We learn to speak in early childhood, but the precise brain processes that bring words to our lips are often poorly understood. However, a new study by researchers from NYU Langone Medical Center and the University of Iowa has managed to pinpoint the separate areas of the brain responsible for speech timing and word formation.

The research team built on the methods that scientists have been using to study the brain circuits that allow birds to sing to find out. Patients who were already undergoing brain operations were evaluated for the study. Because they were put under local anesthesia for the beginning of the operations, patients were awake and able to verbally help researchers map speaking abilities to specific regions of the brain.

During the surgery, researchers placed small devices on the patients’ brains that cooled specific regions (areas about the size of a quarter) by up to 10 degrees Celsius in less than 60 seconds. The change in temperature altered the brain function in these spots, causing patients to speak in slowed or blurred speech when asked to recite simple lists, like the days of the week. Differences corresponding to each brain area confirmed which areas affected which parts of speech.

“Our study results… represent a major advance in the understanding of the roles played by the areas of the brain that enable us to form words,” said Dr. Michael Long, an assistant professor in the Neuroscience Institute at NYU Langone, in a statement. “When we lowered the temperature in specific brain areas during brain surgery and asked people to speak, we saw distinct and complementary roles emerge for specific brain regions.”

More specifically, the team discovered that the movement of muscles — including the lips and tongue — that allow for articulation is the responsibility of the speech motor cortex. Nearby, a brain region called Broca’s Area was found to plan the actions of the speech motor cortex, including the timing and speed of muscle movements needed to form syllables and words.

In all, 16 surgical patients had 42 distinct brain sites cooled, all of which had been previously been suggested to play a role in speech signaling. All patients were given general anesthesia once the brain mapping was done, and recovered safely from the operation with no damage to their ability to speak. Long notes that focal cooling is a “vast improvement” over other, older brain mapping techniques that involved electrical stimulation, which carries with it the risk of triggering an epileptic seizure during surgery.

“This study confirms that cooling is a safe and effective means of protecting important brain centers during neurosurgery,” Long said.

Looking forward, Long explained that the team will use the cooling technique to explore, and hopefully better understand, how brain regions help with word interpretation. The ultimate goal is to develop therapies for those who have lost their ability to speak due to injury or disease.

Source: Long M, Katlowitz K, Svirsky M, Clary R, Byun T, Majaj N, et al. Functional Segregation of Cortical Regions Underlying Speech Timing and Articulation. Neuron. 2016.