It may be scary to you But not to a patient known as SM, whose amygdala damage makes her immune to fear. The amygdala is a brain structure that is active in processing events with the power to generate feelings of fear. So while this character from the 1973 horror film The Exorcist caused audience members at the time to scream, faint, and run out of the theatre during scenes of demonic possession, SM would not have felt any fear at all.