Unconscious perception of non-threatening facial emotion in parietal extinction.

The success of humans as social animals relies heavily on our ability to perceive the emotional expressions conveyed by others' faces. Functional brain imaging has shown that expressions of fear and anger selectively activate the amygdala, even when the faces conveying the emotion are presented briefly and masked to prevent conscious perception (Morris et al. 1998; Whalen et al. 1998). Such results suggest that facial emotions signalling potential threat can be extracted rapidly and automatically by the human visual system, in the absence of conscious face perception. Here we asked whether a patient with spatial extinction, a profound disorder of perception due to right parietal lobe damage, would be sensitive to non-threatening (happy and sad) emotional expressions of faces that are not consciously perceived. We show that the emotion conveyed by an extinguished face in the contralesional hemifield can influence judgements of the emotion of a subsequent target face presented foveally. The finding of significant affective priming from extinguished faces fits with the proposal that facial emotion can be processed in the absence of conscious perception, and that preserved limbic and inferotemporal structures retain privileged access to the emotional content of 'unseen' faces.