Functional resting-state fMRI connectivity correlates with serum levels of the S100B protein in the acute phase of traumatic brain injury.
Neuroimage Clin. 2016;12:1004-1012
Authors: Thompson WH, Thelin EP, Lilja A, Bellander BM, Fransson P
The S100B protein is an intra-cellular calcium-binding protein that mainly resides in astrocytes in the central nervous system. The serum level of S100B is used as biomarker for the severity of brain damage in traumatic brain injury (TBI) patients. In this study we investigated the relationship between intrinsic resting-state brain connectivity, measured 1-22 days (mean 8 days) after trauma, and serum levels of S100B in a patient cohort with mild-to-severe TBI in need of neuro-intensive care in the acute phase. In line with previous investigations, our results show that the peak level of S100B acquired during the acute phase of TBI was negatively correlated with behavioral measures (Glasgow Outcome Score, GOS) of functional outcome assessed 6 to 12 months post injury. Using a multi-variate pattern analysis-informed seed-based correlation analysis, we show that the strength of resting-state brain connectivity in multiple resting-state networks was negatively correlated with the peak of serum levels of S100B. A negative correspondence between S100B peak levels recorded 12-36 h after trauma and intrinsic connectivity was found for brain regions located in the default mode, fronto-parietal, visual and motor resting-state networks. Our results suggest that resting-state brain connectivity measures acquired during the acute phase of TBI is concordant with results obtained from molecular biomarkers and that it may hold a capacity to predict long-term cognitive outcome in TBI patients.
PMID: 27995066 [PubMed - in process]
Decreased Subcortical and Increased Cortical Degree Centrality in a Nonclinical College Student Sample with Subclinical Depressive Symptoms: A Resting-State fMRI Study.
Front Hum Neurosci. 2016;10:617
Authors: Gao C, Wenhua L, Liu Y, Ruan X, Chen X, Liu L, Yu S, Chan RC, Wei X, Jiang X
Abnormal functional connectivity (FC) at rest has been identified in clinical depressive disorder. However, very few studies have been conducted to understand the underlying neural substrates of subclinical depression. The newly proposed centrality analysis approach has been increasingly used to explore the large-scale brain network of mental diseases. This study aimed to identify the degree centrality (DC) alteration of the brain network in subclinical depressive subjects. Thirty-seven candidates with subclinical depression and 34 well-matched healthy controls (HCs) were recruited from the same sample of college students. All subjects underwent a resting-state fMRI (rs-fMRI) scan to assess the DC of the whole brain. Compared with controls, subclinical depressive subjects displayed decreased DC in the right parahippocampal gyrus (PHG), left PHG/amygdala, and left caudate and elevated DC in the right posterior parietal lobule (PPL), left inferior frontal gyrus (IFG) and left middle frontal gyrus (MFG). In addition, by using receiver operating characteristic (ROC) analysis, we determined that the DC values in the regions with altered FC between the two groups can be used to differentiate subclinical depressive subjects from HCs. We suggest that decreased DC in subcortical and increased DC in cortical regions might be the neural substrates of subclinical depression.
PMID: 27994546 [PubMed]
Propofol attenuates low-frequency fluctuations of resting-state fMRI BOLD signal in the anterior frontal cortex upon loss of consciousness.
Neuroimage. 2016 Dec 16;:
Authors: Liu X, Lauer KK, Douglas Ward B, Roberts C, Liu S, Gollapudy S, Rohloff R, Gross W, Chen G, Xu Z, Binder JR, Li SJ, Hudetz AG
Recent studies indicate that spontaneous low-frequency fluctuations (LFFs) of resting-state functional magnetic resonance imaging (rs-fMRI) blood oxygen level-dependent (BOLD) signals are driven by the slow (<0.1Hz) modulation of ongoing neuronal activity synchronized locally and across remote brain regions. How regional LFFs of the BOLD fMRI signal are altered during anesthetic-induced alteration of consciousness is not well understood. Using rs-fMRI in 15 healthy participants, we show that during administration of propofol to achieve loss of behavioral responsiveness indexing unconsciousness, the fractional amplitude of LFF (fALFF index) was reduced in comparison to wakeful baseline in the anterior frontal regions, temporal pole, hippocampus, parahippocampal gyrus, and amygdala. Such changes were absent in large areas of the motor, parietal, and sensory cortices. During light sedation characterized by the preservation of overt responsiveness and therefore consciousness, fALFF was reduced in the subcortical areas, temporal pole, medial orbital frontal cortex, cingulate cortex, and cerebellum. Between light sedation and deep sedation, fALFF was reduced primarily in the medial and dorsolateral frontal areas. The preferential reduction of LFFs in the anterior frontal regions is consistent with frontal to sensory-motor cortical disconnection and may contribute to the suppression of consciousness during general anesthesia.
PMID: 27993673 [PubMed - as supplied by publisher]
Looking for answers to bariatric surgery for losing weight using resting state functional MRI.
Eur J Neurosci. 2016 Dec 19;:
Authors: Zhang B
Obesity is a worldwide public health epidemic. Research demonstrates that obesity is associated with an increased risk of developing many physical conditions including diabetes and high blood cholesterol (Ogden et al., 2014). Bariatric surgery is one efficient therapy to losing weight. Previous functional MRI (fMRI) studies have found that obese patients undergoing surgery demonstrate aberrant neural activity and resting state functional connectivity (Frank et al., 2014; Lepping et al., 2015). However, no previous studies have tested the difference in resting state neural activity before and after bariatric surgery. This article is protected by copyright. All rights reserved.
PMID: 27992097 [PubMed - as supplied by publisher]
Interhemispheric Functional Connectivity in Anorexia and Bulimia Nervosa.
Eur J Neurosci. 2016 Dec 19;:
Authors: Canna A, Prinster A, Monteleone AM, Cantone E, Monteleone P, Volpe U, Maj M, Di Salle F, Esposito F
The functional interplay between hemispheres is fundamental for behavioral, cognitive and emotional control. Anorexia nervosa (AN) and bulimia nervosa (BN) have been largely studied with brain magnetic resonance imaging (MRI) in relation to the functional mechanisms of high-level processing, but not in terms of possible inter-hemispheric functional connectivity anomalies. Using resting-state functional MRI (fMRI), voxel-mirrored homotopic connectivity (VMHC) and regional inter-hemispheric spectral coherence (IHSC) were studied in 15 AN and 13 BN patients and 16 healthy controls (HC). Using T1-weighted and diffusion tensor imaging MRI scans, regional VMHC values were correlated with the left-right asymmetry of corresponding homotopic gray matter volumes and with the white matter callosal fractional anisotropy (FA). Compared to HC, AN patients exhibited reduced VMHC in cerebellum, insula, and precuneus, while BN patients showed reduced VMHC in dorso-lateral prefrontal and orbito-frontal cortices. The regional IHSC analysis highlighted that the inter-hemispheric functional connectivity was higher in the 'Slow-5' band in all regions except the insula. No group differences in left-right structural asymmetries and in VMHC vs. callosal FA correlations were significant in the comparisons between cohorts. These anomalies, not explained by structural changes, indicate that AN and BN, at least in their acute phase, are associated with a loss of inter-hemispheric connectivity in regions implicated in self-referential, cognitive control and reward processing. These findings may thus gather novel functional markers to explore aberrant features of these eating disorders. This article is protected by copyright. All rights reserved.
PMID: 27992088 [PubMed - as supplied by publisher]
Bursty properties revealed in large-scale brain networks with a point-based method for dynamic functional connectivity.
Sci Rep. 2016 Dec 19;6:39156
Authors: Thompson WH, Fransson P
The brain is organized into large scale spatial networks that can be detected during periods of rest using fMRI. The brain is also a dynamic organ with activity that changes over time. We developed a method and investigated properties where the connections as a function of time are derived and quantified. The point based method (PBM) presented here derives covariance matrices after clustering individual time points based upon their global spatial pattern. This method achieved increased temporal sensitivity, together with temporal network theory, allowed us to study functional integration between resting-state networks. Our results show that functional integrations between two resting-state networks predominately occurs in bursts of activity. This is followed by varying intermittent periods of less connectivity. The described point-based method of dynamic resting-state functional connectivity allows for a detailed and expanded view on the temporal dynamics of resting-state connectivity that provides novel insights into how neuronal information processing is integrated in the human brain at the level of large-scale networks.
PMID: 27991540 [PubMed - in process]
Salience Network Connectivity Modulates Skin Conductance Responses in Predicting Arousal Experience.
J Cogn Neurosci. 2016 Dec 19;:1-10
Authors: Xia C, Touroutoglou A, Quigley KS, Feldman Barrett L, Dickerson BC
Individual differences in arousal experience have been linked to differences in resting-state salience network connectivity strength. In this study, we investigated how adding task-related skin conductance responses (SCR), a measure of sympathetic autonomic nervous system activity, can predict additional variance in arousal experience. Thirty-nine young adults rated their subjective experience of arousal to emotionally evocative images while SCRs were measured. They also underwent a separate resting-state fMRI scan. Greater SCR reactivity (an increased number of task-related SCRs) to emotional images and stronger intrinsic salience network connectivity independently predicted more intense experiences of arousal. Salience network connectivity further moderated the effect of SCR reactivity: In individuals with weak salience network connectivity, SCR reactivity more significantly predicted arousal experience, whereas in those with strong salience network connectivity, SCR reactivity played little role in predicting arousal experience. This interaction illustrates the degeneracy in neural mechanisms driving individual differences in arousal experience and highlights the intricate interplay between connectivity in central visceromotor neural circuitry and peripherally expressed autonomic responses in shaping arousal experience.
PMID: 27991182 [PubMed - as supplied by publisher]
Core brain networks interactions and cognitive control in internet gaming disorder individuals in late adolescence/early adulthood.
Brain Struct Funct. 2016 Apr;221(3):1427-42
Authors: Yuan K, Qin W, Yu D, Bi Y, Xing L, Jin C, Tian J
Regardless of whether it is conceptualized as a behavioral addiction or an impulse-control disorder, internet gaming disorder (IGD) has been speculated to be associated with impaired cognitive control. Efficient cognitive behavior involves the coordinated activity of large-scale brain networks, however, whether the interactions among these networks during resting state modulated cognitive control behavior in IGD adolescents remain unclear. Twenty-eight IGD adolescents and twenty-five age-, gender-, and education-matched healthy controls participated in our study. Stroop color-word task was conducted to evaluate the cognitive control deficits in IGD adolescents. Functional connectivity and Granger Causal Analysis were employed to investigate the functional and effective connections within and between the salience, central executive, and default mode networks. Meanwhile, diffusion tensor imaging was used to assess the structural integrity of abnormal network connections. The abnormal functional connectivity within central executive networks and effective connectivity within salience network in IGD adolescents were detected. Moreover, the inefficient interactions between these two brain networks were observed. In addition, we identified reduced fractional anisotropy in salience network, right central executive network tracts, and between-network (the anterior cingulate cortex-right dorsolateral prefrontal cortex tracts) pathways in IGD individuals. Notably, we observed a significant correlation between the effective and structural connection from salience network to central executive network and the number of errors during incongruent condition in Stroop task in both IGD and control subjects. Our results suggested that impaired cognitive control in IGD adolescents is likely to be mediated through the abnormal interactions and structural connection between intrinsic large-scale brain networks.
PMID: 25573247 [PubMed - indexed for MEDLINE]
Promises, Pitfalls, and Basic Guidelines for Applying Machine Learning Classifiers to Psychiatric Imaging Data, with Autism as an Example.
Front Psychiatry. 2016;7:177
Authors: Kassraian-Fard P, Matthis C, Balsters JH, Maathuis MH, Wenderoth N
Most psychiatric disorders are associated with subtle alterations in brain function and are subject to large interindividual differences. Typically, the diagnosis of these disorders requires time-consuming behavioral assessments administered by a multidisciplinary team with extensive experience. While the application of Machine Learning classification methods (ML classifiers) to neuroimaging data has the potential to speed and simplify diagnosis of psychiatric disorders, the methods, assumptions, and analytical steps are currently opaque and not accessible to researchers and clinicians outside the field. In this paper, we describe potential classification pipelines for autism spectrum disorder, as an example of a psychiatric disorder. The analyses are based on resting-state fMRI data derived from a multisite data repository (ABIDE). We compare several popular ML classifiers such as support vector machines, neural networks, and regression approaches, among others. In a tutorial style, written to be equally accessible for researchers and clinicians, we explain the rationale of each classification approach, clarify the underlying assumptions, and discuss possible pitfalls and challenges. We also provide the data as well as the MATLAB code we used to achieve our results. We show that out-of-the-box ML classifiers can yield classification accuracies of about 60-70%. Finally, we discuss how classification accuracy can be further improved, and we mention methodological developments that are needed to pave the way for the use of ML classifiers in clinical practice.
PMID: 27990125 [PubMed - in process]
Altered regional homogeneity of brain spontaneous signals in SIV infected rhesus macaque model.
Magn Reson Imaging. 2016 Oct 27;:
Authors: Zhao J, Jing B, Chen F, Liu J, Wang Y, Li H
BACKGROUND: Regional homogeneity (ReHo), a measurement from resting-state functional magnetic imaging (rs-fMRI) to reflect local synchronization of brain activities, has been widely explored in previous studies of neurological diseases. SIV infected model for detecting the neurological changes with progression was studied.
METHODS: In the study, six rhesus macaques infected by simian immunodeficiency virus (SIV) were scanned by resting-state fMRI at the following time points: before SIV inoculation (baseline), 12weeks and 24weeks post inoculation (12wpi, 24wpi). Meanwhile, the immunological parameters including serum percentage of CD4+ T cell, CD4/CD8 ratio and absolute CD4+ T cell number were measured and analyzed.
RESULTS: In comparison of baseline, significant decreased ReHo was found in the left superior frontal gyrus, left superior temporal gyrus, left hippocampus, right precuneus, left angular gyrus, and bilateral occipital gyrus; in contrast increased ReHo in putamen at 12wpi. Moreover, at the time of 24wpi, decreased ReHo was observed in the right postcentral gyrus, left precentral gyrus, posterior cingulated gyrus and thalamus, while ReHo was increased in the left putamen, hippocampus, left anterior cingulated cortex and precentral cortex. The correlation analysis revealed that ReHo in the superior frontal gyrus showed negative association with CD4/CD8 ratio and positive with absolute CD4+ T cell number. The correlation analysis showed that percentage of CD4+ was correlated with the ReHo values in right middle frontal gyrus, bilateral thalamus and amygdala positively; negative relationship with left putamen, left superior frontal gyrus, left superior and middle temporal gyrus.
CONCLUSION: The study first indicates that hippocampus, putamen, frontal and occipital lobe were impaired by using rs-fMRI and correlated with immunological parameters. Thus, ReHo value can be utilized as a noninvasive biomarker of spontaneous brain activity changes caused by the progression of neurological impairments.
PMID: 27989909 [PubMed - as supplied by publisher]
Tracking thoughts: Exploring the neural architecture of mental time travel during mind-wandering.
Neuroimage. 2016 Dec 15;:
Authors: Karapanagiotidis T, Bernhardt BC, Jefferies E, Smallwood J
The capacity to imagine situations that have already happened or fictitious events that may take place in the future is known as mental time travel (MTT). Studies have shown that MTT is an important aspect of spontaneous thought, yet we lack a clear understanding of how the neurocognitive architecture of the brain constrains this element of human cognition. Previous functional magnetic resonance imaging (MRI) studies have shown that MTT involves the coordination between multiple regions that include mesiotemporal structures such as the hippocampus, as well as prefrontal and parietal regions commonly associated with the default mode network (DMN). The current study used a multimodal neuroimaging approach to identify the structural and functional brain organisation that underlies individual differences in the capacity to spontaneously engage in MTT. Using regionally unconstrained diffusion tractography analysis, we found increased diffusion anisotropy in right lateralised temporo-limbic, corticospinal, inferior fronto-occipital tracts in participants who reported greater MTT. Probabilistic connectivity mapping revealed a significantly higher connection probability of the right hippocampus with these tracts. Resting-state functional MRI connectivity analysis using the right hippocampus as a seed region revealed greater functional coupling to the anterior regions of the DMN with increasing levels of MTT. These findings demonstrate that the interactions between the hippocampus and regions of the cortex underlie the capacity to engage in MTT, and support contemporary theoretical accounts that suggest that the integration of the hippocampus with the DMN provides the neurocognitive landscape that allows us to imagine distant times and places.
PMID: 27989779 [PubMed - as supplied by publisher]
Aberrant default mode network homogeneity in patients with first-episode treatment-naive melancholic depression.
Int J Psychophysiol. 2016 Dec 15;:
Authors: Cui X, Guo W, Wang Y, Yang TX, Yang XH, Wang Y, Gong J, Tan C, Xie G
BACKGROUND: Melancholic depression is a relatively homogenous subtype of major depressive disorders (MDD). The condition has several endogenous symptoms and represents strong biological components. However, its specific neurobiological mechanisms remain unknown. Previous neuroimaging findings indicated that default mode network (DMN) is closely related to MDD. The present study examined the network homogeneity (NH) of the DMN in patients with melancholic MDD.
METHODS: A total of33 first-episode, treatment-naive melancholic MDD patients and 32 healthy controls underwent a resting-state functional magnetic resonance imaging scan. The data were analyzed using the NH method.
RESULTS: Compared with healthy controls, patients with melancholic MDD showed low NH values in the right middle temporal gyrus and temporal pole (MTG/TP). The abnormal NH of this region and clinical characteristics were not correlated.
CONCLUSION: Abnormal NH pattern of DMN exists in patients with melancholic MDD. This feature may be part of the pathophysiological basis of this disorder.
PMID: 27989405 [PubMed - as supplied by publisher]
Beef assessments using functional magnetic resonance imaging and sensory evaluation.
Meat Sci. 2016 Dec 08;126:11-17
Authors: Tapp WN, Davis TH, Paniukov D, Brooks JC, Brashears MM, Miller MF
Functional magnetic resonance imaging (fMRI) has been used to unveil how some foods and basic rewards are processed in the human brain. This study evaluated how resting state functional connectivity in regions of the human brain changed after differing qualities of beef steaks were consumed. Functional images of participants (n=8) were collected after eating high or low quality beef steaks on separate days, after consumption a sensory ballot was administered to evaluate consumers' perceptions of tenderness, juiciness, flavor, and overall liking. Imaging data showed that high quality steak samples resulted in greater functional connectivity to the striatum, medial orbitofrontal cortex, and insular cortex at various stages after consumption (P≤0.05). Furthermore, high quality steaks elicited higher sensory ballot scores for each palatability trait (P≤0.01). Together, these results suggest that resting state fMRI may be a useful tool for evaluating the neural process that follows positive sensory experiences such as the enjoyment of high quality beef steaks.
PMID: 27984700 [PubMed - as supplied by publisher]
Altered spontaneous brain activity pattern in patients with late monocular blindness in middle-age using amplitude of low-frequency fluctuation: a resting-state functional MRI study.
Clin Interv Aging. 2016;11:1773-1780
Authors: Li Q, Huang X, Ye L, Wei R, Zhang Y, Zhong YL, Jiang N, Shao Y
OBJECTIVE: Previous reports have demonstrated significant brain activity changes in bilateral blindness, whereas brain activity changes in late monocular blindness (MB) at rest are not well studied. Our study aimed to investigate spontaneous brain activity in patients with late middle-aged MB using the amplitude of low-frequency fluctuation (ALFF) method and their relationship with clinical features.
METHODS: A total of 32 patients with MB (25 males and 7 females) and 32 healthy control (HC) subjects (25 males and 7 females), similar in age, sex, and education, were recruited for the study. All subjects were performed with resting-state functional magnetic resonance imaging scanning. The ALFF method was applied to evaluate spontaneous brain activity. The relationships between the ALFF signal values in different brain regions and clinical features in MB patients were investigated using correlation analysis.
RESULTS: Compared with HCs, the MB patients had marked lower ALFF values in the left cerebellum anterior lobe, right parahippocampal gyrus, right cuneus, left precentral gyrus, and left paracentral lobule, but higher ALFF values in the right middle frontal gyrus, left middle frontal gyrus, and left supramarginal gyrus. However, there was no linear correlation between the mean ALFF signal values in brain regions and clinical manifestations in MB patients.
CONCLUSION: There were abnormal spontaneous activities in many brain regions including vision and vision-related regions, which might indicate the neuropathologic mechanisms of vision loss in the MB patients. Meanwhile, these brain activity changes might be used as a useful clinical indicator for MB.
PMID: 27980398 [PubMed - in process]
Decreased Thalamocortical Connectivity in Chronic Ketamine Users.
PLoS One. 2016;11(12):e0167381
Authors: Liao Y, Tang J, Liu J, Xie A, Yang M, Johnson M, Wang X, Deng Q, Chen H, Xiang X, Liu T, Chen X, Song M, Hao W
Disintegration in thalamocortical integration suggests its role in the mechanistic 'switch' from recreational to dysregulated drug seeking/addiction. In this study, we aimed to address whether thalamic nuclear groups show altered functional connectivity within the cerebral cortex in chronic ketamine users. One hundred and thirty subjects (41 ketamine users and 89 control subjects) underwent rsfMRI (resting-state functional Magnetic Resonance Imaging). Based on partial correlation functional connectivity analysis we partitioned the thalamus into six nuclear groups that correspond well with human histology. Then, in the area of each nuclear group, the functional connectivity differences between the chronic ketamine user group and normal control group were investigated. We found that the ketamine user group showed significantly less connectivity between the thalamic nuclear groups and the cortical regions-of-interest, including the prefrontal cortex, the motor cortex /supplementary motor area, and the posterior parietal cortex. However, no increased thalamic connectivity was observed for these regions as compared with controls. This study provides the first evidence of abnormal thalamocortical connectivity of resting state brain activity in chronic ketamine users. Further understanding of pathophysiological mechanisms of the thalamus in addiction (ketamine addiction) may facilitate the evaluation of much-needed novel pharmacological agents for improved therapy of this complex disease.
PMID: 27977717 [PubMed - in process]
Compensatory increase of functional connectivity density in adolescents with internet gaming disorder.
Brain Imaging Behav. 2016 Dec 14;
Authors: Du X, Yang Y, Gao P, Qi X, Du G, Zhang Y, Li X, Zhang Q
Behavioral studies have demonstrated visual attention bias and working memory deficits in individuals with internet gaming disorder (IGD). Neuroimaging studies demonstrated that individuals with IGD presented abnormalities in brain structures and functions including resting-state functional connectivity (rsFC) disturbance. However, most previous studies investigated IGD-related rsFC alterations by using hypothesis-driven methods with priori selection of a region of interest, which cannot provide a full picture of the rsFC changes in IGD individuals. In this study, we recruited 27 male IGD adolescents and 35 demographically matched healthy controls (HCs) to investigate abnormal connective property of each voxel within whole brain of IGD adolescents using resting-state functional connectivity density (rsFCD) method, and further to evaluate the relationship between altered rsFCD and behavioral performances of visual attention and working memory. The results exhibited no significant intergroup difference in behavioral performance (visual working memory and attention). The IGD adolescents exhibited higher global/long-range rsFCD in the bilateral dorsal lateral prefrontal cortex (DLPFC) and the right inferior temporal cortex (ITC)/fusiform compared with the HCs. Although no significant correlation survived after Bonferroni correction, higher global/long-range rsFCD of the bilateral DLPFC was correlated with the Young's internet addiction test (IAT) score and/or behavioral performance in IGD adolescents using an uncorrected threshold of P < 0.05. In conclusion, IGD adolescents demonstrated increased rsFCD in the brain regions involved in working memory, spatial orientation and attention processing, which indicated that increased rsFCD may reflect a compensatory mechanism for maintaining the normal behavioral performance in IGD adolescents compared with the HCs.
PMID: 27975158 [PubMed - as supplied by publisher]
Resting-state hemodynamics are spatiotemporally coupled to synchronized and symmetric neural activity in excitatory neurons.
Proc Natl Acad Sci U S A. 2016 Dec 14;:
Authors: Ma Y, Shaik MA, Kozberg MG, Kim SH, Portes JP, Timerman D, Hillman EM
Brain hemodynamics serve as a proxy for neural activity in a range of noninvasive neuroimaging techniques including functional magnetic resonance imaging (fMRI). In resting-state fMRI, hemodynamic fluctuations have been found to exhibit patterns of bilateral synchrony, with correlated regions inferred to have functional connectivity. However, the relationship between resting-state hemodynamics and underlying neural activity has not been well established, making the neural underpinnings of functional connectivity networks unclear. In this study, neural activity and hemodynamics were recorded simultaneously over the bilateral cortex of awake and anesthetized Thy1-GCaMP mice using wide-field optical mapping. Neural activity was visualized via selective expression of the calcium-sensitive fluorophore GCaMP in layer 2/3 and 5 excitatory neurons. Characteristic patterns of resting-state hemodynamics were accompanied by more rapidly changing bilateral patterns of resting-state neural activity. Spatiotemporal hemodynamics could be modeled by convolving this neural activity with hemodynamic response functions derived through both deconvolution and gamma-variate fitting. Simultaneous imaging and electrophysiology confirmed that Thy1-GCaMP signals are well-predicted by multiunit activity. Neurovascular coupling between resting-state neural activity and hemodynamics was robust and fast in awake animals, whereas coupling in urethane-anesthetized animals was slower, and in some cases included lower-frequency (<0.04 Hz) hemodynamic fluctuations that were not well-predicted by local Thy1-GCaMP recordings. These results support that resting-state hemodynamics in the awake and anesthetized brain are coupled to underlying patterns of excitatory neural activity. The patterns of bilaterally-symmetric spontaneous neural activity revealed by wide-field Thy1-GCaMP imaging may depict the neural foundation of functional connectivity networks detected in resting-state fMRI.
PMID: 27974609 [PubMed - as supplied by publisher]
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Brain Training with Video Games in Covert Hepatic Encephalopathy.
Am J Gastroenterol. 2016 Dec 13;:
Authors: Bajaj JS, Ahluwalia V, Thacker LR, Fagan A, Gavis EA, Lennon M, Heuman DM, Fuchs M, Wade JB
Despite the associated adverse outcomes, pharmacologic intervention for covert hepatic encephalopathy (CHE) is not the standard of care. We hypothesized that a video game-based rehabilitation program would improve white matter integrity and brain connectivity in the visuospatial network on brain magnetic resonance imaging (MRI), resulting in improved cognitive function in CHE subjects on measures consistent with the cognitive skill set emphasized by the two video games (e.g., IQ Boost-visual working memory, and Aim and Fire Challenge-psychomotor speed), but also generalize to thinking skills beyond the focus of the cognitive training (Hopkins verbal learning test (HVLT)-verbal learning/memory) and improve their health-related quality of life (HRQOL). The trial included three phases over 8 weeks; during the learning phase (cognitive tests administered twice over 2 weeks without intervening intervention), training phase (daily video game training for 4 weeks), and post-training phase (testing 2 weeks after the video game training ended). Thirty CHE patients completed all visits with significant daily achievement on the video games. In a subset of 13 subjects that underwent brain MRI, there was a significant decrease in fractional anisotropy, and increased radial diffusivity (suggesting axonal sprouting or increased cross-fiber formation) involving similar brain regions (i.e., corpus callosum, internal capsule, and sections of the corticospinal tract) and improvement in the visuospatial resting-state connectivity corresponding to the video game training domains. No significant corresponding improvement in HRQOL or HVLT performance was noted, but cognitive performance did transiently improve on cognitive tests similar to the video games during training. Although multimodal brain imaging changes suggest reductions in tract edema and improved neural network connectivity, this trial of video game brain training did not improve the HRQOL or produce lasting improvement in cognitive function in patients with CHE.Am J Gastroenterol advance online publication, 6 December 2016; doi:10.1038/ajg.2016.544.
PMID: 27958279 [PubMed - as supplied by publisher]
METHODS FOR CLEANING THE BOLD FMRI SIGNAL.
Neuroimage. 2016 Dec 09;:
Authors: Caballero-Gaudes C, Reynolds RC
Blood oxygen-level-dependent functional magnetic resonance imaging (BOLD fMRI) has rapidly become a popular technique for the investigation of brain function in healthy individuals, patients as well as in animal studies. However, the BOLD signal arises from a complex mixture of neuronal, metabolic and vascular processes, being therefore an indirect measure of neuronal activity, which is further severely corrupted by multiple non-neuronal fluctuations of instrumental, physiological or subject-specific origin. This review aims to provide a comprehensive summary of existing methods for cleaning the BOLD fMRI signal. The description is given from a methodological point of view, focusing on the operation of the different techniques in addition to pointing out the advantages and limitations in their application. Since motion-related and physiological noise fluctuations are two of the main noise components of the signal, techniques targeting their removal are primarily addressed, including both data-driven approaches and using external recordings. Data-driven approaches, which are less specific in the assumed model and can simultaneously reduce multiple noise fluctuations, are mainly based on data decomposition techniques such as principal and independent component analysis. Importantly, the usefulness of strategies that benefit from the information available in the phase component of the signal, or in multiple signal echoes is also highlighted. The use of global signal regression for denoising is also addressed. Finally, practical recommendations regarding the optimization of the preprocessing pipeline for the purpose of denoising and future venues of research are indicated. Through the review, we summarize the importance of signal denoising as an essential step in the analysis pipeline of task-based and resting state fMRI studies.
PMID: 27956209 [PubMed - as supplied by publisher]