The seemingly effortless act of chewing is actually a complex process that involves intricate coordination between the brain and the muscles. Researchers at Université de Montréal have delved into the mechanisms behind chewing, shedding light on the broader understanding of rhythmic movements in general.
Chewing, walking, and breathing are all examples of rhythmic movements. These movements can be consciously controlled to an extent but are primarily carried out automatically and do not demand our attention. Arlette Kolta, a professor at Université de Montréal, specializes in studying how the brain controls the numerous movements involved in chewing.
Kolta and her student Dominic Falardeau recently published a literature review in Current Opinion in Neurobiology, describing the complex processes at play in what they refer to as the “masticatory machinery.” By studying how chewing works, researchers gain insights into the coordination of rhythmic movements in the brain.
The review highlights the intricate nature of chewing. It begins with sensory receptors in the mouth, such as those around the teeth and jaw muscles, gathering information about the food being chewed. This sensory information is then transmitted to specific areas of the brain, including the sensory nuclei of the trigeminal nerve and premotor interneurons in the brainstem. These brain regions utilize motor neurons to coordinate the muscles responsible for opening and closing the jaws, ultimately producing the chewing motion.
Contrary to the perception that chewing is a repetitive and monotonous process, Falardeau explains that the individual movements involved are precisely adapted to the consistency and position of the food in the mouth. Continual sensory input plays a vital role in optimizing the food’s position and regulating the forces applied by the chewing muscles. As a result, different foods are chewed in different ways.
Once the food has been sufficiently chewed and mixed with saliva, the next stage is swallowing. This process requires careful synchronization of muscles in the pharynx, larynx, and esophagus to prevent choking. The medulla oblongata, located in the brainstem, handles this critical task.
Interestingly, chewing has been found to have significant cognitive effects. It has been linked to various cognitive benefits, demonstrating the complexity of the circuits responsible for coordinating chewing and other orofacial actions. Chewing movements enhance vigilance and attention by increasing the levels of specific neurotransmitters associated with alertness. Additionally, chewing induces theta rhythm, a type of electrical activity that facilitates learning and memory, in the hippocampus.
Furthermore, studies have shown that chewing increases blood flow and oxygenation in brain areas crucial for cognition. Animal studies have revealed that a liquid diet, even if nutritionally equivalent to a solid diet, leads to cognitive decline. Teachers have even discovered that giving gum to children with attention deficit disorder can improve their concentration during tests. However, it is essential to consider the potential drawbacks, such as the wear and tear on the temporomandibular joints and teeth, the presence of sugar, and the associated risks of artificial sweeteners like aspartame.
Overall, the research conducted by Kolta and Falardeau highlights the intricate nature of chewing and its impact on brain function. Understanding the complexities of rhythmic movements, such as chewing, provides valuable insights into brain coordination and cognitive processes.
