Dynamic noise and visual stimuli with cognitive content: A neuromagnetic experiment of stochastic resonance in human vision

Meaningful words embedded in dynamic noise and presented visually to human volunteers in a "threshold stochastic resonance" [threshold-SR model] stimulus paradigm evoke cortical brain responses. The source equivalents identified by neuromagnetic methods (306-channel MEG system, Elekta Neuromag) indicate sequential activation of the primary and associative visual cortex and of cortical areas involved in language processing. The topography of identified dipoles was common to all subjects, with the dipole latency/amplitude measures fitting the contrast-to-noise function of the word+noise threshold-SR stimuli regardless of activated cortical sites. This observation suggests that the "threshold-SR" stimulus function can be transferred across activated brain structures dedicated to visual and language processing, with the conceivable involvement of basic neuronal mechanisms.