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    Simulation of the Self-organized Critical Models on the
    Human’s Brain Network

    , M.Sc. Thesis Sharif University of Technology Shokouhi, Fatemeh (Author) ; Moghimi Araghi, Saman (Supervisor)
    Self-organized critical phenomena are interesting phenomena which are ubiquitous in nature. Examples include mountain ranges , coastlines and also activities in the hu-man's brain. In these processes, without fine-tuning of any external parameter such as the temperature, the system exhibits critical behavior. In other words, the dynamics of the system, drives it towards an state in which long range correlations in space and scaling behaviors can be seen.The first successful model which could characterize such systems was BTW model, introduced by Bak , Tang and Wiesenfeld in 1987. This model, later named Abelian sandpile model, was very simple and because of this simplicity, a large amount of... 

    Rotating field gradient (RFG) MR offers improved orientational sensitivity

    , Article Proceedings - International Symposium on Biomedical Imaging, 16 April 2015 through 19 April 2015 ; Volume 2015-July , 2015 , Pages 955-958 ; 19457928 (ISSN) ; 9781479923748 (ISBN) Ozarslan, E ; Memic, M ; Avram, A. V ; Afzali, M ; Basser, P. J ; Westin, C. F ; Sharif University of Technology
    IEEE Computer Society  2015
    Rotating field gradients (RFGs), generated by simultaneously applying sine- and cosine-modulated gradient waveforms along two perpendicular directions, provide an alternative diffusion sensitization mechanism for magnetic resonance imaging and spectroscopy. Two RFGs with a 90-degree phase shift between them are applied around the 180-degree RF pulse in a spin echo sequence to measure the diffusion orientation distribution function (dODF) directly. The technique obviates transforming the data from a space reciprocal to the displacement space. Here, we compare RFG results with those obtained by two pulsed field gradient (PFG) techniques: q-ball imaging (QBI) and its extension to constant solid... 

    Complementary hemispheric lateralization of language and social processing in the human brain

    , Article Cell Reports ; Volume 41, Issue 6 , 2022 ; 22111247 (ISSN) Rajimehr, R ; Firoozi, A ; Rafipoor, H ; Abbasi, N ; Duncan, J ; Sharif University of Technology
    Elsevier B.V  2022
    Humans have a unique ability to use language for social communication. The neural architecture for language comprehension and production may have prominently emerged in the brain areas that were originally involved in social cognition. Here, we directly tested the fundamental link between language and social processing using functional magnetic resonance data (MRI) data from over 1,000 human subjects. Cortical activations in language and social tasks showed a striking similarity with a complementary hemispheric lateralization. Within core language areas, left-lateralized activations in the language task were mirrored by right-lateralized activations in the social task. Outside these areas,... 

    Directed functional networks in Alzheimer's disease: disruption of global and local connectivity measures

    , Article IEEE Journal of Biomedical and Health Informatics ; Volume 21, Issue 4 , 2017 , Pages 949-955 ; 21682194 (ISSN) Afshari, S ; Jalili, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    Techniques available in graph theory can be applied to signals recorded from human brain. In network analysis of EEG signals, the individual nodes are EEG sensor locations and the edges correspond to functional relations between them that are extracted from EEG time series. In this paper, we study EEG-based directed functional networks in Alzheimer's disease (AD). To this end, directed connectivity matrices of 25 AD patients and 26 healthy subjects are processed and a number of meaningful graph theory metrics are studied. Our data show that functional networks of AD brains have significantly reduced global connectivity in alpha and beta bands (P < 0.05). The AD brains have significantly...