Impaired mimicry response to angry faces following severe traumatic brain injury

This study examined whether severe traumatic brain injuries (TBIs) interfere with normal facial mimicry when observing facial expressions. A total of 21 adults with severe TBI and 20 control participants viewed angry and happy facial expressions taken from the Ekman and Friesen (1976) series while facial movement of the corrugator supercilii (brow) and zygomaticus major (cheek) was monitored. Faces were presented both statically and dynamically (gradually morphing from neutral to the final expression). The control group showed increased brow activity to angry expressions and increased cheek activity to happy expressions. This activity was evident as early as 500 ms, consistent with previous research suggesting that facial mimicry commences as an automatic process. The TBI group showed similar activity to happy expressions but no clear response to angry expressions, either early (500-1,000 ms) or over the entire 6-s duration of the displayed image. This was the case for both static and dynamic displays. There was no relationship between facial mimicry and accuracy in identifying (matching) facial expressions for either the TBI or control participants. These results are consistent with the view that ventral frontal structures mediate early responses to angry expressions and that these are frequently compromised as a result of severe TBI. The results did not support the view that simulation (mimicry) facilitates emotion recognition.