Influence of contralateral noise stimulation on wave I of the ABR, elicited with condensation and rarefaction clicks in humans

Sound‐evoked efferent effects can be examined by comparing the response amplitudes of the auditory nerve with and without contralateral stimulation. It has been suggested that the efferent system modifies the mechanical characteristics of the cochlear partition by varying outer hair cell tonus and regulating the mean position of the basilar membrane [E. L. LePage, Hear. Res. 38, 177–198 (1989)]. If this is the case, the effect of contralateral stimulation may be different for responses elicited with clicks of opposite polarity (condensation versus rarefaction), as such stimuli cause initial movement of the basilar membrane either toward scala tympani or scala vestibuli. Furthermore, such stimuli are known to elicit dissimilar ABR waveforms [V. Rawool and S. Zerlin, Stand. Audiol. 17 (1988)]. Results of the surface recorded wave of the ABR obtained from human subjects, with and without contralateral noise, for rarefaction and condensation clicks as well as the possible underlying mechanisms will be presented.