Entropy measures of signal in the presence of noise: evidence for 'byte' versus 'bit' processing in the nervous system.

A method for detecting signal in the presence of noise in a highly specific way is described. Using action potential interval data from 12 neurons in rat cerebellum, we have demonstrated that the sequential ordering of spike intervals contains both noise and signal. We have identified and quantified the magnitude of relative entropy (uncertainty) of specified sets of interval patterns, ranging in length from 3-5 successive intervals. Some of these sets have exceptionally low entropy and thus seem to be especially meaningful as a set ('word') to the brain.