In the final episode of Season 7 of Game of Thrones, the Night King uses a terrifying weapon—the recently deceased dragon Viserion, now reanimated—to destroy the massive, magic-infused Wall that has for millennia stopped the White Walkers from invading Westeros. As the Army of the Dead lumbers through the gap, it’s pretty clear: Winter is here.
We’ve only seen the Army of the Dead in action a few times now: Hardhome, in Season 5, and Season 7’s epic Wight Hunt, but it seems like Episode 3 of Game of Thrones’ final season is setting us up for an absolutely titanic clash at the Stark’s ancestral home of Winterfell.
But wights—or zombies to use a more common parlance—aren’t just a well-worn trope for fantasy writers. The possibility of reanimating dead tissue—including braaaaains—has challenged neurobiologists around the world.
So what are the wights, how do they work, and why does an entire army psychically linked together seem to be controlled by just one mind—the Night King?
What Kind of Zombies?
First off, are wights zombies at all? There are actually two types of zombies, the shambling dead—as representing George A. Romero’s classics—and the zombies of Haitian legend.
“There’s the socio-cultural definition of zombie from tales in Haitian voodoo, where someone was put into a state similar to death and then ‘brought back to life,’” says Bradley Voytek, avid Game of Thrones fan, neuroscientist at the University of California-San Diego, and co-author of , which uses zombies as the basis for an introduction to serious neuroscience.
In his book anthropologist Wade Davis controversially documented the case of Clairvius Narcisse, a Haitian man who re-appeared almost 20 years after he was declared dead at a hospital, claiming he’d been brought back to life by a bokor, or sorcerer. Davis theorized that Narcisse hadn’t died, but had been put into a coma-like state by a powerful neurotoxin and then revived.
Skepticism over Wade’s claims aside, there are other examples of zombie-like behavior in nature: a parasitic fungus called ophiocordyceps can infect the brains of carpenter ants and control their behavior. The Jewel Wasp uses a neurotoxin to turn cockroaches into willing hosts for its larvae (an Ecuadorian wasp does much the same with a species of spider). And toxoplasmosis gondii, a parasite that only reproduces in cat intestines, lives on rodents and works essentially by removing their fear of cats, which is how the parasite ends up inside the cat, where it can procreate.
But the Night King isn’t a pufferfish or parasitic fungi; he’s just bringing the dead back to life with good old magic. In the case of the Wights, says Voytek, it’s clear that we’re dealing with a classic, beyond-the-grave zombie.
Zombies Eat Brains, But Do They Need Brains?
With wights firmly classified as dead zombies, next we figure out how they work. Last week, , researchers detailed a similar experiment, where they were able to restart some cellular activity in the brains of pigs who’d been dead for hours.
“At no point did we observe the kind of organized electrical activity associated with perception, awareness, or consciousness,” .
Restoring signs of life without consciousness? Sounds like a zombie to us.
But the Army of the Dead has some puzzling elements for Voytek. Let’s start with the fact that some of them are pretty much walking skeletons that don’t appear to have a lot of soft tissue left. How can there be neuroscience if there’s no brain?
“It’s pretty clear that some of the wights have been dead a long time and without tissue you’re out of the realm of science,” he says.
While these boney wights defy neuroscience, you don't need much of your brain to perform certain functions.
“You have about 86 billion neurons in your brain, and in some parts of it you can lose millions of them and without a careful medical exam, you might not even notice,” Voytek says. “In other parts, you could lose just hundreds and die. If your brain stem is damaged, that controls respiration, so you’re not coming back.”
The cerebellum, by contrast, has roughly half the total neurons in the brain, and yet people can survive with severe damage to it.
The cerebellum, incidentally, might explain the signature slowness zombies are known for. Classic horror movie zombies like Romero’s are called “slow zombies” because they mostly lurch and lumber around (that’s compared to “fast zombies” like in World War Z).
Voytek suggests lumbering is akin to a kind of ataxia, which can happen if the cerebellum, which controls movement, is severely damaged. But the Army of the Dead is both fast and slow.
“I was confused by that because they’re slow and lumbering but then in battle they’re pretty adept and fast,” says Voytek.
A possible explanation: when you learn a new skill—like swordfighting or, for Viserion, flying—lots of different areas of the brain are involved.
“But once it’s learned, the skill becomes a habit and moves to a different area of the brain,” says Voytek. “So it could be that they can still fight so well in battle and move quickly because the brain structures involved in those previous habits are intact.”
Voytek went on to consult primary sources regarding a zombie’s speed, once asking Romero at a comic convention why zombies were so slow.
“Here I am, a PhD neuroscientist, and he must think I’m the dumbest person he’s ever talked to,” says Voytek. “He looks at me and just says, ‘Because they’re dead!’”
Fighting Zombies With Fire
Like most zombies, wights can also sustain heavy damage from weapons without seeming to feel pain. Jon Snow literally cuts one in half in front of Cersei and the thing still keeps coming. But when wights are set on fire, they not only die, but shriek in apparent pain in the process.
“There are very few things that humans respond to instantaneously the way we do to pain from heat or something sharp,” says Voytek.
But it’s not inconsistent that wights might feel one but not the other.
“The pain from heat and sharpness are carried by two different pathways,” he points out. Perhaps the sharp pathway is damaged, but the neural path for transmitting heat pain is somehow intact.
And, they can communicate. Remember in the Wight Hunt when the captured wight’s wordless calls attract attention from the other dead? “That’s a common trope in zombie films,” says Voytek. Zombies don’t talk, but they do verbalize, “and they can hear and detect things like a human crying, so there’s a prototype of communication there.”
Perhaps they have a damaged occipital lobe, which affects their ability to verbalize, but the temporal lobe that processes auditory inputs is more intact.
Questions Left Unanswered
But the most puzzling aspect might be their actions.
We’ve seen that the wights won’t cross open water, even though they can’t exactly drown, but then willingly plunge into holes in the ice trying to get to Snow’s wight-hunting party, which suggests something is controlling their actions. So what is exactly the Night King’s relationship with his undead horde?
Once again, nature might hold the answer: the neurobiological phenomenon known as the hive mind, found famously in the most industrious of the world’s creatures—the ant. Voytek isn’t an expert on collective social behavior, but sees some similarities between zombies and nature.
“(Ant) brains are so tiny but acting in coordination they can do amazing things like build bridges across little streams with their bodies,” Voytek says. “It’s pretty evident the way that wights are portrayed in the show that their survival instinct is collective, not individual.”
Voytek thinks that might explain why the wights are heedless in some instances and cautious in others—the Night King is trying to preserve his army, because it needs more corpses to grow.
In the Wight Hunt, when Snow kills a White Walker with Longclaw, his Valyrian steel sword, almost all the wights around him die too, perhaps because that Walker controlled them or reanimated them from corpses. That gives us a clue to their possible defeat, when Beric Dondarrion points to the Night King and says to Snow, “Kill him. He turned them all.”
Neuroscience can’t explain everything about wights or zombies—at least not yet.