Influence of auditory stimulation and visual attention on otoacoustic emissions.

Transient Evoked otoacoustical Emissions (TEOAEs) express the micromechanical activity of the cochlear outer hair cells (OHCs). The inhibitory effects of contralateral acoustic stimulation and of visual attention tasks on TEOAE amplitude is well-established. Contralateral auditory stimulation and attention affect cochlear micromechanics via the medial olivocochlear efferent system. The present study is a quantitative comparison of the individual and combined effects of these two inhibitory phenomena in the same subjects. TEOAEs were recorded in seven normal-hearing subjects in absence of inhibitory stimulus (S1), under contralateral 95 dB SPL white-noise stimulation (S2), during a visual attention task (S3) and with simultaneous presentation of both forms of stimulus (S4). Significant reductions in TEOAE amplitude were found with contralateral stimulation (S2) and visual attention (S3) (p = 0.01 and 0.05 respectively, in confirmation of previous studies. The inhibitory effect of combined stimulation (S4) was found to be yet more significant (p = 0.004) than the inhibition obtained with each stimulation presented alone.