The Journal of Neurophysiology Vol. 79 No. 2 February 1998, pp. 1098-1101
Copyright ©1998 The American Physiological Society

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Noise-Induced Spiral Waves in Astrocyte Syncytia Show Evidence of Self-Organized Criticality

Peter Jung¹, Ann Cornell-Bell², Kathleen Shaver Madden³, and Frank Moss⁴

¹ School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332; ² Viatech Imaging, Ivoryton, Connecticut 06442; ³ Foundation for International Nonlinear Dynamics, Bethesda, Maryland 20816; and ⁴ Center for Neurodynamics, University of Missouri, St. Louis, Missouri 63121

Jung, Peter, Ann Cornell-Bell, Kathleen Shaver Madden, and Frank Moss. Noise-induced spiral waves in astrocyte syncytia show evidence of self-organized criticality. J. Neurophysiol. 79: 1098-1101, 1998. Long range (a few centimeters), long lived (many seconds), spiral chemical waves of calcium ions (Ca²⁺) are observed in cultured networks of glial cells for normal concentrations of the neurotransmitter kainate. A new method for quantitatively measuring the spatiotemporal size of the waves is described. This measure results in a power law distribution of wave sizes, meaning that the process that creates the waves has no preferred spatial or temporal (size or lifetime) scale. This power law is one signature of self-organized critical phenomena, a class of behaviors found in many areas of science. The physiological results for glial networks are fully supported by numerical simulations of a simple network of noisy, communicating threshold elements. By contrast, waves observed in astrocytes cultured from human epileptic foci exhibited radically different behavior. The background random activity, or "noise", of the network is controlled by the kainate concentration. The mean rate of wave nucleation is mediated by the network noise. However, the power law distribution is invariant, within our experimental precision, over the range of noise intensities tested. These observations indicate that spatially and temporally coherent Ca²⁺ waves, mediated by network noise may play and important role in generating correlated neural activity (waves) over long distances and times in the healthy vertebrate central nervous system.

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