Dynamics of the brain at global and microscopic scales: Neural networks and the EEG

Wright, J.J. and Liley, D.T.L (1996) Dynamics of the brain at global and microscopic scales: Neural networks and the EEG. [Journal (Paginated)]

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There is some complementarity of models for the origin of the electroencephalogram (EEG) and neural network models for information storage in brainlike systems. From the EEG models of Freeman, of Nunez, and of the authors' group we argue that the wavelike 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-function units. The corresponding cellular neural network simulation has properties that include those of attractor neural networks proposed by Amit and by Parisi. 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 the subcortical systems are required to prevent runaway global excitation. Thus, the interaction of cortex and subcortex via corticostriatal and related pathways may partly regulate global dynamics by a principle analogous to adiabatic control of artificial neural networks.

Item Type:Journal (Paginated)
Keywords:dynamics, neural networks, electroencephalogram, eeg, models, nonlinear, chaotic, equilibrium dynamics, global scale, macroscopic scale, microscopic scale, synaptic density, ECoG, wave velocity
Subjects:Neuroscience > Brain Imaging
Neuroscience > Computational Neuroscience
Neuroscience > Neural Modelling
ID Code:47
Deposited By: Wright, James
Deposited On:18 Jun 1998
Last Modified:11 Mar 2011 08:53


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