The influence of auditory stimulation on binocular rivalry

Binocular rivalry is an intriguing visual phenomenon which over recent decades has particularly engaged the interest of scientists. This phenomenon is induced when two different images are viewed, one by each eye, with alternations occurring between perceiving one image for a few seconds, followed by the other image for a few seconds. Thus, despite the constant sensory input, there are striking changes in perception. There are several extrinsic factors (e.g. stimulus variables such as contrast, colour, motion) that are well known to influence rivalry, however, much less work has been conducted on the effect of other extrinsic factors such as non-visual stimulation. Recent studies into multimodal influences (e.g. tactile, olfactory, auditory stimulation) on binocular rivalry indicate that interactions occur between the different senses; whereby there are significant changes in how often subjects perceive either of the presented images. The aim of the study was to further our understanding of the mechanisms involved in rivalry processing, with implications also for understanding how multiple and often conflicting stimuli from the environment are resolved in the human brain. For this purpose, the influence of auditory stimulation on binocular rivalry was explored using unilateral and bilateral auditory stimuli. The investigation was divided into two stages which differed in the frequencies of the auditory stimuli presented and the task involved subjects viewing vertical and horizontal gratings while indicating visual perception in the presence and absence of auditory stimulation. The present results indicate that auditory stimulation influences binocular rivalry, confirming the interaction between audio and visual perceptions. More specifically, the higher frequency (3000Hz) increased visual temporal rate and the perception of horizontal gratings to a greater extent than the lower frequency (1000Hz). The results further suggest that auditory stimulation can modulate the functional status of the cerebral hemispheres, and consequently impact the perception of visual stimuli. i i