Some aspects of low‐frequency neural and cochlear microphonic tuning curves

Abstract

Tuning curves of single auditory nerve fibers of the Mongolian gerbil (Meriones unguiculatus) have been compared to cochlear microphonic (CM) tuning curves corrected for the electrical filtering effect of the cochlea. Results indicate that CM tuning in the second and third turns is similar to the tuning of fibers whose characteristic frequencies (CF's) correspond to the CM best frequencies (2.5 and 0.5 kHz). Accordingly, little sharpening seems to take place for fibers with low CF's. The CM tuning curve recorded from the most apical position is sharper than expected for frequencies below the best frequency. The low‐frequency sharpening probably arises from the shunting effect of the helicotrema. Modeling results have confirmed that the mechanical impedance of the helicotrema can exert an appreciable effect on basilar‐membrane tuning in the apical regions.