Study group discussion: Decerebrate and Decorticate rigidity

Can anyone please explain how do we get decerebrate & decorticate posturing?

The red nucleus is at the level of the superior colliculus. My understanding is the red nucleus is a primitive structure that allows 4 legged animals for movement. But the rubrospinal tract (from the red nucleus to the spine) is mainly filled with upper limb flexor fibres. This nucleus is almost always inhibited by the cortex, so we never really use it.

So when you get a decorticate lesion, you bring your hands to the CORE because your red nucleus lost its inhibition from the CORTEX. I.e. rubrospinal tract is activated, thus you get flexion of upper limbs.

Decerebrate lesions interrupts all cortical AND red nucleus input to the spine, so you lose the red nucleus' flexor signals, and you extend your upper limb.

There's a funny YouTube video on it. Watch "Decorticate vs Decerebrate" on YouTube - https://youtu.be/yZUE2Dvf1Q4

Decerebrate contains more 'e's and it has  'e'xtended posture. A little mnemonic I know! 

Decorticate - caught a cat

Deceberate - de-celebrate

Submitted by Suzanne:
I could not remember how to distinguish decorticate and decerebrate posturing until a party animal ER resident told me. Decorticate = To court a keg. I just think of a frat boy bending around a keg with his wrists bent in to carry it and I can't forget!