Perception of tactile vibrations and a putative neuronal code

We devised a delayed comparison task, appropriate for human and rats, in which subjects discriminate between pairs of vibration delivered either to their whiskers, in rats, or fingertips, in humans, with a delay inserted between the two stimuli. Stimuli were composed of a random time series of velocity values (“noise”) taken from a Gaussian distribution with 0 mean and standard deviation referred to as σ1 for the first stimulus and σ2 for the second stimulus. The subject must select a response depending on the two vibrations’ relative standard deviations, σ1>σ2 or σ1