Compositionality of social gaze in the prefrontal-amygdala circuits.

Each social gaze can be deconstructed into primitive components, including gaze content, social state, and gaze duration. To reduce dimensionality and facilitate generalization, the brain needs to represent primitive components in an abstract format. We examined the compositional aspects of social gaze primitives in the brain when macaques were engaged in real-life social gaze interaction. Interactive social gaze behavior was determined by how primitives were combined, rather than by their independent sums, providing evidence for behavioral compositionality. The amygdala and the anterior cingulate cortex represented content and state in an abstract format and orthogonally to one another, whereas the dorsomedial prefrontal and orbitofrontal cortices exhibited limited generalization. Linear mixed selective neurons facilitated the abstraction underlying generalization. The content and state information had distinct communicative patterns across the prefrontal-amygdala circuits to minimize interference, which was mediated by linear mixed selectivity neurons. Our findings provide the neural grammar supporting the compositionality of social gaze.