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TOM COSTELLO: For sixteen hours a day, we are awake and active.
From getting up in the morning to when we go to bed, our brains
are constantly working. But what are our brains doing for the
other eight hours of our day when we are asleep?
ORIE SHAFER: Quite surprisingly, there are some states of sleep
when the brain actually appears to be more active, more
coordinated than it does when we are awake.
COSTELLO: Dr. Orie Shafer is a neurobiologist at the University
of Michigan and funded by the National Science Foundation. He
is investigating the brain's activity during sleep,
specifically, a part of the brain that governs every aspect
of the daily lives of all animals, from insects to fish,
to humans: the internal clock.
SHAFER: Every brain on the planet, and every animal has
deep within it, a clock. And that clock controls the onset
and the offset of sleep in a way that we're all familiar with, in
that we all tend to wake up and become sleepy at the same
time every day.
COSTELLO: Called the circadian clock, it controls the patterns
in the brain that tells animals when to go to sleep and when
to wake up.
SHAFER: In fact, if you take a human being or a mouse or a
fruit fly and you removed them from the cues from the
environment, daily cues of light, daily cues of
temperature, they continue to show a rhythm
in sleep and wakefulness.
COSTELLO: Instead of studying the human brain, Shafer's
research focuses on the fruit fly, a common household insect
with a tiny brain that offers a lot of clues about what makes
the circadian clock tick.
SHAFER: If you think about the human brain, the estimate is
that there is one times ten to the eleventh neurons in our
brain. That's an impossibly large number of neurons to keep
track of. So the fruit fly, its entire nervous system has one
hundred thousand neurons.
COSTELLO: Though it may be significantly smaller, the fruit
fly's basic brain structure and neural activity is very similar
to that of many other animals, including that of humans.
In mammals, the brain's primary time-keeper is located in the
hypothalamus. Called the suprachiasmatic nucleus, this
tiny area of the brain is responsible for setting
our master clock.
SHAFER: If you don't have a suprachiasmatic nucleus in your
brain, you can't keep time, you have no set rhythm in your sleep
activity cycles. That is the master clock in your brain.
COSTELLO: Shafer hopes the fruit fly will help solve how the
master clock communicates time throughout the vast network of
neurons in the brain.
SHAFER: Where does the time go within the brain? How does that
dedicated network of neurons that keeps track of internal
time, talk to the parts of the brain that controls sleep?
VICTORIA BOOTH: You had the model take a nap by just like
doing a wake bout like up here...
COSTELLO: Helping in this effort is one of Shafer's colleagues,
Dr. Victoria Booth, who is also funded by the National Science
Foundation. She uses mathematical modeling and
analysis as predictive tools to study the problem through a
slightly different perspective.
BOOTH: What we've been motivated by is to actually build a
mathematical model based on what the hypothesized network
looks like, how these different areas of the brain
are connected together.
COSTELLO: By building a mathematical and computational
model, Booth and her students will be able to plug in
different scenarios of sleep cycles to see how the brain
model responds in hopes of further understanding the
circadian clock and its control of other parts of the brain.
BOOTH: By building a math model, we could test some of the ideas
the experimentalists have about how the system may work, and
then identify which areas of the brain might be targets for
future experimental investigation.
SHAFER: I'm confident, very confident that the answers we
get to those fundamental questions in the fly are going
to continue to inform and enrich our attempts to understand
timekeeping in the human brain.
COSTELLO: Combining the fields of math and science, Booth and
Shafer are unraveling one of the mysteries of the brain: how the
circadian clock helps us know when it's time to sleep and when
it’s time to wake up.
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