EEG Dynamics: BBS Call for Commentators
Stevan Harnad
BRAIN DYNAMICS, EEG & NEURAL NETS by JJ Wright & DTJ Liley
This article has been accepted for publication in Behavioral and Brain
Sciences (BBS), an international, interdisciplinary journal providing
Open Peer Commentary on important and controversial current research in
the biobehavioral and cognitive sciences.
Commentators must be current BBS Associates or nominated by a current
BBS Associate. To be considered as a commentator for this article, to
suggest other appropriate commentators, or for information about how to
become a BBS Associate, please send email to:
b...@ecs.soton.ac.uk or write to:
Behavioral and Brain Sciences
Department of Psychology
University of Southampton
Highfield, Southampton
SO17 1BJ UNITED KINGDOM
http://cogsci.ecs.soton.ac.uk/~harnad/bbs.html
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instructions that follow after the abstract.
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DYNAMICS OF THE BRAIN AT GLOBAL AND MICROSCOPIC SCALES:
NEURAL NETWORKS AND THE EEG.
J.J. Wright and D.T.J. Liley
Mental Health Research Institute Parkville
Victoria 3052, Australia
j...@cortex.mhri.edu.au
Swinburne Center for Applied Neuroscience
Hawthorne, Victoria 3122
Melbourne, Australia
KEYWORDS: chaos, EEG simulation, electrocorticogram, neocortex,
network symmetry, neurodynamics.
ABSTRACT: There is some complementarity of models for the
origin of the electroencephalogram (EEG), and neural network
models for information storage in brain-like systems.
From the EEG models of Freeman, Nunez, and the author's group,
we argue that the wave-like processes revealed in the EEG
exhibit linear and near-equilibrium dynamics at macroscopic
scale, despite extremely nonlinear, probably chaotic, dynamics
at microscopic scale. Simulations of cortical neuronal
interactions at global and microscopic scales are then
presented. The simulations depend on anatomical and
physiological estimates of synaptic densities, coupling
symmetries, synaptic gain, dendritic time constants and axonal
delays. It is shown that the frequency content, wave
velocities, frequency/wavenumber spectra and response to
cortical activation of the electrocorticogram (ECoG) can be
reproduced by a "lumped" simulation treating small cortical
areas as single functional units. The corresponding cellular
neural network simulation has properties which include those of
attractor neural networks proposed by Amit, and Paresi.
Within the simulations at both scales, sharp transitions occur
between low and high cell firing rates. These transitions may
form a basis for neural interactions across scale.
To maintain overall cortical dynamics in the normal low
firing-rate range, interactions between the cortex and
subcortical systems are required to prevent runaway global
excitation. Thus the interaction of cortex and subcortex via
cortico-striatal and related pathways, may partly regulate
global dynamics by a principle analogous to adiabatic control
of artificial neural networks
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