Dissociable neural responses to facial expressions of sadness and anger

TLDR

Prior neuroimaging studies have examined neural responses to fear, disgust, and happiness, but not to sadness or anger. The study aimed to determine whether the amygdala responds to sad and/or angry faces and whether the orbitofrontal cortex selectively responds to angry faces. Participants underwent PET scans while performing a sex‑discrimination task on grayscale faces showing varying sadness and anger intensities. Greater sadness intensity activated the left amygdala and right temporal pole, whereas greater anger intensity activated the orbitofrontal and anterior cingulate cortices, with no amygdala response to anger, indicating distinct yet interconnected neural systems for negative expressions.

Abstract

Previous neuroimaging and neuropsychological studies have investigated the neural substrates which mediate responses to fearful, disgusted and happy expressions. No previous studies have investigated the neural substrates which mediate responses to sad and angry expressions. Using functional neuroimaging, we tested two hypotheses. First, we tested whether the amygdala has a neural response to sad and/or angry facial expressions. Secondly, we tested whether the orbitofrontal cortex has a specific neural response to angry facial expressions. Volunteer subjects were scanned, using PET, while they performed a sex discrimination task involving static grey-scale images of faces expressing varying degrees of sadness and anger. We found that increasing intensity of sad facial expression was associated with enhanced activity in the left amygdala and right temporal pole. In addition, we found that increasing intensity of angry facial expression was associated with enhanced activity in the orbitofrontal and anterior cingulate cortex. We found no support for the suggestion that angry expressions generate a signal in the amygdala. The results provide evidence for dissociable, but interlocking, systems for the processing of distinct categories of negative facial expression.