RT Journal Article
SR Electronic
T1 Ambiguous Pitch and the Temporal Representation of Inharmonic Iterated Rippled Noise in the Ventral Cochlear Nucleus
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 11925
OP 11938
DO 10.1523/JNEUROSCI.3137-08.2008
VO 28
IS 46
A1 Mark Sayles
A1 Ian M. Winter
YR 2008
UL http://www.jneurosci.org/content/28/46/11925.abstract
AB Neural coding of the pitch of complex sounds is vital for animals' ability to communicate and to perceptually organize natural acoustic scenes. Harmonic complex sounds typically have a well defined pitch corresponding to their fundamental frequency, whereas inharmonic sounds can exhibit pitch ambiguity: their pitch can have more than one value. Iterated rippled noise (IRN), a common “pitch stimulus,” is generated from broadband noise by a cascade of delay-and-add steps, with the delayed noise phase-shifted by φ degrees. By varying φ, the (in)harmonicity, and therefore the pitch ambiguity, of IRN can be manipulated. Recordings were made from single-units in the ventral cochlear nucleus of anesthetized guinea pigs in response to IRN and complex tones, systematically varying the inharmonicity. In their all-order interspike interval distributions, primary-like and chopper units tuned within the phase-locking range of best frequencies represent the waveform temporal fine structure (which varies with φ). In contrast, those units tuned to higher frequencies represent the temporal-envelope modulation (independent of φ). We show a temporal representation of ambiguous pitch for IRN and complex tones based on responses to the stimulus fine structure. Within the dominance region for pitch this representation follows the predictions of classic human behavioral experiments and provides a unifying contribution to possible neuro-temporal explanations for the pitch shift and pitch ambiguity associated with many inharmonic sounds.