Facial Emotion Recognition after Bilateral Amygdala Damage: Differentially Severe Impairment of Fear.

Although the amygdala is widely believed to have a role in the recognition of emotion, a central issue concerns whether it is involved in the recognition of all emotions or whether it is more important to some emotions than to others. We describe studies of two people, DR and SE, with impaired recognition of facial expressions in the context of bilateral amygdala damage. When tested with photographs showing facial expressions of emotion from the Ekman and Friesen (1976) series, both DR and SE showed deficits in the recognition of fear. Problems in recognising fear were also found using photographic quality images interpolated (''morphed'') between prototypes of the six emotions in the Ekman and Friesen (1976) series to create a hexagonal continuum (running from happiness to surprise to fear to sadness to disgust to anger to happiness). Control subjects identified these morphed images as belonging to distinct regions of the continuum, corresponding to the nearest prototype expression. However, DR and SE were impaired on this task, with problems again being most clearly apparent in the region of the fear prototype. An equivalent test of recognition of morphed identities of six famous faces was performed normally by DR, confirming the dissociability of impairments affecting the recognition of identity and expression from the face. Further two-way forced-choice tests showed that DR was unable to tell fear from anger, but could tell happiness from sadness without difficulty. The finding that the recognition of fear can be differentially severely affected by brain injury is consistent with reports of the effects of bilateral amygdala damage in another case (Adolphs, Tranel, Damasio, & Damasio, 1994, 1995). The recognition of facial expressions of basic emotions may therefore be linked, to some extent, to specific neural substrates. [ABSTRACT FROM AUTHOR]