Shared and distinct representational dynamics of phonemes and prosody in ventral and dorsal speech streams

Phonemes and prosodic contours are fundamental building blocks of speech used to convey complementary meanings. Perceiving these elements is thought to involve a neural abstraction from acoustic to categorical representations, occurring serially in time and segregated in space. Using magnetoencephalography and behavioural psychophysics combined with time-resolved representational similarity and multivariate transfer entropy analyses, we show that the abstraction of phonemic and prosodic information does not fully align with this serial hierarchical processing. Instead, we found partially overlapping acoustic and categorical representations in space and time, for both elements. Notably, building on similarly organised acoustic representations along the ventral stream, categorical representations of prosody extended to right premotor cortex along the dorsal stream, whereas those of phonemes focally involved posterior temporal regions. These results highlight shared principles of joint and distributed processing, yet partially distinct mechanisms for the abstraction of phonemes and prosody, key to access the multilayered meaning of speech.