Mesiofrontal cortex
The mesiofrontal cortex was an area of the Vulcan brain, responsible for the suppression of emotions.

In 2372, The Doctor detected a neurochemical imbalance in Lieutenant Tuvok's mesiofrontal cortex, after a mind meld with Lon Suder. This imbalance affected Tuvok's ability to suppress his violent impulses. ()
Brain anatomy