EFFECT OF SLEEP STAGES ON TRANSIENTLY EVOKED OTOACOUSTIC EMISSIONS ININFANTS

Transiently evoked oto-acoustic emissions (TEOAEs) are generated by ac tive contractions of the outer hair cells (OHC) of the organ of Corti. TEOAE are inhibited by the medial efferent olivocochlear system which originates in the brainstem and innervates the OHC. TEOAEs are a rapi d non-invasive objective method of auditory screening in infants. Beca use in infants sleep represents 75% of their time, it was of interest to determine whether sleep stages which are induced in the brainstem c ould concomitantly affect TEOAEs. Repeated TEOAE recordings during pol ygraphic recordings of sleep stages were made on seven, 6-week-old inf ants. Results showed that: (i) TEOAE spectrum frequency components rem ained stable over sleep stages; (ii) TEOAE amplitude tended to increas e during recording sessions; (iii) sleep stages (quiet, active and ind eterminate sleep) did not affect TEOAE amplitude. This pilot study rev eals that sleep mechanisms seem to have no effect on active OHC microm echanical properties. Therefore, in auditory screening, TEOAEs may ser ve to study active cochlear mechanisms in infants even during sleep wh ich is the better time to perform recordings because of the quietness required.