Nerd School: If I Only Had a Brain- Biology and Headshots

by Joe on October 19, 2012

Previously on Nerd School: The Walking Dead-  Off With Their Heads- Katanas in a Post-Walker World

This article deals specifically with the TV Show up to Season 3 Episode 1. The article contains spoilers for anyone not caught up.

People familiar with the zombie sub-genre understand that the best way to deal with a classic “zombie” is to destroy the brain. The Walking Dead has further cemented this idea by showing that the cause of the zombie outbreak is an infection in the brain itself. This means that only through destroying the brain can someone stop a zombie.

The brain is an interesting organ. All mammals have one, and it’s the center point of their nervous system.  The virus only currently affects humans in The Walking Dead universe we will focus on the human brain.

The human brain is generally divided into 4 sections, the cerebrum, the cerebellum, the brain stem, and the limbic system. The cerebrum is the largest part of the human brain. It’s the big wrinkly part associated with higher brain function. The cerebellum is the smaller part of the brain located in the back. It is similar to the cerebrum in that it has two hemispheres and is wrinkly. The cerebellum, however, regulates and coordinates movement, posture, and balance.  The brain stem is responsible for basic vital life functions like breathing, heartbeat, and blood pressure, things that automatically happen in our bodies. Finally there is the limbic system which support a variety of functions including emotion, behavior, motivation, long-term memory, and olfaction.

In Season 1, Episode 6 we find out from Dr. Jenner that the virus that effects the population restarts “just the brainstem. The human part, that doesn’t come back.”  However, the brainstem has very limited functions. The main role of the brain stem is its regulation of automatic functions (it is involved in cardiovascular system control, respiratory control, pain sensitivity control, alertness, awareness, and consciousness). It also plays a major role in relaying all information from the body to the cerebrum and cerebellum and vice-versa. Knee-jerk reactions related to “touch sensations” stop here causing reflex. What’s strange is that a zombie virus would dominate an area that specializes in pain, temperature, and pressure sensation, as well as automatic functions such as blood pumping and breathing. (Things zombies don’t need)

Logically we can assume the virus simply causes the brainstem to reanimate the rest of the brain. According to the progression of the virus as dictated by the show, when a person “dies”, the virus jump starts the brainstem. The brainstem then begins to restart the basic life processes, or at least trick the body into thinking that those processes have begun again. It would not be a stretch then for the  limbic system (or at least parts of it)  to start working again.

Why only the limbic system? While the cerebellum does not initiate movement, it does  contributes to coordination, precision, and accurate timing. Three things the walkers in the show are not known for. Freshly raised walkers may have more use of this region, but we see by the time the survivors make it to the prison, the remaining walkers’ movements suffer much in the same as people suffering from cerebellar diseases. Perhaps the cerebellum quickly “wears out” in this scenario. The cerebrum, with its higher functioning skill set never seems to be reactivated, as the walkers never regain the creative or logical thinking associated with its use.

It’s worth debating the actual restart of the cerebrum, as how would it be possible to have use of certain parts but not others. More than likely the creative and logical thinking would be overrun by the limbic system. The limbic system operates by influencing the endocrine system and the autonomic nervous system. The most important part of this (in this scenareo) is the hypothalamus. This tiny gland rests just above the brainstem (see there it is again), and is responsible for the feelings of hunger and fatigue.

The walkers in The Walking Dead are motivated to find food. This seems to be the vector by which the virus spreads. Although it is stated that all the survivors already possess the virus, the reason for the walkers to attack the living seems to be to harm or outright kill the living so the virus can take over. The way to get the walkers to attack is through the hunger stimulus. The fatigue portion comes in by how they never get tired and  keep moving.

On a side note, The parts of the limbic system associated with the olfactory sense (the piriform cortex) seems to be most active, as it is determined that walkers hunt based on smell. The auditory (cochlear) and ocular nerves also seem to play a part in the hunting patterns of walkers,  but not as much. Walkers are attracted to loud noises, but humans can speak on a lower volume and not attract walkers.

So with everything we have learned about the brain, would a headshot stop a walker. The simple answer is yes. The more complex answer is “well, if you manage to destroy a certain part.” There have been hundreds of documented cases of individuals suffering brain damage and continuing to live long (but not always happy) lives. The classic example is Phineas Gage who in 1848 accidentally had a 13.5 pound iron bar driven through the skull. It pierced his frontal lobe (in the cerebrum), but left much of the brain intact. He went on to live 12 more years. Though it severely affected his personality, the key point is that he lived, and was able to function.

In fact there is speculation that if doctors had not tried to remove the bullets from Abraham Lincoln’s brain, he may have survived.  The cerebrum can take an extreme amount of punishment without causing death. The cerebrum is not even necessary for a walker or even a living human to function. In fact most of the brain can be removed and still allow for a sort of life. That is except the brainstem. Once the brainstem is destroyed auto-functions (including movement) cease.

This is the Perfect example of what you wouldn’t want to happen. The bullet only goes through the cerebrum here leaving the rest of the brain intact.

So a shot to the head is awesome, but if it blows a hole out the other side, it might not be enough to put the walker down. My advice? Aim for the mouth.


Read some other stuff from Joe, hear him on the Planet Arbitrary podcast, or follow him on Twitter @planetarbitrary


Doctor Who: Doctor Who Season 6 Round Up, An Alternate History of the DoctorDoctor Who Season 6 primer, Psychology, and Regeneration, The Pitfalls of Paradoxical Storytelling, The Missing Episodes

Game of Thrones: Casting Roundup 1 and 2, Game of Thrones Primer IIGame of Thrones Primer I, Inn at the Crossroads Interview, Season 1 recap, The Greyjoy Rebellion, Robert’s Rebellion Pt.1, Robert’s Rebellion Pt.2, Robert’s Rebellion Pt. 3, The Religions of Westeros, The Races of Westeros

Star Trek: Evening the OddsStar Trek Blu-rays 1 and 2 Trek in your Queue 1 and 2, Obama TrekStar Trek: A Different Generation, Failed Star Trek Spinoffs

Misc: Sci-Fi ComposersThieving Sci-Fi, Paranormal Activi3The Walking Dead Primer, The Genre Problem, Conan Primer, Mutant Fatigue, Sci-Fi A-Team, A Love Letter to Natalie PortmanThor Primer



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