Abstract
It has been shown that the Stochastic Resonance (SR) phenomenon occurs in different macro, micro and nano systems. From the cyclic recurrence of ice ages, bistable ring lasers, electronic circuits, superconducting quantum interference devices and neurophysiological systems such as receptors in animals. It has been extended to human sensory systems such as auditory, visual, proprioceptive and tactile mechanisms. Regardless of the demonstration of its presence in human sensory systems, there have been no direct demonstrations of cross-modal SR-based interactions in the human cortex. Here we report evidence of cortically based cross-modal effects of stochastically induced transitions. In previous experiments we demonstrated that introducing auditory noise significantly improved tactile sensations of the finger and EMG recordings of the leg muscles and the sweep area of stabilograms during posture maintenance. In the present experiments we presented different levels of auditory broadband noise while observers discriminated between vertical or horizontal luminance and contrast defined sinusoidal gratings. As in our previous auditory-tactile or auditory-proprioceptive experiments, the visual sensitivity profiles of the observers varied as a function of the different auditory noise levels demonstrating a typical SR function with zones of sensitivity values significantly different from baseline (no auditory noise condition). Our results show clear evidence that a stochastic synchronization-like phenomenon is present in the human cortex and that the added signals act upon the multi-sensory integration system creating a state that enhances functionality.
NSERC-Essilor Industrial Research Chair