Dynamics of the Eyeblink EMG at Global and Microscopic Scales

Eyeblink electromyogram (EMG) is a noninvasive and reliable tool for evaluating information processing at different levels of the central nervous system.The recently developed method of fragmentary decompositioncreates the model of a single trial eyeblink EMG as the series of consecutive, partly overlapping components, with the generic mass potential being the basis element. Here we express this model in terms of underlying cellular processes. To our knowledge, this is the first study where the dynamics of a mass potential at global scale is deduced from a stochastic particle model of the ion movements at microscopic scale. We consider generation of the eyeblink EMG as a stimulusinduced creation of an extracellular dipole by the movements of ions at the microscopic scale. These processes are described in terms of an equivalent circuit which is composed of novel circuit elements named sourceoid, sinkoid, and dipoloid. The corresponding equations are formulated in terms of nonhomogeneous birth-and-death processes. The theory brings together the deterministic and stochastic factors underlying the genesis of eyeblink EMG with the minimum number of free parameters. No matter how complex are the particle systems, just a few global scale parameters accumulate essential aspects of microscale activities which appear as significant variables at the global scale. Numerical experiments revealed that the mass effect of multiple elementary dipoles is expected to settle down into a behavior that qualitatively remains unchanged at different levels of a volume conductor. We summarize these findings as the principle of the conservation of the mass potential distributions.