Stochastic Resonance (SR) is a phenomenon, mainly present in nonlinear detection systems,
in which the addition of certain amount of noise, called optimal noise, has proven to
enhance detection performance of subthreshold stimuli. When added noise is present only
during the stimulus, an additional enhancement can be reached. This phenomenon was
called time Coincidence Enhanced Stochastic Resonance (CESR). The aim of this study
was to study the effect of spatially distributed vibrotactile noise in subthreshold stimuli detection.
The correct response rates from two different stimuli conditions were compared, using
four tactile stimulator systems to excite four different spatial locations on the fingertip. Under
two different conditions, the stimuli were present in only one randomly chosen stimulator.
For the first condition, all stimulators contain optimal noise level. In the second condition, the
optimal noise was present only at the stimulator with the stimulus. SR threshold principle
should not produce different correct response rates between the two conditions, since in
both cases the noise enables the subthreshold stimulus to go above threshold. The stimulus
signal used was a rectangular displacement controlled pulse that lasted 300ms within a 1.5s
attention interval, applied to the exploratory zone of the index finger of 13 human subjects.
For all subjects it was found that detection rates were better (p<0.0003) when noise was
spatially coincident with the stimulus, compared to the condition in which noise was present
simultaneously in all the stimulators. According to our literature review this is the first report
of SR being influenced by the spatial location of the noise. These results were not found previously
reported, so represent the discovery of a new phenomenon. We call this phenomenon
Spatial-Coincidence-Enhanced Stochastic Resonance (SCESR). As results show, the
optimal noise level is dependent on the relative position between stimulus and noise.
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Patrocinador
dc.description.sponsorship
Fondecyt grant No.1080593 and by the Department of
Electrical Engineering, Universidad de Chile.