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Resting State Brain Connectivity


Fractal behavior and Brain connectivity

We have developed parsimonious techniques to reveal resting state functional connectivity of the brain through functional magnetic resonance imaging (fMRI). A blood oxygen level dependent (BOLD) signals taken at rest tends to exhibit 1/f power-law scaling or long-range dependence called the fractal behavior (see video 1). In this project, we have proposed a computational model of BOLD signals which describes not only the physical mechanism of fractal behavior in BOLD signals but also the theoretical relationship between fractal behavior and functional connectivity. In addition, we have suggested a novel method which allows us to estimate functional connectivity of endogenous neuronal activities hidden beyond the fractal behavior of BOLD signals (see figure 1).

Figure 1. Comparison of nonfractal connectivity of the rat brain with ordinary functional connectivity
Nonfractal connectivity is defined as the correlation of nonfractal components of resting state BOLD signals.
Modularity of the brain network was enhanced with nonfractal connectivity. (You et al. IJCNN 2012)

Video 1. Fractal Dynamics in the Resting Brain.


  1. Wonsang You, Catherine Limperopoulos, "Study on Linear Combination of Long Memory Processes Corrupted by Additive Noises for fMRI Time Series Analysis,"  bioRxiv 210518 (December 21, 2017).
  2. Wonsang You, "Long memory model of resting state functional MRI," PhD Thesis, Electrical Engineering and Information Technology, Otto-von-Guericke-University of Magdeburg, 2013.
  3. Wonsang You and Jörg Stadler, Fractal-driven distortion of resting state functional networks in fMRI: a simulation study, Brain Connectivity 2012, Vol.0, No.0, September 2012.
  4. Wonsang You, Sophie Achard, and Jörg Stadler, Fractal-based linear model of resting state hemodynamic response in fMRI, BMC Neuroscience 2012, 13(Suppl 1):P35, July 2012.
  5. Wonsang You, Sophie Achard, Jörg Stadler, Bernd Brückner, and Udo Seiffert, "Fractal analysis of resting state functional connectivity of the brain," in 2012 International Joint Conference on Neural Networks, June 2012.
  6. Wonsang You and Wojciech Kordecki, "A Proof on Asymptotics of Wavelet Variance of a Long Memory Process by Using Taylor Expansion," IfN Technical Reports TR10014, 23 July 2010.
  7. Wonsang You and Jörg Stadler, "Fractal-based Correlation Analysis for Resting State Functional Connectivity of the Rat Brain in Functional MRI," CBBS Educational Workshop on Resting State fMRI, April 2010.

Invited Talks and Tutorials

  1. Fractal behavior causes connectivity distortion in resting state fMRI (Department of Biometry and Medical Informatics, University Magdeburg, Germany, 30 July 2012)
  2. Fractal-driven distortion of default-mode functional networks in resting state fMRI (Biointelligence Lab, Seoul National University, South Korea, 20 June 2012)
  3. Fractal-driven distortion of connectivity and information flow in resting state fMRI time series (Asia Pacific Center for Theoretical Physics, South Korea, 18 June 2012)
  4. Fractal analysis of resting state functional connectivity of the brain (2012 International Joint Conference on Neural Networks, Brisbane, Australia, 13 June 2012)
  5. Resting state fMRI: Inferring functional connectivity of spontaneous neuronal activities (2011 LIN Retreat, Leibniz Institute for Neurobiology, Dessau, 4 October 2011)
  6. Inferring network structure of the brain from functional connectivity (Biosystems Engineering, Fraunhofer Institute for Factory Operation and Automation, Magdeburg, Germany, 2 May 2011)
  7. Fractional Gaussian noise and fractal connectivity in the resting brain (Gipsa-lab, Grenoble INP, 3 March 2011)
  8. Fractal-based resting state fMRI analysis (Department of Mathematics and Statistics, University of Konstanz, Germany, 13 July 2010)




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