Increases in spontaneous activity in the dorsal cochlear nucleus of the rat following exposure to high-intensity sound.

The effects of intense sound exposure on neural activity in the dorsal cochlear nucleus (DCN) were studied in the rat. Seventeen anesthetized adult rats were exposed to a 10-kHz tone at 125-130 dB SPL for 4 h. Fourteen unexposed rats served as controls. Spontaneous activity (SA) and neural thresholds at the characteristic frequency were measured in three rows of 8-12 sites along the mediolateral, tonotopic, axis of the DCN surface 27-61 days after exposure. The results showed that intense tone exposure induced chronic increases in SA. This hyperactivity was found to be distributed broadly across the DCN with an emphasis around the 10-kHz locus and was associated with shifted response thresholds. These findings demonstrate the usefulness of the rat for studies of physiological phenomena related to noise-induced tinnitus and hearing loss.