Bayesian network analysis reveals alterations to default mode network connectivity in individuals at risk for Alzheimer's disease.
PLoS One. 2013;8(12):e82104
Authors: Li R, Yu J, Zhang S, Bao F, Wang P, Huang X, Li J
Alzheimer's disease (AD) is associated with abnormal functioning of the default mode network (DMN). Functional connectivity (FC) changes to the DMN have been found in patients with amnestic mild cognitive impairment (aMCI), which is the prodromal stage of AD. However, whether or not aMCI also alters the effective connectivity (EC) of the DMN remains unknown. We employed a combined group independent component analysis (ICA) and Bayesian network (BN) learning approach to resting-state functional MRI (fMRI) data from 17 aMCI patients and 17 controls, in order to establish the EC pattern of DMN, and to evaluate changes occurring in aMCI. BN analysis demonstrated heterogeneous regional convergence degree across DMN regions, which were organized into two closely interacting subsystems. Compared to controls, the aMCI group showed altered directed connectivity weights between DMN regions in the fronto-parietal, temporo-frontal, and temporo-parietal pathways. The aMCI group also exhibited altered regional convergence degree in the right inferior parietal lobule. Moreover, we found EC changes in DMN regions in aMCI were correlated with regional FC levels, and the connectivity metrics were associated with patients' cognitive performance. This study provides novel sights into our understanding of the functional architecture of the DMN and adds to a growing body of work demonstrating the importance of the DMN as a mechanism of aMCI.
PMID: 24324753 [PubMed - in process]
Identify changes of brain regional homogeneity in bipolar disorder and unipolar depression using resting-state FMRI.
PLoS One. 2013;8(12):e79999
Authors: Liang MJ, Zhou Q, Yang KR, Yang XL, Fang J, Chen WL, Huang Z
BACKGROUND: To identify changes in brain activation patterns in bipolar disorder (BD) and unipolar depression (UD) patients.
METHODOLOGY/PRINCIPAL FINDINGS: Resting-state fMRI scans of 16 healthy controls, 17 BD and 16 UD patients were obtained. T-test of normalized regional homogeneity (ReHo) was performed in a voxel-by-voxel manner. A combined threshold of á = 0.05, minimum cluster volume of V = 10503 mm(3) (389 voxels) were used to determine ReHo differences between groups. In UD group, fMRI revealed ReHo increases in the left middle occipital lobe, right inferior parietal lobule, right precuneus and left convolution; and ReHo decreases in the left parahippocampalgyrus, right precentralgyrus, left postcentralgyrus, left precentralgyrus and left cingulated. In BD group, ReHo increases in the right insular cortex, left middle frontal gyrus, left precuneus, left occipital lobe, left parietal, left superior frontal gyrus and left thalamus; and ReHo decreases in the right anterior lobe of cerebellum, pons, right precentralgyrus, left postcentralgyrus, left inferior frontal gyrus, and right cingulate. There were some overlaps in ReHo profiles between UD and BD groups, but a marked difference was seen in the thalamus of BD.
CONCLUSIONS/SIGNIFICANCE: The resting-state fMRI and ReHo mapping are a promising tool to assist the detection of functional deficits and distinguish clinical and pathophysiological signs of BD and UD.
PMID: 24324588 [PubMed - in process]
Exploring mechanisms of spontaneous MEG functional connectivity: How delayed network interactions lead to structured amplitude envelopes of band-pass filtered oscillations.
Neuroimage. 2013 Dec 6;
Authors: Cabral J, Luckhoo H, Woolrich M, Joensson M, Mohseni H, Baker A, Kringelbach ML, Deco G
Spontaneous (or resting-state) brain activity has attracted a growing body of neuroimaging research over the last decades. Whole-brain network models have proved helpful to investigate the source of slow (<0.1Hz) correlated hemodynamic fluctuations revealed in fMRI during rest. However, the mechanisms mediating resting-state long-distance correlations and the relationship with the faster neural activity remain unclear. Novel insights coming from MEG studies have shown that the amplitude envelopes of alpha- and beta-frequency oscillations (~8-30Hz) display similar correlation patterns as the fMRI signals. In this work, we combine experimental and theoretical work to investigate the mechanisms of spontaneous MEG functional connectivity. Using a simple model of coupled oscillators adapted to incorporate realistic whole-brain connectivity and conduction delays, we explore how slow and structured amplitude envelopes of band-pass filtered signals - fairly reproducing MEG data collected from 10 healthy subjects at rest - are generated spontaneously in the space-time structure of the brain network. Our simulation results show that the large-scale neuroanatomical connectivity provides an optimal network structure to support a regime with metastable synchronization. In this regime, different subsystems may temporarily synchronize at reduced collective frequencies (falling in the 8-30Hz range due to the delays) while the global system never fully synchronizes. This mechanism modulates the frequency of the oscillators on a slow time-scale (<0.1Hz) leading to structured amplitude fluctuations of band-pass filtered signals. Taken overall, our results reveal that the structured amplitude envelope fluctuations observed in resting-state MEG data may originate from spontaneous synchronization mechanisms naturally occurring in the space-time structure of the brain.
PMID: 24321555 [PubMed - as supplied by publisher]
A kernel machine-based fMRI physiological noise removal method.
Magn Reson Imaging. 2013 Oct 19;
Authors: Song X, Chen NK, Gaur P
Functional magnetic resonance imaging (fMRI) technique with blood oxygenation level dependent (BOLD) contrast is a powerful tool for noninvasive mapping of brain function under task and resting states. The removal of cardiac- and respiration-induced physiological noise in fMRI data has been a significant challenge as fMRI studies seek to achieve higher spatial resolutions and characterize more subtle neuronal changes. The low temporal sampling rate of most multi-slice fMRI experiments often causes aliasing of physiological noise into the frequency range of BOLD activation signal. In addition, changes of heartbeat and respiration patterns also generate physiological fluctuations that have similar frequencies with BOLD activation. Most existing physiological noise-removal methods either place restrictive limitations on image acquisition or utilize filtering or regression based post-processing algorithms, which cannot distinguish the frequency-overlapping BOLD activation and the physiological noise. In this work, we address the challenge of physiological noise removal via the kernel machine technique, where a nonlinear kernel machine technique, kernel principal component analysis, is used with a specifically identified kernel function to differentiate BOLD signal from the physiological noise of the frequency. The proposed method was evaluated in human fMRI data acquired from multiple task-related and resting state fMRI experiments. A comparison study was also performed with an existing adaptive filtering method. The results indicate that the proposed method can effectively identify and reduce the physiological noise in fMRI data. The comparison study shows that the proposed method can provide comparable or better noise removal performance than the adaptive filtering approach.
PMID: 24321306 [PubMed - as supplied by publisher]
Resting state fMRI reveals a default mode dissociation between retrosplenial and medial prefrontal subnetworks in ASD despite motion scrubbing.
Front Hum Neurosci. 2013;7:802
Authors: Starck T, Nikkinen J, Rahko J, Remes J, Hurtig T, Haapsamo H, Jussila K, Kuusikko-Gauffin S, Mattila ML, Jansson-Verkasalo E, Pauls DL, Ebeling H, Moilanen I, Tervonen O, Kiviniemi VJ
In resting state functional magnetic resonance imaging (fMRI) studies of autism spectrum disorders (ASDs) decreased frontal-posterior functional connectivity is a persistent finding. However, the picture of the default mode network (DMN) hypoconnectivity remains incomplete. In addition, the functional connectivity analyses have been shown to be susceptible even to subtle motion. DMN hypoconnectivity in ASD has been specifically called for re-evaluation with stringent motion correction, which we aimed to conduct by so-called scrubbing. A rich set of default mode subnetworks can be obtained with high dimensional group independent component analysis (ICA) which can potentially provide more detailed view of the connectivity alterations. We compared the DMN connectivity in high-functioning adolescents with ASDs to typically developing controls using ICA dual-regression with decompositions from typical to high dimensionality. Dual-regression analysis within DMN subnetworks did not reveal alterations but connectivity between anterior and posterior DMN subnetworks was decreased in ASD. The results were very similar with and without motion scrubbing thus indicating the efficacy of the conventional motion correction methods combined with ICA dual-regression. Specific dissociation between DMN subnetworks was revealed on high ICA dimensionality, where networks centered at the medial prefrontal cortex and retrosplenial cortex showed weakened coupling in adolescents with ASDs compared to typically developing control participants. Generally the results speak for disruption in the anterior-posterior DMN interplay on the network level whereas local functional connectivity in DMN seems relatively unaltered.
PMID: 24319422 [PubMed - as supplied by publisher]
BrainCAT - a tool for automated and combined functional magnetic resonance imaging and diffusion tensor imaging brain connectivity analysis.
Front Hum Neurosci. 2013;7:794
Authors: Marques P, Soares JM, Alves V, Sousa N
Multimodal neuroimaging studies have recently become a trend in the neuroimaging field and are certainly a standard for the future. Brain connectivity studies combining functional activation patterns using resting-state or task-related functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) tractography have growing popularity. However, there is a scarcity of solutions to perform optimized, intuitive, and consistent multimodal fMRI/DTI studies. Here we propose a new tool, brain connectivity analysis tool (BrainCAT), for an automated and standard multimodal analysis of combined fMRI/DTI data, using freely available tools. With a friendly graphical user interface, BrainCAT aims to make data processing easier and faster, implementing a fully automated data processing pipeline and minimizing the need for user intervention, which hopefully will expand the use of combined fMRI/DTI studies. Its validity was tested in an aging study of the default mode network (DMN) white matter connectivity. The results evidenced the cingulum bundle as the structural connector of the precuneus/posterior cingulate cortex and the medial frontal cortex, regions of the DMN. Moreover, mean fractional anisotropy (FA) values along the cingulum extracted with BrainCAT showed a strong correlation with FA values from the manual selection of the same bundle. Taken together, these results provide evidence that BrainCAT is suitable for these analyses.
PMID: 24319419 [PubMed - as supplied by publisher]
A Method for handling intensity inhomogenieties in fMRI sequences of moving anatomy of the early developing brain.
Med Image Anal. 2013 Nov 6;18(2):285-300
Authors: Seshamani S, Cheng X, Fogtmann M, Thomason ME, Studholme C
This paper presents a method for intensity inhomogeniety removal in fMRI studies of a moving subject. In such studies, subtle changes in signal as the subject moves in the presence of a bias field can be a significant confound for BOLD signal analysis. The proposed method avoids the need for a specific tissue model or assumptions about tissue homogeneity by making use of the multiple views of the underlying bias field provided by the subject's motion. A parametric bias field model is assumed and a regression model is used to estimate the basis function weights of this model. Quantitative evaluation of the effects of motion and noise in motion estimates are performed using simulated data. Results demonstrate the strength and robustness of the new method compared to the state of the art 4D nonparametric bias estimator (N4ITK). We also qualitatively demonstrate the impact of the method on resting state neuroimage analysis of a moving adult brain with simulated motion and bias fields, as well as on in vivo moving fetal fMRI.
PMID: 24317121 [PubMed - as supplied by publisher]
Global Resting-State Functional Magnetic Resonance Imaging Analysis Identifies Frontal Cortex, Striatal, and Cerebellar Dysconnectivity in Obsessive-Compulsive Disorder.
Biol Psychiatry. 2013 Nov 4;
Authors: Anticevic A, Hu S, Zhang S, Savic A, Billingslea E, Wasylink S, Repovs G, Cole MW, Bednarski S, Krystal JH, Bloch MH, Li CS, Pittenger C
BACKGROUND: Obsessive-compulsive disorder (OCD) is associated with regional hyperactivity in cortico-striatal circuits. However, the large-scale patterns of abnormal neural connectivity remain uncharacterized. Resting-state functional connectivity studies have shown altered connectivity within the implicated circuitry, but they have used seed-driven approaches wherein a circuit of interest is defined a priori. This limits their ability to identify network abnormalities beyond the prevailing framework. This limitation is particularly problematic within the prefrontal cortex (PFC), which is large and heterogeneous and where a priori specification of seeds is therefore difficult. A hypothesis-neutral, data-driven approach to the analysis of connectivity is vital.
METHODS: We analyzed resting-state functional connectivity data collected at 3T in 27 OCD patients and 66 matched control subjects with a recently developed data-driven global brain connectivity (GBC) method, both within the PFC and across the whole brain.
RESULTS: We found clusters of decreased connectivity in the left lateral PFC in both whole-brain and PFC-restricted analyses. Increased GBC was found in the right putamen and left cerebellar cortex. Within regions of interest in the basal ganglia and thalamus, we identified increased GBC in dorsal striatum and anterior thalamus, which was reduced in patients on medication. The ventral striatum/nucleus accumbens exhibited decreased global connectivity but increased connectivity specifically with the ventral anterior cingulate cortex in subjects with OCD.
CONCLUSIONS: These findings identify previously uncharacterized PFC and basal ganglia dysconnectivity in OCD and reveal differentially altered GBC in dorsal and ventral striatum. Results highlight complex disturbances in PFC networks, which could contribute to disrupted cortical-striatal-cerebellar circuits in OCD.
PMID: 24314349 [PubMed - as supplied by publisher]
Functional connectivity of hippocampal networks in temporal lobe epilepsy.
Epilepsia. 2013 Dec 6;
Authors: Haneef Z, Lenartowicz A, Yeh HJ, Levin HS, Engel J, Stern JM
OBJECTIVE: Temporal lobe epilepsy (TLE) affects brain areas beyond the temporal lobes due to connections of the hippocampi and other temporal lobe structures. Using functional connectivity magnetic resonance imaging (MRI), we determined the changes of hippocampal networks in TLE to assess for a more complete distribution of abnormality.
METHODS: Regions of interest (ROIs) were defined in the right and left hippocampi in three groups of participants: left TLE (n = 13), right TLE (n = 11), and healthy controls (n = 16). Brain regions functionally connected to these ROIs were identified by correlating resting-state low-frequency functional MRI (fMRI) blood oxygenation level-dependent (BOLD) signal fluctuations. The grouped results were compared using independent sample t-test.
RESULTS: TLE was associated with increased hippocampal connectivity involving several key areas of the limbic network (temporal lobe, insula, thalamus), frontal lobes, angular gyrus, basal ganglia, brainstem, and cerebellum, along with reduced connectivity involving areas of the sensorimotor cortex (visual, somatosensory, auditory, primary motor) and the default mode network (precuneus). Left TLE had more marked connectivity changes than right TLE.
SIGNIFICANCE: The observed connectivity changes in TLE indicate dysfunctional networks that underlie widespread brain involvement in TLE. There are identifiable differences in the connectivity of the hippocampi between left and right TLE.
PMID: 24313597 [PubMed - as supplied by publisher]
Disruption of transfer entropy and inter-hemispheric brain functional connectivity in patients with disorder of consciousness.
Front Neuroinform. 2013;7:24
Authors: Mäki-Marttunen V, Diez I, Cortes JM, Chialvo DR, Villarreal M
Severe traumatic brain injury can lead to disorders of consciousness (DOC) characterized by deficit in conscious awareness and cognitive impairment including coma, vegetative state, minimally consciousness, and lock-in syndrome. Of crucial importance is to find objective markers that can account for the large-scale disturbances of brain function to help the diagnosis and prognosis of DOC patients and eventually the prediction of the coma outcome. Following recent studies suggesting that the functional organization of brain networks can be altered in comatose patients, this work analyzes brain functional connectivity (FC) networks obtained from resting-state functional magnetic resonance imaging (rs-fMRI). Two approaches are used to estimate the FC: the Partial Correlation (PC) and the Transfer Entropy (TE). Both the PC and the TE show significant statistical differences between the group of patients and control subjects; in brief, the inter-hemispheric PC and the intra-hemispheric TE account for such differences. Overall, these results suggest two possible rs-fMRI markers useful to design new strategies for the management and neuropsychological rehabilitation of DOC patients.
PMID: 24312048 [PubMed - as supplied by publisher]
Functional clustering of the human inferior parietal lobule by whole brain connectivity mapping of resting state fMRI signals.
Brain Connect. 2013 Dec 5;
Authors: Zhang S, Li CS
The human inferior parietal lobule (IPL) comprised the lateral bank of the intraparietal sulcus, angular gyrus and supramarginal gyrus, defined on the basis of anatomical landmarks and cytoarchitechtural organization of neurons. However, it is not clear whether the three areas represent functional subregions within the IPL. For instance, imaging studies frequently identified clusters of activities that cut across areal boundaries. Here, we used resting state functional magnetic resonance imaging (fMRI) data to examine how individual voxels within the IPL are best clustered according to their connectivity to the whole brain. The results identified a best estimate of 7 clusters which are hierarchically arranged as the anterior, middle, and posterior subregions. The anterior, middle, and posterior IPL are each significantly connected to the somatomotor areas, superior/middle/inferior frontal gyri, and regions of the default mode network. This functional segregation is supported by recent cytoarchitechtonics and tractography studies. IPL showed hemispheric differences in connectivity that accord with a predominantly left parietal role in tool use and language processing and a right parietal role in spatial attention and mathematical cognition. The functional clusters may also provide a more parsimonious and perhaps even accurate account of regional activations of the IPL during a variety of cognitive challenges, as reported in earlier fMRI studies.
PMID: 24308753 [PubMed - as supplied by publisher]
Memory consolidation by replay of stimulus-specific neural activity.
J Neurosci. 2013 Dec 4;33(49):19373-83
Authors: Deuker L, Olligs J, Fell J, Kranz TA, Mormann F, Montag C, Reuter M, Elger CE, Axmacher N
Memory consolidation transforms initially labile memory traces into more stable representations. One putative mechanism for consolidation is the reactivation of memory traces after their initial encoding during subsequent sleep or waking state. However, it is still unknown whether consolidation of individual memory contents relies on reactivation of stimulus-specific neural representations in humans. Investigating stimulus-specific representations in humans is particularly difficult, but potentially feasible using multivariate pattern classification analysis (MVPA). Here, we show in healthy human participants that stimulus-specific activation patterns can indeed be identified with MVPA, that these patterns reoccur spontaneously during postlearning resting periods and sleep, and that the frequency of reactivation predicts subsequent memory for individual items. We conducted a paired-associate learning task with items and spatial positions and extracted stimulus-specific activity patterns by MVPA in a simultaneous electroencephalography and functional magnetic resonance imaging (fMRI) study. As a first step, we investigated the amount of fMRI volumes during rest that resembled either one of the items shown before or one of the items shown as a control after the resting period. Reactivations during both awake resting state and sleep predicted subsequent memory. These data are first evidence that spontaneous reactivation of stimulus-specific activity patterns during resting state can be investigated using MVPA. They show that reactivation occurs in humans and is behaviorally relevant for stabilizing memory traces against interference. They move beyond previous studies because replay was investigated on the level of individual stimuli and because reactivations were not evoked by sensory cues but occurred spontaneously.
PMID: 24305832 [PubMed - in process]
The effects of high-intensity exercise on neural responses to images of food.
Am J Clin Nutr. 2013 Dec 4;
Authors: Crabtree DR, Chambers ES, Hardwick RM, Blannin AK
BACKGROUND: Acute bouts of high-intensity exercise modulate peripheral appetite regulating hormones to transiently suppress hunger. However, the effects of physical activity on central appetite regulation have yet to be fully investigated.
OBJECTIVE: We used functional magnetic resonance imaging (fMRI) to compare neural responses to visual food stimuli after intense exercise and rest.
DESIGN: Fifteen lean healthy men (mean ± SD age: 22.5 ± 3.1 y; mean ± SD body mass index: 24.2 ± 2.4 kg/m(2)) completed two 60-min trials-exercise (EX; running at ∼70% maximum aerobic capacity) and a resting control trial (REST)-in a counterbalanced order. After each trial, an fMRI assessment was completed in which images of high- and low-calorie foods were viewed.
RESULTS: EX significantly suppressed subjective appetite responses while increasing thirst and core-body temperature. Furthermore, EX significantly suppressed ghrelin concentrations and significantly enhanced peptide YY release. Neural responses to images of high-calorie foods significantly increased dorsolateral prefrontal cortex activation and suppressed orbitofrontal cortex (OFC) and hippocampus activation after EX compared with REST. After EX, low-calorie food images increased insula and putamen activation and reduced OFC activation compared with REST. Furthermore, left pallidum activity was significantly elevated after EX when low-calorie images were viewed and was suppressed when high-calorie images were viewed, and these responses correlated significantly with thirst.
CONCLUSIONS: Exercise increases neural responses in reward-related regions of the brain in response to images of low-calorie foods and suppresses activation during the viewing of high-calorie foods. These central responses are associated with exercise-induced changes in peripheral signals related to appetite-regulation and hydration status. This trial was registered at www.clinicaltrials.gov as NCT01926431.
PMID: 24305681 [PubMed - as supplied by publisher]
Present and future of fMRI in multiple sclerosis.
Expert Rev Neurother. 2013 Dec;13(12 Suppl):27-31
Authors: Filippi M, Rocca MA
Studies with functional MRI (fMRI) of the motor, visual and cognitive networks have consistently demonstrated functional cortical changes in the major multiple sclerosis (MS) clinical phenotypes. Compared with healthy subjects, these fMRI modifications are characterized by an altered recruitment of regions normally devoted to the performance of a given task, recruitment of additional areas, different resting state activity and disrupted connectivity. Studies that applied fMRI longitudinally have shown that such abnormalities vary over the course of the disease, not only after an acute relapse but also in clinically stable patients. fMRI and structural MRI abnormalities of the MS brain are correlated. Movement- and cognitive-associated fMRI changes were found to correlate with the amount of damage to brain normal-appearing white and gray matter and to the spinal cord. This suggests that, at least in some phases of the disease, increased recruitment of 'critical' central nervous system regions might contribute to limiting the functional impact of MS-related injury. fMRI has recently been applied to the assessment of functional modifications in the cervical cord of patients with MS. Evidence to date shows that cervical cord fMRI can reliably identify regions involved with tactile and proprioceptive stimulation in MS patients and different clinical phenotypes. As shown in brain studies, these investigations have detected increased recruitment in MS patients compared with healthy controls. At present, fMRI is a useful research tool, and reliable analysis and display methods have been developed. Future perspectives include development of fMRI paradigms for patients with MS-related disability and application of this technique in longitudinal studies to define the temporal evolution of functional cortical changes in different MS phenotypes as well as the effects of various therapeutic approaches on central nervous system plasticity.
PMID: 24289839 [PubMed - in process]
The neurosteroids allopregnanolone and dehydroepiandrosterone modulate resting-state amygdala connectivity.
Hum Brain Mapp. 2013 Dec 2;
Authors: Sripada RK, Welsh RC, Marx CE, Liberzon I
The neurosteroids allopregnanolone and dehydroepiandrosterone (DHEA) are integral components of the stress response and exert positive modulatory effects on emotion in both human and animal studies. Although these antidepressant and anxiolytic effects have been well established, to date, little research has examined their neural correlates, and no research has been conducted into the effects of neurosteroids on large-scale networks at rest. To investigate the neurosteroid impact on intrinsic connectivity networks, participants were administered 400 mg of pregnenolone (N = 16), 400 mg of DHEA (N = 14), or placebo (N = 15) and underwent 3T fMRI. Resting-state brain connectivity was measured using amygdala as a seed region. When compared with placebo, pregnenolone administration reduced connectivity between amygdala and dorsal medial prefrontal cortex, between amygdala and precuneus, and between amygdala and hippocampus. DHEA reduced connectivity between amygdala and periamygdala and between amygdala and insula. Reductions in amygdala to precuneus connectivity were associated with less self-reported negative affect. These results demonstrate that neurosteroids modulate amygdala functional connectivity during resting state and may be a target for pharmacological intervention. Additionally, allopregnanolone and DHEA may shift the balance between salience network and default network, a finding that could provide insight into the neurocircuitry of anxiety psychopathology. Hum Brain Mapp, 2013. © 2013 Wiley Periodicals, Inc.
PMID: 24302681 [PubMed - as supplied by publisher]
Brain regional homogeneity changes following transjugular intrahepatic portosystemic shunt in cirrhotic patients support cerebral adaptability theory-A resting-state functional MRI study.
Eur J Radiol. 2013 Nov 15;
Authors: Ni L, Qi R, Zhang LJ, Zhong J, Zheng G, Wu X, Fan X, Lu GM
PURPOSE: The exact neuro-pathophysiological effect of transjugular intrahepatic portosystemic shunt (TIPS) on brain function remains unclear. The purpose of this study was to investigate the longitudinal brain activity changes in cirrhotic patients with TIPS insertion using resting-state functional MRI (fMRI) with regional homogeneity (ReHo) method.
METHODS: Fifteen cirrhotic patients without overt hepatic encephalopathy (OHE) planned for TIPS procedure and 15 age- and gender-matched healthy controls were included in this study. Eleven of the 15 patients underwent repeated fMRI examinations at median 7-day following TIPS, 8 patients in median 3-month, and 7 patients in median 1-year follow-up duration, respectively. Regional homogeneity was calculated by the Kendall's coefficient of concordance (KCC) and compared between patients before TIPS and healthy controls with two-sample t test as well as pre-and post-TIPS patients with paired t test. Correlations between the pre- and post-TIPS changes of ReHo and the changes of venous blood ammonia level and number connection test type A (NCT-A)/digit symbol test (DST) scores were calculated by crossing subjects.
RESULTS: Compared with healthy controls, 15 cirrhotic patients before TIPS procedure showed decreased ReHo in the bilateral frontal, parietal, temporal and occipital lobes and increased ReHo in the bilateral caudate. Compared with the pre-TIPS patients, 11 post-TIPS patients in the median 7-day follow-up examinations demonstrated decreased ReHo in the medial frontal gyrus (MFG), superior parietal gyrus (SPG), middle/superior temporal gyrus (M/STG), anterior cingulate cortex (ACC), caudate, and increased ReHo in the insula. Eight post-TIPS patients in the median 3-month follow-up examinations showed widespread decreased ReHo in the bilateral frontal and parietal lobes, ACC, caudate, and increased ReHo in the insula and precuneus/cuneus. In the median 1-year follow-up studies, seven post-TIPS patients displayed decreased ReHo in the bilateral frontal and parietal lobes, ACC, supplementary motor area (SMA), posterior cingulate cortex (PCC), and increased ReHo in the caudate and insula (P<0.05, Alphasim corrected). The changes of ReHo values in bilateral IPL, MFG, caudate and SMA were correlated with changes of DST scores during the median 3-month follow-up (all P<0.05).
CONCLUSION: The TIPS implantation had a persistent effect on brain function in cirrhotic patients including both predominant impairment and compensation mechanisms, with the most significant alterations in the median 3-month period after TIPS. The ReHo analysis may be potentially valuable for uncovering the mechanism of TIPS' effects on brain function.
PMID: 24299611 [PubMed - as supplied by publisher]
Resting state FMRI research in child psychiatric disorders.
Eur Child Adolesc Psychiatry. 2013 Dec 3;
Authors: Oldehinkel M, Francx W, Beckmann CF, Buitelaar JK, Mennes M
Concurring with the shift from linking functions to specific brain areas towards studying network integration, resting state FMRI (R-FMRI) has become an important tool for delineating the functional network architecture of the brain. Fueled by straightforward data collection, R-FMRI analysis methods as well as studies reporting on R-FMRI have flourished, and already impact research on child- and adolescent psychiatric disorders. Here, we review R-FMRI analysis techniques and outline current methodological debates. Furthermore, we provide an overview of the main R-FMRI findings related to child- and adolescent psychiatric disorders. R-FMRI research has contributed significantly to our understanding of brain function in child and adolescent psychiatry: existing hypotheses based on task-based FMRI were confirmed and new insights into the brain's functional architecture of disorders were established. However, results were not always consistent. While resting state networks are robust and reproducible, neuroimaging research in psychiatric disorders is especially complicated by tremendous phenotypic heterogeneity. It is imperative that we overcome this heterogeneity when integrating neuroimaging into the diagnostic and treatment process. As R-FMRI allows investigating the richness of the human functional connectome and can be easily collected and aggregated into large-scale datasets, it is clear that R-FMRI can be a powerful tool in our quest to understand psychiatric pathology.
PMID: 24297675 [PubMed - as supplied by publisher]
Age differences in the intrinsic functional connectivity of default network subsystems.
Front Aging Neurosci. 2013;5:73
Authors: Campbell KL, Grigg O, Saverino C, Churchill N, Grady CL
Recent work suggests that the default mode network (DMN) includes two core regions, the ventromedial prefrontal cortex and posterior cingulate cortex (PCC), and several unique subsystems that are functionally distinct. These include a medial temporal lobe (MTL) subsystem, active during remembering and future projection, and a dorsomedial prefrontal cortex (dmPFC) subsystem, active during self-reference. The PCC has been further subdivided into ventral (vPCC) and dorsal (dPCC) regions that are more strongly connected with the DMN and cognitive control networks, respectively. The goal of this study was to examine age differences in resting state functional connectivity within these subsystems. After applying a rigorous procedure to reduce the effects of head motion, we used a multivariate technique to identify both common and unique patterns of functional connectivity in the MTL vs. the dmPFC, and in vPCC vs. dPCC. All four areas had robust functional connectivity with other DMN regions, and each also showed distinct connectivity patterns in both age groups. Young and older adults had equivalent functional connectivity in the MTL subsystem. Older adults showed weaker connectivity in the vPCC and dmPFC subsystems, particularly with other DMN areas, but stronger connectivity than younger adults in the dPCC subsystem, which included areas involved in cognitive control. Our data provide evidence for distinct subsystems involving DMN nodes, which are maintained with age. Nevertheless, there are age differences in the strength of functional connectivity within these subsystems, supporting prior evidence that DMN connectivity is particularly vulnerable to age, whereas connectivity involving cognitive control regions is relatively maintained. These results suggest an age difference in the integrated activity among brain networks that can have implications for cognition in older adults.
PMID: 24294203 [PubMed - as supplied by publisher]
Altered nigrostriatal and nigrocortical functional connectivity in rapid eye movement sleep behavior disorder.
Authors: Ellmore TM, Castriotta RJ, Hendley KL, Aalbers BM, Furr-Stimming E, Hood AJ, Suescun J, Beurlot MR, Hendley RT, Schiess MC
STUDY OBJECTIVES: Rapid eye movement sleep behavior disorder (RBD) is a condition closely associated with Parkinson disease (PD). RBD is a sleep disturbance that frequently manifests early in the development of PD, likely reflecting disruption in normal functioning of anatomical areas affected by neurodegenerative processes. Although specific neuropathological aspects shared by RBD and PD have yet to be fully documented, further characterization is critical to discovering reliable biomarkers that predict PD onset. In the current study, we tested the hypothesis of altered functional connections of the substantia nigra (SN) in patients in whom RBD was diagnosed.
DESIGN: Between-groups, single time point imaging.
SETTING: UTHSC-H 3 telsa MRI center.
PARTICIPANTS: Ten patients with RBD, 11 patients with PD, and 10 age-matched controls.
MEASUREMENTS AND RESULTS: We measured correlations of SN time series using resting state blood oxygen level-dependent functional magnetic resonance imaging (BOLD-fMRI) in patients with idiopathic RBD who were at risk for developing PD, patients in whom PD was diagnosed, and age-matched controls. Using voxelwise analysis of variance, different correlations (P < 0.01, whole-brain corrected) between left SN and left putamen were found in patients with RBD compared with controls and patients with PD. SN correlations with right cuneus/precuneus and superior occipital gyrus were significantly different for patients with RBD compared with both controls and patients with PD.
CONCLUSIONS: The results suggest that altered nigrostriatal and nigrocortical connectivity characterizes rapid eye movement sleep behavior disorder before onset of obvious motor impairment. The functional changes are discussed in the context of degeneration in dopaminergic and cognition-related networks.
CITATION: Ellmore TM; Castriotta RJ; Hendley KL; Aalbers BM; Furr-Stimming E; Hood AJ; Suescun J; Beurlot MR; Hendley RT; Schiess MC. Altered nigrostriatal and nigrocortical functional connectivity in rapid eye movement sleep behavior disorder. SLEEP 2013;36(12):1885-1892.
PMID: 24293763 [PubMed - in process]
Predictive models of resting state networks for assessment of altered functional connectivity in mild cognitive impairment.
Brain Imaging Behav. 2013 Dec 1;
Authors: Jiang X, Zhu D, Li K, Zhang T, Wang L, Shen D, Guo L, Liu T
Due to the difficulties in establishing correspondences between functional regions across individuals and populations, systematic elucidation of functional connectivity alterations in mild cognitive impairment (MCI) in comparison with normal controls (NC) is still a challenging problem. In this paper, we assessed the functional connectivity alterations in MCI via novel, alternative predictive models of resting state networks (RSNs) learned from multimodal resting state fMRI (R-fMRI) and diffusion tensor imaging (DTI) data. First, ICA-clustering was used to construct RSNs from R-fMRI data in NC group. Second, since the RSNs in MCI are already altered and can hardly be constructed directly from R-fMRI data, structural landmarks derived from DTI data were employed as the predictive models of RSNs for MCI. Third, given that the landmarks are structurally consistent and correspondent across NC and MCI, functional connectivities in MCI were assessed based on the predicted RSNs and compared with those in NC. Experimental results demonstrated that the predictive models of RSNs based on multimodal R-fMRI and DTI data systematically and comprehensively revealed widespread functional connectivity alterations in MCI in comparison with NC.
PMID: 24293138 [PubMed - as supplied by publisher]