They conducted an experiment in which participants learned to pronounce altered sounds that were played back to them through headphones. This forced the brain to adapt its speech. Then, using transcranial magnetic stimulation (TMS), the researchers temporarily suppressed activity in three key areas: the auditory cortex, the somatosensory cortex, and the motor cortex.
The results were unexpected. When the auditory or somatosensory cortex was “switched off,” participants were significantly worse at retaining the new speech patterns the next day. Disabling the motor cortex had almost no effect on the outcome.
Conclusion: speech learning and memory are more sensory than motor in nature. The brain relies more on how speech sounds and feels than on precise commands to the muscles.
The discovery has practical implications. It may improve speech therapy after stroke, help develop more effective brain-computer interfaces, and change our understanding of how speech skills are formed in children and adults.