttraumatic stress disorder (PTSD). Recent studies also revealed decreased functional connectivity in the default mode network in PTSD. The present study aims to investigate, in war-zone-related PTSD, the spontaneous activity and functional connectivity of the amygdala and the precuneus, which are two representative brain regions of the two networks, respectively. Two groups of 52 male US Operation Iraqi Freedom (OIF) and Operation Enduring Freedom (OEF) veterans (PTSD vs. controls), well matched on age and ethnicity, were clinically assessed and then studied in a resting state functional magnetic resonance imaging (fMRI) procedure. Functional connectivity analysis was conducted on the resting state fMRI data with the amygdala and precuneus as seeds. Compared with controls, veterans with PTSD had lower functional connectivity in the default mode network, as well as lower amygdala-frontal functional connectivity. Both the PTSD and the control group had a significant positive precuneal-amygdala functional connectivity without a significant group difference. The magnitudes of spontaneous activity of the amygdala and the precuneus were negatively correlated in the PTSD group and showed significant quadratic relationships with the amount of emotional abuse in early life trauma. These findings may improve our understanding about the relationships between fear circuitry and the default mode network in the context of war-zone-related PTSD.
PMID: 25561375 [PubMed - as supplied by publisher]
White matter abnormalities of microstructure and physiological noise in schizophrenia.
Brain Imaging Behav. 2015 Jan 6;
Authors: Cheng H, Newman SD, Kent JS, Bolbecker A, Klaunig MJ, O'Donnell BF, Puce A, Hetrick WP
White matter abnormalities in schizophrenia have been revealed by many imaging techniques and analysis methods. One of the findings by diffusion tensor imaging is a decrease in fractional anisotropy (FA), which is an indicator of white matter integrity. On the other hand, elevation of metabolic rate in white matter was observed from positron emission tomography (PET) studies. In this report, we aim to compare the two structural and functional effects on the same subjects. Our comparison is based on the hypothesis that signal fluctuation in white matter is associated with white matter functional activity. We examined the variance of the signal in resting state fMRI and found significant differences between individuals with schizophrenia and non-psychiatric controls specifically in white matter tissue. Controls showed higher temporal signal-to-noise ratios clustered in regions including temporal, frontal, and parietal lobes, cerebellum, corpus callosum, superior longitudinal fasciculus, and other major white matter tracts. These regions with higher temporal signal-to-noise ratio agree well with those showing higher metabolic activity reported by studies using PET. The results suggest that individuals with schizophrenia tend to have higher functional activity in white matter in certain brain regions relative to healthy controls. Despite some overlaps, the distinct regions for physiological noise are different from those for FA derived from diffusion tensor imaging, and therefore provide a unique angle to explore potential mechanisms to white matter abnormality.
PMID: 25560665 [PubMed - as supplied by publisher]
Resting-state functional connectivity of the sensorimotor network in individuals with non-specific low back pain and the association with the sit-to-stand-to-sit task.
Brain Connect. 2015 Jan 4;
Authors: Pijnenburg M, Brumagne S, Caeyenberghs K, Janssens L, Goossens N, Marinazzo D, Swinnen S, Claeys K, Siugzdaite R
Individuals with non-specific low back pain (NSLBP) show a decreased sit-to-stand-to-sit performance. This dynamic sensorimotor task requires integration of sensory and motor information in the brain. Therefore, better understanding of the underlying central mechanisms of impaired sensorimotor control and the presence of NSLBP is needed. The aims of this study were to characterize alterations in functional connectivity in individuals with NSLBP and to investigate whether the patterns of sensorimotor functional connectivity underlie the impaired sit-to-stand-to-sit performance. Seventeen individuals with NSLBP and 17 healthy controls were instructed to perform five consecutive sit-to-stand-to-sit movements as fast as possible. Based on the center of pressure displacement, the total duration of the sit-to-stand-to-sit task was determined. In addition, resting-state functional connectivity images were acquired and analysed on a multivariate level using both functional connectivity density mapping and independent component analysis. Individuals with NSLBP needed significantly more time to perform the sit-to-stand-to-sit task compared to healthy controls. In addition, decreased resting-state functional connectivity of brain areas related to the integration of sensory and/or motor information was shown in the individuals with NSLBP. Moreover, the decreased functional connectivity at rest of the left precentral gyrus and lobule IV and V of the left cerebellum was associated with a longer duration of the sit-to-stand-to-sit task in both individuals with NSLBP and healthy controls. In summary, individuals with NSLBP showed a reorganization of the sensorimotor network at rest and the functional connectivity of specific sensorimotor areas was associated with the performance of a dynamic sensorimotor task.
PMID: 25557846 [PubMed - as supplied by publisher]
Association of resting-state network dysfunction with their dynamics of inter-network interactions in depression.
J Affect Disord. 2014 Dec 12;174C:527-534
Authors: Wei M, Qin J, Yan R, Bi K, Liu C, Yao Z, Lu Q
BACKGROUND: Network-level brain analysis on resting state has demonstrated that depression is not only associated with intra-network dysfunction, but relates to the disturbed interplay between the networks. However, the underlying associations between the intra-network dysfunction and the disturbed inter-network interactions remain unexplored. This study was aimed to explore the association of resting-state networks dysfunction with their dynamics of inter-network interactions in depression.
METHODS: Resting-state functional magnetic resonance imaging (fMRI) data were collected from 20 depressed patients and 20 matched healthy controls. We evaluated the Hurst exponents of the time series from resting-state networks, and employed multivariate pattern analysis to capture depression-associated networks with increased or decreased Hurst values. Granger causalities between these networks were explored to undertake an intensive study of the dynamic inter-network interactions.
RESULTS: The default mode network (DMN) exhibited decreased Hurst value, indicative of more irregular oscillation within the DMN implicated in depressive symptoms. The ventromedial prefrontal network (vmPFN) and salience network (SN) with increased Hurst values, as compensatory mechanisms, continually enhanced the interactions to the DMN for trying hard to impel the DMN to function synchronously. On the other side, the DMN exerted frequently enhanced causality on the left fronto-parietal network with elevated Hurst exponent, accompanied by imbalance between the fronto-parietal network and DMN circuits in depression.
LIMITATIONS: This study suffers from small sample size and is confined to large-scale networks.
CONCLUSIONS: Our preliminary findings mainly revealed the DMN-related dynamic interactions with the vmPFN, SN and the fronto-parietal network in depression, which might offer useful information for discovering the neuropathological mechanisms underlying the depressive symptoms.
PMID: 25556670 [PubMed - as supplied by publisher]
Ketamine Interactions with Biomarkers of Stress: A randomized placebo-controlled repeated measures resting-state fMRI and PCASL pilot study in healthy men.
Neuroimage. 2014 Dec 29;
Authors: Mahani NK, Niesters M, van Osch MJ, Oitzl M, Veer I, de Rooij M, van Gerven J, van Buchem MA, Beckmann CF, Rombouts SA, Dahan A
Ketamine, an NMDA receptor antagonist, is increasingly used to study the link between glutamatergic signaling dysregulation and mood and chronic pain disorders. Glutamatergic neurotransmittion and stress corticosteroids (cortisol in human) are critical for Ca(2+) mediated neuroplasticity and behavioral adaptation. The mechanisms of action of glutamatergic neurotransmission and stress corticosteroids on the NMDA-receptors of the hippocampus have been long studied in animals, but given little attention in human studies. In this randomized single-blinded placebo-controlled crossover study (12 healthy young men), five sets of resting-state fMRI (RSFMRI), pseudocontinuous arterial spin labeling (PCASL), and corresponding salivary cortisol samples were acquired over 4 hours, at given intervals under pharmacokinetically-controlled infusion of subanaesthetic ketamine (20 & 40 mg/70 kg/h). An identical procedure was repeated under a sham placebo condition. Differences in the profile of ketamine versus placebo effect over time were examined. Compared to placebo, ketamine mimicked a stress-like response (increased cortisol, reduced calmness and alertness, and impaired working memory). Ketamine effects on the brain included a transient prefrontal hyperperfusion and a dose-related reduction of relative hippocampal perfusion, plus emerging hyperconnectivity between the hippocampus and the occipital, cingulate, precuneal, cerebellar and basal ganglia regions. The spatiotemporal profiles of ketamine effects on different hippocampal subnetworks suggest a topographically dissociable change in corticohippocampal functional connectivity. We discuss our findings in the context of the negative feedback inhibition theory of the hippocampal stress control. This pilot study provides a methodological framework for multimodal functional neuroimaging under resting-state conditions, which may be generalized for translational studies of glutamatergic- or stress-related etiology of neuropsychiatric disorders.
PMID: 25554429 [PubMed - as supplied by publisher]
Alteration of spontaneous neuronal activity within the salience network in partially remitted depression.
Brain Res. 2014 Dec 29;
Authors: Liu C, Ma X, Song L, Tang L, Jing B, Zhang Y, Li F, Zhou Z, Fan J, Wang C
Of major depression patients, 29% to 66% show only partial remission on a single antidepressant trial. Such patients are characterized by residual depressive symptoms such as anhedonia, psychic anxiety, sleep disturbance, and cognitive dysfunction. However, the neural mechanisms of partially remitted depression remain unclear. Using the amplitude of low-frequency fluctuations (ALFF) approach, we investigated the intrinsic neural oscillation alterations during resting state in partially remitted depression. A total of 23 partially remitted depression patients and 68 healthy controls underwent 3.0T magnetic resonance imaging for functional imaging. We compared ALFF differences between groups as well as correlations between clinical measurements and ALFF measurements in the brain regions showing significant group differences. Compared with healthy controls, partially remitted depression patients showed increased ALFF measurements in the left ventral anterior insula, bilateral posterior insula, and bilateral supramarginal gyrus, and decreased ALFF measurements in the left calcarine gyrus. A trend positive correlation was found between the number of depressive episodes and ALFF values in the right posterior insula in the partially remitted depression group. In addition, the ALFF values of the right supramarginal gyrus were negatively correlated with Hamilton Depression Rating Scale scores. Consistent with the emerging theory of the role of the salience network in sensing the changes of homeostasis in contributing to partially remitted depression, the current findings suggest that the increased intrinsic neural oscillation of the insula may be related to the refractoriness to treatment and might be an imaging marker for predicting future depression recurrence.
PMID: 25553621 [PubMed - as supplied by publisher]
Frequency-dependent amplitude alterations of resting-state spontaneous fluctuations in idiopathic generalized epilepsy.
Epilepsy Res. 2014 Jul;108(5):853-60
Authors: Wang Z, Zhang Z, Liao W, Xu Q, Zhang J, Lu W, Jiao Q, Chen G, Feng J, Lu G
PURPOSE: Amplitude of low-frequency fluctuation (ALFF) of blood-oxygenation level-dependent (BOLD) has proven a promising way to detect disease-related local brain activity. However, routine approach employs an arbitrary frequency band of 0.01-0.08 Hz, which lacks frequency specificity and blinds to the information contained in other frequency bands. This study investigated the amplitude of fluctuations in full BOLD frequency bands, and addressed how amplitudes of fluctuations change in each specific frequency range in idiopathic generalized epilepsy (IGE).
METHODS: Thirty-four IGE patients with generalized tonic-clonic seizure and the same number of age- and sex-matched healthy controls were included. Functional MRI data were acquired using a 2s repetition time. Routine amplitude of low-frequency fluctuation analysis was first performed. The regions showing group difference were set as Region-of-interest for analysis of amplitudes of full-frequency. The amplitudes of BOLD fluctuations were consecutively performed at each frequency bin of 0.002 Hz, and specific frequency amplitude analyses were performed in five different frequency ranges (0-0.01 Hz, 0.01-0.027 Hz, 0.027-0.073 Hz, 0.073-0.198 Hz, and 0.198-0.25 Hz).
KEY FINDINGS: The thalamus and prefrontal cortex showed significant group differences in routine amplitude analysis. For amplitude of full-frequency analysis, a reverse pattern was found in the dynamic changes between the thalamus and prefrontal cortex in IGE. Moreover, the prefrontal cortex showed amplitude difference in the 0.01-0.027 Hz band, while the thalamus showed amplitude difference in the 0.027-0.073 Hz band. Both these two regions showed amplitude differences in 0.198-0.25 Hz band.
SIGNIFICANCE: We demonstrated the characteristic alterations of amplitude of BOLD fluctuations in IGE in frequency domain. The amplitude analysis of full frequency may potentially help to select specific frequency range for detecting epilepsy-related brain activity, and provide insights into the pathophysiological mechanism of IGE.
PMID: 24721198 [PubMed - indexed for MEDLINE]
Functional Anatomy of the Thalamus as a Model of Integrated Structural and Functional Connectivity of the Human Brain In Vivo.
Brain Topogr. 2014 Dec 31;
Authors: Mastropasqua C, Bozzali M, Spanò B, Koch G, Cercignani M
While methods of measuring non-invasively both, functional and structural brain connectivity are available, the degree of overlap between them is still unknown. In this paper this issue is addressed by investigating the connectivity pattern of a brain structure with many, well characterized structural connections, namely the thalamus. Diffusion-weighted and resting state (RS) functional MRI (fMRI) data were collected in a group of 38 healthy participants. Probabilistic tractography was performed to parcellate the thalamus into regions structurally connected to different cortical areas. The resulting regions were used as seeds for seed-based analysis of RS fMRI data. The tractographic parcellation was thus cross-validated against functional connectivity data by evaluating the overlap between the functional and structural thalamo-cortical connections originating from the parcellated regions. Our data show only a partial overall correspondence between structural and functional connections, in the same group of healthy individuals, thus suggesting that the two approaches provide complementary and not overlapping information. Future studies are warranted to extend the results we obtained in the thalamus to other structures, and to confirm that the mechanisms behind functional connectivity are more complex than just expressing structural connectivity.
PMID: 25549779 [PubMed - as supplied by publisher]
Prefrontal brain network connectivity indicates degree of both schizophrenia risk and cognitive dysfunction.
Schizophr Bull. 2014 May;40(3):653-64
Authors: Unschuld PG, Buchholz AS, Varvaris M, van Zijl PC, Ross CA, Pekar JJ, Hock C, Sweeney JA, Tamminga CA, Keshavan MS, Pearlson GD, Thaker GK, Schretlen DJ
OBJECTIVE: Cognitive dysfunction is a core feature of schizophrenia, and persons at risk for schizophrenia may show subtle deficits in attention and working memory. In this study, we investigated the relationship between integrity of functional brain networks and performance in attention and working memory tasks as well as schizophrenia risk.
METHODS: A total of 235 adults representing 3 levels of risk (102 outpatients with schizophrenia, 70 unaffected first-degree relatives of persons with schizophrenia, and 63 unrelated healthy controls [HCs]) completed resting-state functional magnetic resonance imaging and a battery of attention and working memory tasks (Brief Test of Attention, Hopkins Verbal Learning Test, and Brief Visuospatial Memory Test) on the same day. Functional networks were defined based on coupling with seeds in the dorsal anterior cingulate cortex, dorsolateral prefrontal cortex (DLPFC), medial prefrontal cortex (MPFC), and primary visual cortex. Networks were then dissected into regional clusters of connectivity that were used to generate individual interaction matrices representing functional connectivity within each network.
RESULTS: Both patients with schizophrenia and their first-degree relatives showed cognitive dysfunction compared with HCs. First canonicals indicated an inverse relationship between cognitive performance and connectivity within the DLPFC and MPFC networks. Multivariate analysis of variance revealed multivariate main effects of higher schizophrenia risk status on increased connectivity within the DLPFC and MPFC networks.
CONCLUSIONS: These data suggest that excessive connectivity within brain networks coupled to the DLPFC and MPFC, respectively, accompany cognitive deficits in persons at risk for schizophrenia. This might reflect compensatory reactions in neural systems required for cognitive processing of attention and working memory tasks to brain changes associated with schizophrenia.
PMID: 23778975 [PubMed - indexed for MEDLINE]
Effect of integrated cognitive therapy on hippocampal functional connectivity patterns in stroke patients with cognitive dysfunction: a resting-state FMRI study.
Evid Based Complement Alternat Med. 2014;2014:962304
Authors: Yang S, Jiang C, Ye H, Tao J, Huang J, Gao Y, Lin Z, Chen L
Objective. This study aimed to identify abnormal hippocampal functional connectivity (FC) following ischemic stroke using resting-state fMRI. We also explored whether abnormal hippocampal FC could be modulated by integrated cognitive therapy and tested whether these alterations were associated with cognitive performance. Methods. 18 right-handed cognitively impaired ischemic stroke patients and 18 healty control (HC) subjects were included in this study. Stroke subjects were scanned at baseline and after integrated cognitive therapy, while HCs were only scanned at baseline, to identify regions that show significant correlations with the seed region. Behavioral and cognitive assessments were obtained before each scan. Results. During the resting state, we found abnormal hippocampal FC associated with temporal regions, insular cortex, cerebellum, and prefrontal cortex in stroke patients compared to HCs. After integrated cognitive therapy, however, the stroke group showed increased hippocampal FC mainly located in the prefrontal gyrus and the default mode network (DMN). Altered hippocampal FC was associated with cognitive improvement. Conclusion. Resting-state fMRI may provide novel insight into the study of functional networks in the brain after stroke. Furthermore, altered hippocampal FC may be a compensatory mechanism for cognitive recovery after ischemic stroke.
PMID: 25548595 [PubMed]
Spatiotemporal consistency of local neural activities: A new imaging measure for functional MRI data.
J Magn Reson Imaging. 2014 Dec 24;
Authors: Dong L, Luo C, Cao W, Zhang R, Gong J, Gong D, Yao D
PURPOSE: To characterize the local consistency by integrating temporal and spatial information in the local region using functional magnetic resonance imaging (fMRI).
MATERIALS AND METHODS: One simulation was implemented to explain the definition of FOur-dimensional (spatiotemporal) Consistency of local neural Activities (FOCA). Then three experiments included resting state data (33 subjects), resting state reproducibility data (16 subjects), and event state data (motor execution task, 26 subjects) were designed. Finally, FOCA were respectively analyzed using statistical analysis methods, such as one-sample t-test and paired t-test, etc.
RESULTS: During resting state (Experiment 1), the FOCA values (P < 0.05, family-wise error [FWE] corrected, voxel size >621 mm(3) ) were found to be distinct at the bilateral inferior frontal gyrus, middle frontal gyrus, angular gyrus, and precuneus/cuneus. In Experiment 2 (reproducibility), a high degree of consistency within subjects (correlation ≈0.8) and between subjects (correlation ≈0.6) of FOCA were obtained. Comparing event with resting state in Experiment 3, enhanced FOCA (P < 0.05, FWE-corrected, voxel size >621 mm(3) ) was observed mainly in the precentral gyrus and lingual gyrus.
CONCLUSION: These findings suggest that FOCA has the potential to provide further information that will help to better understand brain function in neural imaging. J. Magn. Reson. Imaging 2014.
PMID: 25538009 [PubMed - as supplied by publisher]
Is functional integration of resting state brain networks an unspecific biomarker for working memory performance?
Neuroimage. 2014 Dec 20;
Authors: Alavash M, Doebler P, Holling H, Thiel CM, Gießing C
Is there one optimal topology of functional brain networks at rest from which our cognitive performance would profit? Previous studies suggest that functional integration of resting state brain networks is an important biomarker for cognitive performance. However, it is still unknown whether higher network integration is an unspecific predictor for good cognitive performance or, alternatively, whether specific network organization during rest predicts only specific cognitive abilities. Here, we investigated the relationship between network integration at rest and cognitive performance using two tasks that measured different aspects of working memory; one task assessed visual-spatial and the other numerical working memory. Network clustering, modularity and efficiency were computed to capture network integration on different levels of network organisation, and to statistically compare their correlations with the performance in each working memory test. The results revealed that each working memory aspect profits from a different resting state topology, and the tests showed significantly different correlations with each of the measures of network integration. While higher global network integration and modularity predicted significantly better performance in visual-spatial working memory, both measures showed no significant correlation with numerical working memory performance. In contrast, numerical working memory was superior in subjects with highly clustered brain networks, predominantly in the intraparietal sulcus, a core brain region of the working memory network. Our findings suggest that a specific balance between local and global functional integration of resting state brain networks facilitates special aspects of cognitive performance. In the context of working memory, while visual-spatial performance is facilitated by globally integrated functional resting state brain networks, numerical working memory profits from increased capacities for local processing, especially in brain regions involved in working memory performance.
PMID: 25536495 [PubMed - as supplied by publisher]