A model of neuron electrical activity.

1. Every theory is based on some simplifications of observed phenomena. This simplified abstract phenomenon is usually called a "model". Depending on the level of simplification the model enables us to predict more or less accurately the original situation. The scientist who tries to describe a physical phenomenon in terms of mathematical equations, or, more generally, by means of some mathematical algorithm, deals in fact with a particular type of model which, due to its abstract form, is more flexible and in which the number of parameters used is less restricted than in models of a different kind. However, the similarity between the original and model phenomena is clearer in mathematical models because we never deal with the similarity between two obscure situations and at least one side of the relation, namely the mathematical side, can be fully explained. Now the form of a model might be very simple, therefore the similarity is very superficial. In the case of a mathematical model such a simple form gives only the possibility of reconstruction of the original ])henomenon using the values of several parameters and we usually try lo use a miilimal number of such parameters. Such a simple model of the electrical aclivity of the neuron will be described in this paper. The deeper, sense of creating models is to extract such information as enables us to predict behavior: if the model agrees with some actual phenomenon then perhaps a physiological experiment can be designed which will clarify its physical or chemical mechanisms. The procedure described below should be treated as the first step to obtain a more complete model. 2. The information carried by the signals from the sensory unit to the central nervous system is, as it is commonly believed, coded by a pattern of activity. However, we do not know the coding system.