The truth about zombies

As Halloween approaches, all the horror movies are coming out, and they’re bringing the zombies. I personally, am a big fan of AMC’s The Walking Dead. So what’s the deal with zombies? How would zombies actually work and could they really exist?
First of all, let’s define a zombie as an immortal and flesh craving “animal” that no longer has any semblance of humanity (hopes, dreams, empathy).

The Brain
Zombies are typically imagined to be fast, incapacitated by hunger, and immune to pain. So what does that mean for the brain? Much of the brain would still need to be “on” and working with degradation to some very specific parts, despite what some of those science fiction shows have taught you.

Analyzing the zombie. Graphic by Jilletta Becker
Analyzing the zombie. Graphic by Jilletta Becker

To be immune to pain, zombies would likely have some sort of damage or brain lesions on their sensory cortex, which receives information from touch, pressure, pain, vibration, and temperature receptors. Without the sensory cortex, the brain would be unable to receive any information from those receptors, and therefore wouldn’t register pain, temperature, pressure, vibration, or touch. Another explanation, would also be degradation of the receptors themselves; no receptors, no pain!

In terms of those poor decision-making skills, the brain affected could potentially be the prefrontal cortex. The prefrontal cortex is on the front of your head (right behind your forehead), and is one you’ve probably heard is still developing through your late teens. The prefrontal cortex helps you to coordinate information to form associations between information, and therefore gain an understanding of consequences of actions events. So having a damaged prefrontal cortex is what could cause the whole “closed door” predicament for zombies, as in “How do I get through this closed door?”

As for the crazy hunger for flesh and the general ability to function (minus the humanity), several parts of the zombie brain would have to continue working. An important grouping is the midbrain (plus the thalamus and hypothalamus) and the cerebellum. The midbrain is, as per its name, located in the much protected middle of the brain, connecting from the inside to the spinal cord. The midbrain, along with the thalamus and hypothalamus, work to process incoming sensory information, such as visual and auditory information, as well as outgoing motor information (as in, “move your arm now”). More importantly, these parts of the brain control the endocrine system, allowing or disallowing, changes in mood, sleep, energy, and metabolism. It’s possible changes in these parts of the brain would allow for some of those “zombie-like” qualities like hunger and sleeplessness. The cerebellum is what directs the involuntary coordination and control of ongoing body movements (Run, Zombie, Run) and would be necessary to successfully coordinate the movements that make zombies so fast.

The Cause
Imagine the complexity of a pathogen that would be so selective in its damage to some areas and leave others intact. Even if there were such a selective pathogen, it probably wouldn’t be able to limit it’s feeding to those areas forever, and would eventually move on to damage more until the zombie eventually died of dementia. In nature, such examples do exist, but can only be sustained for a limited amount of time for these reasons.

Another important point, is why? What’s in it for this pathogen to make these symptoms? In nature, zombification has occurred to promote reproduction of the pathogen/virus/fungus, which zombies definitely do through biting. Also, the inoculation/incubation would have to occur quickly, or the zombie would eat its prey before infection even occurred. Why then, is there no zombie vs. zombie action? It could be explained in the World War Z fashion: another zombie would be a poor host for infection. The idea is brilliant, but would be practically impossible to come into existence. Overall, it seems like a losing battle, if zombies were too good at what they do, they’d eventually run out of hosts and die off anyway.

Keep in mind, this article only touches on the possible mechanism of the zombie, and are only guesses based on the functions of the brain. There are many different ways to bring about the qualities that zombies exemplify. Even with damage in the regions suggested above, the brain is an amazing, unpredictable organ that will often find ways to “rewire” and avoid damaged areas. Therefore, if you’re getting ready for the apocalypse, it’s probably better to prepare for radiation or an airborne pathogen — or just not worry about it!