Discovery of “Functions of Brain” As far as I know, Physical Experimentation of Human Brain is not possible. So how does people come up with the idea that different parts of brain is associated with different specific functions? and Who found it?

Example:


Cerebrum for memory, speech etc..
Cerebellum for motor, sensory etc..
Often, we learn about brain functions when parts of the brain become damaged. One famous example is that of Phineas Gage. He survived severe brain damage, and his character and abilities were noticeably different. From the article:-

Some months after the accident, probably in about the middle of 1849, Phineas felt strong enough to resume work.  But because his personality had changed so much, the contractors who had employed him would not give him his place again.  Before the accident he had been their most capable and efficient foreman, one with a well-balanced mind, and who was looked on as a shrewd smart business man.  He was now, Harlow said, fitful, irreverent, and grossly profane, showing little deference for his fellows.  He was also impatient and obstinate, yet capricious and vacillating, unable to settle on any of the plans he devised for future action.  His friends said he was "No longer Gage."