Impaired Resting-State Functional Integrations within Default Mode Network of Generalized Tonic-Clonic Seizures Epilepsy

Generalized tonic-clonic seizures (GTCS) are characterized by unresponsiveness and convulsions, which cause complete loss of consciousness. Many recent studies have found that the ictal alterations in brain activity of the GTCS epilepsy patients are focally involved in some brain regions, including thalamus, upper brainstem, medial prefrontal cortex, posterior midbrain regions, and lateral parietal cortex. Notably, many of these affected brain regions are the same and overlap considerably with the components of the so-called default mode network (DMN). Here, we hypothesize that the brain activity of the DMN of the GTCS epilepsy patients are different from normal controls, even in the resting state. To test this hypothesis, we compared the DMN of the GTCS epilepsy patients and the controls using the resting state functional magnetic resonance imaging. Thirteen brain areas in the DMN were extracted, and a complete undirected weighted graph was used to model the DMN for each participant. When directly comparing the edges of the graph, we found significant decreased functional connectivities within the DMN of the GTCS epilepsy patients comparing to the controls. As for the nodes of the graph, we found that the degree of some brain areas within the DMN was significantly reduced in the GTCS epilepsy patients, including the anterior medial prefrontal cortex, the bilateral superior frontal cortex, and the posterior cingulate cortex. Then we investigated into possible mechanisms of how GTCS epilepsy could cause the reduction of the functional integrations of DMN. We suggested the damaged functional integrations of the DMN in the GTCS epilepsy patients even during the resting state, which could help to understand the neural correlations of the impaired consciousness of GTCS epilepsy patients

Trait mindfulness and autobiographical memory specificity

Training in mindfulness skills has been shown to increase autobiographical memory specificity. The aim of this study was to examine whether there is also an association between individual differences in trait mindfulness and memory specificity using a non-clinical student sample (N = 70). Also examined were the relationships between other memory characteristics and trait mindfulness, self-reported depression and rumination. Participants wrote about 12 autobiographical memories, which were recalled in response to emotion word cues in a minimal instruction version of the Autobiographical Memory Test, rated each memory for seven characteristics, and completed the Freiburg Mindfulness Inventory, the Depression, Anxiety, and Stress Scale, and the Ruminative Responses Scale. Higher rumination scores were associated with more reliving and more intense emotion during recall. Depression scores were not associated with any memory variables. Higher trait mindfulness was associated with lower memory specificity and with more intense and more positive emotion during recall. Thus, trait mindfulness is associated with memory specificity, but the association is opposite to that found in mindfulness training studies. It is suggested that this difference may be due to an influence of trait mindfulness on memory encoding as well as retrieval processes and an influence on the mode of self-awareness that leads to a greater focus on momentary rather than narrative self-reference

Resting-State Brain Organization Revealed by Functional Covariance Networks

BACKGROUND: Brain network studies using techniques of intrinsic connectivity network based on fMRI time series (TS-ICN) and structural covariance network (SCN) have mapped out functional and structural organization of human brain at respective time scales. However, there lacks a meso-time-scale network to bridge the ICN and SCN and get insights of brain functional organization. METHODOLOGY AND PRINCIPAL FINDINGS: We proposed a functional covariance network (FCN) method by measuring the covariance of amplitude of low-frequency fluctuations (ALFF) in BOLD signals across subjects, and compared the patterns of ALFF-FCNs with the TS-ICNs and SCNs by mapping the brain networks of default network, task-positive network and sensory networks. We demonstrated large overlap among FCNs, ICNs and SCNs and modular nature in FCNs and ICNs by using conjunctional analysis. Most interestingly, FCN analysis showed a network dichotomy consisting of anti-correlated high-level cognitive system and low-level perceptive system, which is a novel finding different from the ICN dichotomy consisting of the default-mode network and the task-positive network. CONCLUSION: The current study proposed an ALFF-FCN approach to measure the interregional correlation of brain activity responding to short periods of state, and revealed novel organization patterns of resting-state brain activity from an intermediate time scale

Fronto-Temporal Circuits in Musical Hallucinations: A PET-MR Case Study

The aim of the study is to investigate morphofunctional circuits underlying musical hallucinations (MH) in a 72-years old female that underwent a simultaneous 18fluoredeoxyglucose positron emission tomography (PET) and advanced magnetic resonance (MR) exam. This represents a particular case of MH occurred in an healthy subject, not displaying neurological or psychopathological disorders, and studied simultaneously with a multimodal approach. For the resting-state fMRI analysis a seed to seed approach was chosen. For the task-based fMRI, 4 different auditory stimuli were presented. Imaging findings were compared with data obtained by ten healthy controls matched for age and sex. Neuropsychological evaluation and questionnaires investigating depression and anxiety were also administered. PET findings showed hypermetabolism of: superior temporal gyri, anterior cingulate, left orbital frontal, and medial temporal cortices. Structural MRI did not show macroscopical lesions except for gliotic spots along the uncinate fascicle pathways with an increased cortical thickness for the right orbitofrontal cortex (p = 0.003). DTI showed increased fractional anisotropy values in the left uncinate fascicle, when compared to controls (p = 0.04). Resting-state fMRI showed increased functional connectivity between the left inferior frontal gyrus and the left temporal fusiform cortex (p = 0.01). Task-based fMRI confirmed PET findings showing an increased activation of the superior temporal gyrus in all the auditory tasks except for the monotone stimulus, with a significant activation of the left orbital frontal cortex only during the song in foreign language, object of MH. Results on cognitive test did not show cognitive impairment, excepting for the performance on Frontal Assessment Battery where the patient fails in the cognitive domains of conceptualization, sensitive to interference, and inhibitory control. The subject did not show depressive or anxiety symptoms. Summarizing, multimodal imaging analyses in the MH case showed a microstructural alteration of the left uncinate fascicle paralleled by an increased metabolism and functional connectivity of cortical regions that receive left uncinate projections (orbital frontal cortex, and medial temporal cortex). This alteration of fronto-hyppocampal circuits could be responsible of retrieval of known songs even in the absence of real stimuli

The Neuronal Correlates of Digits Backward Are Revealed by Voxel-Based Morphometry and Resting-State Functional Connectivity Analyses

Digits backward (DB) is a widely used neuropsychological measure that is believed to be a simple and effective index of the capacity of the verbal working memory. However, its neural correlates remain elusive. The aim of this study is to investigate the neural correlates of DB in 299 healthy young adults by combining voxel-based morphometry (VBM) and resting-state functional connectivity (rsFC) analyses. The VBM analysis showed positive correlations between the DB scores and the gray matter volumes in the right anterior superior temporal gyrus (STG), the right posterior STG, the left inferior frontal gyrus and the left Rolandic operculum, which are four critical areas in the auditory phonological loop of the verbal working memory. Voxel-based correlation analysis was then performed between the positive rsFCs of these four clusters and the DB scores. We found that the DB scores were positively correlated with the rsFCs within the salience network (SN), that is, between the right anterior STG, the dorsal anterior cingulate cortex and the right fronto-insular cortex. We also found that the DB scores were negatively correlated with the rsFC within an anti-correlation network of the SN, between the right posterior STG and the left posterior insula. Our findings suggest that DB performance is related to the structural and functional organizations of the brain areas that are involved in the auditory phonological loop and the SN

Influence of meditation on anti-correlated networks in the brain

Human experiences can be broadly divided into those that are external and related to interaction with the environment, and experiences that are internal and self-related. The cerebral cortex appears to be divided into two corresponding systems: an “extrinsic” system composed of brain areas that respond more to external stimuli and tasks and an “intrinsic” system composed of brain areas that respond less to external stimuli and tasks. These two broad brain systems seem to compete with each other, such that their activity levels over time is usually anti-correlated, even when subjects are “at rest” and not performing any task. This study used meditation as an experimental manipulation to test whether this competition (anti-correlation) can be modulated by cognitive strategy. Participants either fixated without meditation (fixation), or engaged in non-dual awareness (NDA) or focused attention (FA) meditations. We computed inter-area correlations (“functional connectivity”) between pairs of brain regions within each system, and between the entire extrinsic and intrinsic systems. Anti-correlation between extrinsic vs. intrinsic systems was stronger during FA meditation and weaker during NDA meditation in comparison to fixation (without mediation). However, correlation between areas within each system did not change across conditions. These results suggest that the anti-correlation found between extrinsic and intrinsic systems is not an immutable property of brain organization and that practicing different forms of meditation can modulate this gross functional organization in profoundly different ways

Hypnosis, hypnotic suggestibility, and meditation : an integrative review of the associated brain regions and networks

The number of neuroimaging studies on hypnosis and meditation has multiplied rapidly in recent years. The methods and analytic techniques that are being applied are becoming increasingly sophisticated and approaches focusing on connectomics have offered novel ways to investigate the practices, enabling brain function to be investigated like never before. This chapter provides a review of the literature on the effects of hypnosis and meditation on brain network functional connectivity. Numerous cross-sectional as well as longitudinal studies have also reported enduring transformations in brain structure and function in practitioners of meditation, while evidence is mounting which demonstrates a relationship between hypnotic suggestibility and variations in neuroanatomy/functional connectivity that may facilitate hypnosis. The similarities (and differences) between the brain regions and networks associated with each type of practice are highlighted, while links are tentatively made between these and the reported phenomenology

휴지기 뇌 포도당 대사와 BOLD 신호 관계에 관한 다중모달리티 다변량 분석법: 하이브리드 PET/MR 연구

학위논문 (박사)-- 서울대학교 대학원 : 협동과정 인지과학전공, 2015. 8. 이동수.Glucose consumption and hemodynamic response to neural activity at rest reflect intrinsic brain function in general. Investigating the relationship between them should be needed to better understand how the brain works. I applied the multivariate partial least squares for investigating the relationship between FDG uptake and BOLD signal at rest (n = 38, mean age 44 ± 13.9 years), as representative measurements for capturing those different aspects of brain function using a hybrid PET/MR scanner. This approach can consider the interdependency between voxels as well as the relationship between modalities. As a result, the relationship which was reproducible by a split-half resampling, was found in brain areas in respect to their functional roles. For example, the FDG uptake and BOLD signal showed positive relationship within the brain regions such as (1) sensory system, and (2) default mode network system. The negative relationship was found between the above regions. The principal component analysis was also performed to investigate the interregional correlation patterns within modality. The first principal component image of FDG-PET was almost the same to the first singular image of FDG-PET. While, the first and second principal component images of fMRI were similar to the first singular image of fMRI. The first principal component image of fMRI represented the (1) visual system, and (2) default mode network system. The second principal component image of fMRI represented the (1) auditory and motor systems, and (2) default mode network system. The results proved that the interregional correlation patterns derived by the spontaneous ongoing neural activity were divided into the specialized independent systems compared to the interregional correlation patterns derived by the relatively stable FDG uptake. This present work showed that the relationship between FDG uptake and BOLD signal was changed by age. By applying the partial least squares to the younger adults (n = 19, mean age 32 ± 6.9 years) and older adults groups (n = 19, mean age 56 ± 7.7 years) respectively, the different relationship between FDG uptake and BOLD signal was observed. The changes of brain function due to aging can be observed by the changes of the relationship between FDG uptake and BOLD signal.Abstract i Contents iv List of Figures vii List of Tables ix 1. Introduction 1 1.1. Multimodal and multivariate analyses of human brain 1 1.2. The relationship between FDG uptake and BOLD signal of the brain 3 1.3. Investigating relationship between FDG uptake and BOLD signal by bimodal and multivariate PLS 6 2. Materials and Methods 10 2.1. Participants 10 2.2. Images scanning acquisition 12 2.3. Images preprocessing 15 2.3.1. FDG-PET images preprocessing 15 2.3.2. Functional MR images preprocessing 16 2.4. General approach and practical application of the partial least squares analysis 18 2.4.1. Partial least squares analysis ? general approach 18 2.4.1.1. Procedures of partial least squares analysis 18 2.4.1.2. Significance test of singular images by a permutation method 20 2.4.1.3. Cross-validation of singular images by a split-half resampling 21 2.4.2. Partial least squares analysis ? practical approach 28 2.5. Estimating principal component images of FDG-PET and fMRI 30 2.6. Partial least squares analysis applied to the younger adults and older adults groups 31 2.6.1. The effect of age to the significant latent variables 31 2.6.2. Partial least squares analysis 31 3. Results 32 3.1. The relationship between FDG uptake and BOLD signal 32 3.2. The reproducibility of the singular images 35 3.3. The principal component images of the FDG-PET and fMRI 40 3.4. The effect of age to the significant latent variables 46 3.5. The relationship between FDG uptake and BOLD signal in the younger adults and older adults groups 48 4. Discussion 51 4.1. Relationship between FDG uptake and BOLD signal at rest 51 4.2. The association of the singular images with the principal component images of FDG-PET and fMRI 55 4.3. The effect of age to the relationship between FDG uptake and BOLD signal………. 57 5. Conclusion and limitations 60 References 63 국문초록 71Docto

Ethical Leadership as a Balance Between Opposing Neural Networks

In this article, we explore the implications of opposing domains theory for developing ethical leaders. Opposing domains theory highlights a neurological tension between analytic reasoning and socioemotional reasoning. Specifically, when we engage in analytic reasoning, we suppress our ability to engage in socioemotional reasoning and vice versa. In this article, we bring together the domains of neuroscience, psychology, and ethics, to inform our theorizing around ethical leadership. We propose that a key issue for ethical leadership is achieving a healthy balance between analytic reasoning and socioemotional reasoning. We argue that organizational culture often encourages too heavy a reliance on nonemotional forms of reasoning to arrive at moral judgments. As a result, leaders run the risk of suppressing their ability to pay attention to the human side of moral dilemmas and, in doing so, dehumanize colleagues, particularly subordinates, and clients