The prefrontal cortex (PFCx) is a region of the cerebral cortex now thought to be unique to primates (the same area in rats, for example, is broadly thought to be used for generating movements and processing the emotions and rewards associated with them).
This region has undergone an enormous expansion over the course of human evolution, and the structure can now be divided into various sections according to where they lie within the very front part of the brain.
- The orbitofrontal cortex lies just on top of the eyes, and seems to have a role in adding an emotional element to planning and decisions - the gut feeling.
- The ventrolateral PFCx lies on the side of the front bit of the forehead, and is important in working memory. This is the bit to blame if you can't listen to someone tell you their phone number and then write it down ten seconds later, but it has nothing to do with your inability to then (i) remember the number the next day, or (ii) actually call them back.
- The dorsolateral PFCx lies behind the bit of the forehead that people touch to mean 'Oh God, I should know that'. It is important in decision making, and particularly in switching and maintaining 'attentional set' - the ability to choose whether to concentrate on the TV or your partner, and then stay focused for more than a few seconds. However, some researchers think that it's nothing more than a glorified version of the ventrolateral PFCx...
Some people also include the anterior bits of the cingulate cortex with the PFCx, but really it deserves a writeup all of its own.
Problems with the PFCx have been implicated at some point in just about every psychiatric disorder in existence. For example, depression, schizophrenia, and obsessive-compulsive disorder are all thought to involve problems in communication between neurones on various scales here. On the other hand, without it we'd be unable to make long-term plans, and Machiavelli would never have written The Prince (or indeed anything else).