Researchers at the Yale-affiliated Haskins Laboratories have uncovered a link between motor learning and sensory perception, a discovery that could help to treat motor disorders such as Parkinson’s disease. Scientists previously thought sensory and motor faculties developed and functioned independently, but the Haskins study, published Nov. 2 in the Proceedings of the National Academy of Sciences, shows otherwise.
“It only makes sense [that] speech motor learning affects auditory function,” Haskins researcher David Ostry said.
Ostry and fellow researcher Sazzad Nasir found that learning to speak a word under physical stress changed subjects’ auditory perception of that word.
Ostry and Nasir asked adult subjects to say “had” while a robot applied pressure to their jaw. As the subject repeated the word, he or she gradually adjusted to the pressure to say “had” correctly. Afterward, subjects listened to computer-generated words that sounded like a blend of “had” and “head.” The subjects were then asked to determine whether the words sounded more like “had” or “head.”
By comparing how the subjects classified the computer-generated words before and after the experiment, Ostry and Nasir found that subjects who were able to say “had” correctly under the robot’s pressure were more likely to identify the computer-generated words as “head” after the experiment. Subjects who did not learn to say “had” correctly under the robot’s pressure showed no difference when identifying the computer-generated words as “head” or “had” before the experiment as compared to afterward.
Ostry said neuroplasticity, or the brain’s ability to make new connections between nerve cells to adapt to a person’s habitual actions, was a likely explanation for the results. For the first time, Ostry explained, neuroplasticity was found to exist between motor nerve cells and sensory nerve cells specializing in hearing.
Ostry said the findings will aid the treatment of disorders and traumas related to impaired motor and sensory function. For example, he said, Parkinson’s disease affects both motor function and the senses. Understanding the biological basis behind a potential motor-sensory link in the brain may give scientists better insight into Parkinson’s disease and similar disorders.
In the future, Ostry said, he and Nasir hope to show that sensory learning affects motor function, the reverse of their current findings. Ostry said that this would let scientists treat motor disorders through the sensory areas of the brain.
Funding for the study came from the National Institute on Deafness and Other Communication Disorders, the Natural Sciences and Engineering Research Council of Canada and the Fonds Québécois de la Recherche sur la Nature et les Technologies.