That subtle rise in pitch when someone asks a question? The emphasis placed on certain words to convey importance? It turns out our brains process these vocal nuances much earlier—and in a different brain region—than scientists have believed for decades.
New research published March 3 in Nature Communications reveals that Heschl’s gyrus, a brain region previously thought to handle only basic sound processing, actually plays a sophisticated role in interpreting the melody of speech, technically known as prosody. This discovery challenges long-held assumptions about how our brains extract meaning from the way words are spoken.
“The results redefine our understanding of the architecture of speech perception,” said Bharath Chandrasekaran, the study’s co-principal investigator and professor and chair of the Roxelyn and Richard Pepper Department of Communication Sciences and Disorders at Northwestern University. “We’ve spent a few decades researching the nuances of how speech is abstracted in the brain, but this is the first study to investigate how subtle variations in pitch that also communicate meaning is processed in the brain.”
Electrodes in the Brain Reveal Hidden Processing
The multi-institutional study leveraged a rare research opportunity: access to 11 adolescent patients undergoing treatment for severe epilepsy who had electrodes implanted deep within their brains. This unique setup allowed scientists to record neural activity with unprecedented precision as participants listened to an audiobook of “Alice’s Adventures in Wonderland.”
“Typically, communication and linguistics research rely on non-invasive recordings from the surface of the skin, which makes it accessible but not very precise,” explained Dr. Taylor Abel, chief of pediatric neurosurgery at the University of Pittsburgh School of Medicine, who collaborated on the study. “A collaboration between neurosurgeon-scientists and neuroscientists, like ours, allowed us to collect high-quality recordings of brain activity that would not have been possible otherwise, and learn about the mechanisms of brain processing in a completely new way.”
The researchers specifically tracked how the brain processed “pitch accents“—those subtle variations in tone that signal which words carry more importance or convey specific meanings in an utterance. For example, the difference between saying “I didn’t take your BOOK” (implying you took something else) versus “I didn’t take YOUR book” (implying you took someone else’s).
A Specialized Neural System
The findings revealed that Heschl’s gyrus does much more than simply process sound—it creates abstract representations of pitch patterns, transforming subtle acoustic variations into meaningful linguistic categories. This brain region handles prosody as a discrete, phonological entity separate from the processing of the actual words being spoken.
“Our study challenges the long-standing assumptions how and where the brain picks up on the natural melody in speech—those subtle pitch changes that help convey meaning and intent,” said G. Nike Gnanataja of University of Wisconsin-Madison’s Department of Communication Sciences and Disorders and co-first author of the study. “Even though these pitch patterns vary each time we speak, our brains create stable representations to understand them.”
Previous theories suggested that this level of speech processing happened primarily in the superior temporal gyrus, a region further along the auditory processing pathway. Instead, it appears that our brains begin interpreting these meaningful pitch patterns much earlier in the processing stream.
A Uniquely Human Skill
To confirm whether this ability might be unique to humans, the researchers conducted parallel experiments with non-human primates. Despite processing the same acoustic information, the primates’ brains didn’t create the abstract representations of pitch accents that human brains did—suggesting this ability might be specific to human language experience.
This finding highlights the specialized nature of human communication. While monkeys can process the raw sound information in speech melody, they lack the neural machinery to categorize and interpret those patterns in the sophisticated way human brains do.
Beyond “What” to “How”
The discovery provides scientific evidence for the adage that it’s not just what you say, but how you say it. Our brains have specialized neural circuits that extract meaning from vocal melodies, enabling us to interpret emphasis, intent, and emotional context.
These pitch patterns are critical for everyday communication. They help distinguish questions from statements, signal irony or sarcasm, and highlight important information. Without them, speech would be monotone and much meaning would be lost.
Applications Beyond Basic Science
Understanding how the brain processes prosody could have wide-ranging implications. As Chandrasekaran noted, “Our findings could transform speech rehabilitation, AI-powered voice assistants, and our understanding of what makes human communication unique.”
For individuals with certain neurodevelopmental conditions like autism, or those recovering from strokes that affect speech patterns, this research might lead to more targeted therapies that address prosody processing specifically.
The findings could also improve artificial intelligence systems that interact with humans through speech. Current voice assistants often struggle with interpreting intonation and emphasis, but a better understanding of how human brains process these features could lead to more natural-sounding and intuitive AI interactions.
The research was conducted by Northwestern University’s School of Communication in collaboration with the University of Pittsburgh and the University of Wisconsin-Madison, with funding from the National Institutes of Health.
As scientists continue to unravel the complex neural mechanisms behind human communication, this study serves as a reminder that speech comprehension involves far more than simply decoding words—it’s also about interpreting the rich melodic patterns that give those words their full meaning.