Discharge Rate as a Function of Stimulus Level for Tones or Noise in Cat Auditory-Nerve Fibers

Abstract

Discharge rate in response to noise bursts and tone bursts was measured for single fibers in the auditory nerve of anesthetized cats. Rate was plotted as a function of stimulus level (in decibels). In each experimental run, various levels of tone bursts at fiber characteristic frequency (CF) were presented in a random sequence with the same number of levels of noise bursts or tone bursts at an off-CF frequency. In this way, rate versus level functions for noise or off-CF tones could be compared with functions for CF tones measured during the same time period. In general, rate versus level functions for noise were less steep than those for CF tones; maximum rates evoked by noise were less than those evoked by tones at the CF. The slopes of rate versus level functions for tone bursts at frequencies greater than CF were generally a decreasing function of frequency. For frequencies less than the CF, slopes were approximately equal to those at CF. [Supported by the National Institutes of Neurological Diseases and Stroke and General Medical Sciences and the U. S. Air Force Office of Scientific Research.]