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graph theory connectivity

Fabrizio Vecchio, Riccardo Di Iorio, Francesca Miraglia, Giuseppe Granata, Roberto Romanello, Placido Bramanti, Paolo Maria Rossini
Transcranial direct current stimulation (tDCS) is a non-invasive technique able to modulate cortical excitability in a polarity-dependent way. At present, only few studies investigated the effects of tDCS on the modulation of functional connectivity between remote cortical areas. The aim of this study was to investigate-through graph theory analysis-how bipolar tDCS modulate cortical networks high-density EEG recordings were acquired before and after bipolar cathodal, anodal and sham tDCS involving the primary motor and pre-motor cortices of the dominant hemispherein 14 healthy subjects...
February 13, 2018: Experimental Brain Research. Experimentelle Hirnforschung. Expérimentation Cérébrale
Yan Zhu, Dongqing Wang, Zhe Liu, Yuefeng Li
BACKGROUND: Neuroimaging studies have shown that major depressive disorder is associated with altered activity patterns of the default-mode network (DMN). In this study, we sought to investigate the topological organization of the DMN in patients with remitted geriatric depression (RGD) and whether RGD patients would be more likely to show disrupted topological configuration of the DMN during the resting-state. METHODS: Thirty-three RGD patients and thirty-one healthy control participants underwent clinical and cognitive evaluations as well as resting-state functional magnetic resonance imaging scans...
February 12, 2018: International Psychogeriatrics
Jason Z Kim, Jonathan M Soffer, Ari E Kahn, Jean M Vettel, Fabio Pasqualetti, Danielle S Bassett
Networked systems display complex patterns of interactions between components. In physical networks, these interactions often occur along structural connections that link components in a hard-wired connection topology, supporting a variety of system-wide dynamical behaviors such as synchronization. While descriptions of these behaviors are important, they are only a first step towards understanding and harnessing the relationship between network topology and system behavior. Here, we use linear network control theory to derive accurate closed-form expressions that relate the connectivity of a subset of structural connections (those linking driver nodes to non-driver nodes) to the minimum energy required to control networked systems...
2018: Nature Physics
Guillaume Bastille-Rousseau, Iain Douglas-Hamilton, Stephen Blake, Joseph M Northrup, George Wittemyer
Network (graph) theory is a popular analytical framework to characterize the structure and dynamics among discrete objects, particularly effective at identifying critical hubs and patterns of connectivity. The identification of such attributes is a fundamental objective of animal movement research, yet network theory has rarely been applied directly to animal relocation data. We develop an approach that allows the analysis of movement data using network theory by defining occupied pixels as nodes and connection among these pixels as edges...
February 8, 2018: Ecological Applications: a Publication of the Ecological Society of America
Milovan Šuvakov, Miroslav Andjelković, Bosiljka Tadić
Multilevel self-assembly involving small structured groups of nano-particles provides new routes to development of functional materials with a sophisticated architecture. Apart from the inter-particle forces, the geometrical shapes and compatibility of the building blocks are decisive factors. Therefore, a comprehensive understanding of these processes is essential for the design of assemblies of desired properties. Here, we introduce a computational model for cooperative self-assembly with the simultaneous attachment of structured groups of particles, which can be described by simplexes (connected pairs, triangles, tetrahedrons and higher order cliques) to a growing network...
January 31, 2018: Scientific Reports
Jeong-Hyeon Shin, Yu Hyun Um, Chang Uk Lee, Hyun Kook Lim, Joon-Kyung Seong
BACKGROUND: Coordinated and pattern-wise changes in large scale gray matter structural networks reflect neural circuitry dysfunction in late life depression (LLD), which in turn is associated with emotional dysregulation and cognitive impairments. However, due to methodological limitations, there have been few attempts made to identify individual-level structural network properties or sub-networks that are involved in important brain functions in LLD. METHODS: In this study, we sought to construct individual-level gray matter structural networks using average cortical thicknesses of several brain areas to investigate the characteristics of the gray matter structural networks in normal controls and LLD patients...
January 5, 2018: Journal of Affective Disorders
Frigyes Samuel Racz, Peter Mukli, Zoltan Nagy, Andras Eke
Brain function is organized as a network of functional connections between different neuronal populations with connection strengths dynamically changing in time and space. Studies investigating functional connectivity (FC) usually follow a static approach when describing FC by considering the connectivity strengths constant, however a dynamic approach seems more reasonable, as this way the spatio-temporal dynamics of the underlying system can also be captured. Objective: The scale-free, i.e. fractal nature of neural dynamics is an inherent property of the nervous system...
January 19, 2018: Physiological Measurement
Joaquin Jimenez-Martinez, Christian F A Negre
Solving flow and transport through complex geometries such as porous media is computationally difficult. Such calculations usually involve the solution of a system of discretized differential equations, which could lead to extreme computational cost depending on the size of the domain and the accuracy of the model. Geometric simplifications like pore networks, where the pores are represented by nodes and the pore throats by edges connecting pores, have been proposed. These models, despite their ability to preserve the connectivity of the medium, have difficulties capturing preferential paths (high velocity) and stagnation zones (low velocity), as they do not consider the specific relations between nodes...
July 2017: Physical Review. E
Bertrand Ottino-Löffler, Jacob G Scott, Steven H Strogatz
We study a stochastic model of infection spreading on a network. At each time step a node is chosen at random, along with one of its neighbors. If the node is infected and the neighbor is susceptible, the neighbor becomes infected. How many time steps T does it take to completely infect a network of N nodes, starting from a single infected node? An analogy to the classic "coupon collector" problem of probability theory reveals that the takeover time T is dominated by extremal behavior, either when there are only a few infected nodes near the start of the process or a few susceptible nodes near the end...
July 2017: Physical Review. E
Yun-An Huang, Jan Jastorff, Jan Van den Stock, Laura Van de Vliet, Patrick Dupont, Mathieu Vandenbulcke
Psychological construction models of emotion state that emotions are variable concepts constructed by fundamental psychological processes, whereas according to basic emotion theory, emotions cannot be divided into more fundamental units and each basic emotion is represented by a unique and innate neural circuitry. In a previous study, we found evidence for the psychological construction account by showing that several brain regions were commonly activated when perceiving different emotions (i.e. a general emotion network)...
January 12, 2018: NeuroImage
Miha Kastelic, Vojko Vlachy
This study presents the theory for liquid--liquid phase separation for systems of molecules modeling monoclonal antibodies. Individual molecule is depicted as an assembly of seven hard spheres, organized to mimic the Y--shaped antibody. We consider the antibody--antibody interactions either through Fab, Fab' (two Fab fragments may be different), or Fc domain. Interaction between these three domains of the molecule (hereafter denoted as A, B, and C, respectively) is modeled by a short--range square--well attraction...
January 16, 2018: Journal of Physical Chemistry. B
Chris Rorres, Maria Romano, Jennifer A Miller, Jana M Mossey, Tony H Grubesic, David E Zellner, Gary Smith
Contact tracing is a crucial component of the control of many infectious diseases, but is an arduous and time consuming process. Procedures that increase the efficiency of contact tracing increase the chance that effective controls can be implemented sooner and thus reduce the magnitude of the epidemic. We illustrate a procedure using Graph Theory in the context of infectious disease epidemics of farmed animals in which the epidemics are driven mainly by the shipment of animals between farms. Specifically, we created a directed graph of the recorded shipments of deer between deer farms in Pennsylvania over a timeframe and asked how the properties of the graph could be exploited to make contact tracing more efficient should Chronic Wasting Disease (a prion disease of deer) be discovered in one of the farms...
December 14, 2017: Epidemics
Jiehui Jiang, Hucheng Zhou, Huoqiang Duan, Xin Liu, Chuantao Zuo, Zhemin Huang, Zhihua Yu, Zhuangzhi Yan
Mapping the human brain is one of the great scientific challenges of the 21st century. Brain network analysis is an effective technique based on graph theory that is widely used to investigate network patterns in the human brain. Currently, mapping an individual brain network using a single image has been a hotspot in the field of brain science; techniques, such as the Kullback-Leibler (KL) method, have applications in structural Magnetic Resonance (MR) imaging. However, maintaining an image's intensity, shape, texture and gradient information during feature extraction is very challenging...
December 2017: Heliyon
Qianqian Meng, Yu Han, Gang Ji, Guanya Li, Yang Hu, Li Liu, Qingchao Jin, Karen M von Deneen, Jizheng Zhao, Guangbin Cui, Huaning Wang, Dardo Tomasi, Nora D Volkow, Jixin Liu, Yongzhan Nie, Yi Zhang, Gene-Jack Wang
Neuroimaging studies have revealed brain functional abnormalities in frontal-mesolimbic regions in obesity. However, the effects of obesity on brain network topology remains largely unknown. In the current study, we employed resting-state functional magnetic resonance imaging and graph theory methods to investigate obesity-related changes in brain network topology in 26 obese patients and 28 normal weight subjects. Results revealed that the whole-brain networks of the two groups exhibited typical features of small-world topology...
January 9, 2018: Brain Imaging and Behavior
Youngwook Lyoo, Jieun E Kim, Sujung Yoon
The human connectome is a complex network that transmits information between interlinked brain regions. Using graph theory, previously well-known network measures of integration between brain regions have been constructed under the key assumption that information flows strictly along the shortest paths possible between two nodes. However, it is now apparent that information does flow through non-shortest paths in many real-world networks such as cellular networks, social networks, and the internet. In the current hypothesis, we present a novel framework using the maximum flow to quantify information flow along all possible paths within the brain, so as to implement an analogy to network traffic...
January 2018: Medical Hypotheses
František Váša, Edward T Bullmore, Ameera X Patel
Functional connectomes are commonly analysed as sparse graphs, constructed by thresholding cross-correlations between regional neurophysiological signals. Thresholding generally retains the strongest edges (correlations), either by retaining edges surpassing a given absolute weight, or by constraining the edge density. The latter (more widely used) method risks inclusion of false positive edges at high edge densities and exclusion of true positive edges at low edge densities. Here we apply new wavelet-based methods, which enable construction of probabilistically-thresholded graphs controlled for type I error, to a dataset of resting-state fMRI scans of 56 patients with schizophrenia and 71 healthy controls...
December 19, 2017: NeuroImage
Jorge G Álvarez-Romero, Adrián Munguía-Vega, Maria Beger, Maria Del Mar Mancha-Cisneros, Alvin N Suárez-Castillo, Georgina G Gurney, Robert L Pressey, Leah R Gerber, Hem Nalini Morzaria-Luna, Héctor Reyes-Bonilla, Vanessa M Adams, Melanie Kolb, Erin M Graham, Jeremy VanDerWal, Alejandro Castillo-López, Gustavo Hinojosa-Arango, David Petatán-Ramírez, Marcia Moreno-Baez, Carlos R Godínez-Reyes, Jorge Torre
Marine reserves are widely used to protect species important for conservation and fisheries and to help maintain ecological processes that sustain their populations, including recruitment and dispersal. Achieving these goals requires well-connected networks of marine reserves that maximize larval connectivity, thus allowing exchanges between populations and recolonization after local disturbances. However, global warming can disrupt connectivity by shortening potential dispersal pathways through changes in larval physiology...
December 22, 2017: Global Change Biology
Feng-Mei Lu, Jing Dai, Tania A Couto, Chun-Hong Liu, Heng Chen, Shun-Li Lu, Li-Rong Tang, Chang-Le Tie, Hua-Fu Chen, Man-Xi He, Yu-Tao Xiang, Zhen Yuan
Neuroimaging studies have revealed that insomnia is characterized by aberrant neuronal connectivity in specific brain regions, but the topological disruptions in the white matter (WM) structural connectivity networks remain largely unknown in insomnia. The current study uses diffusion tensor imaging (DTI) tractography to construct the WM structural networks and graph theory analysis to detect alterations of the brain structural networks. The study participants comprised 30 healthy subjects with insomnia symptoms (IS) and 62 healthy subjects without IS...
2017: Frontiers in Human Neuroscience
Jing-Na Jin, Xin Wang, Ying Li, Fang Jin, Zhi-Peng Liu, Tao Yin
It has recently been reported that repetitive transcranial magnetic stimulation combined with motor training (rTMS-MT) could improve motor function in post-stroke patients. However, the effects of rTMS-MT on cortical function using functional connectivity and graph theoretical analysis remain unclear. Ten healthy subjects were recruited to receive rTMS immediately before application of MT. Low frequency rTMS was delivered to the dominant hemisphere and non-dominant hand performed MT over 14 days. The reaction time of Nine-Hole Peg Test and electroencephalography (EEG) in resting condition with eyes closed were recorded before and after rTMS-MT...
2017: Frontiers in Behavioral Neuroscience
Ying Wang, Shuming Zhong, Guanmao Chen, Tao Liu, Lianping Zhao, Yao Sun, Yanbin Jia, Li Huang
OBJECTIVES: Several recent studies have reported a strong association between the cerebellar structural and functional abnormalities and psychiatric disorders. However, there are no studies to investigate possible changes in cerebellar functional connectivity in bipolar disorder. This study aimed to examine the whole-brain functional connectivity pattern of patients with remitted bipolar disorder II, in particular in the cerebellum. METHODS: A total of 25 patients with remitted bipolar disorder II and 25 controls underwent resting-state functional magnetic resonance imaging and neuropsychological tests...
December 1, 2017: Australian and New Zealand Journal of Psychiatry
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