Under the Hood

Broca's Area Of The Brain May Not Control Speech, Actually Shuts Down When We Speak

Human speech
Scientists challenge the age-old idea the Broca's area of the brain produces human speech. Photo courtesy of Shutterstock

French physician Pierre Paul Broca first proposed the prefrontal brain region is “the seat of speech.” This means it’s the region solely responsible for speech production, thus the region being known today as Broca’s area. But the results of a new study have challenged this 150-year-old idea.

Scientists from the University of California-Berkeley and Johns Hopkins University in Maryland tracked electrical signals emitted from the brain of epilepsy patients as they repeated spoken and written words aloud. Patients processed the words they heard in their auditory cortex, prepared spoken words in Broca’s area, and they actually spoke words aloud with the help of their motor cortex. Interestingly, Broca’s area was shut down during the actual delivery of speech.

This could be a major breakthrough for not only epilepsy patients, but stroke and brain-injured patients, too.

"Every year millions of people suffer from stroke, some of which can lead to severe impairments in perceiving and producing language when critical brain areas are damaged," Adeen Flinker, lead study author and post-doctoral researcher at New York University, said in a press release. "Our results could help us advance language mapping during neurosurgery, as well as the assessment of language impairments."

Before now, the brain’s language center was split into two categories: one category worked to perceive speech and the other produced it. Flinker and his team found the Broca’s area engages with the brain’s temporal cortex, the region responsible for organizing sensory input, before engaging with the motor cortex. So based on this study, the Broca’s area doesn’t so much produce speech as it does integrate and coordinate information across other brain regions.

"Broca's area shuts down during the actual delivery of speech, but it may remain active during conversation as part of planning future words and full sentences," Flinker said.

The Oklahoma State Department of Education's special education services reported a "speech or language impairment means a communication disorder, such as stuttering, impaired articlation, language impairments, or a voice impairment." In addition to brain injury and neurological disorders, additional causes include hearing loss, developmental delays, autism, drug abuse, and physical impairments, such as a cleft lip or palate.

Source: Flinker A et al. Redefining the role of Broca’s area in speech. Proceedings of the National Academy of Sciences. 2015.

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