Ever wondered why you do not bite your tongue even when you do not pay attention to your chewing? Interconnected neurons in the brain that coordinate the movement of the tongue and jaw usually keep the tongue safe from injury, a new study said. “Chewing is an activity that you can con-sciously control but if you stop paying at-tention, these interconnected neurons in the brain actually do it all for you,” said Ed-ward Stanek from Duke University School of Medicine in the US. Chewing requires a complex interplay be-tween the tongue and jaw, with the tongue positioning food between the teeth and then moving out of the way every time the jaw clamps down to grind it up. Previous studies have shown that move-ment of the muscles in the jaw and tongue are governed by special neurons called motoneurons and that these are, in turn, controlled by another set of neurons called premotor neurons. But the exact nature of these connections – which premotor neurons connect to which motoneurons – was not defined. For the new study, researchers used a spe-cial form of the rabies virus to trace the ori-gins of chewing movements in mice. They found that a group of premotor neu-rons simultaneously connect to the mo-toneurons that regulate jaw opening and those that trigger tongue protrusion. Another group that connects to both mo-toneurons that regulate jaw closing and those responsible for tongue retraction was also found. “Using shared premotor neurons to control multiple muscles may be a general feature of the motor system,” Stanek said. The study appeared in the journal eLife.
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