GENDER DIFFERENCES IN COCHLEAR RESPONSE-TIME - AN EXPLANATION FOR GENDER AMPLITUDE DIFFERENCES IN THE UNMASKED AUDITORY BRAIN-STEM RESPONSE

Derived narrow-band auditory brain-stem responses (ABRs) in young norm al-hearing subjects revealed a significant gender difference in respon se time between frequency regions of the cochlea. Females showed short er delays than males between derived bands. This differential has not been previously reported. As in many early studies, the unmasked ampli tude of the wave V complex was significantly larger (30%) in females t han males. However, differences in amplitudes of the narrow-band respo nses were too small to account for the differential in the unmasked re sponse. It is hypothesized that the larger amplitude of the unmasked w ave V complex in females occurs because of a faster response time acro ss the cochlea leading to better neural synchrony and, therefore, larg er amplitudes. Furthermore, results can be explained by assuming that the stiffness gradient in the cochlea is 13% larger in females than in males. If males and females have the same cochlear tonotopic mapping, the female cochlea should be 13% shorter. This prediction is highly c onsistent with recent anatomical studies of cochlear length and gender . The results of the present study indicated possibly important cochle ar mechanisms that influence the main parameters of ABRs. An understan ding of these cochlear mechanisms may improve the diagnostic capabilit ies of ABRs in patients with peripheral hearing loss.