W.S. McCulloch and W.L. Kilmer


Throughout the life of the vertebrates, the core of the central nervous system, sometimes called the reticular formation, has retained the power to commit the whole animal to one mode of behavior rather than another. Its anatomy, or wiring diagram, is fairly well known, but to date no theory of its circuit action has been proposed that could possibly account for its known performance. Its basic structure is that of a string of similar modules, wide but shallow in computation everywhere, and connected not merely from module to adjacent module, but by long jumpers between distant modules. Analysis of its circuit actions, heretofore proposed in terms of finite automata or coupled nonlinear oscillators, has failed. We have proposed probabilistic automata which handle regular events as proper modules, and proved some novel stability theorems regarding them. The behavior of a connected chain of such modules is still under investigation.

In the present presentation we will begin with a description of its component neurons, their effective connections, the general scheme of their arrangements and an enlarged description of its role in determining well defined incompatible modes of behavior. We will review the evidence as to its electrical activity so far discernible with it. In so doing we will make clear the extent, and in some cases the manner, of the control it exerts over receptors, specialized computers, like the cerebrum and the cerebellum, and over programmed activities and pools of motor neurons.

We regard this as the central problem of neurophysiology, and as Nature's basic solution for the design of a command and control system which has insured the life of the vertebrates. It enjoys a redundancy of potential command, in which the requisite information constitutes authority. The attempt to model it on a digital computer is underway at Michigan State University, but we have been compelled to resort to rather special considerations in order to insure that activities of the system shall converge promptly upon solutions stable enough to insure the completion of the required performances.


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Keywords: Modules, Vertebrates, Action, Behavior, Automata, Actions, System, Structure, Module, Events

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1 Reprinted from Proceedings of the International Federation for Information Processing Congress (1965). 1966, 2:636.