Sensorimotor dynamics differentiate singing and speaking

Singing and speaking often dissociate clinically-people who stutter can sing fluently, and individuals with aphasia and speech output problems from stroke may express sentences fluently in song-yet the neural mechanisms of this centuries-old clinical phenomenon remain unclear. We recorded intracranial EEG while neurosurgical patients produced matched sentences by singing or speaking, sampling millimeter- and millisecond-scale activity across bilateral sensorimotor cortex (SMC). During articulation, high-frequency activity (70-150 Hz) lateralized oppositely across behaviors, with right-dominant SMC activation for singing and left-dominant activation for speaking. Mu-band (∼10 Hz) synchrony further differentiated the dynamics: speaking showed an early left-led pattern, whereas singing exhibited a ramping of synchrony within the left sensorimotor cortex and between the two motor cortices, supporting progressive interhemispheric recruitment. Frequency-domain Granger-Geweke causality revealed that the left primary somatosensory cortex drives both motor cortices at speech onset. In contrast in singing, control over motor cortices relied on both hemispheres. These results provide evidence that song and speech rely on dissociable sensorimotor dynamics. This bilaterally coordinated SMC pathway may enable preserved singing in individuals with impaired speech output.