Effects of interaural time differences on the responses of chinchilla inferior colliculus neurons to consonant-vowel syllables

The responses of 100 inferior colliculus neurons to syllables differing in voice onset time (VOT) presented binaurally were studied. As in a previous study of monaural responses (Chen et al., 1996), the responses consisted of 1-3 response 'components', referred to as release responses, VOT responses or vowel responses. The discharge rate of all response components could vary cyclically with the interaural time difference (ITD). The maximal rate often occurred at an ITD around +0.2 ms (contralateral ear leading). Response frequencies (RF) based on the periodicity of the delay curves varied with the characteristic frequency (CF) and VOT. RF also varied across response components. Overall, RF was correlated with the 'most effective frequency', the spectral component with the highest amplitude, relative to the tuning curve. VOT response latency for a given syllable could change by a few ms with ITD, but those changes were small, relative to the range of latencies observed over the entire range of VOTs. Changes in ITD produced large changes in the overall shape of the peristimulus time histogram. There was no relation between the histogram shape and perceptual consonant categories.