Responses of primary auditory fibers to transient sounds

Abstract

Responses of primary auditory fibers to clicks, short tone bursts, FM sweeps and consonant‐vowel syllables were obtained in the anesthetized cat. Tone‐burst responses depend on the fiber's characteristic frequency (CF). Fibers of high CF (above 10 kHz) responded to 2‐ms bursts with practically steady‐state frequency selectivity. Fibers with low CF (below 1 kHz) needed 10‐ms bursts to approach steady‐state rate selectivity. However, temporal encoding of the stimulus frequency was established in low‐CF fibers within 5 ms. Rapid establishment of temporal encoding is also characteristic of responses to the consonant‐vowel sounds: response patterns in successive 8‐ms epochs accurately reflected formant frequencies in those epochs. Responses to FM sweeps essentially encoded instantaneous stimulus frequency. The basic characteristics of click responses for any fiber were generally predictable by a minimum‐phase model derived from its threshold‐response curve. This model also generated realistic tone‐burst responses. Our evidence indicates that each primary fiber is a short‐term spectral analyzer whose transient behavior approximates that of a filter having its threshold‐response curve. [Work supported by NIH.]