How our brains manage speaking and breathing at the same time

In an enlightening discovery at MIT, researchers have shown how our brains manage speaking and breathing. Interestingly, they found a brain circuit that coordinates vocalization mainly during exhalation and interrupts speech to inhale, ensuring these actions work together smoothly.

Furthermore, the core of this finding is a mechanism that adjusts the voice by controlling the larynx and airflow, crucial for sound production. Additionally, this system is overseen by a specific area in the brainstem that also controls our breathing patterns, prioritizing the need to breathe over the desire to speak.

According to Professor Fan Wang from MIT’s McGovern Institute, this interaction is vital. Firstly, he points out that vocalization stops when we need to inhale. Secondly, Wang mentions that speech-controlling neurons receive inhibitory signals from the brain area managing our breath rhythm.

This research is led by Jaehong Park, a graduate student from Duke University now at MIT, and his team. They’ve published their findings in Science, offering deep insights into how we communicate. Notably, this work highlights the complex biological processes behind speech.

Mechanics of speaking and breathing

The vocal cords, situated within the larynx, are essential for phonation, facilitating sound production as they vibrate from the flow of exhaled air when nearly closed.

Consequently, scientists investigating the neurological control of phonation have turned to mice and their ultrasonic vocalizations (USVs), which parallel human vocal mechanisms, to unravel the complexities of our communication systems.

“Our aim was to unravel the neuronal control behind vocal cord closure and how these controls integrate with the breathing circuit,” Wang shares, highlighting the study’s primary objective.

Through innovative techniques that map synaptic connections, the team uncovered that a group of premotor neurons in the hindbrain’s retroambiguus nucleus (RAm) plays a crucial role. These neurons, activated during USVs, are instrumental in vocalization, marking a significant advancement in our understanding of speech production.

Experiments demonstrated that silencing these RAmVOC neurons halted vocalization, while stimulating them facilitated speech, albeit temporarily interrupted by inhalations if the stimulation extended. This finding underscores the dominance of the breathing control system, even in the face of artificial stimulation aimed at inducing speech.

Breathing: The conductor of speech

Further investigations revealed that the pre-Bötzinger complex, a brainstem region responsible for generating breathing rhythms, directly inhibits the RAmVOC neurons. This ensures that our need to breathe maintains its primacy, artfully weaving pauses into our speech for inhalation.

This research not only sheds light on the biological intricacies of speech production but also hints at the universal aspects of vocalization shared across species.

“Despite the differences in vocalization mechanics between mice and humans, the core process involving vocal cord closure and exhalation is a common thread,” Park notes, drawing parallels between the communication methods of the two species.

The team now sets its sights on exploring how this brain circuit influences other functions like coughing and swallowing, further expanding our understanding of the brain’s control over essential life processes.

This discovery opens new doors to appreciating the sophisticated neural choreography that enables us to communicate, breathe, and live harmoniously.

The full study was published in the journal Science.

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