STATE TRANSITIONS IN PHYSIOLOGICAL SYSTEMS - A COMPLEXITY MODEL FOR LOSS OF CONSCIOUSNESS

Complex physiologic systems in which the emergent global (observable) behavior results from the interplay among local processes cannot be st udied effectively by conventional mathematical models, In contrast to traditional computational methods which provide linear or nonlinear in put-output data mapping without regard to the internal workings of the system, complexity theory offers scientifically and computationally t ractable models which take into account microscopic mechanisms and int eractions responsible for the overall input-output behavior, This arti cle offers a brief introduction to some of the tenets of complexity th eory and outlines the process involved in the development and testing of a model that duplicates the global dynamics of the induction of los s of consciousness (LOC) in humans due to cerebral ischemia, Under the broad definition of complexity; we view the brain of humans as a comp lex system, Successful development of a model for this complex system requires careful combination of basic knowledge of the physiological s ystem both at the local (microscopic) and global (macroscopic) levels with experimental data and the appropriate mathematical tools. It repr esents an attempt to develop a model that can both replicate human dat a and provide insights about possible underlying mechanisms.