Here's my theory:
Alcohol attacks the weakest brain cells first and kills them off. That leaves only the stronger/smarter/better brain cells to operate unfettered from the constraints of the dead weight cells that were holding back the rest of the brain.
The problem with too much alcohol, though, is that it then weakens all of the brain cells. When the weak cells have been killed, the alcohol has no choice but to begin targeting the stronger brain cells.
Hangovers the next morning are the body's way of telling you that it's ok to purge the brain of the laggard cells, but you have to draw the line so that you don't kill off the good cells, too.
And yes, I am in fact an educated neuropsychologist.