Sensorimotor dynamics differentiate singing and speaking

Area of Science:

• Neuroscience
• Speech and Hearing Sciences
• Music Cognition

Background:

• Clinical observations show a dissociation between singing and speaking abilities in individuals with neurological conditions.
• The underlying neural mechanisms for preserved singing in the presence of speech deficits remain largely unknown.

Purpose of the Study:

• To investigate the neural dynamics of singing versus speaking in the sensorimotor cortex (SMC).
• To elucidate the brain mechanisms underlying the dissociation between singing and speaking.

Main Methods:

• Recorded intracranial electroencephalography (EEG) in neurosurgical patients producing matched sentences by singing and speaking.
• Analyzed high-frequency activity (70-150 Hz) and mu-band (∼10 Hz) synchrony across bilateral SMC.
• Utilized frequency-domain Granger-Causality to assess directional influence between brain regions.

Main Results:

• High-frequency activity showed opposite lateralization: right-dominant for singing, left-dominant for speaking.
• Mu-band synchrony revealed distinct temporal dynamics, with speaking showing left-led patterns and singing demonstrating progressive interhemispheric recruitment.
• Causality analysis indicated left primary somatosensory cortex drives both motor cortices during speech, while singing involves bilateral control.

Conclusions:

• Singing and speaking engage dissociable sensorimotor network dynamics.
• A bilaterally coordinated SMC pathway for singing may underlie preserved vocalization in individuals with speech impairments.