The Journal of Neuroscience, March 15, 2003, 23(6):1997
BRIEF COMMUNICATION
Stochastic Resonance within the Somatosensory System: Effects of
Noise on Evoked Field Potentials Elicited by Tactile Stimuli
Elías
Manjarrez,
Gerardo
Rojas-Piloni,
Ignacio
Méndez, and
Amira
Flores
Instituto de Fisiología, Benemérita Universidad Autónoma de
Puebla, Puebla, Pue CP 72570, México
Stochastic resonance (SR) is commonly understood to be the
enhancement, by noise, of the response of a system to a weak input signal. The aim of this study was to demonstrate the occurrence of SR
in spinal and cortical evoked field potentials (EFPs) elicited by
periodic tactile stimuli in the anesthetized cat. The electrodes were
positioned in spinal and cortical somatosensory regions in which the
largest negative EFPs were detected. The periodic tactile stimuli
consisted of local skin displacements on the central pad of the
hindpaw. Two series of experiments were performed. First, periodic
tactile stimuli and the noisy tactile stimuli were applied with the
same indenter. Second, noisy tactile stimuli were applied with an
additional indenter placed on the glabrous skin of the third hindpaw
digit. This last protocol ensured that the signal and noise were mixed
not in the skin but in the somatosensory regions of the CNS. All cats
showed distinct SR behavior at the spinal and cortical stages of the
sensory encoding. Such SR was abolished in the cortical but not in the
spinal recording after sectioning of the dorsal columns and the
ipsilateral dorsolateral funiculus. This suggests that the spinal
neurons may also contribute to the SR observed at the cortical level.
To the best of our knowledge, this is the first documented evidence
that such a remarkable phenomenon embodies electrical processes of the
spinocortical somatosensory system itself.
Key words:
noise; tactile; information capacity; stochastic
resonance; somatosensory; evoked potentials
Copyright © 2003 Society for Neuroscience 0270-6474/03/2361997-05$05.00/0