von Neumann, John: The Computer and the Brain

The following quotes are from John Von Neumann's unfinished notes published after his death in 1958 in a little book called The Computer and the Brain.

"... we know a certain amount about how the nervous system transmits numerical data. They are usually transmitted by periodic or nearly periodic trains of pulses.

It is noteworthy that the frequency in question is not directly equal to any intensity of stimulus, but rather that it is a monotone function of the later. This permits the introduction of all kinds of scale effects and expressions of precision in terms that are conveniently and favorably dependent on the scales that arise.

It should also be noted that the message-system used in the nervous system, as described in the above, is of an essentially statistical character. In other words, what matters are not the precise positions of definite markers, digits, but the statistical characteristics of their occurrence, i.e. frequencies of periodic or nearly periodic pulse-trains, etc.

In the above, the frequencies of certain periodic or nearly periodic pulse-trains carried the message, i.e. the information. These were distinctly statistical traits of the message.

So far, the only property of the message that was used to transmit information was its frequency in terms of pulses per second, it being understood that the message was a periodic or nearly periodic train of pulses.

Clearly, other traits of the (statistical) message could also be used: indeed, the frequency referred to is a property of a single train of pulses whereas every one of the relevant nerves consists of a large number of fibers, each of which transmits numerous trains of pulses. It is, therefore, perfectly plausible that certain (statistical) relationships between such trains of pulses should also transmit information. In this connection it is natural to think of various correlation-coefficents, and the like."

The Computer and the Brain is an incredible book which I've reread many times.