Frequency discrimination in noise: Comparison of cat performances with auditory-nerve models

Pure-tone frequency discrimination (AF) performances were measured in cats and compared to neural models of these AF performances based on auditory-nerve data in cats. Animal psychophysical techniques were used to train cats to discriminate frequency changes for pulsed pure tones in background noise at both 1.0 and 3.0 kHz. A go-left, go-right procedure was employed, and AF”s were measured in noise as a function of signal level at a constant signal-to-noise ratio. In contrast to human listeners, cats showed increases in AF at 1.0 kHz with increasing signal level. Model estimates of AF's based on rate responses in the cat auditory nerve predict increasing AFwith increasing signal level, the trendobserved in the cat psychophysical data. Model estimates of AF's based on temporal (phase-locking) properties in cat auditory nerve, on the other hand, predict decreases in AF that have been observed in previous data from human listeners [Dye and Hafter, J. Acoust. Soc. Am. 67, 1746–1753 (1980)]. These results suggest that for cats, average rate, rather than phase-locking, may be used by the central nervous system in performing frequency discrimination in background noise at 1.0 kHz. At 3.0 kHz cats showed little change in af sls a function of signal level, aresult similar to the trend for human listeners to show no change or slight increases in AFwith increases in signal level for tones in the 2- to 3-kHz range.