Neuronal processing of facial expressions in the primate superior colliculus.

Fast processing of emotionally salient facial expressions is widely believed to depend on a subcortical visual circuit from the superior colliculus through the thalamus to the amygdala, but the specific processing steps remain unclear. Here we identified two largely nonoverlapping groups of neurons in the superior colliculus significantly modulated by facial expressions. One group exhibited a short-latency preference for threat and the other exhibited a delayed preference for fear.