Modulation of spontaneous otoacoustic emissions (SOAE) during auditory and visual attention

Otoacoustic emissions (OAEs) are faint, high frequency sounds elicited by the inner ear. They reflect fine-tuning of the basilar membrane, modulation of the cochlear amplification, and presumably attentional mechanisms in general. For evoked and distortion product OAEs it is well-established that they are reduced when attention is focused on the visual modality while there is a distractive acoustic stimulation. It is speculated that this decrease is top-down modulated by the auditory cortex via the auditory efferent pathway. In the past it was demonstrated that there is no attentional modulation of spontaneous OAEs (SOAEs). This study aims to investigate if SOAEs truly do not show any effects of intermodal attention modulation albeit the innervation of OHCs eliciting SOAEs is the same as for OHCs eliciting the other types of OAEs. The results revealed that SOAEs were decreased for periods of selective visual attention and distracting acoustic stimulation. Additionally, this is the first study simultaneously recording OAEs and magnetoencephalography to shed light on the cortical mechanisms that modulate SOAEs during selective attention. An explorative analysis demonstrated higher cortico-cochlear coherence for the auditory cortex when attention was shifted to the auditory modality. These findings indicate that SOAEs are modulated by attention processes.