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

won his nickel, you were proving
    yourself to be a remarkably sophisticated animal.
    Walking or chewing demonstrates your brain’s ability to generate a rhythm. Animals can generate
    cycles on a wide range of time scales, from seconds (heartbeat, breathing), to days (sleeping), to a
    month (menstrual cycles), and even longer (hibernation). All these rhythms are generated by built-in
    mechanisms and adjusted based on external events or commands.
    Your ability to generate rhythms simultaneously shows that your brain can generate multiple
    patterns at once, often independently. Walking involves a tightly coordinated set of events in which
    your left leg is instructed to rise, move forward, and then lower, as your body simultaneously moves
    forward. Your right leg follows close behind. The sequence of events has to happen smoothly and in
    order. These commands are generated mainly by a network of neurons in your spinal cord, all
    working together as what’s called a central pattern generator—central because commands originate
    here and go to the muscles. This pattern generator can work on its own, since headless cockroaches
    and chickens can produce walking movements, but they still need their brains to keep everything
    coordinated and to negotiate obstacles. Chewing is driven by another network of neurons distributed
    through your brainstem to generate repeated jaw movements. The networks for walking and chewing
    can work independently (or together, as Uncle Larry discovered).
    Practical tip: Overcoming jet lag
    When you travel, the clocks in your body are able to shift by about an hour per day to
    reset and get synchronized with the world again. However, you can use your knowledge of
    circadian rhythms to help you get over jet lag more quickly. The best way to adjust your
    brain’s circadian rhythm is to use light. Melatonin supplements are a distant second. Both
    are more effective than simply getting up earlier or later and work better than other tricks
    such as exercise. Here are some guidelines for using light and melatonin to help your body
    adjust.
    • Get some afternoon light. The best way to adjust your circadian rhythm is to take a
    dose of light when your brain can use it as a signal. Light does different things to your
    circadian rhythm depending on the time of day, just as the timing of your push on a swing

    affects its movement. In the morning—or, rather, when your body thinks it is morning—light
    helps you wake up. Exposure to light at this time will get you up earlier the next day—as if
    the light is telling your body that this time is morning. Exposure to light at night, on the other
    hand, will get you up later the next day, as if the light is telling your body that the day is not
    over yet, so it needs to stay awake longer.
    So when you fly east, such as from the Americas to Europe or Africa, you should go
    outside to get some bright light a couple of hours before people back home start to wake up.
    Finding a source of light is easy at this time because at your destination it is afternoon. This
    should help you get up more easily the next day. If you’ve traveled east across eight time
    zones or more, try to avoid light first thing in the morning (when it’s evening at home),
    because that will push your clock in the wrong direction. Conversely, when you fly west
    (from Europe or Africa to the Americas), make sure to get a dose of bright light when you
    feel sleepy, before it’s bedtime back at the place where your flight started.
    The simple way to remember both these rules is as follows: On your first day at your
    destination, get some light in the afternoon. On each subsequent day, as your brain clock
    adjusts, get some light two or three hours earlier. Lather. Rinse. Repeat.
    • Put out that bedside light! Enhancing your brain’s built-in morning or evening feeling
    is usually easy because it will still be daytime outside when you need the light. However, it
    is important to avoid the