Unless you’ve been under a rock, you should be familiar with the zombie apocalypse hype these past few years. Shows and movies such as “The Walking Dead” and I Am Legend depict flesh-eating monster endemics in the modern world. I rarely give in to shows about zombies because I doubt that a decomposing half-dead body wants to consume my brains, but zombie-like behavior is quite prevalent in the animal kingdom. The parasitic hairworm develops in a cricket, then eventually takes control of its brain and forces it to commit suicide; wasps use ladybugs as living incubators for their young, who burst through their abdomen a la Alien. If we are going to take the impending doom of the zombie apocalypse seriously, we should look into the biology of the zombie brain to determine if zombification of a human is truly possible.
The figure of the zombie is commonplace in contemporary culture: mindless, stumbling monsters that don’t feel pain and have an insatiable appetite for human flesh. Before we go whacking off hoards of zombies, it is imperative we know the enemy: how is the zombie brain different from a living human’s? Dr. Steven C. Schlozman, an assistant professor of psychiatry at Harvard Medical School, approached this problem by drafting a series of science-backed explanations of the neurobiology of the living dead.
The frontal lobe, the part of the brain involved in executive functioning and enables us to think carefully, is seriously lacking in those who have the misfortune of being afflicted with a living dead condition. Zombies can clearly see and sense us, so their frontal lobe activity is just enough for it to communicate with the thalamus. Without a fully functioning frontal lobe, a zombie is driven by purely base emotions, such as rage. Such emotions are housed in the amygdala, the most primitive part of our brain. When the amygdala is stimulated by fear, anger or lust, the anterior cingulate cortex — the modulator between amygdala and frontal lobe — steps on it a bit, giving the frontal lobe time to rethink a potentially rash decision. A zombie would possess a dysfunctional anterior cingulate cortex, resulting in hyper-aggression. A dysfunctional cerebellum and basal ganglia, the parts of the brain that make fluidity of motion possible, could be the cause of their staggered walk. In movies, a zombie’s appetite is never satiated despite the number of supporting actors it consumes. In this instance, the ventromedial hypothalamus, the region of the brain that tells you when to stop eating, is likely damaged, resulting in hyperphagia, an abnormally large appetite.
Although we see zombies as staggering idiots that can barely function, they must possess some level of memory and ability to navigate. However, we must take into consideration their lack of sleep. Because sleep enhances memory and learning in humans, their resulting insomnia leaves them with an inability to collect data and thus cognitively advance. In “The Walking Dead,” zombies can climb fences and overcome complex obstacles. They even show cognitive advancement by utilizing tools and weapons. Perhaps modern zombies are beginning to evolve, becoming an even greater threat than artificial intelligence.
There are various ways in which you can become infected. Remember mad cow disease? That was caused by a prion, an incorrectly folded protein that replicates by converting its properly folded counterparts. Another prion-related disease is Creutzfeld-Jakob disease, a degenerative neurological disorder that results in sponge-like brain tissue. There was an outbreak of Kuru, a relative to CJD, that left its victims in a zombie-like state: slurred speech, decreased muscle control, tremors and sporadic laughter. It was then found that this was caused by cannibalistic funeral practices in which relatives consumed the bodies of the deceased. Interestingly, the women and children were eight to nine times more likely to be infected because they were left with the remaining brain after the men took the choice cuts. Additionally, tetrodotoxin, poison from a pufferfish, was used by Haitian voodoo masters to psychologically enslave their chosen victims. If the correct dosage is used, the toxin mimics death in the victim, whose vitals will slow to an immeasurable state and the body will show signs of rigor mortis and even produce the odor of rot.
A zombie’s bite, however, is the most efficient way of passing the disease. Infection by bite bypasses the traditional levels of the immune system and delivers a huge dose of pathogen directly into the bloodstream, all while contaminating the flesh directly exposed, so watch out for those stumbling students in zombie ‘costumes’ this Wednesday.