The primitive human brain was obviously successful because we as a species endured and are now the dominant life-form on earth. But despite our evolved complicated cognitive abilities, the original primitive brain functions didn’t go away. If anything, they became more important; having language and reasoning skills doesn’t really amount to much if you keep dying from simple things like forgetting to eat or wandering off cliffs.
The brain needs the body to sustain it, and the body needs the brain to control it and make it do necessary things. (They’re actually far more intertwined than this description suggests, but just go with it for now.) As a result, much of the brain is dedicated to basic physiological processes, monitoring internal workings, coordinating responses to problems, cleaning up mess. Maintenance, essentially. The regions that control these fundamental aspects, the brainstem and cerebellum, are sometimes referred to as the “reptile” brain, emphasizing their primitive nature, because it’s the same thing the brain was doing when we were reptiles, back in the mists of time. (Mammals were a later addition to the whole “life-on-earth” scene.) By contrast, all the more advanced abilities we modern humans enjoy—consciousness, attention, perception, reasoning—are found in the neocortex, “neo” meaning “new.” The actual arrangement is far more complex than these labels suggest, but it’s a useful shorthand.
So you might hope that these parts—the reptile brain and the neocortex—would work together harmoniously, or at least ignore each other. Some hope. If you’ve ever worked for someone who’s a micromanager, you know how incredibly inefficient this arrangement can be. Having someone less experienced (but technically higher ranking) hovering over you, issuing ill-informed orders and asking dumb questions can only ever make it harder. The neocortex does this with the reptile brain all the time.
It’s not all one way though. The neocortex is flexible and responsive; the reptile brain is set in its ways. We’ve all met people who think they know best because they’re older or have been doing something for longer. Working with these people can be a nightmare, like trying to write computer programs with someone who insists on using a typewriter because “that’s how it’s always been done.” The reptile brain can be like that, derailing useful things by being incredibly obstinate. This chapter looks at how the brain messes up the more basic functions of the body.
Stop the book, I want to get off!
(How the brain causes motion sickness)
Modern humans spend a lot more time sitting down than ever before. Manual-labor jobs have largely been replaced by office jobs. Cars and other means of transport mean we can travel while sitting down. The Internet means it is possible to spend practically your whole life sitting down, what with telecommuting, online banking and shopping.
This has its down sides. Obscene sums are spent on ergonomically designed office chairs to make sure people don’t get damaged or injured due to excessive sitting. Sitting too long on an aeroplane can even be fatal, due to deep vein thrombosis. It seems odd, but very little movement is damaging.
Because moving is important. Humans are good at it and we do it a lot, as evidenced by the fact that, as a species, we’ve pretty much covered the surface of the earth, and actually been to the moon. Walking two miles a day has been reported as being good for the brain, but then it’s probably good for every part of the body.1 Our skeletons have evolved to allow long periods of walking, as the arrangement and properties of our feet, legs, hips and general body layout are ideally suited to regular ambulation. But it’s not just the structure of our bodies; we’re seemingly “programmed” to walk without even getting the brain involved.
There are nerve clusters in our spines that help control our locomotion without any conscious involvement.2 These bundles of nerves are called pattern generators, and are found in the lower parts of the spinal cord in the central nervous system. These pattern generators stimulate the muscles and tendons of the legs to move in specific patterns (hence the name) to produce walking. They also receive feedback from the muscles, tendons, skin and joints—such as detecting if we’re walking down a slope—so we can tweak and adjust the manner of movement to match the situation. This may explain why an unconscious person can still wander about, as we’ll see in the phenomenon of sleepwalking later in this chapter.
This ability to move around easily and without thinking about it—whether fleeing dangerous environments, finding food sources, pursuing prey or outrunning predators—ensured our species’s survival. The first organisms to leave the sea and colonise the land led to all air-breathing life on earth; they wouldn’t have done so if they’d stayed put.
But here’s the question: if moving is integral to our well-being and survival, and we’ve actually evolved sophisticated biological systems to ensure it happens as often and as easily as possible, why does it sometimes make us throw up? This is the phenomenon known as motion sickness or travel sickness. Sometimes, often apropos of nothing, being in transit makes us bring up our breakfast, lose our lunch, or eject some other more recent but non-alliterative meal.
It’s the brain that’s actually responsible for this, not the stomach or innards (despite how it may feel at the time). What possible reason could there be for our brains to conclude, in defiance of aeons of evolution, that going from A to B is a legitimate cause for vomiting? In actual fact, the brain isn’t defying our evolved tendencies at all. It’s the numerous systems and mechanisms we have to facilitate motion that are causing the problem. Motion sickness occurs only when you’re traveling by artificial means—when you’re in a vehicle. Here’s why.
Humans have a sophisticated array of senses and neurological mechanisms that give rise to proprioception, the ability to sense how our body is currently arranged, and which parts are going where. Put your hand behind your back and you can still sense the hand, know where it is and what rude gesture it’s making, without actually seeing it. That’s proprioception.
There’s also the vestibular system, found in our inner ear. It’s a bunch of fluid-filled canals (meaning “bony tubes” in this context) to detect our balance and position. There’s enough space in there for fluid to move about in response to gravity, and there are neurons throughout it that can detect the location and arrangement of the fluids, letting our brain know our current position and orientation. If the fluid is at the top of the tubes, this means we’re upside-down, which probably isn’t ideal and should be remedied as soon as possible.