3 functional layers of brain

These are not literal separation. But functionally you can divide the brain into 3 layers.
The flow of command is bidirectional b/w layers.

Layer 1

Automatic functions.
Body temperature drops then send shiver signal.

Layer 2

About emotions.
It's found in mammals.
If you saw something gruesome, it sends signal to layer 1.

Layer 3

Cognition, memory storage, sensory processing, abstractions and philosophies.
If you read something gruesome, layer 3 sends signal to layer 2 which sends signal to layer 1 and makes you shiver.