Transformation of speech sequences in human sensorimotor circuits

Area of Science:

• Neuroscience
• Cognitive Science

Background:

• Humans can mentally rehearse spoken words after hearing them.
• It remains unclear if this mental replay reactivates original perceptual brain dynamics.

Purpose of the Study:

• To investigate whether silent mental rehearsal of sentences involves reactivation of perceptual brain dynamics.
• To differentiate between reactivation and transformation of neural representations during speech perception and rehearsal.

Main Methods:

• Electrocorticography (ECoG) activity was recorded from the lateral cerebral cortex.
• Participants heard spoken sentences and then mentally rehearsed them.
• Neural responses were analyzed for sentence-specific representations during perception versus rehearsal.

Main Results:

• Sensorimotor and premotor cortex showed precise speech responses that transformed into distinct representations during rehearsal.
• Prefrontal and temporoparietal cortex exhibited less precise responses, with higher-order semantic representations shared between perception and rehearsal.
• Speech perception and mental rehearsal involve distinct neural processing.

Conclusions:

• Mental rehearsal of speech transforms stimulus-locked representations in sensorimotor and premotor areas.
• Higher-order semantic representations are reactivated across perception and rehearsal in prefrontal and temporoparietal regions.
• Neural mechanisms for speech recall involve both transformation and reactivation.