Neutral faces activate the amygdala during identity matching.

Although the amygdala has been described as a "fear module", a growing body of work suggests that it is a more general "relevance detector." A well-established face matching task has been shown to robustly activate the amygdala and has been used to investigate the influence of age, drugs, and genetics on the amygdala. In order to examine more specifically the emotion processing component in this task, we added a condition in which neutral faces are matched by identity. The left and right amygdalae responded to both the emotion and the identity matching condition, and the only selective response to emotion matching was at the left inferior prefrontal sulcus. The left amygdalar response habituated to emotion matching but not to identity matching. We concluded that the amygdalar response to face matching is driven at least in part by relevance detection, independent of emotion processing, although there appears to be additional emotion-specific processing at the left amygdala.