Structural changes in auditory hairs during temporary deafness

The stereocilia of auditory hair cells were examined with a scanning electron microscope during periods of noise-induced temporary threshold shift. The stereocilia in the tallest row of each tuft of the noise-exposed ears were clumped together compared with control ears. This suggests to us that clumping of the longest stereocilia might be a reversible mechanism of the hair cell to protect itself from overstimulation. The rate of recovery following exposure to noise was monitored by measuring the first neural component of the cochlear potential response. The duration of the noise was adjusted to ensure sufficient time to fix the ears during the period of temporary deafness. Alcian blue was added to the fixative to preserve the glycocalyx of the stereocilia. The experiments were done in the basal region of the auditory organ of the alligator lizard. This region is characterized by hair cells with long free-standing stereocilia.