which part of the nervous system is stimulated during deep thinking?

Answer 1

Part?

Parts.

If by 'deep thinking' you also include meditation, it has been found that even the most primitive and hands-off part of the nervious system, the autonomic system, which usually regulates breating and heartbeats and gastrointestinal motion, can be affected, if not completely controlled.

But, if you are trying to ask in which part of the brain it occurs, it is in the frontal lobes.. althought I am not expert enough to help you pinpoint which parts of which lobe are usually dedicated to which kinds of thoughts.