SPEED, NOISE, INFORMATION AND THE GRADED NATURE OF NEURONAL RESPONSES

How the firing rate of a neuron carries information depends on the tim e over which rates are measured. For very short times, the amount of i nformation conveyed depends, in a universal way, on the mean rates onl y (trial-to-trial variability is irrelevant) and the cell response can be taken to be binary (although an ideal binary response would convey more). For longer times, noise as well as the graded nature of the re sponse come into play, with opposite effects. Which times can be consi dered 'short' varies with the brain area considered and, possibly, wit h the processing speed it is required to operate at.