Popular Mechanics recently investigated the forensics of the zombie head shot:
Dr. Steven Schlozman, has written extensively about the brain function of undead zombies (as opposed to voodoo victim zombies). He’s co-director of Medical Student Education in Psychiatry at Harvard Medical School and, much more importantly, on the advisory board of the Zombie Research Society.
His self-appointed mission is to use zombie fiction to help teach people about the way the human brain works. One of the useful points he makes is that, contrary to the idea that the brain stem (medulla oblongata) must be destroyed in order to destroy a zombie, their behavior indicates that several parts of their brains are still functioning in a coordinated way. They hear noise, stagger toward it and attack the target on sight. These are sure signs that the zombie frontal lobe is active enough to process sensory input through the thalamus. Of course, the frontal lobe must be damaged because the zombie acts on base impulses, like pursuing and eating other people. Other brain damage accounts for the lack of motor coordination and general poor manners.
The good news here for zombie apocalypse survivors—and defenders of the logic of zombie shows—is that damage to other parts of the brain could put a zombie down for good.
Shoot the head. Kill the ghoul. And here’s a Harvard medical professor (and a survey of the published literature) to tell you why.