Aaron Helzinger was attempting to have his homicidal rages removed, but the doctor who did it didn't know the difference of a amygdala and the hypothalamus. When his amygdala was removed his rages grew even stronger. Amygdala has a very childlike personality and is often used by many villians, but Amygdala has medication for his conditon which helps him stay calm and peaceful. Batman and Amygdala first fought when he was being manipulated by Jeremiah Arkham, however Batman was able to beat him despite his size. He was also one of the inmates released by Bane and was controlled by the Ventriloquist, however Batman was able to beat Amygdala again.Amygdala was set free while under his medication and soon became a friend of Nightwing. He was also a warden for Lockhaven Prison. Amygdala was living in the apartment that Blockbuster destroyed in his attack on Nightwing. However Amygdala was able to survive, but has taken the death of his friends death hard.