Parallel Processing of Facial Expression and Head Orientation in the Macaque Brain

Area of Science:

• Neuroscience
• Cognitive Science
• Primate Research

Background:

• Social interactions rely on interpreting facial cues.
• Understanding how the brain processes dynamic facial information, like expressions and head movements, is crucial for social cognition.
• Existing research highlights specialized cortical mechanisms for face identity but less on transient signals.

Purpose of the Study:

• To investigate how the observer's brain encodes and uses information from facial movements and head turns.
• To identify specific brain regions involved in processing facial expressions versus head orientation.

Main Methods:

• Utilized a functional MRI (fMRI) adaptation paradigm in awake male macaques.
• Focused on face-selective patches within the superior temporal sulcus (STS).

Main Results:

• Identified a double dissociation within the STS: face-selective patches in the STS fundus processed facial expression, while those on the lower, lateral edge processed head orientation.
• The amygdala also showed sensitivity to facial expression.
• Demonstrated segregation of face-selective patches within the STS based on the type of information processed.

Conclusions:

• The findings reveal a novel functional organization within the STS, with distinct areas specializing in facial expression and head orientation.
• This segregation challenges previous understandings of the face-processing system's role in representing actions and supporting social cognition.
• The study provides new insights into the neural mechanisms underlying the interpretation of dynamic social cues.