Influence of cortical inhibition on auditory efferents in humans

Abstract

Auditory activity in humans is influenced by feedback networks in the brain. The final leg of this pathway originates in the brainstem and plays an important role in protecting and aiding communication in competing noise. Previous studies have used auditory and/or visual attention tasks to manipulate cortical activity when exploring its influence on the periphery via the auditory efferent system. Using subjective attention does not control for variability across individuals in attentional state, alertness, and arousal. Hence, a consensus on the relationship between cortical activity and how it influences more caudal efferent reflexes is still needed. Here we describe the first assay to non-invasively influence the human auditory cortex activity using repetitive transcranial magnetic stimulation and measure its consequence on peripheral structures using otoacoustic emissions. We hypothesized that depressing brain activity temporarily affects auditory functioning. By instigating a virtual cortical lesion in normal hearing participants, we were able to characterize the influence that the auditory cortex has on the sensory cells in the cochlea, mediated via the medial olivocochlear reflex. Our results will open avenues for further research into new diagnostic and therapeutic approaches for hearing disorders.