Ellie Bennett uses neuroscience to explore what has gone wrong in the zombie brain to make them the lumbering, flesh-hungry creatures depicted on our screens.
A lumbering gait, no recognition of loved ones, the inability to verbalise above moans and grunts, and an insatiable appetite. It’s the archetypal zombie. He’s been staggering his way through popular culture ever since George A. Romero’s 1968 film, Night of the Living Dead. There have been a few deviations from this trope along the way, with the romanticisation of zombies occurring in films such as Warm Bodies. The zombie protagonist, named R, is not only depicted as a human love interest, but also has some of his more human traits preserved–the ability to display empathy and build meaningful connections (albeit with his food source).
In actual fact, having the odd human quality thrown in might be a more scientifically accurate way to portray a zombie, if zombies were real, which they’re not. I say this because the typical zombie characteristics almost always come as a collective. According to neuroscientists Timothy Verstynen and Bradley Voytek, to see these behaviours repeated in the same combination across a human population, creating a uniformly unfeeling, unintelligible army of the undead, would be extremely unlikely. This is because there are specific regions of the brain that would need to be affected to turn humans into the zombies we see on screen.
For zombie development, the higher functioning parts of the brain (which regulate our emotions, process language and allow personality expression) would need to be damaged or destroyed completely, whilst leaving the more ‘primitive’ areas alone. If we think about what could actually cause a zombie apocalypse – a viral or bacterial pandemic, prions, or even brain-infecting worms – it is unlikely that any of these agents could enter something as complex as the human brain, and only damage specific parts. Viruses like herpes simplex for example, have been found to infect the brain in rare circumstances, but they don’t do so strategically – instead they wreak random havoc throughout our grey matter.
So we can put down our baseball bats and flamethrowers, a zombie apocalypse is not going to happen. But that doesn’t mean we can’t learn anything useful from studying zombie neurology. In fact, it’s a really interesting perspective for learning more about our own brains.
In their book ‘Do Zombies Dream of Undead Sheep?’, Verstynen and Voytek take a neuroscientific lens to the zombie brain and attempt to define ‘zombieism’, and the behaviours that go with it, as a clinical disorder. Consciousness Deficit Hypoactivity Disorder (CDHD) is the name they came up with, and it comes with a very familiar set of symptoms.
Most obvious is the way zombies move. Their typical gait is wide and lumbering with their arms out, reaching for your brains. There are three main areas in the brain that control movement: the cortico-motor area, basal ganglia and the cerebellum. Damage to the cerebellum has the most visually obvious effect on a zombie’s walk. By definition it controls motor timing, coordination and error correction, in effect doing the quality assessment of your movements. Degeneration of the cerebellum in people can cause spinocerebellar ataxia and moving with this condition reportedly feels a bit like being drunk. This is in fact the reason that you stumble around haphazardly after a number of pints – alcohol affects your cerebellum, although the effect wears off as you sober up.
Whilst their stumbling, awkward gait is the most recognisable zombie feature to us humans, it’s their aggression and penchant for biting that we’re really afraid of. That’s the thing that makes zombies so hard to live with. You never hear about a vampire or werewolf apocalypse and that’s because, despite being equally as terrifying, these creatures are more rational and in control (unless there’s a full moon). They are able to coexist with us and stay relatively covert.
The main reason your undead sister doesn’t recognise you, going in for your jugular instead of a hug, is because the part of her brain that recognises faces doesn’t function properly.
Zombies are just really hungry and really angry. Once they catch a whiff of your flesh they can’t really think about much else until that craving is satiated. Increased appetite is one of the main symptoms of diabetes and is seen in some thyroid conditions. However, zombies aren’t technically living so there’s really no need for them to worry about nutrition. When your digestive system is dragging along the floor, it’s hard to imagine where the hunger signals would come from. Zombie blood is very congealed and without a beating heart, it cannot travel around the body. This means any nutrients or energy they consume can’t be transported and used by the body.
But a 2016 Austrian study into a particular brain protein could explain why zombies still desperately seek out something to eat. FosB, a protein found in the reward centre of the brain, is thought to be related to addiction. It appears to accumulate more readily in the brains of heroin addicts and drug abusers, but crucially (for zombies) it remains present in the brain until long after death. So perhaps that coffee addiction you built up over a lifetime could manifest itself as a craving for human flesh, if you were ever reanimated as a zombie. After all, zombies don’t have the motor coordination to make themselves a cappuccino.
As anybody who’s seen a zombie film will know, one waft of your body odour is all it takes to snap a pack of zombies from their trance-like state into dangerously aggressive predators. This type of aggression, known as ‘reactive-impulsive aggression’ is well defined in humans, resulting in a sudden, heightened aggressive response. It involves very little forethought and is mostly the result of impulsive emotions. Road rage is one example. On the other hand, the type of aggression not displayed by the classical zombie is calculated aggression. This is demonstrated in school shooters and violent terrorists, who use it to gain something in a cold, premeditated way. The reason zombies don’t experience the latter type of aggression is because they lack the brain regions needed for higher cognitive functioning. They can’t think about their actions or make plans, nor can they suppress their anger until it’s needed.
A school shooter will likely plan their rampage weeks, even months, prior to the event, and in the meantime their feelings of aggression will be kept at bay. They can subconsciously control their anger due to their intact orbital frontal cortex (OFC). This higher-level brain area acts as the cooling system for the amygdala, which in contrast is a highly reactive, primitive brain area involved in the flight or fight response. Zombies lack the regulating effects of the OFC and so their aggression response is sudden, red-hot and uncontrolled.
Zombies cannot recognise their loved ones, nor their own faces. The main reason your undead sister doesn’t recognise you, going in for your jugular instead of a hug, is because the part of her brain that recognises faces doesn’t function properly. Conveniently described as the face network, this set of brain areas are found on the underside of the neocortex and are able to deconstruct a person’s face in order to analyse it, and then link it categorically to an individual. Any damage to this area may result in prosopagnosia, or ‘facial blindness’, which can occur after a traumatic event such as a stroke, or may have a genetic component, passed down through generations.
So, your relative doesn’t recognise your face and is trying to eat you: what if you just explained to them who you are instead? Unfortunately, that’s not going to work either. Damage to two brain regions known as Broca’s and Wernicke’s areas means that zombies cannot articulate or understand language. Broca’s is related to the more physical side of language creation, playing a part in mouth movements and even gestures. Wernicke’s is important for language comprehension. Damage to this area means that sufferers are unable to string together comprehendible sentences or understand what other people are saying.
Unfortunately, Verstynen and Voytek haven’t come up with a suitable treatment or cure for CDHD, other than chopping off the head or running away very, very fast. But if there’s one positive takeaway, it’s that the zombies in an apocalypse are probably having a worse time than you. Whilst we’ve established that the destruction of the human race by a zombie army isn’t something we need to worry about, the practice of introducing science into science fiction isn’t as frivolous an endeavour as it may seem. It is a more immersive way for us non-specialists to understand especially complicated areas of science, like that of the brain. And perhaps now when we watch World War Z or contemplate switching off half-way through season 8 of the Walking Dead, we will remember that there’s some very interesting neuroscience going on behind those dead eyes, and even have a little sympathy for those zombies.
Written by Ellie Bennet and edited by Ailie McWhinnie.
Ellie is a former biologist, currently studying a masters in Medical Law and Ethics at the University of Edinburgh. Find her on Twitter @ellieb2302 and Linkedin @Eleanor Bennett.
