Abnormal peripheral auditory asymmetry in schizophrenia

Objective-Auditory processing difficulties have been reported in schizophre nia. This study explores peripheral auditory function in patients with schi zophrenia in whom certain early disturbances of auditory message filtering have been found and may be associated with certain abnormalities which are particularly localised in the left temporal lobe. Methods-Otoacoustic emissions, including click evoked and spontaneous emiss ions and measurements of functioning of the medial olivocochlear efferent s ystem were obtained from 12 chronic schizophrenic patients and compared wit h normative data recorded from 12 normal controls. Results-Otoacoustic emission amplitudes and medial olivocochlear functionin g were similar between the normal controls and schizophrenic patients; the schizophrenic patients did, however, differ from the normal controls in oto acoustic emission intensity and in medial olivocochlear asymmetry. A tenden cy to a higher number of spontaneous peaks, and a significantly higher clic k evoked otoacoustic emission response amplitude were found in the right ea r compared with the left ear of schizophrenic patients. For the medial, oli vocochlear system, whereas normal controls showed greater attenuation in th e right than in the left ear, schizophrenic patients lacked such an asymmet ry. Conclusion-In the absence of any attention task, the findings show disturbe d peripheral lateralisation in schizophrenia of mechanisms involved in audi tory information filtering. Such a lack of right ear advantage in medial ol ivocochlear functioning may thus be a peripheral reflection of central late ralisation anomalies.