Volume 10 Supplement 1

Eighteenth Annual Computational Neuroscience Meeting: CNS*2009

Open Access

Emergent phenomena in human EEG: a bifurcation theory approach

  • Federico Frascoli1,
  • Lennaert Van Veen2,
  • Ingo Bojak3,
  • Mathew P Dafilis1 and
  • David TJ Liley1
BMC Neuroscience200910(Suppl 1):P286

DOI: 10.1186/1471-2202-10-S1-P286

Published: 13 July 2009

A recently proposed mesoscopic mean-field theory of mammalian cortex electro-rhythmogenesis describes the salient features of electrical activity in the cerebral macrocolumn, with the use of inhibitory and excitatory neuronal populations [1]. Numerical solutions to the defining non-linear equations have revealed two interesting emergent phenomena: i) the appearance of large-scale spatial coherent 40 Hz oscillations in the model cortex, which has shown to be experimentally related to cognitive activity [2], and ii) a surge in spectral EEG power – when the brain is subject to general anesthetics – as a function of their concentration [3], a clinically established effect known as the "biphasic" response. Given that quasi-linear approximations have been unable to capture the dynamical mechanism that trigger these phenomena, a bifurcation analysis [4] of physiologically relevant parameter sets was performed.

Because of the predicted importance of inhibitory-inhibitory population strength in determining many fundamental dynamical features of the model, bifurcation parameters were chosen that modified inhibitory post-synaptic potential amplitudes and anatomical coupling strengths of the inhibitory neural population (respectively R and k in Figure 1). The analysis revealed the existence of a pattern of recurring bifurcation diagrams and specific "phase" transitions that constitute the dynamical requirements for the genesis and unfolding of 40 Hz and biphasic behaviors. This result also reaffirms the relevance of inhibition for the genesis of global collaborative events in the cortex and sheds light on the organization of the parameter space and the variability of EEG in the model respect to those perturbations and collective responses that are physiologically admissible.
https://static-content.springer.com/image/art%3A10.1186%2F1471-2202-10-S1-P286/MediaObjects/12868_2009_Article_1471_Fig1_HTML.jpg
Figure 1

An example of codimension two bifurcation plots for a parameter set displaying coherent gamma oscillations. The right-most branch of Hopf points corresponds to the emergence of approximately 37 Hz limit cycle activity via a subcritical Hopf bifurcation above the point labeled "gh" (generalized Hopf). Also, a homoclinic doubling cascade takes place along the line of homoclinics emanating from "bt" (Bogdanov-Takens point).

Authors’ Affiliations

(1)
Brain Sciences Institute (BSI), Swinburne University of Technology
(2)
Department of Mathematics and Statistics, Faculty of Arts and Sciences, Concordia University
(3)
Donders Institute for Brain, Cognition and Behaviour, Centre for Neuroscience, Radboud University Nijmegen (Medical Centre)

References

  1. Liley DTJ, Cadusch PJ, Dafilis MP: A spatially continuous mean field theory of electrocortical activity. Network: Comput Neural Syst. 2002, 13: 67-113. 10.1088/0954-898X/13/1/303.View ArticleGoogle Scholar
  2. Bojak I, Liley DTJ: Self-organized 40 hz synchronization in a physiological theory of EEG. Neurocomp. 2007, 70: 2085-2090. 10.1016/j.neucom.2006.10.087.View ArticleGoogle Scholar
  3. Bojak I, Liley DTJ: Modeling the effects of anesthesia on the electroencephalogram. Phys Rev E. 2005, 71: 041902(1–22).Google Scholar
  4. Kuznetsov YA: Elements of applied bifurcation theory. 2004, New York, Springer-Verlag, 3View ArticleGoogle Scholar

Copyright

© Frascoli et al; licensee BioMed Central Ltd. 2009

This article is published under license to BioMed Central Ltd.

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