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https://www.readbyqxmd.com/read/29906848/linear-time-general-decoding-algorithm-for-the-surface-code
#1
Andrew S Darmawan, David Poulin
A quantum error correcting protocol can be substantially improved by taking into account features of the physical noise process. We present an efficient decoder for the surface code which can account for general noise features, including coherences and correlations. We demonstrate that the decoder significantly outperforms the conventional matching algorithm on a variety of noise models, including non-Pauli noise and spatially correlated noise. The algorithm is based on an approximate calculation of the logical channel using a tensor-network description of the noisy state...
May 2018: Physical Review. E
https://www.readbyqxmd.com/read/29887338/unsupervised-discovery-of-demixed-low-dimensional-neural-dynamics-across-multiple-timescales-through-tensor-component-analysis
#2
Alex H Williams, Tony Hyun Kim, Forea Wang, Saurabh Vyas, Stephen I Ryu, Krishna V Shenoy, Mark Schnitzer, Tamara G Kolda, Surya Ganguli
Perceptions, thoughts, and actions unfold over millisecond timescales, while learned behaviors can require many days to mature. While recent experimental advances enable large-scale and long-term neural recordings with high temporal fidelity, it remains a formidable challenge to extract unbiased and interpretable descriptions of how rapid single-trial circuit dynamics change slowly over many trials to mediate learning. We demonstrate a simple tensor component analysis (TCA) can meet this challenge by extracting three interconnected, low-dimensional descriptions of neural data: neuron factors, reflecting cell assemblies; temporal factors, reflecting rapid circuit dynamics mediating perceptions, thoughts, and actions within each trial; and trial factors, describing both long-term learning and trial-to-trial changes in cognitive state...
May 31, 2018: Neuron
https://www.readbyqxmd.com/read/29884723/tau-induced-focal-neurotoxicity-and-network-disruption-related-to-apathy-in-alzheimer-s-disease
#3
Soichiro Kitamura, Hitoshi Shimada, Fumitoshi Niwa, Hironobu Endo, Hitoshi Shinotoh, Keisuke Takahata, Manabu Kubota, Yuhei Takado, Shigeki Hirano, Yasuyuki Kimura, Ming-Rong Zhang, Satoshi Kuwabara, Tetsuya Suhara, Makoto Higuchi
OBJECTIVE: Apathy is a common neuropsychological symptom in Alzheimer's disease (AD), and previous studies demonstrated that neuronal loss and network disruption in some brain regions play pivotal roles in the pathogenesis of apathy. However, contributions of tau and amyloid-β (Aβ) depositions, pathological hallmarks of AD, to the manifestation of apathy remain elusive. METHODS: Seventeen patients with AD underwent positron emission tomography (PET) with 11 C-pyridinyl-butadienyl-benzothiazole 3 (11 C-PBB3) and 11 C-Pittsburgh compound-B (11 C-PiB) to estimate tau and Aβ accumulations using standardised uptake value ratio (SUVR) images...
June 8, 2018: Journal of Neurology, Neurosurgery, and Psychiatry
https://www.readbyqxmd.com/read/29877178/white-matter-network-alterations-in-patients-with-depersonalization-derealization-disorder
#4
Anika Sierk, Judith K Daniels, Antje Manthey, Jelmer G Kok, Alexander Leemans, Michael Gaebler, Jan-Peter Lamke, Johann Kruschwitz, Henrik Walter
BACKGROUND: Depersonalization/derealization disorder (DPD) is a chronic and distressing condition characterized by detachment from oneself and/or the external world. Neuroimaging studies have associated DPD with structural and functional alterations in a variety of distinct brain regions. Such local neuronal changes might be mediated by altered interregional white matter connections. However, to our knowledge, no research on network characteristics in this patient population exists to date...
June 6, 2018: Journal of Psychiatry & Neuroscience: JPN
https://www.readbyqxmd.com/read/29876962/impact-of-transcranial-direct-current-stimulation-on-structural-plasticity-of-the-somatosensory-system
#5
Raphael Hirtz, Thomas Weiss, Ralph Huonker, Otto W Witte
While there is a growing body of evidence regarding the behavioral and neurofunctional changes in response to the longitudinal delivery of transcranial direct current stimulation (tDCS), there is limited evidence regarding its structural effects. Therefore, the present study was intended to investigate the effect of repeatedly applied anodal tDCS over the primary somatosensory cortex on the gray matter (GM) and white matter (WM) compartment of the brain. Structural tDCS effects were, moreover, related to effects evidenced by functional imaging and behavioral assessment...
August 2018: Journal of Neuroscience Research
https://www.readbyqxmd.com/read/29874072/large-eigenvalue-problems-in-coarse-grained-dynamic-analyses-of-supra-molecular-systems
#6
Patrice Koehl
Computational methods ranging from all-atom molecular dynamics simulations to coarse-grained normal mode analyses based on simplified elastic networks provide a general framework to studying molecular dynamics. Despite recent successes in analyzing very large systems with up to a hundred million atoms, those methods are currently limited to studying small to medium size molecular systems when used on standard desktop computers due to computational limitations. The hope to circumvent those limitations rests on the development of improved algorithms with novel implementations that mitigate their computationally challenging parts...
June 6, 2018: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/29867729/structural-and-functional-brain-mapping-correlates-of-impaired-eye-movement-control-in-parkinsonian-syndromes-a-systems-based-concept
#7
REVIEW
Martin Gorges, Hans-Peter Müller, Jan Kassubek
The investigation of the human oculomotor system by eye movement recordings provides an approach to behavior and its alterations in disease. The neurodegenerative process underlying parkinsonian syndromes, including Parkinson's disease (PD), progressive supranuclear palsy (PSP), and multisystem atrophy (MSA) changes structural and functional brain organization, and thus affects eye movement control in a characteristic manner. Video-oculography has been established as a non-invasive recording device for eye movements, and systematic investigations of eye movement control in a clinical framework have emerged as a functional diagnostic tool in neurodegenerative parkinsonism...
2018: Frontiers in Neurology
https://www.readbyqxmd.com/read/29803958/disrupted-topology-of-the-resting-state-structural-connectome-in-middle-aged-apoe-%C3%AE%C2%B54-carriers
#8
L E Korthauer, L Zhan, O Ajilore, A Leow, I Driscoll
The apolipoprotein E (APOE) ε4 allele is the best characterized genetic risk factor for Alzheimer's disease to date. Older APOE ε4 carriers (aged 60 + years) are known to have disrupted structural and functional connectivity, but less is known about APOE-associated network integrity in middle age. The goal of this study was to characterize APOE-related differences in network topology in middle age, as disentangling the early effects of healthy versus pathological aging may aid early detection of Alzheimer's disease and inform treatments...
May 24, 2018: NeuroImage
https://www.readbyqxmd.com/read/29791077/alterations-of-brain-network-hubs-in-reflex-syncope-evidence-from-a-graph-theoretical-analysis-based-on-dti
#9
Bong Soo Park, Yoo Jin Lee, Jin-Han Park, Il Hwan Kim, Si Hyung Park, Ho-Joon Lee, Kang Min Park
OBJECTIVE: We evaluated global topology and organization of regional hubs in the brain networks and microstructural abnormalities in the white matter of patients with reflex syncope. METHODS: Twenty patients with reflex syncope and thirty healthy subjects were recruited, and they underwent diffusion tensor imaging (DTI) scans. Graph theory was applied to obtain network measures based on extracted DTI data, using DSI Studio. We then investigated differences in the network measures between the patients with reflex syncope and the healthy subjects...
May 23, 2018: Brain and Behavior
https://www.readbyqxmd.com/read/29781583/altered-white-matter-connectivity-associated-with-visual-hallucinations-following-occipital-stroke
#10
Sara A Rafique, John R Richards, Jennifer K E Steeves
INTRODUCTION: Visual hallucinations that arise following vision loss stem from aberrant functional activity in visual cortices and an imbalance of activity across associated cortical and subcortical networks subsequent to visual pathway damage. We sought to determine if structural changes in white matter connectivity play a role in cases of chronic visual hallucinations associated with visual cortical damage. METHODS: We performed diffusion tensor imaging (DTI) and probabilistic fiber tractography to assess white matter connectivity in a patient suffering from continuous and disruptive phosphene (simple) visual hallucinations for more than 2 years following right occipital stroke...
May 21, 2018: Brain and Behavior
https://www.readbyqxmd.com/read/29776166/normal-stresses-in-semiflexible-polymer-hydrogels
#11
M Vahabi, Bart E Vos, Henri C G de Cagny, Daniel Bonn, Gijsje H Koenderink, F C MacKintosh
Biopolymer gels such as fibrin and collagen networks are known to develop tensile axial stress when subject to torsion. This negative normal stress is opposite to the classical Poynting effect observed for most elastic solids including synthetic polymer gels, where torsion provokes a positive normal stress. As shown recently, this anomalous behavior in fibrin gels depends on the open, porous network structure of biopolymer gels, which facilitates interstitial fluid flow during shear and can be described by a phenomenological two-fluid model with viscous coupling between network and solvent...
March 2018: Physical Review. E
https://www.readbyqxmd.com/read/29776027/tensor-network-method-for-reversible-classical-computation
#12
Zhi-Cheng Yang, Stefanos Kourtis, Claudio Chamon, Eduardo R Mucciolo, Andrei E Ruckenstein
We develop a tensor network technique that can solve universal reversible classical computational problems, formulated as vertex models on a square lattice [Nat. Commun. 8, 15303 (2017)2041-172310.1038/ncomms15303]. By encoding the truth table of each vertex constraint in a tensor, the total number of solutions compatible with partial inputs and outputs at the boundary can be represented as the full contraction of a tensor network. We introduce an iterative compression-decimation (ICD) scheme that performs this contraction efficiently...
March 2018: Physical Review. E
https://www.readbyqxmd.com/read/29761954/-research-on-brain-white-matter-network-in-cerebral-palsy-infant
#13
Jun Li, Cheng Yang, Yuanjun Wang, Shengdong Nie
Present study used diffusion tensor image and tractography to construct brain white matter networks of 15 cerebral palsy infants and 30 healthy infants that matched for age and gender. After white matter network analysis, we found that both cerebral palsy and healthy infants had a small-world topology in white matter network, but cerebral palsy infants exhibited abnormal topological organization: increased shortest path length but decreased normalize clustering coefficient, global efficiency and local efficiency...
October 1, 2017: Sheng Wu Yi Xue Gong Cheng Xue za Zhi, Journal of Biomedical Engineering, Shengwu Yixue Gongchengxue Zazhi
https://www.readbyqxmd.com/read/29758651/characterizing-granular-networks-using-topological-metrics
#14
Joshua A Dijksman, Lenka Kovalcinova, Jie Ren, Robert P Behringer, Miroslav Kramar, Konstantin Mischaikow, Lou Kondic
We carry out a direct comparison of experimental and numerical realizations of the exact same granular system as it undergoes shear jamming. We adjust the numerical methods used to optimally represent the experimental settings and outcomes up to microscopic contact force dynamics. Measures presented here range from microscopic through mesoscopic to systemwide characteristics of the system. Topological properties of the mesoscopic force networks provide a key link between microscales and macroscales. We report two main findings: (1) The number of particles in the packing that have at least two contacts is a good predictor for the mechanical state of the system, regardless of strain history and packing density...
April 2018: Physical Review. E
https://www.readbyqxmd.com/read/29758374/age-and-alzheimer-s-pathology-disrupt-default-mode-network-functioning-via-alterations-in-white-matter-microstructure-but-not-hyperintensities
#15
Christopher A Brown, Yang Jiang, Charles D Smith, Brian T Gold
The default mode network (DMN) comprises defined brain regions contributing to internally-directed thought processes. Reductions in task-induced deactivation in the DMN have been associated with increasing age and poorer executive task performance, but factors underlying these functional changes remain unclear. We investigated contributions of white matter (WM) microstructure, WM hyperintensities (WMH) and Alzheimer's pathology to age-related alterations in DMN function. Thirty-five cognitively normal older adults and 29 younger adults underwent working memory task fMRI and diffusion tensor imaging...
April 19, 2018: Cortex; a Journal Devoted to the Study of the Nervous System and Behavior
https://www.readbyqxmd.com/read/29756856/global-anomaly-detection-in-two-dimensional-symmetry-protected-topological-phases
#16
Nick Bultinck, Robijn Vanhove, Jutho Haegeman, Frank Verstraete
Edge theories of symmetry-protected topological phases are well known to possess global symmetry anomalies. In this Letter we focus on two-dimensional bosonic phases protected by an on-site symmetry and analyze the corresponding edge anomalies in more detail. Physical interpretations of the anomaly in terms of an obstruction to orbifolding and constructing symmetry-preserving boundaries are connected to the cohomology classification of symmetry-protected phases in two dimensions. Using the tensor network and matrix product state formalism we numerically illustrate our arguments and discuss computational detection schemes to identify symmetry-protected order in a ground state wave function...
April 13, 2018: Physical Review Letters
https://www.readbyqxmd.com/read/29748646/the-effect-of-the-total-small-vessel-disease-burden-on-the-structural-brain-network
#17
Xiaopei Xu, Kui Kai Lau, Yuen Kwun Wong, Henry K F Mak, Edward S Hui
Different cerebral small vessel disease (SVD) lesion types have been shown to disrupt structural brain network individually. Considering that they often coexist, we investigated the relation between their collective effect using the recently proposed total SVD score and structural brain network on MRI in 95 patients with first transient ischemic attack (TIA) or ischemic stroke. Fifty-nine patients with and 36 without any SVD lesions were included. The total SVD score was recorded. Diffusion tensor imaging was performed to estimate structural brain connections for subsequent brain connectivity analysis...
May 10, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29738718/bilateral-thalamocortical-abnormalities-in-focal-cortical-dysplasia
#18
Arthur Rezayev, Henry A Feldman, Jacob Levman, Emi Takahashi
BACKGROUND AND PURPOSE: Focal cortical dysplasia (FCD), a congenital malformation of the neocortex and one of the most common causes of medication resistant epilepsy in pediatric populations, can be studied noninvasively by diffusion tensor imaging (DTI). The present study aimed to quantify changes in the thalamus and thalamocortical pathways with respect to fractional anisotropy (FA), apparent diffusion coefficient (ADC), volume, and other common measures. MATERIALS & METHODS: The study quantified data collected from pediatric patients with a prior diagnosis of FCD; 75 patients (35 females, 10...
May 5, 2018: Brain Research
https://www.readbyqxmd.com/read/29737956/connection-disruption-underlying-attention-deficit-in-subcortical-stroke
#19
Jingchun Liu, Caihong Wang, Qingqing Diao, Wen Qin, Jingliang Cheng, Chunshui Yu
Purpose To investigate neural substrates underlying attention deficit in patients with chronic subcortical stroke by combining voxel-based lesion-symptom mapping (VLSM) and diffusion-tensor (DT) tractography. Materials and Methods Institutional review board approval and written informed consent were obtained. Diffusion magnetic resonance imaging data were prospectively acquired from August 1, 2014, to March 30, 2015, in 49 patients (32 men, 17 women; mean age, 55.7 years ± 8.0; age range, 40-71 years) with subcortical infarctions in the basal ganglia and neighboring regions and 52 control subjects (30 men, 22 women; mean age, 54...
May 8, 2018: Radiology
https://www.readbyqxmd.com/read/29734951/disrupted-rich-club-organization-and-structural-brain-connectome-in-unmedicated-bipolar-disorder
#20
Ying Wang, Feng Deng, Yanbin Jia, Junjing Wang, Shuming Zhong, Huiyuan Huang, Lixiang Chen, Guanmao Chen, Huiqing Hu, Li Huang, Ruiwang Huang
BACKGROUND: Bipolar disorder (BD) has been associated with altered brain structural and functional connectivity. However, little is known regarding alterations of the structural brain connectome in BD. The present study aimed to use diffusion-tensor imaging (DTI) and graph theory approaches to investigate the rich club organization and white matter structural connectome in BD. METHODS: Forty-two patients with unmedicated BD depression and 59 age-, sex- and handedness-matched healthy control participants underwent DTI...
May 8, 2018: Psychological Medicine
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