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Communication in the Brain: What Allows us to Speak?

Author: Simone Maimon

Editor: Serena Tsao

Artist: Francesca Huang


Why can humans speak, but not apes? One main difference between us and other species is our ability to communicate complex words and ideas. Sure, other animals may be able to gesture, echolocate, and dance. But none can create coherent speech. The scientific zeitgeist explains that our development of speech comes from unique physical capabilities that make certain sounds. On the other hand, other scientists propose a different explanation: the mental capacity of other animals is not evolved enough to express their thoughts through sound. But, how exactly does the human brain process and create speech? Broca’s speech area and Wernicke's area are the two key areas that coordinate our ability to form sentences and process dialogue, respectively. 

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Broca’s area is located in the frontal lobe, which is responsible for many decision-making and motor abilities. It helps plan each sentence, including its structure and the placement of verbs and nouns in their correct order. Additionally, Broca’s area programs the actual muscle movements we need to vary our tone and produce precise, distinct sounds.

Wernicke's area is located in the temporal lobe, which generally processes sensory information. In addition to speech, this region interprets both hearing and memory. Wernicke's area processes auditory information, recognizing and distinguishing sounds that arrive in a particular sequence. This area also enables us to understand written information; it is partially responsible for speech processing/understanding, not just for sound reception. Scientists previously understood Wernicke's area as responsible for making “meaningful” speech: what led them to this conclusion?

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One way scientists discover a body part's function is by observing the effects when that part is damaged or knocked out. Wernicke's aphasia is the prime example of this: those who suffer damage to Wernicke's area can enunciate every word, yet, most notably, they may still incorrectly use words. Thus, their speech doesn't make sense. Additionally, they struggle to understand others and recognize their own language errors.  

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Another type of aphasia is caused by damage to Broca’s area, mainly resulting in a lack of speech fluency. People with this condition may take a longer time to form sentences, use incorrect grammar, or repeat themselves. Yet, they can understand their own incoherence and get frustrated by it. Plus, they can understand what others say because their Wernicke's area is intact.

Scientists are still figuring out the exact connections in the brain associated with speech. A group of scientists at New York University conducted an experiment that allowed them to differentiate the brain signals associated with planning and producing speech by examining brain activity in a new area near Broca’s area. As we continue to discover more about the brain, we build new understandings of evolution, which can reveal more about what differentiates us from other species.

Citations:

Boudreau, S. (2023, March 31). How humans speak—and why chimps don’t. Visible Body Blog.

Hathaway, B. (2020, October 5). Neurobiology of conversation: Brain activity depends on who you

NYU Langone. (2022, January 5). Study reveals brain networks enabling human conversation. NYU

Langone News. https://nyulangone.org/news/study-reveals-brain-networks-enabling-human-

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