A FUNCTIONAL-MODEL OF THE CIRCADIAN SYSTEM BASED ON THE DEGREE OF INTERCOMMUNICATION IN A COMPLEX SYSTEM

A model of the circadian system is presented. It was developed initial ly for rats, but after introducing several modifications, we consider that it may be extended to many other living systems. It was not the p urpose of the study to develop an oversimplified model of the circadia n system but rather to explore the elements and rules that govern the dynamics of a complex circadian system, assuming its multioscillatory nature. The formulation of the model is based on the concept of interc ommunication in a population of autonomous oscillators. Most environme ntal effects (including rhythm entrainment) can be simulated with the model simply by controlling the degree of intercommunication. The mode l introduces the concept of neutral elements (probably glial cells in real systems) that shorten or lengthen the period in response to chang es in illumination intensity as a consequence of their presence. Feedb ack in the system facilitates the emergence of. split patterns. By def ining the oscillatory units to have similar intrinsic period and a rel atively low level of internal coupling, it is possible to obtain compl ex circadian patterns, maintaining stable phases among their component s, which resemble ultradian rhythms. A computer program was developed allowing experimentation with a variety of different definitions and e nvironmental conditions. Although the computer implementation of the m odel has required the formulation of the model in mathematical terms, the strength of the model (and its functional properties) lies more in the conceptual definition than in its formal aspects.