Idiot Brain (4 page)

But the activation and maintenance of the memories causes them to be effectively “relived.” Very old experiences and more recent imaginings are all thrown into the mix together. There's no specific order or logical structure to the sequence of experiences this results in, hence dreams are invariably so other-worldly and bizarre. It's also theorized that the frontal regions of the brain responsible for attention and logic are trying to impose some sort of rationale on this ramshackle sequences of events, which explains why we still feel as if dreams are real while they're happening and the impossible occurrences don't strike us as unusual at the time.

Despite the wild and unpredictable nature of dreams, certain dreams can be recurring, and these are usually associated with some issue or problem. Indeed, if there's a certain thing in your life stressing you out (like a deadline for finishing a book you've agreed to write) then you're going to think about this a lot. As a result, you'll have a lot of new memories about it that need to be organized, so will occur more in dreams, so it crops up more often and you end up regularly dreaming about burning down a publisher's office.

Another theory about REM sleep is that it's especially important for small children as it aids neurological development, going beyond just memories and shoring up and reinforcing all the connections in the brain. This would help explain why babies and the very young have to sleep a lot more than adults (often more than half the day) and spend a great
deal longer in REM sleep (about 80 percent of total sleep time as opposed to about 20 percent in adults). Adults retain REM sleep but at lower levels to keep the brain efficient.

Yet another theory is that sleep is essential to clear out the waste products of the brain. The ongoing complex cellular processes of the brain produce a wide variety of by-products that need to be cleared away, and studies have shown that this occurs at a higher rate during sleep, so it could be that sleep for the brain is the equivalent of a restaurant closing down to clear up between lunchtime and evening openings; it's just as busy, but doing different things.

Whatever the true reason for it, sleep is essential for normal brain functioning. People deprived of sleep, particularly of REM sleep, quickly show a serious decline in cognitive focus, attention and problem-solving skills, an increase in stress levels, lower moods, irritability, and a drop in all-round task performance; the nuclear disasters of Chernobyl and Three Mile Island have been linked to overworked and exhausted engineers, so has the
Challenger
shuttle disaster, and let's not go into the long-term consequences of decisions made by sleep-deprived doctors on their third successive twelve-hour shift in two days.
²⁰
If you go too long without sleep, your brain starts initiating “micro sleeps,” where you grab snatches of sleep for minutes or even seconds at a time. But we've evolved to expect and utilize long periods of unconsciousness, and we can't really make do with small crumbs here and there. Even if we do manage to persevere with all the cognitive problems a lack of sleep causes, it's associated with impaired immune systems, obesity, stress and heart problems.

So if you happen to nod off while reading this book, it's not boring, it's medicinal.

It's
either an old bathrobe or a bloodthirsty axe murderer

(The brain and the fight-or-flight response)

As living, breathing humans, our survival depends on our biological requirements—sleeping, eating, moving—being met. But these aren't the only things essential to our existence. There are plenty of dangers lurking in the wider world, just waiting for the opportunity to snuff us out. Luckily, millions of years of evolution have equipped us with a sophisticated and reliable system of defensive measures in order to respond to any potential threat, coordinated with admirable speed and efficiency by our marvelous brains. We even have an emotion dedicated to recognizing and focusing on threats: fear. One down side of this is that our brains have an inherent “better safe than sorry” approach that means we regularly experience fear in situations where it's not really warranted.

Most people can relate to this. Maybe you are lying awake in a dark bedroom when the shadows on the walls start looking less like the branches of the dead tree outside and more like the outstretched skeletal arms of some hideous monster. Then you see the hooded figure by the door.

It's clearly the axe murderer your friend told you about. So, obviously, you collapse into a terrified panic. The axe murderer doesn't move though. He can't. Because he's not an axe murderer, he's a bathrobe. The one you hung up on the bedroom door earlier.

It makes no logical sense, so why on earth do we have such powerful fear reactions to things that are clearly utterly harmless?
Our brains, however, aren't convinced of this harmlessness. We could all live in sterilized bubbles with every sharp edge smoothed down, but as far as the brain is concerned death could come leaping out of the nearest bush at any point. To our brains, daily life is like tightrope-walking over a vast pit full of furious honey badgers and broken glass; one wrong move and you'll end up as a gruesome mess in temporary but exquisite pain.

Such a tendency is understandable. Humans evolved in a hostile, wild environment with dangers at every turn. Those humans who developed a healthy paranoia and jumped at shadows (that genuinely may have had teeth) survived long enough to pass on their genes. As a result, when presented with any conceivable threat or danger, the modern human has a suite of (mostly unconscious) response mechanisms providing a reflex that enables them to deal better with said threat, and this reflex is still very much alive and kicking (as are humans, thanks to it). This reflex is the fight-or-flight response, which is a great name as it concisely but accurately describes its function. When presented with a threat, people can either fight it or run away.

The fight-or-flight response starts in the brain, as you'd expect. Information from the senses reaches the brain and enters the thalamus, which is basically a central hub for the brain. If the brain were a city, the thalamus would be like the main station where everything arrives before being sent to where it needs to be.
²¹
The thalamus connects to both the advanced conscious parts of the brain in the cortex and the more primitive “reptile” regions in the midbrain and brainstem. It's an important area.

Sometimes the sensory information that reaches the
thalamus is worrying. It might be unfamiliar, or familiar but worrying in context. If you're lost in the woods and you hear a growl, that's unfamiliar. If you're home alone and you hear footsteps upstairs, that's familiar, but in a bad way. In either case, the sensory information reporting this is tagged “This isn't good.” In the cortex, where it's processed further, the more analytical part of the brain looks at the information and wonders “Is this something to worry about?” while checking the memory to see if anything similar has occurred before. If there's not enough information to determine that whatever we're experiencing is safe, it can trigger the fight-or-flight response.

However, as well as the cortex, the sensory information is relayed to the amygdala, the part of the brain responsible for strong emotional processing, and fear in particular. The amygdala doesn't do subtlety; it senses something might be amiss and initiates a red alert straight away, a response far faster than the more complex analysis in the cortex could ever hope to be. This is why a scary sensation, like a balloon popping unexpectedly, produces a fear response almost instantly, before you can process it enough to realize it's harmless.
²²

The hypothalamus is then signaled. This is the region right under the thalamus (hence the name), and is largely responsible for “making things happen” in the body. To extend my earlier metaphor, if the thalamus is the station, the hypothalamus is the taxi stand outside it, taking important things into the city where they get stuff done. One of the roles of the hypothalamus is triggering the fight-or-flight response. It does this by getting the sympathetic nervous system to put the body effectively at “battle stations.”

At this point you may be wondering, “What's the sympathetic nervous system?” Good question.

The nervous system, the network of nerves and neurons spread throughout the body, allows the brain to control the body and the body to communicate with and influence the brain. The central nervous system—the brain and the spinal cord—is where the big decisions are made, and as such these areas are protected by a sturdy layer of bone (the skull and the spinal column). But many major nerves branch out from these structures, dividing and spreading further until they innervate (the actual term for supplying organs and tissue with nerves) the rest of the body. These far-reaching nerves and branches, outside the brain and spinal cord, are referred to as the peripheral nervous system.

The peripheral nervous system has two components. There's the somatic nervous system, also known as the voluntary nervous system, which links the brain to our musculoskeletal system to allow conscious movement. There's also the autonomic nervous system, which controls all the unconscious processes that keep us functioning, so is largely linked to internal organs.

But, just to make it more complicated, the autonomic nervous system also has two components: the sympathetic and parasympathetic nervous systems. The parasympathetic nervous system is responsible for maintaining the more calm processes of the body, such as gradual digestion after meals or regulating the expulsion of waste. If someone were to make a sitcom starring the different parts of the human body, the parasympathetic nervous system would be the laidback character, telling people to “chill out” while rarely getting off the couch.

In contrast, the sympathetic nervous system is incredibly highly strung. It would be the twitchy paranoid one, constantly wrapping itself in tinfoil and ranting about the CIA
to anyone who'll listen. The sympathetic nervous system is often labeled the fight-or-flight system because it's what causes the various responses the body employs to deal with threats. The sympathetic nervous system dilates our pupils, to ensure more light enters our eyes so we can better spot dangers. It increases the heart rate while shunting blood away from peripheral areas and non-essential organs and systems (including digestion and salivation—hence the dry mouth when we're scared) and towards the muscles, to ensure that we have as much energy as possible for running or fighting (and feel quite tense as a result).

The sympathetic system and parasympathetic systems are constantly active and usually balance each other and ensure normal functioning of our bodily systems. But in times of emergency, the sympathetic nervous system takes over and adapts the body for fighting or (metaphorical) flying. The fight-or-flight response triggers the adrenal medulla (just above the kidneys) as well, meaning our bodies are flooded with adrenalin, which produces many more of the familiar responses to a threat: tension, butterflies in the stomach, rapid breathing for oxygenation, even relaxing of the bowels (you don't want to be carrying unnecessary “weight” while running for your life).

Our awareness is also turned up, making us extra sensitive to potential dangers, reducing our ability to concentrate on any minor issues we were dealing with before the scary thing happened. This is the result of both the brain being alert to danger anyway and by the adrenalin suddenly hitting it, enhancing some forms of activity and limiting others.
²³

The brain's emotional processing also steps up a gear,
²⁴
largely because the amygdala is involved. If we're dealing
with a threat, we need to be motivated to take it on or get away from it asap, so we rapidly become intensely fearful or angry, providing further focus and ensuring we don't waste time with tedious “reasoning.”

When faced with a potential threat, both brain and body rapidly shift to a state of enhanced awareness and physical readiness to deal with it. But the problem with this is the “potential” aspect. The fight-or-flight response kicks in
before
we know whether it's actually needed.

Again, this makes logical sense; the primitive human who runs from something that
might
be a tiger was more likely to survive and reproduce than the one who said, “Let's just wait so we can be sure.” The first human arrives back at the tribe intact, whereas the second is the tiger's breakfast.

This is a useful survival strategy in the wild, but for the modern human it's quite disruptive. The fight-or-flight response involves many real and demanding physical processes, and it takes time for the effects of these to wear off. The adrenalin surge alone takes a while to leave the bloodstream, so having our whole bodies enter combat mode whenever a balloon pops unexpectedly is rather inconvenient.
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We can experience all the tension and build-up required for a fight-or-flight response, only to realize quickly that it's not required. But we still have tense muscles and a rapid heartbeat and so on, and not relieving this with a frantic sprint or wrestling session with an intruder can cause cramps, knots in muscles, trembling and many other unpleasant consequences as the tension becomes too much.

There's also the increased emotional sensation. Someone primed to be terrified or angry can't just switch it off in an instant, so it often ends up being directed at less deserving
targets. Tell an incredibly tense person to “relax” and see what happens.

The demanding physical aspect of the fight-or-flight response is only part of the issue. The brain being so attuned to seek out and focus on danger and threats is increasingly problematic. Firstly, the brain can take account of the present situation and become more alert to danger. If we're in a darkened bedroom, the brain is aware that we can't see as much, so is attuned for any suspicious noise, and we know it should be quiet at night, so any noises that
do
occur get far more attention and are more likely to trigger our alarm systems. Also, our brain's complexity means humans now have the ability to anticipate, rationalize and imagine, meaning we can now be scared of things that haven't happened or aren't there such as the axe-murderer bathrobe.