Functional overlap and divergence between ALS and bvFTD.
Neurobiol Aging. 2014 Jun 28;
Authors: Trojsi F, Esposito F, de Stefano M, Buonanno D, Conforti FL, Corbo D, Piccirillo G, Cirillo M, Monsurrò MR, Montella P, Tedeschi G
Amyotrophic lateral sclerosis (ALS) and behavioral variant frontotemporal dementia (bvFTD) lie on a clinical, pathologic, and genetic continuum. Neuroimaging techniques have proven to be potentially useful to unravel the shared features of these syndromes. Using resting-state functional magnetic resonance imaging (RS-fMRI), we investigated functional connectivity of brain networks in 15 ALS and 15 bvFTD patients in early stages of disease and 15 healthy controls, looking expressly for connectivity pattern divergence or overlap between the 2 disorders. Compared with controls, we found decreased RS-fMRI signals within sensorimotor, right frontoparietal, salience, and executive networks in both patient groups. Within the default mode network (DMN), divergent connectivity patterns were observed, with RS-fMRI signals in the posterior cingulate cortex enhanced in bvFTD patients and suppressed in ALS patients. Our findings confirm that ALS and bvFTD not only broadly share common RS-fMRI connectivity patterns, probably representing different phenotypical expressions of the same neurodegenerative process, but also differ in the DMN, probably reflecting a different stage of neurodegeneration.
PMID: 25063233 [PubMed - as supplied by publisher]
Altered spontaneous neuronal activity of visual cortex and medial anterior cingulate cortex in treatment-naïve posttraumatic stress disorder.
Compr Psychiatry. 2014 Jun 27;
Authors: Zhu H, Zhang J, Zhan W, Qiu C, Wu R, Meng Y, Cui H, Huang X, Li T, Gong Q, Zhang W
BACKGROUND: Although no more traumatic stimuli exists, a variety of symptoms are persisting in chronic Posttraumatic Stress Disorder (PTSD) patients. It is therefore necessary to explore the spontaneous brain activity of treatment-naïve PTSD patients during resting-state.
METHOD: Seventeen treatment-naïve PTSD patients and twenty traumatized controls were recruited and underwent a resting functional magnetic resonance imaging (Rs-fMRI) scan. The differences of regional brain spontaneous activity between the participants with and without PTSD were measured by Amplitude of Low-frequency fluctuation (ALFF). The relationship between the altered brain measurements and the symptoms of PTSD were analyzed.
RESULT: Compared to traumatized controls, the PTSD group showed significantly altered ALFF in many emotion-related brain regions, such as the medial anterior cingulate cortex (MACC), dorsolateral prefrontal cortex (DLPFC), insular (IC), middle temporal gyrus (MTG), and ventral posterior cingulate cortex (VPCC). Interestingly this is the first report of a hyperactive visual cortex (V1/V2) during resting-state in treatment-naïve PTSD patients. There were significant positive correlations between ALFF values in the bilateral visual cortex and re-experiencing or avoidance in PTSD. Negative correlation was observed between ALFF values in MACC and avoidance.
CONCLUSION: This study suggested that the visual cortex and the MACC may be involved in the characteristic symptoms of chronic PTSD, such as re-experiencing and avoidance. Future studies that focus on these areas of the brain are required, as alteration of these areas may act as a biomarker and could be targeted in future treatments for PTSD.
PMID: 25060989 [PubMed - as supplied by publisher]
Improved mapping of interictal epileptiform discharges with EEG-fMRI and voxel-wise functional connectivity analysis.
Epilepsia. 2014 Jul 24;
Authors: Liu JV, Kobylarz EJ, Darcey TM, Lu Z, Wu YC, Meng M, Jobst BC
OBJECTIVE: We describe a novel method to spatially map interictal epileptiform discharges (IEDs) through voxel-wise functional connectivity analysis of the functional magnetic resonance imaging (fMRI) portion of simultaneous electroencephalography (EEG)-fMRI data. This method measures the local synchronicity of fMRI signals associated with IED and, in contrast to conventional methods, does not require modeling of neural activities or hemodynamic response.
METHODS: Simultaneous EEG-fMRI was performed on six patients with focal epilepsy. IED events were detected from the EEG data. The fMRI data was subdivided into time segments of 20 s in length, and then reorganized into one set of concatenated time series containing the IED events and many sets without IEDs. Local degree centrality (LDC), a metric of functional connectivity, was computed for each brain voxel to summarize its signal correlations to brain voxels within 14 mm of physical distance. This computation was repeated for each set of concatenated time series, yielding one whole-brain LDC map for time with the IED events and many maps for time without IED. A statistical score was computed for each voxel to detect the voxels with significant LDC value differences associated with IEDs. The fMRI data were also processed separately by conventional methods for comparison.
RESULTS: In all six patients, regions with significant LDC increase during IEDs were concordant in location to both simultaneous EEG and the epileptogenic focus determined from separate clinical studies. In contrast, results from the conventional methods were concordant in only three patients.
SIGNIFICANCE: We show that for focal epilepsy, voxel-wise functional connectivity analysis of EEG-fMRI data may improve IED localization and EEG concordance compared to the conventional analysis. This new analytic method may improve the robustness of interictal EEG-fMRI as a technique for mapping the epileptogenic focus, and helps study the local synchronization aspect of the epileptic network.
PMID: 25060924 [PubMed - as supplied by publisher]
In search of neural endophenotypes of postpartum psychopathology and disrupted maternal caregiving.
J Neuroendocrinol. 2014 Jul 24;
Authors: Moses-Kolko E, Horner, Phillips M, Hipwell A, Swain J
This is a selective review which provides the context for study of perinatal affective disorder mechanisms and outlines directions for future research. We integrate existing literature (Table) along neural networks of interest for affective disorders and maternal caregiving: 1) the salience/fear network, 2) the executive network, 3) the reward/social attachment network, and 4) the default mode network. Extant salience/fear network research reveals disparate responses and corticolimbic coupling to various stimuli based upon a predominantly depressive versus anxious (posttraumatic stress disorder, PTSD) clinical phenotype. Executive network and default mode connectivity abnormalities have been described in postpartum depression (PPD), but studies are very limited in these domains. Reward/Social attachment studies confirm a robust ventral striatal response to infant stimuli including cry and happy infant faces, which is diminished in depressed, insecurely attached, and substance-using mothers. Adverse parenting experiences received and attachment insecurity of current mothers are factors which are associated with diminution in infant stimulus-related neural activity similar to than in PPD, and raise the need for additional studies that integrate mood and attachment concepts in larger study samples. Several studies which have examined functional connectivity in resting state and emotional activation functional magnetic resonance imaging (fMRI) paradigms have revealed attenuated corticolimbic connectivity which remains an important outcome to dissect with increasing precision to better define neural treatment targets. Methodological progress is expected in the coming years in terms of refining clinical phenotypes of interest and experimental paradigms as well as enlarging samples to facilitate examination of multiple constructs. Functional imaging promises to elucidate neural mechanisms underlying maternal psychopathology and impaired caregiving such that earlier and more precise detection of abnormalities will be possible. Ultimately, discovery of such mechanisms will promote refinement of treatment approaches toward maternal affective disturbance, parenting behaviors as well as augmentation of parenting resiliency. This article is protected by copyright. All rights reserved.
PMID: 25059408 [PubMed - as supplied by publisher]
Effects of resveratrol on memory performance, hippocampal functional connectivity, and glucose metabolism in healthy older adults.
J Neurosci. 2014 Jun 4;34(23):7862-70
Authors: Witte AV, Kerti L, Margulies DS, Flöel A
Dietary habits such as caloric restriction or nutrients that mimic these effects may exert beneficial effects on brain aging. The plant-derived polyphenol resveratrol has been shown to increase memory performance in primates; however, interventional studies in older humans are lacking. Here, we tested whether supplementation of resveratrol would enhance memory performance in older adults and addressed potential mechanisms underlying this effect. Twenty-three healthy overweight older individuals that successfully completed 26 weeks of resveratrol intake (200 mg/d) were pairwise matched to 23 participants that received placebo (total n = 46, 18 females, 50-75 years). Before and after the intervention/control period, subjects underwent memory tasks and neuroimaging to assess volume, microstructure, and functional connectivity (FC) of the hippocampus, a key region implicated in memory functions. In addition, anthropometry, glucose and lipid metabolism, inflammation, neurotrophic factors, and vascular parameters were assayed. We observed a significant effect of resveratrol on retention of words over 30 min compared with placebo (p = 0.038). In addition, resveratrol led to significant increases in hippocampal FC, decreases in glycated hemoglobin (HbA1c) and body fat, and increases in leptin compared with placebo (all p < 0.05). Increases in FC between the left posterior hippocampus and the medial prefrontal cortex correlated with increases in retention scores and with decreases in HbA1c (all p < 0.05). This study provides initial evidence that supplementary resveratrol improves memory performance in association with improved glucose metabolism and increased hippocampal FC in older adults. Our findings offer the basis for novel strategies to maintain brain health during aging.
PMID: 24899709 [PubMed - indexed for MEDLINE]
Resting States Are Resting Traits - An fMRI Study of Sex Differences and Menstrual Cycle Effects in Resting State Cognitive Control Networks.
PLoS One. 2014;9(7):e103492
Authors: Hjelmervik H, Hausmann M, Osnes B, Westerhausen R, Specht K
To what degree resting state fMRI is stable or susceptible to internal mind states of the individual is currently an issue of debate. To address this issue, the present study focuses on sex differences and investigates whether resting state fMRI is stable in men and women or changes within relative short-term periods (i.e., across the menstrual cycle). Due to the fact that we recently reported menstrual cycle effects on cognitive control based on data collected during the same sessions, the current study is particularly interested in fronto-parietal resting state networks. Resting state fMRI was measured in sixteen women during three different cycle phases (menstrual, follicular, and luteal). Fifteen men underwent three sessions in corresponding time intervals. We used independent component analysis to identify four fronto-parietal networks. The results showed sex differences in two of these networks with women exhibiting higher functional connectivity in general, including the prefrontal cortex. Menstrual cycle effects on resting states were non-existent. It is concluded that sex differences in resting state fMRI might reflect sexual dimorphisms in the brain rather than transitory activating effects of sex hormones on the functional connectivity in the resting brain.
PMID: 25057823 [PubMed - as supplied by publisher]
The Neural Mechanisms Underlying the Acute Effect of Cigarette Smoking on Chronic Smokers.
PLoS One. 2014;9(7):e102828
Authors: Wang K, Yang J, Zhang S, Wei D, Hao X, Tu S, Qiu J
Although previous research had related structural changes and impaired cognition to chronic cigarette smoking, recent neuroimaging studies have associated nicotine, which is a main chemical substance in cigarettes, with improvements in cognitive functions (e.g. improved attention performance). However, information about the alterations of whole-brain functional connectivity after acute cigarette smoking is limited. In this study, 22 smokers underwent resting-state functional magnetic resonance imaging (rs-fMRI) after abstaining from smoking for 12 hours (state of abstinence, SOA). Subsequently, the smokers were allowed to smoke two cigarettes (state of satisfaction, SOS) before they underwent a second rs-fMRI. Twenty non-smokers were also recruited to undergo rs-fMRI. In addition, high-resolution 3D T1-weighted images were acquired using the same magnetic resonance imaging(fMRI)scanner for all participants. The results showed that smokers had structural changes in insula, thalamus, medial frontal cortex and several regions of the default mode network (DMN) compared with non-smokers. Voxel-wise group comparisons of newly developed global brain connectivity (GBC) showed that smokers in the SOA condition had higher GBC in the insula and superior frontal gyrus compared with non-smokers. However, smokers in the SOS condition demonstrated significantly lower GBC in several regions of the DMN, as compared with smokers in the SOA condition. These results suggest that structural integrity combined with dysfunction of the DMN might be involved in relapses after a short period of time among smokers.
PMID: 25051341 [PubMed - as supplied by publisher]
Neuronal oscillations and functional interactions between resting state networks.
Hum Brain Mapp. 2014 Jul;35(7):3517-28
Authors: Lei X, Wang Y, Yuan H, Mantini D
Functional magnetic imaging (fMRI) studies showed that resting state activity in the healthy brain is organized into multiple large-scale networks encompassing distant regions. A key finding of resting state fMRI studies is the anti-correlation typically observed between the dorsal attention network (DAN) and the default mode network (DMN), which - during task performance - are activated and deactivated, respectively. Previous studies have suggested that alcohol administration modulates the balance of activation/deactivation in brain networks, as well as it induces significant changes in oscillatory activity measured by electroencephalography (EEG). However, our knowledge of alcohol-induced changes in band-limited EEG power and their potential link with the functional interactions between DAN and DMN is still very limited. Here we address this issue, examining the neuronal effects of alcohol administration during resting state by using simultaneous EEG-fMRI. Our findings show increased EEG power in the theta frequency band (4-8 Hz) after administration of alcohol compared to placebo, which was prominent over the frontal cortex. More interestingly, increased frontal tonic EEG activity in this band was associated with greater anti-correlation between the DAN and the frontal component of the DMN. Furthermore, EEG theta power and DAN-DMN anti-correlation were relatively greater in subjects who reported a feeling of euphoria after alcohol administration, which may result from a diminished inhibition exerted by the prefrontal cortex. Overall, our findings suggest that slow brain rhythms are responsible for dynamic functional interactions between brain networks. They also confirm the applicability and potential usefulness of EEG-fMRI for central nervous system drug research.
PMID: 25050432 [PubMed - in process]
Functional centrality of amygdala, striatum and hypothalamus in a "small-world" network underlying joy: an fMRI study with music.
Hum Brain Mapp. 2014 Jul;35(7):3485-98
Authors: Koelsch S, Skouras S
Current knowledge about small-world networks underlying emotions is sparse, and confined to functional magnetic resonance imaging (fMRI) studies using resting-state paradigms. This fMRI study applied Eigenvector Centrality Mapping (ECM) and functional connectivity analysis to reveal neural small-world networks underlying joy and fear. Joy and fear were evoked using music, presented in 4-min blocks. Results show that the superficial amygdala (SF), laterobasal amygdala (LB), striatum, and hypothalamus function as computational hubs during joy. Out of these computational hubs, the amygdala nuclei showed the highest centrality values. The SF showed functional connectivity during joy with the mediodorsal thalamus (MD) and nucleus accumbens (Nac), suggesting that SF, MD, and Nac modulate approach behavior in response to positive social signals such as joyful music. The striatum was functionally connected during joy with the LB, as well as with premotor cortex, areas 1 and 7a, hippocampus, insula and cingulate cortex, showing that sensorimotor, attentional, and emotional processes converge in the striatum during music perception. The hypothalamus showed functional connectivity during joy with hippocampus and MD, suggesting that hypothalamic endocrine activity is modulated by hippocampal and thalamic activity during sustained periods of music-evoked emotion. Our study indicates high centrality of the amygdala nuclei groups within a functional network underlying joy, suggesting that these nuclei play a central role for the modulation of emotion-specific activity within this network.
PMID: 25050430 [PubMed - in process]
Functional dissociation of ventral frontal and dorsomedial default mode network components during resting state and emotional autobiographical recall.
Hum Brain Mapp. 2014 Jul;35(7):3302-13
Authors: Bado P, Engel A, de Oliveira-Souza R, Bramati IE, Paiva FF, Basilio R, Sato JR, Tovar-Moll F, Moll J
Humans spend a substantial share of their lives mind-wandering. This spontaneous thinking activity usually comprises autobiographical recall, emotional, and self-referential components. While neuroimaging studies have demonstrated that a specific brain "default mode network" (DMN) is consistently engaged by the "resting state" of the mind, the relative contribution of key cognitive components to DMN activity is still poorly understood. Here we used fMRI to investigate whether activity in neural components of the DMN can be differentially explained by active recall of relevant emotional autobiographical memories as compared with the resting state. Our study design combined emotional autobiographical memory, neutral memory and resting state conditions, separated by a serial subtraction control task. Shared patterns of activation in the DMN were observed in both emotional autobiographical and resting conditions, when compared with serial subtraction. Directly contrasting autobiographical and resting conditions demonstrated a striking dissociation within the DMN in that emotional autobiographical retrieval led to stronger activation of the dorsomedial core regions (medial prefrontal cortex, posterior cingulate cortex), whereas the resting state condition engaged a ventral frontal network (ventral striatum, subgenual and ventral anterior cingulate cortices) in addition to the IPL. Our results reveal an as yet unreported dissociation within the DMN. Whereas the dorsomedial component can be explained by emotional autobiographical memory, the ventral frontal one is predominantly associated with the resting state proper, possibly underlying fundamental motivational mechanisms engaged during spontaneous unconstrained ideation.
PMID: 25050426 [PubMed - in process]
Developmental changes in effective connectivity associated with relational reasoning.
Hum Brain Mapp. 2014 Jul;35(7):3262-76
Authors: Bazargani N, Hillebrandt H, Christoff K, Dumontheil I
Rostrolateral prefrontal cortex (RLPFC) is part of a frontoparietal network of regions involved in relational reasoning, the mental process of working with relationships between multiple mental representations. RLPFC has shown functional and structural changes with age, with increasing specificity of left RLPFC activation for relational integration during development. Here, we used dynamic causal modeling (DCM) to investigate changes in effective connectivity during a relational reasoning task through the transition from adolescence into adulthood. We examined fMRI data of 37 healthy female participants (11–30 years old) performing a relational reasoning paradigm. Comparing relational integration to the manipulation of single relations revealed activation in five regions: the RLPFC, anterior insula, dorsolateral PFC, inferior parietal lobe, and medial superior frontal gyrus. We used a new exhaustive search approach and identified a full DCM model, which included all reciprocal connections between the five clusters in the left hemisphere, as the optimal model. In line with previous resting state fMRI results, we showed distinct developmental effects on the strength of long-range frontoparietal versus frontoinsular short-range fixed connections. The modulatory connections associated with relational integration increased with age. Gray matter volume in left RLPFC, which decreased with age, partly accounted for changes in fixed PFC connectivity. Finally, improvements in relational integration performance were associated with greater modulatory and weaker fixed PFC connectivity. This pattern provides further evidence of increasing specificity of left PFC function for relational integration compared to the manipulation of single relations, and demonstrates an association between effective connectivity and performance during development.
PMID: 25050424 [PubMed - in process]
Hippocampal-parietal dysconnectivity and glutamate abnormalities in unmedicated patients with schizophrenia.
Hippocampus. 2014 Jul 17;
Authors: Kraguljac NV, White DM, Hadley J, Reid MA, Lahti AC
Objectives. Abnormalities in resting state connectivity in schizophrenia are now well established, but the biological substrates of these functional alterations remain to be elucidated. Experimental design. We performed a combined functional magnetic resonance imaging (fMRI) and magnetic resonance spectroscopy ((1) H-MRS) study in 22 unmedicated patients with schizophrenia and 22 matched healthy controls to evaluate resting state functional connectivity of the hippocampus and Glx/Cr (a combined glutamate+glutamine peak normalized to creatine) in the hippocampus and investigate functional and neurometabolic abnormalities and examine the relationship between these. Major observations. Functional connectivity between the left hippocampus and bilateral precuneus was significantly decreased in unmedicated patients with schizophrenia when compared to healthy controls [t(4.22), cluster extent (kE)= 751, pFDRcorr =.001, MNI coordinates: x= -4, y= -56, z= 44]. Glx/Cr in the hippocampus was significantly elevated in schizophrenia (HC: mean= 0.60+/- 0.10 SZ: 0.67+/- 0.10; F= 5.742; p=.02), but was not correlated with functional connectivity deficits (p >.05). Conclusions. In this study, we found hippocampal resting state functional connectivity deficits to the precuneus in unmedicated patients with schizophrenia and an increase of Glx/Cr in the hippocampus, but did not observe a direct relationship between these abnormalities. However, our findings do not exclude the possibility of a shared underlying pathology which warrants further investigation. © 2014 Wiley Periodicals, Inc.
PMID: 25045047 [PubMed - as supplied by publisher]
Isoflurane induces dose-dependent alterations in the cortical connectivity profiles and dynamic properties of the brain's functional architecture.
Hum Brain Mapp. 2014 Jul 12;
Authors: Hutchison RM, Hutchison M, Manning KY, Menon RS, Everling S
Despite their widespread use, the effect of anesthetic agents on the brain's functional architecture remains poorly understood. This is particularly true of alterations that occur beyond the point of induced unconsciousness. Here, we examined the distributed intrinsic connectivity of macaques across six isoflurane levels using resting-state functional MRI (fMRI) following the loss of consciousness. The results from multiple analysis strategies showed stable functional connectivity (FC) patterns between 1.00% and 1.50% suggesting this as a suitable range for anesthetized nonhuman primate resting-state investigations. Dose-dependent effects were evident at moderate to high dosages showing substantial alteration of the functional topology and a decrease or complete loss of interhemispheric cortical FC strength including that of contralateral homologues. The assessment of dynamic FC patterns revealed that the functional repertoire of brain states is related to anesthesia depth and most strikingly, that the number of state transitions linearly decreases with increased isoflurane dosage. Taken together, the results indicate dose-specific spatial and temporal alterations of FC that occur beyond the typically defined endpoint of consciousness. Future work will be necessary to determine how these findings generalize across anesthetic types and extend to the transition between consciousness and unconsciousness. Hum Brain Mapp, 2014. © 2014 Wiley Periodicals, Inc.
PMID: 25044934 [PubMed - as supplied by publisher]
Computer-automated focus lateralization of temporal lobe epilepsy using fMRI.
J Magn Reson Imaging. 2014 Jul 9;
Authors: Chiang S, Levin HS, Haneef Z
PURPOSE: To compare the performance of computer-automated diagnosis using functional magnetic resonance imaging (fMRI) interictal graph theory (CADFIG) to that achieved in standard clinical practice with MRI, for lateralizing the affected hemisphere in temporal lobe epilepsy (TLE).
MATERIALS AND METHODS: Interictal resting state fMRI and high-resolution MRI were performed on 14 left and 10 right TLE patients. Functional topology measures were calculated from fMRI using graph theory, and used to lateralize the epileptogenic hemisphere using quadratic discriminant analysis. Leave-one-out cross-validation prediction accuracy of CADFIG was compared to performance based on expert manual analysis (MA) of MRI, using video EEG as the "gold standard" for focus lateralization.
RESULTS: CADFIG correctly lateralized 95.8% (23/24) of cases, compared to 66.7% (16/24) with expert MA of MRI. Combining MA with CADFIG allowed all cases (24/24) to be correctly lateralized. CADFIG correctly identified the affected hemisphere for all patients (8/8) where MRI failed to lateralize.
CONCLUSION: CADFIG based on fMRI lateralized the affected hemisphere in TLE with superior performance compared to expert MA of MRI. These results demonstrate that functional patterns in fMRI can be used with automated machine learning for diagnostic lateralization in TLE. Addition of fMRI-based tests to existing protocols for identifying the affected hemisphere in presurgical assessment can improve diagnostic accuracy and surgical outcome in TLE.J. Magn. Reson. Imaging 2014. © 2014 Wiley Periodicals, Inc.
PMID: 25044773 [PubMed - as supplied by publisher]
Decreased limbic and increased fronto-parietal connectivity in unmedicated patients with obsessive-compulsive disorder.
Hum Brain Mapp. 2014 Jul 12;
Authors: Göttlich M, Krämer UM, Kordon A, Hohagen F, Zurowski B
Obsessive-compulsive disorder (OCD) is characterized by recurrent intrusive thoughts and ritualized, repetitive behaviors, or mental acts. Convergent experimental evidence from neuroimaging and neuropsychological studies supports an orbitofronto-striato-thalamo-cortical dysfunction in OCD. Moreover, an over excitability of the amygdala and over monitoring of thoughts and actions involving the anterior cingulate, frontal and parietal cortex has been proposed as aspects of pathophysiology in OCD. We chose a data driven, graph theoretical approach to investigate brain network organization in 17 unmedicated OCD patients and 19 controls using resting-state fMRI. OCD patients showed a decreased connectivity of the limbic network to several other brain networks: the basal ganglia network, the default mode network, and the executive/attention network. The connectivity within the limbic network was also found to be decreased in OCD patients compared to healthy controls. Furthermore, we found a stronger connectivity of brain regions within the executive/attention network in OCD patients. This effect was positively correlated with disease severity. The decreased connectivity of limbic regions (amygdala, hippocampus) may be related to several neurocognitive deficits observed in OCD patients involving implicit learning, emotion processing and expectation, and processing of reward and punishment. Limbic disconnection from fronto-parietal regions relevant for (re)-appraisal may explain why intrusive thoughts become and/or remain threatening to patients but not to healthy subjects. Hyperconnectivity within the executive/attention network might be related to OCD symptoms such as excessive monitoring of thoughts and behavior as a dysfunctional strategy to cope with threat and uncertainty. Hum Brain Mapp, 2014. © 2014 Wiley Periodicals, Inc.
PMID: 25044747 [PubMed - as supplied by publisher]
Role of the sensorimotor cortex in tourette syndrome using multimodal imaging.
Hum Brain Mapp. 2014 Jul 15;
Authors: Tinaz S, Belluscio BA, Malone P, van der Veen JW, Hallett M, Horovitz SG
Tourette syndrome (TS) is a neuropsychiatric disorder characterized by motor and vocal tics. Most patients describe uncomfortable premonitory sensations preceding the tics and a subjective experience of increased sensitivity to tactile stimuli. These reports indicate that a sensory processing disturbance is an important component of TS together with motor phenomena. Thus, we focused our investigation on the role of the sensorimotor cortex (SMC) in TS using multimodal neuroimaging techniques. We measured the gamma-aminobutyric acid (GABA)+/Creatine (Cre) ratio in the SMC using GABA (1) H magnetic resonance spectroscopy. We recorded the baseline beta activity in the SMC using magnetoencephalography and correlated GABA+/Cre ratio with baseline beta band power. Finally, we examined the resting state functional connectivity (FC) pattern of the SMC using functional magnetic resonance imaging (fMRI). GABA+/Cre ratio in the SMC did not differ between patients and controls. Correlation between the baseline beta band power and GABA+/Cre ratio was abnormal in patients. The anterior insula showed increased FC with the SMC in patients. These findings suggest that altered limbic input to the SMC and abnormal GABA-mediated beta oscillations in the SMC may underpin some of the sensorimotor processing disturbances in TS and contribute to tic generation. Hum Brain Mapp, 2014. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
PMID: 25044024 [PubMed - as supplied by publisher]
Link between hippocampus' raised local and eased global intrinsic connectivity in AD.
Alzheimers Dement. 2014 Jul 17;
Authors: Pasquini L, Scherr M, Tahmasian M, Meng C, Myers NE, Ortner M, Mühlau M, Kurz A, Förstl H, Zimmer C, Grimmer T, Wohlschläger AM, Riedl V, Sorg C
BACKGROUND: The hippocampus (HP) is part of the default mode network (DMN), and both are key targets of Alzheimer's disease (AD). Because of widespread network degeneration, it has been suggested that increasing HP disconnection from the DMN may lead to progressive disinhibition of intra-HP synchronized activity.
METHODS: To analyze HP local (i.e., within HP) and global (i.e., within DMN) intrinsic functional connectivity (local/global intrinsic functional connectivity [iFC]), healthy controls and patients with mild cognitive impairment and AD dementia were assessed by spatial high and normal resolution resting-state functional magnetic resonance imaging.
RESULTS: Although patients' parietal local-iFC was reduced and positively correlated with reduced global-iFC within the DMN, HP local connectivity was progressively increased and negatively correlated with HP decreased global connectivity. Increased intra-HP connectivity was associated with impaired memory.
CONCLUSION: Our result demonstrates a link between increased local and reduced global hippocampal connectivity in AD. Increased intra-HP synchrony may contribute to distinct symptoms such as memory impairment or more speculatively epileptic seizure.
PMID: 25043909 [PubMed - as supplied by publisher]
Increased interhemispheric resting-state in idiopathic generalized epilepsy with generalized tonic-clonic seizures: A resting-state fMRI study.
Epilepsy Res. 2014 Jul 7;
Authors: Yang T, Ren J, Li Q, Li L, Lei D, Gong Q, Zhou D
PURPOSE: The aim is to examine the resting state functional connectivity (RSFC) between the two hemispheres and its relationships with clinical characteristic in idiopathic generalized epilepsy with generalized tonic-clonic seizures only (IGE-GTCS) patients using a technique called "voxel-mirrored homotopic connectivity (VMHC)".
METHODS: The resting-state functional MRI (Rs-fMRI) was used to measure the RSFC in patients with IGE-GTC and age-gender matched healthy subjects. The between-group difference in interhemispheric RSFC was examined after the interhemispheric RSFC map was obtained by an automated VMHC approach.
RESULTS: Compared to the controls, the IGE-GTCS patients showed significant increases in VMHC in the bilateral anterior cingulate and medial prefrontal gyrus. No areas showed decreased VMHC in patients. Moreover, the VMHC in bilateral thalamus, orbital frontal cortex as well as cerebellum showed significant negative correlations with the illness duration.
CONCLUSIONS: The current findings provide preliminary evidence of increased interhemispheric RSFC in patients with IGE-GTCS during the interictal period. These VMHC deficits in these regions and the inverse relations between VMHC and clinical characteristic may play an important role in the pathophysiology of IGE-GTCS. Our study may contribute to the understanding of neuro-pathophysiological mechanism of epilepsy and psychosocial function impairments in patients with IGE-GTCS.
PMID: 25043752 [PubMed - as supplied by publisher]
Disrupted small world networks in patients without overt hepatic encephalopathy: A resting state fMRI study.
Eur J Radiol. 2014 Jul 2;
Authors: Zhang LJ, Zheng G, Zhang L, Zhong J, Li Q, Zhao TZ, Lu GM
PURPOSE: To explore changes in functional connectivity and topological organization of brain functional networks in cirrhotic patients with minimal hepatic encephalopathy (MHE) and non hepatic encephalopathy (nonHE) and their relationship with clinical markers.
MATERIALS AND METHODS: Resting-state functional MR imaging was acquired in 22 MHE, 29 nonHE patients and 33 healthy controls. Functional connectivity networks were obtained by computing temporal correlations between any pairs of 90 cortical and subcortical regions. Graph analysis measures were quantitatively assessed for each subject. One-way analysis of covariance was applied to identify statistical differences of functional connectivity and network parameters among three groups. Correlations between clinical markers, such as Child-Pugh scores, venous blood ammonia level, and number connection test type A (NCT-A)/digit symbol test (DST) scores, and connectivity/graph metrics were calculated.
RESULTS: Thirty functional connectivities represented by edges were found to be abnormal (P<0.05, FDR corrected) in cirrhotic patients, in which 16 edges (53.3%) were related with sub-cortical regions. MHE patients showed abnormal small-world attributes in the functional connectivity networks. Cirrhotic patients had significantly reduced nodal degree in 8 cortical regions and increased nodal centrality in 3 cortical regions. Twenty edges were correlated with either NCT-A or DST scores, in which 13 edges were related with sub-cortical regions. No correlation was found between Child-Pugh scores and graph theoretical measures in cirrhotic patients.
CONCLUSION: Disturbances of brain functional connectivity and small world property loss are associated with neurocognitive impairment of cirrhotic patients. Reorganization of brain network occurred during disease progression from nonHE to MHE.
PMID: 25043497 [PubMed - as supplied by publisher]
Posture alters human resting-state.
Cortex. 2014 Jun 28;58C:199-205
Authors: Thibault RT, Lifshitz M, Jones JM, Raz A
Neuroimaging is ubiquitous; however, neuroimagers seldom investigate the putative impact of posture on brain activity. Whereas participants in most psychological experiments sit upright, many prominent neuroimaging techniques (e.g., functional magnetic resonance imaging (fMRI)) require participants to lie supine. Such postural discrepancies may hold important implications for brain function in general and for fMRI in particular. We directly investigated the effect of posture on spontaneous brain dynamics by recording scalp electrical activity in four orthostatic conditions (lying supine, inclined at 45°, sitting upright, and standing erect). Here we show that upright versus supine posture increases widespread high-frequency oscillatory activity. Our electroencephalographic findings highlight the importance of posture as a determinant in neuroimaging. When generalizing supine imaging results to ecological human cognition, therefore, cognitive neuroscientists would benefit from considering the influence of posture on brain dynamics.
PMID: 25041937 [PubMed - as supplied by publisher]