A recent study from Northwestern University, in collaboration with the University of Pittsburgh and the University of Wisconsin-Madison, has unveiled new insights into how the brain processes speech. Published in "Nature Communications," the research identifies Heschl’s gyrus as a key region for interpreting subtle changes in pitch, known as prosody, which help convey emphasis and intent in conversation.
Previously, scientists believed that prosody was mainly processed by the superior temporal gyrus. However, Bharath Chandrasekaran, co-principal investigator and professor at Northwestern, noted that these findings challenge established notions about speech perception. "The results redefine our understanding of the architecture of speech perception," he said.
The study involved 11 adolescent patients undergoing neurosurgery for severe epilepsy. They had electrodes implanted deep within their brains to track activity while listening to an audiobook recording of “Alice in Wonderland.” Dr. Taylor Abel from the University of Pittsburgh highlighted the precision this method provided: “Typically, communication and linguistics research rely on non-invasive recordings from the surface of the skin... A collaboration between neurosurgeon-scientists and neuroscientists allowed us to collect high-quality recordings.”
Researchers observed that Heschl’s gyrus processes voice pitch changes not just as sound but as meaningful linguistic units. G. Nike Gnanataja from UW-Madison explained that these pitch patterns are encoded earlier than previously thought: “Our study challenges long-standing assumptions about how and where the brain picks up on natural melody in speech.”
The implications of this discovery are significant for fields such as speech rehabilitation and AI-powered voice assistants. Chandrasekaran stated that understanding early prosodic processing could lead to new interventions for various disorders and enhance AI-driven systems.
This study is titled “Cortical processing of discrete prosodic patterns in continuous speech” and was supported by several NIH grants along with funding from UW Madison.