Eye Movement-Related Eardrum Oscillations (EMREOs) Occur without Visual Input But Are Reduced during Closed Eyelids

Recent investigations have shown that the tympanic membranes exhibit synchronous oscillations with each saccadic eye movement (Gruters et al., 2018), a phenomenon known as eye movement-related eardrum oscillations (EMREOs). However, the dependence of these saccade-associated EMREOs on ongoing visual activity remains to be elucidated. Given the direct projections from motor areas to primary auditory and visual cortices and the observation that EMREOs' onset occurs concurrently with, or even precedes, saccades, we hypothesized that EMREOs would persist in the absence of visual stimulation. This report presents a study wherein 16 healthy male and female participants executed horizontal saccades under three distinct conditions: (1) in a well-lit environment, (2) in a darkened environment with eyes open, and (3) in a darkened environment with eyes closed. Ocular movements were quantified via electrooculography, and tympanic membrane oscillations were registered using in-ear microphones. The results demonstrated the presence of EMREOs concurrent with both visually guided and memory-guided saccades, although a late minor reduction in amplitude was observed in the "dark with open eyes" condition. Significant attenuation of EMREOs was evident when participants performed saccades with their eyelids closed, despite maintaining the same saccade amplitude and initial velocity. This amplitude reduction may reflect modulations in cortical states associated with predictive coding.