Dynamics of pitch perception in the auditory cortex

The ability to perceive pitch allows human listeners to experience music, recognize the identity and emotion conveyed by conversational partners, and make sense of their auditory environment. A pitch percept is formed by weighting different acoustic cues (e.g., signal fundamental frequency and inter-harmonic spacing) and contextual cues (expectation). How and when such cues are neurally encoded and integrated remains debated. In this study, twenty-eight participants listened to tone sequences with different acoustic cues (pure tones, complex missing fundamental tones, and ambiguous mixtures), placed in predictable and less predictable sequences, while magnetoencephalography was recorded. Decoding analyses revealed that pitch was encoded in neural responses to all three tone types, in the low-to-mid auditory cortex, bilaterally, with right-hemisphere dominance. The pattern of activity generalized across cue-types, offset in time: pitch was neurally encoded earlier for harmonic tones (∼85ms) than pure tones (∼95ms). For ambiguous tones, pitch emerged significantly earlier in predictable contexts, and could be decoded even before tone onset. The results suggest that a unified neural representation of pitch emerges by integrating independent pitch cues, and that context alters the dynamics of pitch generation when acoustic cues are ambiguous.