Discharge Rates of Single Auditory‐Nerve Fibers as Functions of Tone Level

Plots of firing rate versus stimulus level were obtained for single auditory‐nerve fibers in anesthetized cats with cut middle‐ear muscles. For tones, the shape of the rate‐versus‐SPL curve for a given fiber varies considerably with frequency. For some frequencies, the curves are monotonic; for others, there is a rise followed by a dip that may go down to the spontaneous rate. Within a 10‐dB range following the dip, the response rate rises to a maximum. Dips have been found for units over a wide range of characteristic frequency (CF). Although dips can be found for frequencies at or above a unit's CF, the lowest SPL at which dips occur is always at frequencies below CF. At high stimulus levels (above 90 dB SPL) where dips occur, responses of units with low CF show large phase changes relative to the stimulus. [Supported by NIH grants and the Joint Services Electronics Program.]