Toward a physical approach to integrative physiology. I. Brain dynamics and physical causality.

This report treats the fundamental question raised by Yates [Am. J. Physiol. 238 (Regulatory Integrative Comp. Physiol. 7): R277-R290, 1980.]: "Why should neuroscience look to physics for its theories?" This is the viewpoint of an experimentalist who needs a physical approach to brain theories to interpret the results of physically oriented experiments on electroencephalogram and evoked potentials. The fundamental physical theories are briefly outlined; the phenomena of enhancement of brain potentials, frequency stabilization effects, and phase-resetting phenomena of populations of neurons in the brain are explained. The results of experiments are interpreted in the light of a variety of physical theories: coupled oscillators, induced magnetization, laser physics, and synergetics. Further, analogies with nonlinear mechanics, theory of dissipative structures, and the S-matrix formalism of quantum mechanics are provided to predict the brain's excitability. The homeokinetic approach of Iberall, the electromagnetic theory of Adey, and the quantumlike theories of Walter are discussed. It is concluded that brain scientists need an ensemble of physical approaches and concepts to understand various brain mechanisms.