Development of human cochlear function

Abstract

The time course for functional development of the human cochlea is not clear. The advent of otoacoustic emissions (OAE) methodology has made it possible to noninvasively probe cochlear function in humans. Distortion product OAE isosuppression tuning curves indirectly reflect cochlear frequency selectivity. They are generated by presenting a third suppressor tone simultaneously with the stimulating tones f1 and f2 and increasing the level of the suppressor until a criterion amount of suppression is achieved. When the suppressor level required to achieve criterion reduction in DPOAE amplitude is plotted as a function of frequency, a DPOAE suppression tuning curve (STC) can be generated. DPOAE (2f1−f2) STCs have been generated in adults and neonates to investigate development of cochlear tuning in humans [Abdala et al. (1996); Abdala and Sininger (1996)]. Results of these studies suggest that the human cochlea is resolving frequency in an adultlike fashion by term birth. Other findings also support this contention [Bargones and Burns (1988); Eggermont et al. (1996)]. However, results of a recent study conducted with very premature neonates [Abdala (1997)] suggest that STC width and growth of suppression is not adultlike in premature neonates. These results may be indicative of cochelear immaturity just prior to term birth.