Stability of auditory evoked potentials during simultaneous visual stimulation

Abstract

During sensory interaction, an accessory stimulus in a second modality can have a facilitating or inhibiting effect upon some measurable response to a stimulus applied to a primary modality. This study examined whether increased intensity of an accessory light stimulus facilitates or inhibits auditory evoked potentials to click stimuli. Click-evoked potentials were recorded from the round window (cochlear microphonic and auditory nerve), cochlear nucleus, and auditory cortex of unanesthetized cats, and measured before, during, and after simultaneous accessory light stimulation of different intensities. At all electrode sites, the mean peak-to-peak amplitudes of click-evoked potentials were not significantly different during simultaneous visual and auditory stimulation when compared with the pretest and posttest control periods of auditory stimulation. In addition, at all sites, the amplitude of the click-evoked potentials remained constant as accessory light stimulation was increased in intensity. The results suggest that sensory interaction effects do not occur when both the auditory and visual stimuli are irrelevant. If such effects do occur, they are so weak as to be undemonstrable for a wide range of visual stimulus intensities.