Research findings challenge long-held assumptions about how we learn or regain speech
Learning to speak a new language,聽or聽regaining speech,聽depends more on聽areas of聽the brain聽that聽process聽sound and physical sensation than on聽the聽parts of the聽brain that聽govern聽motor control,聽according聽to new research findings.聽
The聽study,聽by聽researchers at聽91黑料网 and the Yale School of Medicine,聽has聽implications for speech-learning theory and聽for聽the聽development of聽speech processing and recognition technologies.聽
Until now, learning and remembering聽the聽movements of the聽face聽and mouth聽underlying the ability to speak聽was聽widely thought to depend on motor regions of the brain. The new findings challenge that assumption, pointing instead to the聽central role聽of auditory and somatosensory systems.聽
鈥淪ensorimotor neuroscience has traditionally focused on frontal motor areas as the principal drivers of movement. This study changes that understanding by showing that human聽speech聽learning is extensively sensory in nature,鈥� said聽David Ostry, Professor of Psychology at 91黑料网.聽
The findings could support聽new approaches聽to聽emerging聽brain-speech technologies聽that聽could聽restore speech聽after a聽stroke, for example,聽by encouraging the integration of sensory processes to improve functionality and聽ease聽of聽use.聽
Retention tested through brain stimulation聽
To聽test聽the role of sensory brain regions in聽learning聽and聽retaining聽speech movements,聽researchers altered participants鈥� speech in real time and fed it back through headphones, inducing聽speech聽motor聽learning.聽
Next, transcranial magnetic stimulation (TMS), a non-invasive brain stimulation technique, was used to disrupt neural activity in key speech areas of the brain: the auditory cortex, the somatosensory聽cortex聽and the motor cortex. Retention was tested 24 hours later.聽
The researchers hypothesized that if a brain area聽was聽critical for聽acquiring聽and聽retaining聽the聽ability to speak, disrupting it would impair retention; if it聽was聽not, retention would be unaffected.聽
They found that disrupting activity in the sensory cortex聽鈥撀爀ither auditory or somatosensory聽鈥撀爏ignificantly impaired participants鈥� ability to聽retain聽newly learned speech movements, while disrupting聽the motor cortex did not.聽
鈥淥ur study challenges the assumption that new speech memories are solely reliant on changes in motor areas of the brain. Instead, it underscores the importance of changes in auditory and somatosensory brain areas in shaping how we learn to speak,鈥� said study co-author Nishant Rao, Associate Research Scientist at Yale University.聽
The role of brain plasticity聽
The study is part of a broader research program examining how plasticity in the brain鈥檚 sensory systems supports motor learning and memory retention. It complements recent studies from the group on upper-limb movement, which show that disrupting the sensory cortex impairs learning and retention of new movements.聽
Future research will map the cortical brain circuits involved in learning and explore sensory interventions for the treatment of movement disorders, particularly stroke rehabilitation.聽
About this study聽
鈥�,鈥� by聽Nishan Rao,聽Rosalie Gendron, Timothy Manning and聽David聽Ostry, was published in聽Proceedings of the National Academy of Sciences of the United States of America.聽
The research was funded by聽the聽(U.S.)聽National Institute on Deafness and Other Communication Disorders.聽