If you've ever wondered what makes zombies rise up and chase down fresh brains after they're dead, you're not alone. Harvard psychiatry professor and avowed sci-fi geek Dr. Steven C. Schlozman wondered too, and after a great deal of late-night movie watching and necro-diagnostic research, has fashioned himself into probably the world's foremost expert on zombie neurobiology. Mark Strauss of io9 took an in-depth look at some of the good doctor's theories, a few of which I've harvested (word choice!) here for your flossy amusement. (They originally appeared in Schlozman's article "Zombies on my Mind.") Read on ... if you dare!

The Frontal Lobe

This part of the brain is involved with "executive functioning" - enabling us to think carefully and solve problems in an abstract way. Clearly, there's not much going on there if you have the misfortune of being afflicted with living deadness. But we do know that zombies can see us and sense us. Schlozman concludes that zombies possess just enough frontal lobe activity to "listen" to the thalamus, through which sensory input is processed. But the frontal lobe function most relevant to understanding zombie behavior is the control of "impulsivity"-the general term for when you do something and, if you had two more seconds, you might not have done it. For instance, if in a fit of rage you have the sudden urge to punch your boss in the face, the frontal lobe intervenes and allows you to consider why that might be a bad idea.

The Ventromedial Hypothalamus

In the movies, zombies are always hungry, no matter how many supporting actors they consume. The most likely explanation is that zombies don't have a properly functioning ventromedial hypothalamus: the region of the brain that lets you know whether you've eaten enough. The result is hyperphagia. Zombies will eat and eat and eat, but never feel satiated. That raises a slightly awkward question: If zombies are constantly eating, then how come they never poop? Schlozman doesn't know for sure, but he has at least one promising theory: Maybe the living dead are constipated. Now we know why zombies are always moaning.

The Cerebellum and the Basal Ganglia

Science may once and for all settle the heated debate over whether "the infected" in 28 Days Later could be classified as zombies. Schlozman says "no," observing that "the infected" possess "some sort of higher cortical function going on that allows them to hunt humans." Moreover, the fake zombies in 28 Days Later exhibit fluidity of motion. They can run, jump, climb and quickly change direction-activities that the true Romero zombies are incapable of performing. Clearly, zombies suffer from cerebellar and basal ganglia dysfunction (duh!). Those are the parts of the brain that make fluidity of motion possible. The basal ganglia helps us with coordinated movement. The cerebellum helps us with balance. In fact, if you visit the website of the National Institutes of Health and read about cerebellar degeneration (such as ataxia), the symptoms match the familiar gait of the living dead: "a wide-legged, unsteady, lurching walk, usually accompanied by a back and forth tremor in the trunk of the body"¦"

Want more (info on) brains? Check out the rest at io9, or bone up on the classics and watch Night of the Living Dead -- in its entirety -- right here!