Contralateral Suppression of Distortion Product Otoacoustic Emission in Children with Auditory Processing Disorders

Previous research has demonstrated that the amplitude of evoked emissions decreases in human subjects when the contralateral ear is stimulated by noise. The medial olivocochlear bundle (MOCB) is believed to control this phenomenon. Recent research has examined this effect in individuals with auditory processing disorders (APD), specifically with difficulty understanding speech in noise. Results showed transient evoked otoacoustic emissions (TEOAEs) were not affected by contralateral stimulation in these subjects. Much clinical research has measured the function of the MOCB through TEOAEs.This study will use an alternative technique, distortion product otoacoustic emissions (DPOAEs), to examine this phenomenon and evaluate the function of the MOCB. DPOAEs of individuals in a control group with normal hearing and no significant auditory processing difficulties were compared to the DPOAEs of children with significant auditory processing difficulties.Results showed that the suppression effect was observed in the control group at 2 kHz with 3 kHz of narrowband noise. For the auditory processing disorders group, no significant suppression was observed.Overall, DPOAEs showed suppression with contralateral noise, while the APD group levels increased overall.These results provide further evidence that the MOCB may have reduced function in children with APD.