It has been well established that the amygdala is critical for processing various aspects of emotion, and in particular, for the perception of negative emotions such as fear. Perhaps the strongest evidence for this conclusion in humans comes from an extensive series of investigations in patient SM, an extremely rare neurological patient who has complete, focal bilateral amygdala damage.
Case Study: SM had no motor, sensory or cognitive defects but when asked to look at a series of facial expressions, she could identify every expression but did not recognize fear. Next she was asked to draw facial expressions. She drew each emotion but could not reproduce fear. When asked about her drawings, she explained that ‘she did not know what an afraid face would look like’.