Evidence for a cortically mediated release from inhibition in the human cochlea.

PURPOSE To determine cortical influence on the efferent medial olivocochlear bundle system. RESEARCH DESIGN The effects of attention on contralateral suppression (CS) of click-evoked otoacoustic emissions were measured. STUDY SAMPLE Fifteen normal-hearing listeners. RESULTS CS was greatest in the nonattending condition and decreased significantly when attending to the click or broadband noise suppressor. The effects of attention on CS were not frequency dependent or due to changes in recording noise measures. CONCLUSIONS Attention to either the ipsilateral, evoking stimulus or the contralateral suppressor causes a top-down, cortically mediated release from inhibition at the level of the cochlea that is measurable with common audiologic protocols and instrumentation. Future studies assessing the effects of attention on CS of click-evoked otoacoustic emissions in normal controls and individuals with various auditory or attentional deficits may provide valuable information about the capabilities of the cortex to affect peripheral processing in a normal and/or pathological system.