only a 4 mm thin outer layer of the human biological brain is used for thinking

in the human biological brain there is a outer layer of 2 mm to 4 mm thick where the thinking is done, 

that thin layer consists of six layers of nerve cells, 

that's a very small percentage of the brain volume, 

the rest of the volume of the brain is probably used to move body and control organs 

by comparison an insect uses a tiny brain to use legs to move around 

and control organs