Responses of single units in the cat cochlear nucleus to sinusoidal amplitude modulation of tones and noise: linearity and relation to speech perception

Responses to the sinusoidal modulation envelopes of amplitude-modulated tonend noise carriers were recorded from single units in the cochlear nucleus of the cat. The unit discharges were synchronized to the peaks of the modulation envelope. Population-averaged firing rate were independent of the modulation index of the stimulus. Temporal firing patterns, as represented by the shapes and magnitudes of modulation-cycle histograms, were strongly dependent on stimulus intesity and modulation index. Nonlinear nonsinusoidal responses to sinusoidal modulation envelopes were observed, but only at high values of sound intensity. These and other results are discussed in the context of psychological studies concerning the perception of speech information.