Behavioral, compound action potential, and single unit thresholds: Relationship in normal and abnormal ears

Abstract

Comparisons were made for 2 spp. (chinchilla and mongolian gerbil) among mean behavioral audiogram, mean just detectable action potential (AP) responses to tone bursts and single-fiber response thresholds at the characteristic frequency, averaged in 1-octave bands. In normal animals and in a group of Kanamycin-treated chinchillas, these mean measures appeared to have a well-ordered relationship. Unit and AP thresholds were within 10 dB from one another throughout the frequency range. Behavioral thresholds were usually 15-20 dB more sensitive, but the 3 curves were roughly parallel except at the highest frequencies, where the behavioral threshold began to increase approximately 1/2 octave above the physiological ones. Individual examples for 4 gerbils and 4 chinchillas having hair cell losses due to Kanamycin intoxication reinforced the notion based on mean data that in most cases AP thresholds can predict the behavioral threshold configuration.