Aaron Helzinger was attempting to have his homicidal rages removed, but the doctor who did it didn't know the difference between the 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.
During Infinite Crisis Amygdala has appeared as a member of the Secret Society of Super Villains. He was later seen in Penguin's Iceberg Lounge.
Amygdala posses strength that is almost on superhuman level, also he posses durability that is much better than a normal human and he is much more resistant to injuries than a normal human being.
He has few weaknesses like mental problems he cannot control his rage so he is very easy to get mad and starts to destroy everything.He also has problem with his intellect Amygdala has the intellect of a young child and has very low temper.
Justice League Unlimited
Amygdala appears in the Justice League Unlimited episode "The Cat and the Canary." He was seen at Roulette's Meta-Brawl.
Aaron Helzinger appears in Gotham portrayed by Kevin McCormick first appearing the 11th episode "Rouges' Gallery". He said to be an emotionally unstable patient who murdered his family with an axe. While in Arkham, he is taken under the wing of Jack Gruber (Aka Jack Buchinsky, the Electrocutioner) and used as his muscle.