Phase Based Venous Suppression in Resting-State BOLD GE-fMRI.
Neuroimage. 2014 Jun 4;
Authors: Curtis AT, Matthew Hutchison R, Menon RS
Resting-state functional MRI (RS-fMRI) is a widely used method for inferring connectivity between brain regions or nodes. As with task-based fMRI, the spatial specificity of the connectivity maps can be distorted by the strong biasing effect of the BOLD signal in macroscopic veins. In RS-fMRI this effect is exacerbated by the temporal coherences of physiological origin between large veins that are widely distributed in the brain. In gradient echo based EPI, used for the vast majority of RS-fMRI, macroscopic veins that carry BOLD-related changes exhibit a strong phase response. This allows for post-processing identification and removal of venous signals using a phase regressor technique. Here, we employ this approach to suppress macrovascular venous contributions in high-field whole-brain RS-fMRI data sets, resulting in significant changes to both the spatial localization of the networks and the correlations between the network nodes. These effects were observed at both the individual and group analysis level, suggesting that venous contamination is a confounding factor for RS-fMRI studies even at relatively low image resolutions. Suppression of the macrovascular signal using the phase regression approach may therefore help to better identify, delineate, and interpret the true structure of large-scale brain networks.
PMID: 24907484 [PubMed - as supplied by publisher]
Abnormal functional connectivity within the default mode network in Patients with HBV-related cirrhosis without hepatic encephalopathy revealed by resting-state functional MRI.
Brain Res. 2014 Jun 4;
Authors: Qi R, Zhang LJ, Xu Q, Liang X, Luo S, Zhang Z, Huang W, Zheng L, Lu GM
By means of "task free" resting-state functional magnetic resonance imaging (rs-fMRI), abnormal functional connectivity (FC) of the default mode network (DMN) in cirrhotic patients with hepatic encephalopathy (HE) has been reported; however, little is known about the changes of DMN in cirrhotic patients without overt or minimal HE. The aim of this study was to investigate whether there was a disruption of the FC within the DMN in patients with hepatitis B virus (HBV)-related cirrhosis without any signs of HE. Fifty one patients with HBV-related cirrhosis without HE and 61 age- and gender- matched healthy controls underwent the rs-fMRI. Seed-based region-to-region FC was used to analyze the connectivity between each pair of regions within the DMN, including posterior cingulate cortex (PCC), medial prefrontal cortex (mPFC), hippocampal formation (HF), inferior parietal cortex (IPC), and medial temporal lobe (MTL). Pearson correlation analysis was performed between the abnormal FC strength within DMN and venous blood ammonia levels in patients. Compared with the controls, patients with HBV-related cirrhosis without HE demonstrated significantly decreased region-to-region FC between the mPFC and bilateral MTL, right HF, and left IPC, as well as between the right MTL and left IPC, right HF, and PCC. A significant negative relationship was observed between blood ammonia levels and connectivity strength between the mPFC and left IPC in patients. These results suggest that patients with HBV-related cirrhosis without HE had disrupted functional connectivty within the DMN, even before the appearance of minimal HE.
PMID: 24907446 [PubMed - as supplied by publisher]
Acupuncture Stimulation of Taichong (Liv3) and Hegu (LI4) Modulates the Default Mode Network Activity in Alzheimer's Disease.
Am J Alzheimers Dis Other Demen. 2014 Jun 6;
Authors: Liang P, Wang Z, Qian T, Li K
OBJECTIVES: The acupuncture has been used in the therapy of Alzheimer disease (AD), however, its neural underpins are still unclear. The aim of this study is to examine the acupuncture effect on the default mode network (DMN) in AD by using resting state functional magnetic resonance imaging (RS-fMRI).
METHODS: Twenty-eight subjects (14 AD and 14 normal controls (NC)) participated in this study. RS-fMRI data were acquired before and after acupuncture, while during the acupuncture, the procession of acupuncture stimulation on the acupoints of Tai chong (Liv3) and Hegu (LI4) lasted for 3 minutes.
RESULTS: Region of interest analysis showed that the impaired DMN connectivity in AD (identified by comparing the pre-acupuncture RS-fMRI of AD and NC), specifically the left cingulate gyrus (CG) and right inferior parietal lobule (IPL), were significantly changed for the better. The whole-brain exploratory analysis further demonstrated these results and found some new regions respond to the acupuncture effect on AD, with a cluster in the left posterior cingulate cortex (PCC), the right middle temporal gyrus (MTG) together with right IPL showed increased within-DMN connectivity; and the bilateral CG and left PCu showed decreased within-DMN connectivity. Moreover, the acupuncture effect on the right MTG was significantly correlated with disease severity as measured by Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) scores.
CONCLUSION: It was found that the acupuncture stimulation could modulate the DMN activity in AD. The current findings suggest that the acupuncture treatment on the relative earlier AD patients might have a better therapy effect.
PMID: 24906968 [PubMed - as supplied by publisher]
Modeling distinct imaging hemodynamics early after TBI: the relationship between signal amplitude and connectivity.
Brain Imaging Behav. 2014 Jun 7;
Authors: Medaglia JD, McAleavey AA, Rostami S, Slocomb J, Hillary FG
Over the past decade, fMRI studies of cognitive change following traumatic brain injury (TBI) have investigated blood oxygen level dependent (BOLD) activity during working memory (WM) performance in individuals in early and chronic phases of recovery. Recently, BOLD fMRI work has largely shifted to focus on WM and resting functional connectivity following TBI. However, fundamental questions in WM remain. Specifically, the effects of injury on the basic relationships between local and interregional functional neuroimaging signals during WM processing early following moderate to severe TBI have not been examined. This study employs a mixed effects model to examine prefrontal cortex and parietal lobe signal change during a WM task, the n-back, and whether there is covariance between regions of high amplitude signal change, (synchrony of elicited activity (SEA) very early following TBI. We also examined whether signal change and SEA differentially predict performance during WM. Overall, percent signal change in the right prefrontal cortex (rPFC) was and important predictor of both reaction time (RT) and SEA in early TBI and matched controls. Right prefrontal cortex (rPFC) percent signal change positively predicted SEA within and between persons regardless of injury status, suggesting that the link between these neurodynamic processes in WM-activated regions remains unaffected even very early after TBI. Additionally, rPFC activity was positively related to RT within and between persons in both groups. Right parietal (rPAR) activity was negatively related to RT within subjects in both groups. Thus, the local signal intensity of the rPFC in TBI appears to be a critical property of network functioning and performance in WM processing and may be a precursor to recruitment observed in chronic samples. The present results suggest that as much research moves toward large scale functional connectivity modeling, it will be essential to develop integrated models of how local and distant neurodynamics promote WM performance after TBI.
PMID: 24906546 [PubMed - as supplied by publisher]
Corrigendum: Impact of functional MRI data preprocessing pipeline on default-mode network detectability in patients with disorders of consciousness.
Front Neuroinform. 2014;8:50
Authors: Andronache AS, Rosazza C, Sattin D, Leonardi M, D'Incerti L, Minati L
[This corrects the article on p. 16 in vol. 7, PMID: 23986694.].
PMID: 24904396 [PubMed - as supplied by publisher]
Imaging the where and when of tic generation and resting state networks in adult Tourette patients.
Front Hum Neurosci. 2014;8:362
Authors: Neuner I, Werner CJ, Arrubla J, Stöcker T, Ehlen C, Wegener HP, Schneider F, Shah NJ
Introduction: Tourette syndrome (TS) is a neuropsychiatric disorder with the core phenomenon of tics, whose origin and temporal pattern are unclear. We investigated the When and Where of tic generation and resting state networks (RSNs) via functional magnetic resonance imaging (fMRI). Methods: Tic-related activity and the underlying RSNs in adult TS were studied within one fMRI session. Participants were instructed to lie in the scanner and to let tics occur freely. Tic onset times, as determined by video-observance were used as regressors and added to preceding time-bins of 1 s duration each to detect prior activation. RSN were identified by independent component analysis (ICA) and correlated to disease severity by the means of dual regression. Results: Two seconds before a tic, the supplementary motor area (SMA), ventral primary motor cortex, primary sensorimotor cortex and parietal operculum exhibited activation; 1 s before a tic, the anterior cingulate, putamen, insula, amygdala, cerebellum and the extrastriatal-visual cortex exhibited activation; with tic-onset, the thalamus, central operculum, primary motor and somatosensory cortices exhibited activation. Analysis of resting state data resulted in 21 components including the so-called default-mode network. Network strength in those regions in SMA of two premotor ICA maps that were also active prior to tic occurrence, correlated significantly with disease severity according to the Yale Global Tic Severity Scale (YGTTS) scores. Discussion: We demonstrate that the temporal pattern of tic generation follows the cortico-striato-thalamo-cortical circuit, and that cortical structures precede subcortical activation. The analysis of spontaneous fluctuations highlights the role of cortical premotor structures. Our study corroborates the notion of TS as a network disorder in which abnormal RSN activity might contribute to the generation of tics in SMA.
PMID: 24904391 [PubMed]
Habits: bridging the gap between personhood and personal identity.
Front Hum Neurosci. 2014;8:330
Authors: Wagner NF, Northoff G
In philosophy, the criteria for personhood (PH) at a specific point in time (synchronic), and the necessary and sufficient conditions of personal identity (PI) over time (diachronic) are traditionally separated. Hence, the transition between both timescales of a person's life remains largely unclear. Personal habits reflect a decision-making (DM) process that binds together synchronic and diachronic timescales. Despite the fact that the actualization of habits takes place synchronically, they presuppose, for the possibility of their generation, time in a diachronic sense. The acquisition of habits therefore rests upon PI over time; that is, the temporal extension of personal decisions is the necessary condition for the possible development of habits. Conceptually, habits can thus be seen as a bridge between synchronic and diachronic timescales of a person's life. In order to investigate the empirical mediation of this temporal linkage, we draw upon the neuronal mechanisms underlying DM; in particular on the distinction between internally and externally guided DM. Externally guided DM relies on external criteria at a specific point in time (synchronic); on a neural level, this has been associated with lateral frontal and parietal brain regions. In contrast, internally guided DM is based on the person's own preferences that involve a more longitudinal and thus diachronic timescale, which has been associated with the brain's intrinsic activity. Habits can be considered to reflect a balance between internally and externally guided DM, which implicates a particular temporal balance between diachronic and synchronic elements, thus linking two different timescales. Based on such evidence, we suggest a habit-based neurophilosophical approach of PH and PI by focusing on the empirically-based linkage between the synchronic and diachronic elements of habits. By doing so, we propose to link together what philosophically has been described and analyzed separately as PH and PI.
PMID: 24904370 [PubMed]
Phase-amplitude coupling and infraslow (<1 Hz) frequencies in the rat brain: relationship to resting state fMRI.
Front Integr Neurosci. 2014;8:41
Authors: Thompson GJ, Pan WJ, Billings JC, Grooms JK, Shakil S, Jaeger D, Keilholz SD
Resting state functional magnetic resonance imaging (fMRI) can identify network alterations that occur in complex psychiatric diseases and behaviors, but its interpretation is difficult because the neural basis of the infraslow BOLD fluctuations is poorly understood. Previous results link dynamic activity during the resting state to both infraslow frequencies in local field potentials (LFP) (<1 Hz) and band-limited power in higher frequency LFP (>1 Hz). To investigate the relationship between these frequencies, LFPs were recorded from rats under two anesthetics: isoflurane and dexmedetomidine. Signal phases were calculated from low-frequency LFP and compared to signal amplitudes from high-frequency LFP to determine if modulation existed between the two frequency bands (phase-amplitude coupling). Isoflurane showed significant, consistent phase-amplitude coupling at nearly all pairs of frequencies, likely due to the burst-suppression pattern of activity that it induces. However, no consistent phase-amplitude coupling was observed in rats that were anesthetized with dexmedetomidine. fMRI-LFP correlations under isoflurane using high frequency LFP were reduced when the low frequency LFP's influence was accounted for, but not vice-versa, or in any condition under dexmedetomidine. The lack of consistent phase-amplitude coupling under dexmedetomidine and lack of shared variance between high frequency and low frequency LFP as it relates to fMRI suggests that high and low frequency neural electrical signals may contribute differently, possibly even independently, to resting state fMRI. This finding suggests that researchers take care in interpreting the neural basis of resting state fMRI, as multiple dynamic factors in the underlying electrophysiology could be driving any particular observation.
PMID: 24904325 [PubMed]
Identifying and Characterizing Resting State Networks in Temporally Dynamic Functional Connectomes.
Brain Topogr. 2014 Jun 6;
Authors: Zhang X, Li X, Jin C, Chen H, Li K, Zhu D, Jiang X, Zhang T, Lv J, Hu X, Han J, Zhao Q, Guo L, Li L, Liu T
An important application of resting state fMRI data has been to identify resting state networks (RSN). The conventional RSN studies attempted to discover consistent networks through functional connectivity analysis over the whole scan time, which implicitly assumes that RSNs are static. However, the brain undergoes dynamic functional state changes and the functional connectome patterns vary along with time, even in resting state. Hence, this study aims to characterize temporal brain dynamics in resting state. It utilizes the temporally dynamic functional connectome patterns to extract a set of resting state clusters and their corresponding RSNs based on the large-scale consistent, reproducible and predictable whole-brain reference system of dense individualized and common connectivity-based cortical landmarks (DICCCOL). Especially, an effective multi-view spectral clustering method was performed by treating each dynamic functional connectome pattern as one view, and this procedure was also applied on static multi-subject functional connectomes to obtain the static clusters for comparison. It turns out that some dynamic clusters exhibit high similarity with static clusters, suggesting the stability of those RSNs including the visual network and the default mode network. Moreover, two motor-related dynamic clusters show correspondence with one static cluster, which implies substantially more temporal variability of the motor resting network. Particularly, four dynamic clusters exhibited large differences in comparison with their corresponding static networks. Thus it is suggested that these four networks might play critically important roles in functional brain dynamics and interactions during resting state, offering novel insights into the brain function and its dynamics.
PMID: 24903106 [PubMed - as supplied by publisher]
Lennox-Gastaut syndrome and phenotype: Secondary network epilepsies.
Epilepsia. 2014 Jun 5;
Authors: Archer JS, Warren AE, Stagnitti MR, Masterton RA, Abbott DF, Jackson GD
OBJECTIVE: Lennox-Gastaut syndrome (LGS) is a severe epilepsy phenotype with characteristic electroclinical features despite diverse etiologies. We previously found common cerebral networks involved during slow spike-and-wave (SSW) and generalized paroxysmal fast activity (PFA), characteristic interictal discharges. Some patients have a Lennox-Gastaut-like phenotype and cortical lesions. We wished to explore the interaction between cerebral networks and lesions in this group.
METHODS: 3 Tesla electroencephalography-functional magnetic resonance imaging (EEG-fMRI) on six subjects with Lennox-Gastaut phenotype and a structural lesion. Timings of SSW and PFA events were used in an event-related fMRI analysis, and to estimate the time course of the hemodynamic response from key regions.
RESULTS: (1) PFA-robust fMRI signal increases were observed in frontal and parietal association cortical areas, thalamus, and pons, with simultaneous increases in both "attention" and resting-state (default mode) networks, a highly unusual pattern. (2) SSW showed mixed increased and decreased fMRI activity, with preevent increases in association cortex and thalamus, and then prominent postevent reduction. There was decreased fMRI activity in primary cortical areas. (3) Lesion-variable fMRI increases were observed during PFA and SSW discharges. Three subjects who proceeded to lesionectomy are >1 year seizure-free.
SIGNIFICANCE: We conceptualize Lennox-Gastaut phenotype as a being a network epilepsy, where key cerebral networks become autonomously unstable. Epileptiform activity in Lennox-Gastaut phenotype, and by implication in LGS, appears to be amplified and expressed through association cortical areas, possibly because the attention and default-mode networks are widely interconnected, fundamental brain networks. Seizure freedom in the subjects who proceeded to lesionectomy suggests that cortical lesions are able to establish and maintain this abnormal unstable network behavior. LGS may be considered a secondary network epilepsy because the unifying epileptic manifestations of the disorder, including PFA and SSW, reflect network dysfunction, rather than the specific initiating process. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here.
PMID: 24902608 [PubMed - as supplied by publisher]
Intrinsic resting-state activity predicts working memory brain activation and behavioral performance.
Hum Brain Mapp. 2013 Dec;34(12):3204-15
Authors: Zou Q, Ross TJ, Gu H, Geng X, Zuo XN, Hong LE, Gao JH, Stein EA, Zang YF, Yang Y
Although resting-state brain activity has been demonstrated to correspond with task-evoked brain activation, the relationship between intrinsic and evoked brain activity has not been fully characterized. For example, it is unclear whether intrinsic activity can also predict task-evoked deactivation and whether the rest-task relationship is dependent on task load. In this study, we addressed these issues on 40 healthy control subjects using resting-state and task-driven [N-back working memory (WM) task] functional magnetic resonance imaging data collected in the same session. Using amplitude of low-frequency fluctuation (ALFF) as an index of intrinsic resting-state activity, we found that ALFF in the middle frontal gyrus and inferior/superior parietal lobules was positively correlated with WM task-evoked activation, while ALFF in the medial prefrontal cortex, posterior cingulate cortex, superior frontal gyrus, superior temporal gyrus, and fusiform gyrus was negatively correlated with WM task-evoked deactivation. Further, the relationship between the intrinsic resting-state activity and task-evoked activation in lateral/superior frontal gyri, inferior/superior parietal lobules, superior temporal gyrus, and midline regions was stronger at higher WM task loads. In addition, both resting-state activity and the task-evoked activation in the superior parietal lobule/precuneus were significantly correlated with the WM task behavioral performance, explaining similar portions of intersubject performance variance. Together, these findings suggest that intrinsic resting-state activity facilitates or is permissive of specific brain circuit engagement to perform a cognitive task, and that resting activity can predict subsequent task-evoked brain responses and behavioral performance.
PMID: 22711376 [PubMed - indexed for MEDLINE]
Effect of deafferentation from spinal anesthesia on pain sensitivity and resting-state functional brain connectivity in healthy male volunteers.
Brain Connect. 2014 Jun 5;
Authors: Niesters M, Sitsen E, Oudejans L, Vuyk J, Aarts L, Rombouts SA, de Rover M, Khalili-Mahani N, Dahan A
Patients may perceive paradoxical heat sensation during spinal anesthesia. This could be due to deafferentation-related functional changes at cortical, subcortical or spinal levels. In the current study, the effect of spinal deafferentation on sensory (pain) sensitivity was studied and linked to whole-brain functional connectivity as assessed by resting-state functional magnetic resonance imaging (RS-fMRI) imaging. Deafferentation was induced by sham or spinal anesthesia (15 mg bupivacaine injected at L3-4) in 12 male volunteers. RS-fMRI brain connectivity was determined in relation to 8 predefined and 7 thalamic resting-state networks and measured before, and 1 and 2 hours after spinal/sham injection. To measure the effect of deafferentation on pain sensitivity, responses to heat pain were measured at 15-minute intervals on non-deafferented skin and correlated to RS-fMRI connectivity data. Spinal anesthesia altered functional brain connectivity within brain regions involved in the sensory discriminative (ie. pain intensity related) and affective dimensions of pain perception in relation to somatosensory and thalamic resting-state networks. A significant enhancement of pain sensitivity on non-deafferented skin was observed after spinal anesthesia compared to sham (area-under-the-curve (mean (SEM)): 190.4 (33.8) versus 13.7 (7.2); p < 0.001), which significantly correlated to functional connectivity changes observed within the thalamus in relation to the thalamo-prefrontal network, and in the anterior cingulate cortex and insula in relation to the thalamo-parietal network. Enhanced pain sensitivity from spinal deafferentation correlated with functional connectivity changes within brain regions involved in affective and sensory pain processing and areas involved in descending control of pain.
PMID: 24901040 [PubMed - as supplied by publisher]
Evolution of functional connectivity of brain networks and their dynamic interaction in temporal lobe epilepsy.
Brain Connect. 2014 Jun 5;
Authors: Morgan VL, Abou-Khalil B, Rogers B
This study presents a cross-sectional investigation of functional networks in temporal lobe epilepsy (TLE) as they evolve over years of disease. Networks of interest were identified based on a priori hypotheses: the network of seizure propagation ipsilateral to the seizure focus, the same regions contralateral to seizure focus, the cross hemisphere network of the same regions, and a cingulate midline network. Resting functional magnetic resonance imaging data were acquired for twenty minutes in twelve unilateral TLE patients, and twelve age and gender matched healthy controls. Functional changes within and between the four networks as they evolve over years of disease were quantified by standard measures of static functional connectivity and novel measures of dynamic functional connectivity. The results suggest an initial disruption of cross hemispheric networks and an increase in static functional connectivity in the ipsilateral temporal network accompanying the onset of TLE seizures. As seizures progress over years, the static functional connectivity across the ipsilateral network diminishes, while dynamic functional connectivity measures show the functional independence of this ipsilateral network from the network of midline regions of the cingulate declines. This implies a gradual breakdown of the seizure onset and early propagation network involving the ipsilateral hippocampus and temporal lobe as it becomes more synchronous with the network of regions responsible for secondary generalization of the seizures, a process that may facilitate the spread of seizures across the brain. Ultimately, the significance of this evolution may be realized in relating it to symptoms and treatment outcomes of TLE.
PMID: 24901036 [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):7862-7870
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 - as supplied by publisher]
Lasting Impact of Regret and Gratification on Resting Brain Activity and Its Relation to Depressive Traits.
J Neurosci. 2014 Jun 4;34(23):7825-7835
Authors: Eryilmaz H, Van De Ville D, Schwartz S, Vuilleumier P
Obtaining lower gains than rejected alternatives during decision making evokes feelings of regret, whereas higher gains elicit gratification. Although decision-related emotions produce lingering effects on mental state, neuroscience research has generally focused on transient brain responses to positive or negative events, but ignored more sustained consequences of emotional episodes on subsequent brain states. We investigated how spontaneous brain activity and functional connectivity at rest are modulated by postdecision regret and gratification in 18 healthy human subjects using a gambling task in fMRI. Differences between obtained and unobtained outcomes were manipulated parametrically to evoke different levels of regret or gratification. We investigated how individual personality traits related to depression and rumination affected these responses. Medial and ventral prefrontal areas differentially responded to favorable and unfavorable outcomes during the gambling period. More critically, during subsequent rest, rostral anterior and posterior cingulate cortex, ventral striatum, and insula showed parametric response to the gratification level of preceding outcomes. Functional coupling of posterior cingulate with striatum and amygdala was also enhanced during rest after high gratification. Regret produced distinct changes in connectivity of subgenual cingulate with orbitofrontal cortex and thalamus. Interestingly, individual differences in depressive traits and ruminations correlated with activity of the striatum after gratification and orbitofrontal cortex after regret, respectively. By revealing lingering effects of decision-related emotions on key nodes of resting state networks, our findings illuminate how such emotions may influence self-reflective processing and subsequent behavioral adjustment, but also highlight the malleability of resting networks in emotional contexts.
PMID: 24899706 [PubMed - as supplied by publisher]
Resting-state brain activation correlates with short-time antidepressant treatment outcome in drug-naïve patients with major depressive disorder.
J Int Med Res. 2014 Jun 4;
Authors: Wang LJ, Kuang WH, Xu JJ, Lei D, Yang YC
OBJECTIVE: A resting-state functional magnetic resonance imaging study (fMRI) to investigate pretreatment regional differences in brain function, in patients with early treatment responsive (ERD) and early treatment nonresponsive (END) major depressive disorder (MDD).
METHODS: Patients with MDD and healthy control subjects underwent fMRI. Intrinsic neural activity at baseline was evaluated via amplitude of low-frequency fluctuations (ALFF). Antidepressant treatment was initiated after MRI. All patients received selective serotonin reuptake inhibitor type antidepressants at the minimum effective dose.
RESULTS: There were significant differences in brain activity between patients (n = 56) and control subjects (n = 33). Brain activity in patients with ERD (n = 26) differed from those with END (n = 30) in the lingual gyrus and cerebellum. There was a significantly correlation between activity in these regions and disease duration in patients with ERD, and with amelioration of depressive symptoms in patients with END.
CONCLUSIONS: Brain regions related to the neural mechanism of MDD early treatment outcome were identified. These regions may have important implications for the treatment of MDD.
PMID: 24898399 [PubMed - as supplied by publisher]
Safety of EEG-fMRI recordings in newborn infants at 3T: a study using a baby-size phantom.
Clin Neurophysiol. 2014 May;125(5):941-6
Authors: Vanhatalo S, Alnajjar A, Nguyen VT, Colditz P, Fransson P
OBJECTIVE: We aimed to study EEG electrode temperatures during MRI recordings using a neonatal-size phantom to establish the safety of neonatal EEG-MRI.
METHODS: We constructed a phantom set-up for co-registration of EEG and MRI measurements with newborn size configurations. The set-up consisted of a spherical glass phantom fitted with a customised MRI-compatible 64-channel EEG cap and EEG amplifier. Temperatures were recorded during and after five different scanning sequences (two T2∗ sensitised BOLD fMRI, one T1-weighted and two T2-weighted spin echo) in five electrode locations using a thermistor that was integrated into the electrode housing. A temperature increase >4°C was defined a priori as the safety limit.
RESULTS: During fMRI and T1 sequences, none of the electrodes showed meaningful temperature changes. Only one MRI sequence (T2 with Max turbo factor 25; SAR 89%) caused temperature increase in one electrode (Fpz; +4.1°C) that slightly exceeded our predefined safety limit, while the conventional T2 sequence was within safety limits (up to +1.7°C).
CONCLUSIONS: Co-registration of EEG and fMRI can be considered safe in babies with respect to electrode heating, which is the primary safety concern.
SIGNIFICANCE: The present findings open up a possibility to commence studies where EEG and MRI/fMRI are co-registered in human babies. Such studies hold significant promise of a better understanding of the early development of brain function and neurovascular coupling.
PMID: 24252394 [PubMed - indexed for MEDLINE]
Emotional Processing and Brain Activity in Youth at High Risk for Alcoholism.
Alcohol Clin Exp Res. 2014 May 29;
Authors: Cservenka A, Fair DA, Nagel BJ
BACKGROUND: Even in the absence of heavy alcohol use, youth with familial alcoholism (family history positive [FHP]) exhibit atypical brain functioning and behavior. Although emotional and cognitive systems are affected in alcohol use disorders (AUDs), little attention has focused on whether brain and behavior phenotypes related to the interplay between affective and executive functioning may be a premorbid risk factor for the development of AUDs in FHP youth.
METHODS: Twenty-four FHP and 22 family history negative (FHN) 12- to 16-year-old adolescents completed study procedures. After exclusion of participants with clinically significant depressive symptoms and those who did not meet performance criteria during an Emotional Go-NoGo task, 19 FHP and 17 FHN youth were included in functional magnetic resonance imaging (fMRI) analyses. Resting state functional connectivity MRI, using amygdalar seed regions, was analyzed in 16 FHP and 18 FHN youth, after exclusion of participants with excessive head movement.
RESULTS: fMRI showed that brain activity in FHP youth, compared with FHN peers, was reduced during emotional processing in the superior temporal cortex, as well as during cognitive control within emotional contexts in frontal and striatal regions. Group differences in resting state amygdalar connectivity were seen bilaterally between FHP and FHN youth. In FHP youth, reduced resting state synchrony between the left amygdala and left superior frontal gyrus was related to poorer response inhibition, as measured during the fMRI task.
CONCLUSIONS: To our knowledge, this is the first study to examine emotion-cognition interactions and resting state functional connectivity in FHP youth. Findings from this research provide insight into neural and behavioral phenotypes associated with emotional processing in familial alcoholism, which may relate to increased risk of developing AUDs.
PMID: 24890898 [PubMed - as supplied by publisher]
fMRI evidence for abnormal resting-state functional connectivity in euthymic bipolar patients.
J Affect Disord. 2014 Aug;165:182-9
Authors: Favre P, Baciu M, Pichat C, Bougerol T, Polosan M
BACKGROUND: Neural substrates of bipolar disorder (BD) have frequently been characterized by dysregulation of fronto-limbic networks that may persist during euthymic periods. Only a few studies have investigated euthymic bipolar patients (BP) functional connectivity at rest. The current study aims to assess resting-state functional connectivity in euthymic BP in order to identify trait abnormalities responsible for enduring mood dysregulation in these patients.
METHODS: Medial prefrontal cortex (mPFC) functional connectivity was investigated in 20 euthymic BP and 20 healthy subjects (HS). The functional connectivity maps were compared across groups using a between-group random effect analysis. Additional region of interest (ROI) analysis focused on mPFC-amygdala functional connectivity as well as correlations between the clinical features in euthymic BP was also conducted.
RESULTS: A significant difference between euthymic BP and HS was observed in terms of connectivity between the mPFC and the right dorsolateral prefrontal cortex (dlPFC). A significant negative correlation between the activity of these regions was found in HS but not in euthymic BP. In addition, euthymic BP showed greater connectivity between mPFC and right amygdala compared to HS, which was also correlated with the duration of the disease.
LIMITATIONS: The BP group was heterogeneous with respect to the bipolarity subtype and the medication. The robustness of results could be improved with an increased sample size.
CONCLUSIONS: Compared to HS, the euthymic BP showed abnormal decoupling (decreased functional connectivity) activity between mPFC-dlPFC and hyperconnectivity (increased functional connectivity) and between mPFC and amygdala. These abnormalities could underlie the pathophysiology of BD, and may deteriorate further in accordance with disease duration.
PMID: 24882198 [PubMed - in process]
Resting network is composed of more than one neural pattern: an fMRI study.
Neuroscience. 2014 May 29;
Authors: Lee TW, Northoff G, Wu YT
In resting state, the dynamics of blood oxygen level-dependent signals recorded by functional magnetic resonance imaging (fMRI) showed reliable modular structures. To explore the network property, previous research used to construct an adjacency matrix by Pearson's correlation and prune it using stringent statistical threshold. However, traditional analyses may lose useful information at middle to moderate high correlation level. This resting fMRI study adopted full connection as a criterion to partition the adjacency matrix into composite sub-matrices (neural patterns) and investigated the associated community organization and network features. Modular consistency across subjects was assessed using scaled inclusivity index. Our results disclosed 2 neural patterns with reliable modular structures. Concordant with the results of traditional intervention, community detection analysis showed that neural pattern 1, the sub-matrix at highest correlation level, was composed of sensory-motor, visual associative, default mode/midline, temporal limbic and basal ganglia structures. The neural pattern 2 was situated at middle to moderate high correlation level and comprised 2 larger modules, possibly associated with mental processing of outer world (such as visuo-associative, auditory and sensory-motor networks) and inner homeostasis (such as default-mode, midline and limbic systems). Graph theoretical analyses further demonstrated that the network feature of neural pattern 1 was more local and segregate, whereas that of neural pattern 2 was more global and integrative. Our results suggest that future resting fMRI research may take the neural pattern at middle to moderate high correlation range into consideration, which has long been ignored in extant literature. The variation of neural pattern 2 could be relevant to individual characteristics of self-regulatory functions, and the disruption in its topology may underlie the pathology of several neuropsychiatric illnesses.
PMID: 24881572 [PubMed - as supplied by publisher]