Researchers led by Winrich Freiwald in the Laboratory of Neural Systems published a study in Science identifying a distributed network of brain circuits that work with facial muscles to generate expressions. Using fMRI in macaque monkeys, the team located cortical areas that directly access facial musculature and mapped a facial motor network composed of the lateral primary motor cortex, ventral premotor cortex, medial cingulate motor cortex and the primary somatosensory cortex.
To probe specific actions the researchers elicited threatening displays, lipsmacking and voluntary chewing with live interaction, video stimuli and experimenter-controlled digital avatars. They found that both higher and lower cortical regions contribute to emotional and voluntary expressions: all regions participated in all gesture types but on distinct timescales. Lateral regions showed fast neural dynamics changing on the order of milliseconds, while medial regions showed slower, more stable activity.
Related analysis published in PNAS indicated these cortical areas form an interconnected sensorimotor network that adjusts coordination depending on the movement. Future work will study perception and expression together, locate areas controlling emotional states, and explore clinical applications such as improved brain-machine interfaces and more natural communication devices for patients after brain injury.
Difficult words
- distribute — spread across several parts or locationsdistributed
- circuit — connected path of nerve cells or areascircuits
- musculature — the system of muscles in a body part
- cortical — relating to the brain's outer layer
- sensorimotor — involving both sensing and movement functions
- elicit — to cause a response or reactionelicited
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Discussion questions
- What potential benefits could more natural communication devices bring to patients after brain injury? Give reasons.
- How might studying perception and expression together improve brain-machine interfaces or clinical treatments?
- What challenges could arise when applying findings from macaque brain networks to human clinical applications?
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