A Temporal Code for Huggins Pitch?

Abstract

Periodic sound waves produce periodic patterns of phase-locked activity in the auditory nerve and in nuclei throughout the auditory brainstem. It has been suggested that this temporal code is the basis for our sensation of pitch. However, some stimuli evoke a pitch without monaural pitch information (temporal or otherwise). Huggins pitch (HP) is produced by presenting the same wideband noise to both ears except for a narrow frequency band which is interaurally decorrelated. “Complex” HP (CHP) can be produced by generating HP components at harmonic frequencies. The frequency-following response (FFR) is an electrophysiological measure of phase locking in the upper brainstem. The FFR was measured for a 300-Hz CHP in a 0-2 kHz noise, and a perceptually similar stimulus comprising a series of narrowband noise (NBN) harmonics of a 300-Hz fundamental presented in a 0-2 kHz background noise at different relative levels of NBN and background. The FFR measurements revealed a phase-locked response to the NBN harmonics, even for NBN stimuli with pitch salience below that of the CHP. Little evidence for phase locking to the CHP stimulus was found, although there was a weak component in the FFR at 300 Hz relative to neighboring frequencies. The results suggest that HP is not associated with an enhanced temporal response to the decorrelated frequency band at the level of the upper brainstem.