Altered Functional Connectivity Strength in Abstinent Chronic Cocaine Smokers Compared to Healthy Controls.
Brain Connect. 2015 May 25;
Authors: Ray S, Gohel SR, Biswal BB
Past research involving cocaine and resting state functional connectivity (RSFC) has shown altered functional connectivity within frontal and between frontal and other cortical and subcortical brain regions in chronic users of cocaine. However, there have been discrepancies in literature regarding the relationship between RSFC between brain regions and cocaine use behavior. This study explored the RSFC between brain regions in cocaine smokers abstinent from cocaine use for 72 hours and healthy controls. Also, the relationship between RSFC between brain regions and various cocaine use measures (cocaine use duration; frequency and money spent on cocaine/week) was examined. Twenty chronic cocaine users and 17 controls completed a resting state scan and an anatomical MPRAGE scan. Group independent component analysis (ICA) performed on fMRI data identified 13 ICs pertaining to distinct resting state networks, and group level differences were examined. To examine inter-network functional connectivity between brain regions, these 13 ICs were divided into 61 distinct regions of interest (ROIs). Correlations were calculated between 61 ROI time series. For the ROI pairs that significantly differed from controls in connectivity strength, correlations were computed between connectivity strength and cocaine use measures. Results showed an enhanced RSFC within the sensory motor cortex and the left frontal-parietal network in cocaine users than controls. An increased inter-network RSFC between frontal-temporal and frontal-parietal brain regions, and a decreased RSFC between parietal-parietal, occipital-limbic, occipital-occipital, and occipital-parietal brain regions was found in cocaine users. This study demonstrated that intra-network connectivity strength of sensory motor cortex was negatively correlated with years of cocaine use. Inter-network connectivity strength between occipital-limbic brain regions was positively correlated with years of cocaine use, while connectivity strength within occipital brain regions was negatively related to cocaine use frequency and money spent on cocaine per week in abstinent cocaine users.
PMID: 26005203 [PubMed - as supplied by publisher]
Spontaneous Regional Brain Activity Links Restrained Eating to Later Weight Gain Among Young Women.
Biol Psychol. 2015 May 21;
Authors: Dong D, Jackson T, Wang Y, Chen H
Theory and prospective studies have linked restrained eating (RE) to risk for future weight gain and the onset of obesity, but little is known about resting state neural activity may underlie this association. To address this gap, resting fMRI was used to test the extent to which spontaneous neural activity in regions associated with inhibitory control and food reward account for potential relations between baseline RE levels and changes in body weight among dieters over a one-year interval. Spontaneous regional activity patterns corresponding to RE were assessed among 50 young women using regional homogeneity (ReHo) analysis, which measured temporal synchronization of spontaneous fluctuations within a food deprivation condition. Analyses indicated higher baseline RE scores predicted more weight gain at a one-year follow-up. Furthermore, food-deprived dieting women with high dietary restraint scores exhibited more spontaneous local activity in brain regions associated with the expectation and valuation for food reward [i.e., orbitofrontal cortex (OFC)/ventromedial prefrontal cortex (VMPFC)] and reduced spontaneous local activity in inhibitory control regions [i.e., bilateral dorsal-lateral prefrontal cortex (DLPFC)] at baseline. Notably, the association between baseline RE and follow-up weight gain was mediated by decreased local synchronization of the right DLPFC in particular and, to a lesser degree, increased local synchronization of the right VMPFC. In conjunction with previous research, these findings highlight possible neural mechanisms underlying the relation between RE and risk for weight gain.
PMID: 26004091 [PubMed - as supplied by publisher]
Altered brain rhythms and functional network disruptions involved in patients with generalized fixation-off epilepsy.
Brain Imaging Behav. 2015 May 23;
Authors: Solana AB, Martínez K, Hernández-Tamames JA, San Antonio-Arce V, Toledano R, García-Morales I, Alvárez-Linera J, Gil-Nágel A, Del Pozo F
Generalized Fixation-off Sensitivity (CGE-FoS) patients present abnormal EEG patterns when losing fixation. In the present work, we studied two CGE-FoS epileptic patients with simultaneous EEG-fMRI. We aim to identify brain areas that are specifically related to the pathology by identifying the brain networks that are related to the EEG brain altered rhythms. Three main analyses were performed: EEG standalone, where the voltage fluctuations in delta, alpha, and beta EEG bands were obtained; fMRI standalone, where resting-state fMRI ICA analyses for opened and closed eyes conditions were computed per subject; and, EEG-informed fMRI, where EEG delta, alpha and beta oscillations were used to analyze fMRI. Patient 1 showed EEG abnormalities for lower beta band EEG brain rhythm. Fluctuations of this rhythm were correlated with a brain network mainly composed by temporo-frontal areas only found in the closed eyes condition. Patient 2 presented alterations in all the EEG brain rhythms (delta, alpha, beta) under study when closing eyes. Several biologically relevant brain networks highly correlated (r > 0.7) to each other in the closed eyes condition were found. EEG-informed fMRI results in patient 2 showed hypersynchronized patterns in the fMRI correlation spatial maps. The obtained findings allow a differential diagnosis for each patient and different profiles with respect to healthy volunteers. The results suggest a different disruption in the functional brain networks of these patients that depends on their altered brain rhythms. This knowledge could be used to treat these patients by novel brain stimulation approaches targeting specific altered brain networks in each patient.
PMID: 26001771 [PubMed - as supplied by publisher]
The effect of body-mind relaxation meditation induction on major depressive disorder: A resting-state fMRI study.
J Affect Disord. 2015 Apr 28;183:75-82
Authors: Chen F, Lv X, Fang J, Yu S, Sui J, Fan L, Li T, Hong Y, Wang X, Wang W, Jiang T
BACKGROUND: Meditation has been increasingly evaluated as an important complementary therapeutic tool for the treatment of depression. The present study employed resting-state functional magnetic resonance imaging (rs-fMRI) to examine the effect of body-mind relaxation meditation induction (BMRMI) on the brain activity of depressed patients and to investigate possible mechanisms of action for this complex intervention.
METHOD: 21 major depressive disorder patients (MDDs) and 24 age and gender-matched healthy controls (HCs) received rs-fMRI scans at baseline and after listening to a selection of audio designed to induce body-mind relaxation meditation. The rs-fMRI data were analyzed using Matlab toolbox to obtain the amplitude of low-frequency fluctuations (ALFF) of the BOLD signal for the whole brain. A mixed-design repeated measures analysis of variance (ANOVA) was performed on the whole brain to find which brain regions were affected by the BMRMI. An additional functional connectivity analysis was used to identify any atypical connection patterns after the BMRMI.
RESULTS: After the BMRMI experience, both the MDDs and HCs showed decreased ALFF values in the bilateral frontal pole (BA10). Additionally, increased functional connectivity from the right dorsal medial prefrontal cortex (dmPFC) to the left dorsal lateral prefrontal cortex (dlPFC) and the left lateral orbitofrontal cortex (OFC) was identified only in the MDDs after the BMRMI.
LIMITATION: In order to exclude the impact of other events on the participants׳ brain activity, the Hamilton Rating Scales for Depression (HDRS) was not measured after the body-mind relaxation induction.
CONCLUSION: Our findings support the hypothesis that body-mind relaxation meditation induction may regulate the activities of the prefrontal cortex and thus may have the potential to help patients construct reappraisal strategies that can modulate the brain activity in multiple emotion-processing systems.
PMID: 26001666 [PubMed - as supplied by publisher]
Aberrant connectivity within the default mode network in first-episode, treatment-naïve major depressive disorder.
J Affect Disord. 2015 May 8;183:49-56
Authors: Chen Y, Wang C, Zhu X, Tan Y, Zhong Y
BACKGROUND: Convergent studies have highlighted the dysfunction of default mode network (DMN) in major depressive disorder (MDD). The altered connectivity in posterior cingulate cortex (PCC) and medial prefrontal cortex (mPFC) was especially found to be of interest in the resting state functional connectivity analysis. Recently, more attention has turned to the internal functional connectivity within the DMN. However, the internal connection patterns within the DMN remain unclear at the initial onset of MDD.
METHODS: Resting-state fMRI was performed on 38 first-episode, treatment-naïve MDD patients along with 38 matched healthy controls. Seed-based analysis was used to define the DMN and then a region-to-region connectivity analysis was performed to inspect the functional connectivity within the DMN. Spearman׳s rank correlation analysis was performed between significantly abnormal connectivities in MDD patients and clinical measurements.
RESULTS: Decreased region-to-region connectivities within DMN were found between the PCC and dorsal medial prefrontal cortex (dmPFC), between PCC and the right inferior parietal gyrus/angular, as well as between the left thalamus and cerebellar tonsil. No significant increase in connectivity was found. Moreover, functional connectivity between the left thalamus and cerebellar tonsil revealed a marginal significant negative correlation with clinical Hamilton Depression Rating Scale (HDRS) scores.
LIMITATIONS: Noteworthiness in morbidity, a high risk of mortality, and a high rate of medical service utilization of MDD make the current results uncertain to apply to the more complicated situations.
CONCLUSIONS: Each region within DMN may have a specific, individual functional role. The reason to identify the pathological mechanism of MDD may not lie in the abnormal DMN functional connectivity, but rather in the abnormal functional connectivity within DMN.
PMID: 26001663 [PubMed - as supplied by publisher]
Diagnostic approaches to predict persistent posttraumatic symptoms after mild traumatic brain injury - a literature review.
Int J Neurosci. 2015 May 22;:1-30
Authors: Studerus-Germann AM, Thiran JP, Daducci A, Gautschi OP
Mild traumatic brain injury (mTBI) is one of the most frequently diagnosed neurological disorder in emergency departments. Although there are established recommendations for the diagnosis and treatment in the acute stage, there is an ongoing debate which diagnostic methods and risk factors predict unfavourable long-term outcome after mTBI. This literature review addresses the question, which diagnostic approaches may best predict persistent posttraumatic symptoms (pPTS). A literature search for experimental studies from January 2000 to September 2014 evaluating the following diagnostic approaches (1) susceptibility-weighted imaging (SWI), (2) diffusion tensor imaging (DTI), (3) magnetic resonance spectroscopy (MRS), (4) functional magnetic resonance imaging (fMRI), as predictive factors of pPTS or unfavourable cognitive outcome in adult populations with mTBI was performed. DTI has been proved to be a valuable tool to identify diffuse axonal injury (DAI) after mTBI. Additionally, some studies showed associations between DAI and unfavorable cognitive outcome. SWI has shown to be a highly sensitive imaging method to identify microbleeds. The presence and quantity of microbleeds in this imaging technique can further provide etiological evidence for pPTS. MRS provides information about local neurons metabolism and preliminary data show that creatine-phosphocreatine levels measured after mTBI are predictive of cognitive outcome and emotional distress. The results of one study have shown fMRI as a useful tool to differentiate mTBI patients with pPTS from controls and mTBI patients without pPTS in a resting-state condition. From the evaluated diagnostic approaches to predict pPTS after mTBI, DTI, SWI, MRS, and fMRI seem to have adequate sensitivity and specificity as predictive diagnostic tools for pPTS. Large longitudinal clinical trials are warranted to validate the prognostic applicability and practicability in daily clinical practice.
PMID: 26000929 [PubMed - as supplied by publisher]
The BDNF Val66Met polymorphism, resting-state hippocampal functional connectivity and cognitive deficits in acute late-onset depression.
J Affect Disord. 2015 May 8;183:22-30
Authors: Yin Y, Hou Z, Wang X, Sui Y, Yuan Y
OBJECTIVE: To investigate the relationship between hippocampal functional connectivity (HFC), cognitive deficits, and the influence of BDNF Val66Met polymorphism on the HFC in acute late-onset depression (LOD).
METHODS: 26 LOD patients and 33 and normal controls (NCs) completed clinical assessments, neuropsychological testing, blood samples collecting for genotyping, and resting-state functional MRI (R-fMRI) scans. The LOD and NCs groups were further divided into four groups according to BDNF Met allele carrier or not (LOD Met-(n=8); LOD Met+(n=18); NCs Met-(n=9); NCs Met+(n=24)). Then, seed-based correlation analyses and two-way analysis of covariance (ANCOVA) were performed to explore the main effects and interactive effects of LOD and BDNF Val66Met polymorphism on the HFC. Spearman correlation was applied to examine the cognitive and emotional significance of these altered HFC networks.
RESULTS: Compared with NCs, bilateral positive HFC with the right insula, left positive HFC with bilateral orbit-frontal cortex (OFC) and left precuneus, right positive HFC with right dorsolateral prefrontal cortex (dlPFC) were decreased, and bilateral negative HFC with right postcentral gyrus were reversed in LOD patients. BDNF Met allele mainly decreased bilateral positive HFC with the cerebellum. The interaction of LOD and BDNF Met allele primarily influenced the bilateral HFC with the temporal cortex and dorsal nexus. The changed HFC with the OFC, postcentral gyrus, cerebellum and temporal cortex significantly correlated to the cognitive deterioration. There was no significant association between the depressive severity and any altered HFC networks.
CONCLUSION: The cognitive deterioration in LOD patients, BDNF Met allele carriers, and LOD patients carring Met allele were associated with the changed HFC networks in the OFC/postcentral gyrus, cerebellum and temporal cortex respectively.
PMID: 26000753 [PubMed - as supplied by publisher]
Emotion regulation ability varies in relation to intrinsic functional brain architecture.
Soc Cogn Affect Neurosci. 2015 May 21;
Authors: Uchida M, Biederman J, Gabrieli JD, Micco J, de Los Angeles C, Brown A, Kenworthy T, Kagan E, Whitfield-Gabrieli S
This study investigated the neural basis of individual variation in emotion regulation, specifically the ability to reappraise negative stimuli so as to down-regulate negative affect. Brain functions in young adults were measured with functional Magnetic Resonance Imaging during three conditions: (1) attending to neutral pictures; (2) attending to negative pictures; and (3) reappraising negative pictures. Resting-state functional connectivity was measured with amygdala and dorsolateral prefrontal cortical (DLPFC) seed regions frequently associated with emotion regulation. Participants reported more negative affect after attending to negative than neutral pictures, and less negative affect following reappraisal. Both attending to negative versus neutral pictures and reappraising versus attending to negative pictures yielded widespread activations that were significantly right-lateralized for attending to negative pictures and left-lateralized for reappraising negative pictures. Across participants, more successful reappraisal correlated with less trait anxiety and more positive daily emotion, greater activation in medial and lateral prefrontal regions, and lesser resting-state functional connectivity between (1) right amygdala and both medial prefrontal and posterior cingulate cortices, and (2) bilateral DLPFC and posterior visual cortices. The ability to regulate emotion, a source of resilience or of risk for distress, appears to vary in relation to differences in intrinsic functional brain architecture.
PMID: 25999363 [PubMed - as supplied by publisher]
The neurobiological drive for overeating implicated in Prader-Willi syndrome.
Brain Res. 2015 May 18;
Authors: Zhang Y, Wang J, Zhang G, Zhu Q, Cai W, Tian J, Zhang YE, Miller JL, Wen X, Ding M, Gold MS, Liu Y
Prader-Willi syndrome (PWS) is a genetic imprinting disorder characterized mainly by hyperphagia and early childhood obesity. Previous fMRI studies examined the activation of eating-related neural circuits in PWS patients with or without exposures to food cues and found an excessive eating motivation and a reduced inhibitory control of cognitive processing of food. However, the effective connectivity between various brain areas or neural circuitry critically implicated in both the biological and behavioral control of overeating in PWS is largely unexplored. The current study combined resting-state fMRI and Granger causality analysis (GCA) techniques to investigate interactive causal influences among key neural pathways underlying overeating in PWS. We first defined the regions of interest (ROIs) that demonstrated significant alterations of the baseline brain activity levels in children with PWS (n=21) as compared to that of their normal siblings controls (n=18), and then carried out GCA to characterize the region-to-region interactions among these ROIs. Our data revealed significantly enhanced causal influences from the amygdala to the hypothalamus and from both the medial prefrontal cortex and anterior cingulate cortex to the amygdala in patients with PWS (P< 0.001). These alterations offer new explanations for hypothalamic regulation of homeostatic energy intake and impairment in inhibitory control circuit. The deficits in these dual aspects may jointly contribute to the extreme hyperphagia in PWS. This study provides both a new methodological and a neurobiological perspective to aid in a better understanding of neural mechanisms underlying obesity in the general public.
PMID: 25998539 [PubMed - as supplied by publisher]
￼Changes in Visual and Sensory-Motor Resting-State Functional Connectivity Support Motor Learning by ￼Observing.
J Neurophysiol. 2015 May 20;:jn.00286.2015
Authors: McGregor HR, Gribble PL
Motor learning occurs not only through direct first hand experience, but also through observation (Mattar and Gribble, 2005). When observing the actions of others, we activate many of the same brain regions involved in performing those actions ourselves (Malfait et al., 2010). Links between neural systems for vision and action have been reported in neurophysiological (Strafella and Paus, 2000; Watkins et al., 2003), brain imaging (Buccino et al., 2001; Iacoboni et al., 1999) and eye tracking studies (Flanagan and Johansson, 2003). Here we use a force field learning paradigm coupled with resting- state fMRI to investigate the brain areas involved in motor learning by observing. We examined changes in resting-state functional connectivity (FC) following an observational learning task and found a network consisting of V5/MT, cerebellum, primary motor and somatosensory cortices in which changes in FC were correlated with the amount of motor learning achieved through observation, as assessed behaviorally following resting-state fMRI scans. The observed FC changes in this network are not due to visual attention to motion or observation of movement errors, but rather are specifically linked to motor learning. These results support the idea that brain networks linking action observation and motor control also facilitate motor learning.
PMID: 25995349 [PubMed - as supplied by publisher]
Sex Differences in Intrinsic Brain Functional Connectivity Underlying Human Shyness.
Soc Cogn Affect Neurosci. 2015 May 20;
Authors: Yang X, Wang S, Kendrick KM, Wu X, Yao L, Lei D, Kuang W, Bi F, Huang X, He Y, Gong Q
Shyness is a fundamental trait associated with social-emotional maladaptive behaviors, including many forms of psychopathology. Neuroimaging studies have demonstrated that hyper-responsivity to social and emotional stimuli occurs in the frontal cortex and limbic system in shy individuals, but the relationship between shyness and brain-wide functional connectivity remains incompletely understood. Using resting-state functional MRI, we addressed this issue by exploring the relationship between regional functional connectivity strength (rFCS) and scores of shyness in a cohort of 61 healthy young adults and controlling for the effects of social and trait anxiety scores. We observed that the rFCS of the insula positively correlated with shyness scores regardless of sex. Furthermore, we found that there were significant sex-by-shyness interactions in the dorsal anterior cingulate cortex and insula (two core nodes of the salience network) as well as the subgenual anterior cingulate cortex: the rFCS values of these regions positively correlated with shyness scores in females but negatively correlated in males. Taken together, we provide evidence for intrinsic functional connectivity differences in individuals with different degrees of shyness and that these differences are sex-dependent. These findings might have important implications on the understanding of biological mechanisms underlying emotional and cognitive processing associated with shyness.
PMID: 25994971 [PubMed - as supplied by publisher]
Poorly controlled cholesterol is associated with cognitive impairment in T2DM: a resting-state fMRI study.
Lipids Health Dis. 2015 May 21;14(1):47
Authors: Xia W, Zhang B, Yang Y, Wang P, Yang Y, Wang S
BACKGROUND: Debate remains on whether hypercholesterolemia is associated with cognitive impairment. Hence, we investigated whether poorly controlled cholesterol impairs functional connectivity among patients with type 2 diabetes mellitus (T2DM).
METHODS: Resting-state functional connectivity infers to an interregional cooperation characterized by synchronous and low-frequency (<0.08 Hz) fluctuations on blood oxygen level-dependent functional magnetic resonance imaging (fMRI). We used resting-state fMRI to investigate the functional connectivity of 25 T2DM patients with poorly controlled cholesterol, 22 patients with target cholesterol and 26 healthy controls. Further correlation analysis was conducted between the functional connectivity and clinical data as well as neuropsychological tests.
RESULTS: The three groups did not statistically differ in age, sex, education level, body mass index, blood pressure, fasting C-peptides, and triglyceride. Compared with target cholesterol patients, patients with poorly controlled cholesterol showed significantly increased levels of serum cholesterol, low-density lipoprotein (LDL), and LDL/high-density lipoproteins (HDL) ratio, as well as poor performance in Trail Making Test B (TMT-B) (p < 0.05). Disordered functional connectivity of bilateral hippocampus-middle frontal gyrus (MFG) in the poorly controlled group consistently existed when compared with the two other groups. Moreover, the aberrant functional connectivity was associated with the TMT-B scores and the LDL/HDL index in T2DM patients with poorly controlled cholesterol.
CONCLUSIONS: T2DM patients with poorly controlled cholesterol showed impaired attention and executive function. The resting-state connectivity disturbance of the hippocampus-MFG may be involved in this process. Decreasing the LDL/HDL ratio can be taken as precaution against cognitive decrements.
PMID: 25989796 [PubMed - as supplied by publisher]
Optimization of rs-fMRI Pre-processing for Enhanced Signal-Noise Separation, Test-Retest Reliability, and Group Discrimination.
Neuroimage. 2015 May 15;
Authors: Shirer WR, Jiang H, Price CM, Ng B, Greicius MD
Resting-state functional magnetic resonance imaging (rs-fMRI) has become an increasingly important tool in mapping the functional networks of the brain. This tool has been used to examine network changes induced by cognitive and emotional states, neurological traits, and neuropsychiatric disorders. However, noise that remains in the rs-fMRI data after preprocessing has limited the reliability of individual-subject results, wherein scanner artifacts, subject movements, and other noise sources induce non-neural temporal correlations in the blood oxygen level-dependent (BOLD) timeseries. Numerous preprocessing methods have been proposed to isolate and remove these confounds; however, the field has not coalesced around a standard preprocessing pipeline. In comparisons, preprocessing these methods are often assessed with only a single metric of rs-fMRI data quality, such as reliability, without considering other aspects in tandem, such as signal-to-noise ratio and group discriminability. The present study seeks to identify the data preprocessing pipeline that optimizes rs-fMRI data across multiple outcome measures. Specifically, we aim to minimize the noise in the data and maximize result reliability, while retaining the unique features that characterize distinct groups. We examine how these metrics are influenced by bandpass filter selection and noise regression in four datasets, totaling 181 rs-fMRI scans and 38 subject-driven memory scans. Additionally, we perform two different rs-fMRI analysis methods - dual regression and region-of-interest based functional connectivity - and highlight the preprocessing parameters that optimize both approaches. Our results expand upon previous reports of individual-scan reliability, and demonstrate that preprocessing parameter selection can significantly change the noisiness, reliability, and heterogeneity of rs-fMRI data. The application of our findings to rs-fMRI data analysis should improve the validity and reliability of rs-fMRI results, both at the individual-subject level and the group level.
PMID: 25987368 [PubMed - as supplied by publisher]
Brain and cognition abnormalities in long-term anabolic-androgenic steroid users.
Drug Alcohol Depend. 2015 May 7;
Authors: Kaufman MJ, Janes AC, Hudson JI, Brennan BP, Kanayama G, Kerrigan AR, Jensen JE, Pope HG
BACKGROUND: Anabolic-androgenic steroid (AAS) use is associated with psychiatric symptoms including increased aggression as well as with cognitive dysfunction. The brain effects of long-term AAS use have not been assessed in humans.
METHODS: This multimodal magnetic resonance imaging study of the brain compared 10 male weightlifters reporting long-term AAS use with 10 age-matched weightlifters reporting no AAS exposure. Participants were administered visuospatial memory tests and underwent neuroimaging. Brain volumetric analyses were performed; resting-state fMRI functional connectivity (rsFC) was evaluated using a region-of-interest analysis focused on the amygdala; and dorsal anterior cingulate cortex (dACC) metabolites were quantified by proton magnetic resonance spectroscopy (MRS).
RESULTS: AAS users had larger right amygdala volumes than nonusers (P=0.002) and reduced rsFC between right amygdala and frontal, striatal, limbic, hippocampal, and visual cortical areas. Left amygdala volumes were slightly larger in AAS users (P=0.061) but few group differences were detected in left amygdala rsFC. AAS users also had lower dACC scyllo-inositol levels (P=0.004) and higher glutamine/glutamate ratios (P=0.028), possibly reflecting increased glutamate turnover. On a visuospatial cognitive task, AAS users performed more poorly than nonusers, with the difference approaching significance (P=0.053).
CONCLUSIONS: Long-term AAS use is associated with right amygdala enlargement and reduced right amygdala rsFC with brain areas involved in cognitive control and spatial memory, which could contribute to the psychiatric effects and cognitive dysfunction associated with AAS use. The MRS abnormalities we detected could reflect enhanced glutamate turnover and increased vulnerability to neurotoxic or neurodegenerative processes, which could contribute to AAS-associated cognitive dysfunction.
PMID: 25986964 [PubMed - as supplied by publisher]
Altered resting state functional network connectivity in children absence epilepsy.
J Neurol Sci. 2015 May 8;
Authors: Li Q, Cao W, Liao X, Chen Z, Yang T, Gong Q, Zhou D, Luo C, Yao D
Altered functional connectivity has been associated with the influence of epileptic activity. Abnormalities in connectivity, particularly in dorsal attention (DAN), salience (SN) and default mode (DMN) networks, might contribute to the loss of consciousness during seizures and cognitive deficits in patients with children absence epilepsy (CAE). The objective of the present study was to identify whether the functional network connectivity (FNC) is changed between patients with CAE and healthy controls. Using independent component analysis, twelve resting state networks (RSNs) were identified in resting state functional magnetic resonance imaging data sets in eighteen CAE patients and twenty-one healthy controls. Analyses of the group differences in FNC strength were conducted, controlling for age and gender effects. The findings showed that some functional networks were clustered into two subgroups, correlated within subgroups and antagonized with each other. Compared with the controls, patients with CAE demonstrated abnormal FNC strength among three networks: DMN, DAN and SN. In addition, the antagonism of two subgroups was altered. These results might reflect the underlying neuronal functional impairment or altered integration among these RSNs in CAE, suggesting that the abnormal functional connectivity is likely to imply the pathological mechanism associated with the accumulative influence of epileptic activity. These findings contribute to the understanding of the behavior abnormality in CAE, such as disturbed executive and attentional functions and the loss of consciousness during absence seizures.
PMID: 25982500 [PubMed - as supplied by publisher]
Multimodal connectivity mapping of the human left anterior and posterior lateral prefrontal cortex.
Brain Struct Funct. 2015 May 16;
Authors: Reid AT, Bzdok D, Langner R, Fox PT, Laird AR, Amunts K, Eickhoff SB, Eickhoff CR
Working memory is essential for many of our distinctly human abilities, including reasoning, problem solving, and planning. Research spanning many decades has helped to refine our understanding of this high-level function as comprising several hierarchically organized components, some which maintain information in the conscious mind, and others which manipulate and reorganize this information in useful ways. In the neocortex, these processes are likely implemented by a distributed frontoparietal network, with more posterior regions serving to maintain volatile information, and more anterior regions subserving the manipulation of this information. Recent meta-analytic findings have identified the anterior lateral prefrontal cortex, in particular, as being generally engaged by working memory tasks, while the posterior lateral prefrontal cortex was more strongly associated with the cognitive load required by these tasks. These findings suggest specific roles for these regions in the cognitive control processes underlying working memory. To further characterize these regions, we applied three distinct seed-based methods for determining cortical connectivity. Specifically, we employed meta-analytic connectivity mapping across task-based fMRI experiments, resting-state BOLD correlations, and VBM-based structural covariance. We found a frontoparietal pattern of convergence which strongly resembled the working memory networks identified in previous research. A contrast between anterior and posterior parts of the lateral prefrontal cortex revealed distinct connectivity patterns consistent with the idea of a hierarchical organization of frontoparietal networks. Moreover, we found a distributed network that was anticorrelated with the anterior seed region, which included most of the default mode network and a subcomponent related to social and emotional processing. These findings fit well with the internal attention model of working memory, in which representation of information is processed according to an anteroposterior gradient of abstract-to-concrete representations.
PMID: 25982222 [PubMed - as supplied by publisher]
Neurochemical Modulation in Posteromedial Default-mode Network Cortex Induced by Transcranial Magnetic Stimulation.
Brain Stimul. 2015 Apr 24;
Authors: Vidal-Piñeiro D, Martín-Trias P, Falcón C, Bargalló N, Clemente IC, Valls-Solé J, Junqué C, Pascual-Leone A, Bartrés-Faz D
BACKGROUND: The Default Mode Network (DMN) is severely compromised in several psychiatric and neurodegenerative disorders where plasticity alterations are observed. Glutamate and GABA are the major excitatory and inhibitory brain neurotransmitters respectively and are strongly related to plasticity responses and large-scale network expression.
OBJECTIVE: To investigate whether regional Glx (Glutamate + Glutamine) and GABA could be modulated within the DMN after experimentally-controlled induction of plasticity and to study the effect of intrinsic connectivity over brain responses to stimulation.
METHODS: We applied individually-guided neuronavigated Theta Burst Stimulation (TBS) to the left inferior parietal lobe (IPL) in-between two magnetic resonance spectroscopy (MRS) acquisitions to 36 young subjects. A resting-state fMRI sequence was also acquired before stimulation.
RESULTS: After intermittent TBS, distal GABA increases in posteromedial DMN areas were observed. Instead, no significant changes were detected locally, in left IPL areas. Neurotransmitter modulation in posteromedial areas was related to baseline fMRI connectivity between this region and the TBS-targeted area.
CONCLUSIONS: The prediction of neurotransmitter modulation by connectivity highlights the relevance of connectivity patterns to understand brain responses to plasticity-inducing protocols. The ability to modulate GABA in a key core of the DMN by means of TBS may open new avenues to evaluate plasticity mechanisms in a key area for major neurodegenerative and psychiatric conditions.
PMID: 25981159 [PubMed - as supplied by publisher]
Resting state signatures of domain and demand-specific memory performance.
Neuroimage. 2015 May 14;
Authors: van Dam WO, Decker S, Durbin JS, Vendemia JM, Desai RH
Working memory (WM) is one of the key constructs in understanding higher-level cognition. We examined whether patterns of activity in the resting state in individual subjects are correlated with their off-line working and short-term memory capabilities. Participants completed a resting-state fMRI scan and offline working and short-term memory (STM) tests with both verbal and visual materials. We calculated fractional amplitude of low frequency fluctuations (fALFF) from the resting state data, and also computed connectivity between seeds placed in frontal and parietal lobes. Correlating fALFF values with behavioral measures showed that the fALFF values in a widespread fronto-parietal network during rest were positively correlated with a combined memory measure. In addition, STM showed a significant correlation with fALFF within the right angular gyrus and left middle occipital gyrus, whereas WM was correlated with fALFF values within the right IPS and left dorsomedial cerebellar cortex. Furthermore, verbal and visuospatial memory capacities were associated with dissociable patterns of low-frequency fluctuations. Seed-based connectivity showed correlations with the verbal WM measure in the left hemisphere, and with the visual WM in the right hemisphere. These findings contribute to our understanding of how differences in spontaneous low-frequency fluctuations at rest are correlated with differences in cognitive performance.
PMID: 25980975 [PubMed - as supplied by publisher]
Prefrontal hypometabolism in Alzheimer disease is related to longitudinal amyloid accumulation in remote brain regions.
J Nucl Med. 2015 Mar;56(3):399-404
Authors: Klupp E, Grimmer T, Tahmasian M, Sorg C, Yakushev I, Yousefi BH, Drzezga A, Förster S
UNLABELLED: In PET studies of patients with Alzheimer disease (AD), prominent hypometabolism can occur in brain regions without major amyloid load. These hypometabolism-only (HO) areas may not be explained easily as a consequence of local amyloid toxicity. The aim of this longitudinal multimodal imaging study was the investigation of locoregional and remote relationships between metabolism in HO areas and longitudinal amyloid increase in functionally connected brain areas, with a particular focus on intrinsic functional connectivity as a relevant linking mechanism between pathology and dysfunction.
METHODS: Fifteen AD patients underwent longitudinal examinations with (11)C-Pittsburgh compound B ((11)C-PiB) and (18)F-FDG PET (mean follow-up period, 2 y). The peak HO region was identified by the subtraction of equally thresholded statistical T maps (hypometabolism minus amyloid burden), resulting from voxel-based statistical parametric mapping group comparisons between the AD patients and 15 healthy controls. Then functionally connected and nonconnected brain networks were identified by means of seed-based intrinsic functional connectivity analysis of the resting-state functional MRI data of healthy controls. Finally, network-based, region-of-interest-based, and voxel-based correlations were calculated between longitudinal changes of normalized (11)C-PiB binding and (18)F-FDG metabolism.
RESULTS: Positive voxel-based and region-of-interest-based correlations were demonstrated between longitudinal (11)C-PiB increases in the HO-connected network, encompassing bilateral temporoparietal and frontal brain regions, and metabolic changes in the peak HO region as well as locoregionally within several AD-typical brain regions.
CONCLUSION: Our results indicate that in AD amyloid accumulation in remote but functionally connected brain regions may significantly contribute to longitudinally evolving hypometabolism in brain regions not strongly affected by local amyloid pathology, supporting the amyloid- and network-degeneration hypothesis.
PMID: 25678488 [PubMed - indexed for MEDLINE]
Between-Network Connectivity occurs in brain regions lacking layer IV input.
Neuroimage. 2015 May 12;
Authors: Wylie KP, Kronberg E, Maharajh K, Smucny J, Cornier MA, Tregellas JR
To better understand the cortical circuitry underlying connectivity between large-scale neural networks, we develop a novel, data-driven approach to identify potential integration subregions. Between-Network Connectivity (BNC) associated with any anatomical region is the amount of connectivity between that point and all large-scale networks, as measured using simple and multiple correlations. It is straightforward to calculate and applicable to functional networks identified using Independent Components Analysis. We calculated BNC for all fMRI voxels within the brain and compared the results to known regional cytoarchitectural patterns. Based on previous observations of the relationship between macroscopic connectivity and microscopic cytoarchitecture, we predicted that areas with high BNC will be located in paralimbic subregions with an undifferentiated laminar structure. Results suggest that the anterior insula and dorsal posterior cingulate cortices play prominent roles in information integration. Cytoarchitecturely, these areas show agranular or dysgranular cytologies with absent or disrupted cortical layer IV. Since layer IV is the primary recipient of feed-forward thalamocortical connections, and due to the exclusive nature of driving connections to this layer, we suggest that the absence of cortical layer IV might allow for information to be exchanged across networks, and is an organizational characteristic of brain-subregions serving as inter-network communication hubs.
PMID: 25979667 [PubMed - as supplied by publisher]