Macaque facial gestures are more than just a reflex, study finds

Summary

The firing rates in the motor and somatosensory cortex, on the other hand, looked radically different. This suggests there is a dynamic neural code defined by rapidly changing firing rate relationships amongst the neural populations. The team thinks this means that the cingulate cortex manages the social purpose and context of the facial gesture, which is relatively stable. This may be where the brain integrates sensory cues—like the look of another monkey’s expression—with its own internal state to produce the right facial gesture for the occasion. The dynamic code areas implement this expression by driving individual muscles. “They’re driving the kinematics like ‘move this lip a millimeter to the left, now a millimeter to the right,’” Ianni explains. These constant miniscule movements of muscles are necessary because facial expressions are usually dynamic—macaques’ eyelids, lips, cheeks, and ears are constantly twitching and changing their position even if the end effect looks still from a distance. The journey begins But that’s just the beginning of a long journey. “There have been such fabulous, impressive advances in the field of assistive communication devices even since I started this project,” Ianni says, and points to neural prostheses developed by Maitreyee Wairagkar’s team Ars covered in 2025 as one of the examples. Building a similar neural prosthesis for decoding facial gestures is unlikely to happen overnight, though. We’re a rather long way away from truly restoring the ability to communicate through facial gestures to patients who lost it. Ianni’s study is the first that recorded neurons producing facial gestures with multi-electrode arrays. This means we’ve only just begun to build up base science on the neural mechanism behind making faces. This is the point where neural speech decoding technology was in the late 1990s, and we still can’t make that reliable enough for regular clinical products. Still, Ianni remains hopeful. “I hope our work goes to...