The Center for Biomedical Informatics
State University of Campinas, Brazil

Research Abstracts

In the present study we propose a continuous, lumped-parameter, non-linear mathematical model for explaining the quantitatively observed characteristics of a class of experimental reflex epilepsy, namely audiogenic seizures in rodents, and simulate this model with a especially contrived microcomputer program. In a first phase of the study, we have individually stimulated 280 adult Wistar albino rats with a 112 dB white-noise sound source, and recorded the latency, duration and intensity values of the psychomotor components of the audiogenic reaction: after an initial delay one or more circular running phases usually occurs, followed or not by complete tonic-clonic seizures. In the second step, we performed several multivariate statistical analyses of these data, which have revealed many properties of the underlying neural system responsible for the crisis; such as the independence of the running and convulsive phases; and a scale of severity which is correlated to the value of latencies and intensities. Finally, a lumped-parameter model based on a set of differential equations which describes the macro behavior of the interaction of four different populations of excitatory and inhibitory neurons with different time constants and threshold elements has been simulated in a computer, In this model, running waves, which may occur several times before leading or not to the final convulsive phase, are explained by the oscillatory behavior of a controlling neural population, caused by mixed feedback: an early, internal positive feedback which results in the growing of excitation, and a late negative feedback elicited by motor components of the running itself, which causes the oscillation back to inhibition. A second, threshold-triggered population controls the convulsive phase and its subsequent refractory phase. The results of the simulation have been found to explain reasonably well the time course and structural characteristics of the several forms of rodent audiogenic epilepsy and correlates well with the existing knowledge about the neural bases of this phenomenon.

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Last Updated: March 2, 1996

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