Spatio-temporal representation of the pitch of complex tones in the auditory nerve

Although pitch is a fundamental auditory percept that plays an important role in music, speech, and auditory scene analysis, the neural codes and mechanisms for pitch perception are still poorly understood. In a previous study (Cedolin and Delgutte 2005), we tested the effectiveness of two classic representations for the pitch of harmonic complex tones at the level of the auditory nerve (AN) in cat: a rateplace representation based on resolved harmonics and a temporal representation based on pooled interspike-interval distributions (a.k.a. autocorrelation). Both representations supported precise pitch estimation in the F0 range of cat vocalizations (500-1000 Hz), but neither was entirely consistent with human psychophysical data. Specifically, the rate-place representation failed to predict the existence of an upper limit for the pitch of missing-F0 complex tones (Moore 1973). The rateplace representation also degrades rapidly with increasing sound level, in contrast to the relatively robust pitch discrimination performance. The interval representation did not account for the greater salience of pitch based on resolved harmonics compared to pitch based on unresolved harmonics (Carlyon and Shackleton 1994). Here, we investigate an alternative, “spatio-temporal” neural representation of pitch, which may combine the advantages and overcome the limitations of the traditional rate-place and interval representations.