How the brain creates facial expressions: researchers have identified a network of neural circuits in the brain and muscles in the face that work together to create facial expressions
Using these methods, they were able map out a facial motor network composed of neural activity from the different regions of the frontal lobe—the lateral primary motor cortex, ventral premotor cortex, and medial cingulate motor cortex—and the primary somatosensory cortex, in the parietal lobe.
Using this targeted map, the researchers were able to then record neural activity in each cortical region while the monkeys produced facial expressions. The researchers studied three types of facial movements: threatening, lipsmacking, and chewing. A threatening look from a macaque involves staring straight ahead with an open jaw and bared teeth, while lipsmacking involves rapidly puckering the lips while flattening of the ears against the skull. These are both socially meaningful, contextually specific facial gestures that macaques use to navigate social interactions. Chewing is neither social nor emotional, but voluntary.
This news article discusses a study by Rockefeller University's Winrich Freiwald and his team, which reveals how neural circuits in the brain and facial muscles collaborate to produce facial expressions in response to social cues. The research, published in Science, identified a facial motor network and neural mechanisms that control facial movements, challenging the previous assumption that emotional and voluntary expressions were generated separately. The study used fMRI to map brain activity in macaque monkeys while they produced facial expressions, finding that all brain regions involved in facial gestures operate at distinct timescales. The findings could improve brain-machine interfaces and artificial communication designs.