Eye Movement-Related Eardrum Oscillations (EMREOs) Do Not Have a Direct Impact on Auditory Spatial Discrimination

Eye-movement-related eardrum oscillations (EMREOs) are acoustic signals recorded in the ear that are thought to reflect displacements of the tympanic membrane induced by saccadic eye movements. Speculations hold that their underlying mechanisms play a role in aligning visual and acoustic signals. Yet whether and how the eardrum moves during an EMREO remains unclear. Starting from the assumption that the EMREO signal directly reflects eardrum movements, we probed human sound lateralization performance for sounds presented at different times during a saccade, hence the EMREO. Since the EMREO generation involves the two middle ear muscles, whose tension can alter sound transmission, we expected spatial sound discrimination performance to vary with the state of the ERMEO at the time of sound presentation. We contrasted perceptual sensitivity, bias, and reaction times for targets presented during either positive/negative or during small/large EMREO deflections in two tasks, one relying on free-field sounds and one presenting sounds in-ear. However, no analysis revealed any significant effect. Still, and in line with previous studies, we found that sound localization performance was dependent on the congruency of saccade and acoustic target directions. We conclude that either the eardrum does not move as directly reflected by the EMREO signal, or it does so, but the underlying changes at the tympanic membrane only have minimal perceptual impact. These results call for more refined studies to understand how the eardrum moves during a saccade and whether or how the EMREO impacts auditory or multisensory perception.