Welcome to Your Brain by Sam Wang, Sandra Aamodt Read Free Book Online Page A

pitfall of accidentally doing the opposite. Getting light at the
    wrong time can set your clock in the wrong direction. So if you can’t sleep at night, don’t
    turn on the light! Artificial light is less effective than daylight in setting your clock, but you
    should still avoid it.
    • For long trips, pick a virtual direction. If you are doing something really crazy like
    going halfway around the world (Bombay to San Francisco, or New York to Tokyo),
    decide which way to shift your clock (later each day or earlier each day) and stick with that
    plan. For most people, but not all, the easiest thing is to pretend you are going west (through
    Chicago or Honolulu) and get that dose of sun in the very late afternoon. Think of it as a
    layover for your circadian rhythm.
    • When going east, take melatonin at night. Light exposure produces melatonin with
    some time delay, so a pulse of melatonin at night encourages sleep and prepares the next
    cycle of your clock. As a result, melatonin is elevated in the body clock’s evening.
    Taking melatonin helps a little if done at the right moment of your circadian rhythm. A
    dose of melatonin when your body thinks bedtime is soon will help you get up earlier the
    next day—and help you get to sleep earlier the next night. At your destination, take it at
    nightfall, or even in the middle of the night. However, for reasons that are not known,
    melatonin is only helpful if you are going east.
    Melatonin’s effect is small, shifting your waking time by up to an hour per day. Exercise
    has a similar effect, and should be done at the same time of day. What we don’t know is
    whether melatonin or exercise does any additional good beyond the benefit of bright light.
    You don’t always realize it, but you’re always falling. With each step you fall forward
    slightly. And then catch yourself from falling. Over and over, you’re falling. And then
    catching yourself from falling. And this is how you can be walking and falling at the same
    time.
    —Laurie Anderson, Big Science
    Before we get too impressed with ourselves, we should note one more thing: generating repetitive
    patterns is a universal feature of animal life. For instance, scientists have studied rhythmic swimming
    in lampreys, an odd-looking jawless fish that resembles a long thin sock with a ring of teeth at one
    end. Likewise, they study rhythmic chewing in lobsters, which have relatively simple nervous
    systems. Lobsters are also interesting because two chewing patterns are directed by a network of only
    thirty neurons, which adjust themselves and the connections among them throughout life. (And they
    taste great with melted butter.)
    Some patterns are automatic, such as your heartbeat or breathing, but these rhythms can still be
    controlled. For instance, your heartbeat rhythm, which is generated in your heart itself, can be sped up
    or slowed down by commands sent by your central nervous system (see Chapter 3) . Your neuronal
    network for breathing, which is in your brainstem, can act completely on its own; you don’t normally
    think about breathing. It can also be under close control, as when you hold your breath.
    A particularly useful rhythm, found in almost every animal that scientists have studied, is the daily
    sleep-wake cycle, the circadian rhythm. Circadian rhythms help animals anticipate when light, heat,
    and food are likely to be available. The circadian rhythm can run on its own, on an approximately
    twenty-four-hour cycle, and can be reset by correctly timed light exposure. It’s synchronized with the
    daily cycle of light and darkness, which is detected by your eyes. Your circadian rhythms regulate a
    host of activities, including when you need to sleep, your body temperature, and when you get hungry.
    However, these days, circadian rhythms can also trip you up. Nearly anyone who has traveled
    long distances by airplane has experienced the problem of jet lag. For instance, we wrote part of this
    book at a