Dynamic Changes In Functional Connectivity Research Articles

Dynamic functional connectivity of electroencephalogram in the resting state

Assessment of resting-state functional connectivity (FC) has become an important tool in studying brain disease mechanisms. Conclusions from previous resting-state investigations were based upon the hypothesis which assumed that the FC was constant throughout a period of task-free time. However, emerging evidence suggests that it may change over time. Here we investigate the dynamic FC based on the 64 electrodes EEG (electroencephalogram) of 25 healthy subjects in eyes closed (EC) and eyes open (EO) resting-state. A data-driven approach based on independent component analysis, standardized low-resolution tomography analysis, sliding time window, and graph theory are employed. Dynamic changes of FC over time with EC and EO in the visual network, the default mode network etc. are discovered. And the principal component analysis is used to the concatenated dynamic FC matrixes for finding meaningful FC patterns. Our results have complemental the traditional stationary analyses, and revealed novel insights in choosing the type of resting condition in experimental design and EEG clinical research.

Evaluating dynamic bivariate correlations in resting-state fMRI: A comparison study and a new approach

To date, most functional Magnetic Resonance Imaging (fMRI) studies have assumed that the functional connectivity (FC) between time series from distinct brain regions is constant across time. However, recently, there has been an increased interest in quantifying possible dynamic changes in FC during fMRI experiments, as it is thought that this may provide insight into the fundamental workings of brain networks. In this work we focus on the specific problem of estimating the dynamic behavior of pair-wise correlations between time courses extracted from two different regions of the brain. We critique the commonly used sliding-window technique, and discuss some alternative methods used to model volatility in the finance literature that could also prove to be useful in the neuroimaging setting. In particular, we focus on the Dynamic Conditional Correlation (DCC) model, which provides a model-based approach towards estimating dynamic correlations. We investigate the properties of several techniques in a series of simulation studies and find that DCC achieves the best overall balance between sensitivity and specificity in detecting dynamic changes in correlations. We also investigate its scalability beyond the bivariate case to demonstrate its utility for studying dynamic correlations between more than two brain regions. Finally, we illustrate its performance in an application to test–retest resting state fMRI data.

Changes in functional connectivity support changes in visibility

Event Abstract Back to Event Changes in functional connectivity support changes in visibility Fatma Imamoglu1, 2*, Jakob Heinzle1, 2, 3, Adrian Imfeld1 and John-Dylan Haynes1, 2, 4 1 Bernstein Center for Computational Neuroscience, Charite Universitätsmedizin, Germany 2 Berlin Center for Advanced Neuroimaging, Charite Universitätsmedizin, Germany 3 Translational Neuromodeling Unit (TNU) Institute for Biomedical Engineering University of Zurich & ETH Zurich,, Switzerland 4 Humboldt-Universität zu Berlin, Germany The neural basis of stimulus visibility is tightly linked to the quest for the neural correlates of conscious perception. Experimentally, stimulus visibility can be altered using stimulus manipulation techniques such as visual masking. In visual masking a target stimulus is rendered invisible by varying the timing of a mask that is followed by the target stimulus. Importantly, the physical appearance of the target stimulus is not changed during stimulus presentation. Here, we used functional magnetic resonance imaging (fMRI) to investigate to what extent the visibility of the target stimulus is reflected by functional connectivity changes in the human brain. Oriented grating stimuli were presented under varying visibility conditions created by backward masking. Visibility was manipulated by using four different stimulus onset asynchronies (SOA), which created a continuum from invisible to highly visible target stimuli. Masking performance was tested in a separate behavioral experiment prior to the fMRI experiment. In addition, subjects were asked to report the orientation of the grating with a button press during the fMRI scan. Subjects who responded correctly to the highest visibility condition and were at chance level to the lowest visibility condition were selected for the fMRI analysis. First, we selected regions of interests from brain activations that were activated independent of different visibility conditions. This revealed intraparietal sulcus, dorsolateral prefrontal cortex, inferior frontal gyrus, early visual, and higher visual areas. We computed a parametric functional connectivity analysis using these regions of interests and showed that increased stimulus visibility is reflected in the coupling between early and higher visual areas. Specifically, higher visual areas are significantly more correlated with early visual areas when the visual stimulus presented is visible to the subject than when it is invisible. This provides evidence that dynamic changes in functional connectivity reflect conscious perception. Keywords: functional connectivity, functional magnetic resonance imaging (fMRI), Visual awareness Conference: Bernstein Conference 2012, Munich, Germany, 12 Sep - 14 Sep, 2012. Presentation Type: Poster Topic: Sensory processing and perception Citation: Imamoglu F, Heinzle J, Imfeld A and Haynes J (2012). Changes in functional connectivity support changes in visibility. Front. Comput. Neurosci. Conference Abstract: Bernstein Conference 2012. doi: 10.3389/conf.fncom.2012.55.00003 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 07 May 2012; Published Online: 12 Sep 2012. * Correspondence: Miss. Fatma Imamoglu, Bernstein Center for Computational Neuroscience, Charite Universitätsmedizin, Berlin, Germany, fatmaimamoglu@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Fatma Imamoglu Jakob Heinzle Adrian Imfeld John-Dylan Haynes Google Fatma Imamoglu Jakob Heinzle Adrian Imfeld John-Dylan Haynes Google Scholar Fatma Imamoglu Jakob Heinzle Adrian Imfeld John-Dylan Haynes PubMed Fatma Imamoglu Jakob Heinzle Adrian Imfeld John-Dylan Haynes Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

P.1.e.026 Resting state connectivity between amygdala and orbitofrontal cortex reflects state anxiety in social phobia

Numerous studies have revealed the abnormal static functional connectivity (FC) among different brain regions in patients with generalized anxiety disorder (GAD). However, little is known about the dynamic changes of FC in patients with GAD.This study investigated the whole-brain dynamic changes of FC in patients with GAD by combining global FC density (FCD) and sliding window correlation analyses. The standard deviation of dynamic FCD (dFCD) was calculated to evaluate its temporal variability along time. Support vector regression was then employed to predict the symptom severity of patients based on abnormal dynamic connectivity patterns.The abnormal dFCD variability between 81 GAD patients and 80 healthy controls showed that the patients had higher dFCD variability in the bilateral dorsomedial prefrontal cortex (dmPFC) and left hippocampus while lower dFCD variability in the right postcentral gyrus. The abnormal dFCD variability of the left dmPFC is an important feature for anxiety prediction.The selection of sliding window length remains controversial, and most of our patients have been treated with medications. Future studies are expected to rule out the potential confounding effects from applying different parameters of the sliding window and recruiting large samples of medication-free patients.The altered patterns of time-varying brain connectivity in the frontolimbic and sensorimotor areas may reflect abnormal dynamic neural communication between these regions and other regions of the brain, which may deepen our understanding of the disease.

Context-Dependent Changes in Functional Circuitry in Visual Area MT

Animals can flexibly change their behavior in response to a particular sensory stimulus; the mapping between sensory and motor representations in the brain must therefore be flexible as well. Changes in the correlated firing of pairs of neurons may provide a metric of changes in functional circuitry during behavior. We studied dynamic changes in functional circuitry by analyzing the noise correlations of simultaneously recorded MT neurons in two behavioral contexts: one that promotes cooperative interactions between the two neurons and another that promotes competitive interactions. We found that identical visual stimuli give rise to differences in noise correlation in the two contexts, suggesting that MT neurons receive inputs of central origin whose strength changes with the task structure. The data are consistent with a mixed feature-based attentional strategy model in which the animal sometimes alternates attention between opposite directions of motion and sometimes attends to the two directions simultaneously.

Neuronal mechanisms of executive control by the prefrontal cortex.

Executive function is considered to be a product of the coordinated operation of various processes to accomplish a particular goal in a flexible manner. The mechanism or system responsible for the coordinated operation of various processes is called executive control. Impairments caused by damage to the prefrontal cortex are often called dysexecutive syndromes. Therefore, the prefrontal cortex is considered to play a significant role in executive control. Prefrontal participation to executive control can be partly explained by working memory that includes mechanisms for temporary active storage of information and processing stored information. For the prefrontal cortex to exert executive control, neuronal mechanisms for temporary storage of information and dynamic and flexible interactions among them are necessary. In this article, we present the presence of dynamic and flexible changes in the strength of functional interaction and extensive functional interactions among temporal information-storage processes in the prefrontal cortex. In addition, recent imaging studies show dynamic changes in functional connectivity between the prefrontal cortex and other cortical and subcortical structures depending upon the characteristics or the temporal context of the task. These observations indicate that the examination of dynamic and flexible modulation in neuronal interaction among prefrontal neurons as well as between the prefrontal cortex and other cortical and subcortical areas is important for explaining how the prefrontal cortex exerts executive control.

Movement related modulation of sensory transmission in many- neuron ensembles recorded simultaneously in somatosensory cortex and thalamus: Dynamic changes in functional connectivity: [formula omitted]. Department of Physiology and Biophysics, Hahnemann University, Philadelphia, PA 19102

Movement related modulation of sensory transmission in many- neuron ensembles recorded simultaneously in somatosensory cortex and thalamus: Dynamic changes in functional connectivity: [formula omitted]. Department of Physiology and Biophysics, Hahnemann University, Philadelphia, PA 19102