It’s been a long day, and you’re dog tired. You’ve pulled up the covers, closed the book, put your glasses on the nightstand, and turned off the light.
And that’s when your brain kicks in. Thoughts pop in or race around, leaving you there lying awake cursing the night and your own brain: “Why won’t you shut up?”
Barry Gordon, a professor of neurology and cognitive science at Johns Hopkins, tells Scientific American that part of the problem is that our subconscious does a lot of thinking on its own that we’re not even aware of. And that as we’re settling into sleep, our conscious mind starts to let its guard down, letting those unthought thoughts rise to the surface:
Although thoughts appear to “pop” into awareness before bedtime, their cognitive precursors have probably been simmering for a while. Once those preconscious thoughts gather sufficient strength, the full spotlight of consciousness beams down on them. The mind’s freewheeling friskiness is only partly under our control, so shutting our mind off before we sleep is not possible.
So what’s the science behind this? What are brains actually doing on a physical level as we drift off (or not)? What is the mix of electricity and chemicals that are causing our consciousness to change?
Lets start with the stages of sleep: rapid eye movement (aka REM) and non-rapid eye movement (or NREM). REM is the kind of sleep we’re in when we dream. Your eyes move back and forth behind your eyelids, and your brain produces a unique pattern of electrical signals that, on an electroencephalogram (an EEG), look like this:
NREM sleep is really a mix of four sleep stages, all of which look different on an EEG. As our brains progress through the four stages, we shut down more and more; stages 3 and 4 are, in fact, sometimes lumped together into just “deep sleep.”
Those electrical patterns are fueled by different chemical signals in different parts of the brain. At this point, we should step back for a sec and talk about some basic neurobiology. The whole nervous system — our brain, spinal cord, the nerves running through your body — works because chemicals called neurotransmitters pass signals from neuron to neuron. Those neurotransmitters do one of two things: make neurons “fire” (release a burst of electricity), or keep them from firing.
When we’re falling asleep, our neurons don’t all stop firing…some actually start firing and set the stage for our brain to transition from a wakeful state to a sleepy state. In particular, according to this information page from the National Institute of Neurological Disorders and Stroke, nerve cells in the brain stem — which acts like a junction box between the brain and the rest of the body — start to release neurotransmitters called serotonin and norepinephrine that “keep some parts of the brain active while we are awake.” Other nerve cells in the base of the brain itself start to fire when we asleep; their signals turn off other signals in the brain that would otherwise keep us awake. (This is starting to sound like rush hour traffic in Boston, only no one would be signaling in Boston.)
How the biology translates into conscious and subconscious thoughts — including the ones waking you up — isn’t clear. But the thing to remember is that even when we’re asleep, our brains are always active.
While we may not be able to shut our brains off, are there things we can do to at least turn down the noise? Over on PsychCentral, a pair of sleep specialists, Lawrence Epstein from Harvard and Florida psychologist Stephanie Silberman, provide a 12-point plan for getting the brain to settle in (the twelfth of which was, of course, see a sleep specialist). But one point in particular caught my eye:
7. Busy your brain with mental exercises.
Being able to distract yourself from your worries can be enough to help you fall asleep, Silberman says. A mental exercise helps your brain focus away from your worries, she says. It can be as simple as “thinking of fruits and vegetables with a certain letter.”
So does that mean that counting sheep might actually work?