Correlations between cochlear hair cell loss and shifts of masked and absolute behavioral auditory thresholds in the...

Masked and absolute behavioral auditory thresholds were measured in kanamycin-treated C3H mice with a significant damage or loss of outer hair cells (OHCs) near the cochlear base, and in 17--24-month-old NMRI mice with a significant loss of OHCs and inner hair cells (IHCs) in the basal region and of OHCs near the apex. A loss of IHCs is correlated with an increase in absolute thresholds. A moderate damage or loss of OHCs in a cochlear region had no effect on absolute thresholds but correlated with a decrease and other changes of characteristics of masked thresholds in the respective frequency regions. OH C-damage makes masking by continuous white broad-band noise less efficient. It is concluded that masking and critical bands depend on the function of OHCs, which must be assumed to influence intracochlearly the activity of IHCs in processing the information to the brain.