Figure 3.

Despite threshold recovery, suprathreshold neural responses at high frequencies were permanently attenuated, although recovery of otoacoustic emissions suggests cochlear sensory cells are normal. b, d, At 8 weeks postexposure, suprathreshold amplitudes of ABR wave 1, the far-field response of the cochlear nerve, were less than half their preexposure values (d) in regions where temporary threshold shift was maximal (Fig. 2: 32 kHz), but recovered more completely (b) where initial shifts were less severe (Fig. 2: 12 kHz). a, c, In contrast, mean DPOAE amplitudes returned to normal by 8 weeks postexposure at both 12 kHz (a) and 32 kHz (c), suggesting complete recovery of OHC function, endolymphatic potentials, and cochlear mechanics. Together, these data suggest a primary loss of afferent innervation in the 32 kHz region. Group means ± SEMs are shown: n = 7–21 ears per group.