When you lift food to your mouth, your brain pulls off a quiet feat of engineering. Hands, arms, lips, tongue, and jaw all move in perfect sync without conscious effort.
Now, scientists at Duke University School of Medicine say they’ve found a key brain hub that makes that everyday task possible.
In a study in mice, fed angel hair pasta, researchers discovered a previously unknown area of the brain that acts like a conductor, coordinating the hands and mouth into one smooth feeding motion, said senior study author and Duke neuroscientist Josh Huang, PhD.
When this region was activated, animals made movements closely resembling natural eating. But when parts of it are switched off, those movements fell apart.
The findings in Neuron raise the possibility that similar circuits exist in humans. If so, they could help explain why coordination breaks down in conditions such as Parkinson’s disease and stroke and point to new strategies for rehabilitation after brain injury.
Two neuron types, one coordinated act
Using advanced optogenetics — a technique that lets scientists turn specific brain cells on and off with light — researchers scanned the mouse brain, region by region. One spot stood out.
They call it the rostral forelimb-orofacial area, or RFO. When activated, mice lifted their hands, brought them toward their mouths, and made chewing-like motions — even when there was no food.
“But there are different neuron types controlling movement execution versus timing and coordination,” said Huang, a professor of neurobiology and biomedical engineering at Duke University.
The team focused on two major classes of cortical projection neurons within RFO: pyramidal tract (PT) neurons and intratelencephalic (IT) neurons. Although both were active during feeding, they played distinct roles.
Using optopenetics, the researchers showed that reactivating either PT or IT neurons alone was sufficient to drive coordinated hand-mouth movements resembling natural eating. But shutting down each population revealed a division of labor.
Silencing PT neurons weakened the movements themselves — hands pulled with less force and bites lost vigor. In contrast, silencing IT neurons left movements intact but scrambled their timing, causing hands and mouth to fall out of sync.
Watching brains during dinner
To confirm RFO’s real-world role, the Huang Lab recorded brain activity while mice ate freely in a “restaurant-style” task, designed by first study author Xu An, where animals could manipulate and consume food naturally.
During eating, both groups of neurons lit up in sync with hand-mouth manipulation. The more intricate the movement, the stronger the activity.
The study provides a framework for understanding how breakdowns in specific neural circuits could disrupt coordination between body parts. Hand-to-mouth coordination is a defining feature of primates, including humans. From peeling fruit to using utensils, these skills are fundamental to daily life, Huang said.
Many behaviors — from grooming and nest building to human actions like eating, gesturing while speaking, or using tools — depend on precise coordination between hand and mouth.
“This may help explain symptoms seen in disorders such as stroke and Parkinson’s disease, where patients often struggle with sequencing or integrating movements, including hand-assisted eating, even when basic motor abilities remain intact,” said Huang.
The study was supported by the National Institutes of Health and NIH Director’s Pioneer Awards for Huang and Adam Kepecs at Washington University in St. Louis.
Additional authors: Katherine Matho, Hemanth Mohan, Hermione Xu, Francesco Boato, and Ian Q. Whishawd.