The Role of Tuning Curve Variables and Threshold Measures in the Estimation of Sensory Cell Loss

Abstract

Auditory-evoked potential tuning curves were collected at six frequencies before and 30 days after various noise exposures in 363 chinchillas using a simultaneous masking paradigm. Traditional bivariate and multiple linear regression/correlation analyses were performed in an effort to determine the extent to which sensory cell damage could be estimated from a knowledge of audiometric and tuning curve variables. The results showed strong correlations between percent outer hair cell (%OHC) loss and permanent threshold shift (PTS) and between %OHC loss and the tuning curve variables Q_{10 dB} and high- and low-frequency slopes (S_HF, S_LF). The correlations were strongest between PTS and %OHC loss. However, the proportion of variability (r²) in %OHC loss attributable to variability in the predictor variable(s) (i.e., PTS) could be increased significantly by adding the Q_{10 dB} of the tuning curve whose probe frequency was centered in the octave band length of the cochlea corresponding to the frequency at which the PTS occurred. The r² values could be further increased by including audiometric and tuning curve variables from frequencies adjacent to the octave band being evaluated.

Key Words:

• Tuning curve
• Sensory cell loss
• Threshold shift
• Evoked potentials
• Frequency selectivity