Neural responses to the onset of voicing are unrelated to other measures of temporal resolution

Voice onset time (VOT) is a temporal cue that can distinguish consonants such as /d/ from /t/. It has previously been shown that neurons' responses to the onset of voicing are strongly dependent on their static spectral sensitivity. This study examined the relation between temporal resolution, determined from responses to sinusoidally amplitude-modulated (SAM) tones, and responses to syllables with different VOTs. Responses to syllables and SAM tones were obtained from low-frequency neurons in the inferior colliculus (IC) of the chinchilla. VOT and modulation period varied from 10 to 70 ms in 10-ms steps, and discharge rates elicited by stimuli whose amplitude envelopes were modulated over the same temporal interval were compared. Neurons that respond preferentially to syllables with particular VOTs might be expected to respond best to the SAM tones with comparable modulation periods. However, no consistent agreement between responses to VOT syllables and to SAM tones was obtained. These results confirm the previous suggestion that IC neurons' selectivity for VOT is determined by spectral rather than temporal sensitivity.