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 interharmonic spacing) and contextual cues (expectation). How and when such cues are neurally encoded and integrated remains debated. In this study, 28 participants (16 female) listened to tone sequences with different acoustic cues (pure tones, complex missing fundamental tones, and tones with an ambiguous mixture), 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 and sensorimotor 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 ('85 ms) than pure tones ('95 ms). For ambiguous tones, pitch emerged significantly earlier in predictable contexts than in unpredictable. 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.