Read Online Welcome to Your Brain by Sam Wang, Sandra Aamodt - Free Book Online Page B
Authors: Sam Wang, Sandra Aamodt
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this reason, you’d be better off putting your
energy into changing your environment so that the available choices are healthy ones rather than
spending your mental energy trying to resist the urge to reach for that chocolate bar. Your brain will
thank you, and so will your waistline.
Part Two
Coming to Your Senses
Looking Out for Yourself: Vision
How to Survive a Cocktail Party: Hearing
Accounting for Taste (and Smell)
Touching All the Bases: Your Skin’s Senses
Chapter 6
Looking Out for Yourself: Vision
While skiing downhill one day, Mike May realized he was headed toward a huge dark object too
close to dodge. He was sure he was going to die. When he passed through the object, he realized it
was a shadow cast by the ski lift.
Such experiences are common in May’s life, ever since he had his sight restored by a corneal
transplant at age forty-three. May had been blind since a jar of lantern fuel exploded in his face when
he was three. However, blindness did not stop him from becoming an excellent skier. He had claimed
the world record for speed as a blind downhill skier, following his guide down the mountain at sixty-
five miles per hour. During his four decades of blindness, though, his brain had no experience of
natural vision. Now, with his vision restored, he has trouble interpreting what he sees. It’s especially
hard for him to distinguish two-dimensional objects from three-dimensional objects, an essential skill
when you are approaching a large two-dimensional shadow.
Your brain interprets many scenes without making you explicitly aware of what’s going on.
Because May learned to see late in life, the way you might learn a foreign language as an adult, his
brain is unable to accomplish many visual tasks correctly, such as figuring out that the large, dark,
featureless object in front of him was probably a shadow and not a rock. In general, it’s hard for him
to figure out which lines or colors are part of one object, and which are part of another object, or
even part of the background behind the objects. His case illustrates how difficult and important these
processes are in understanding how to see—and how many invisible assumptions your brain needs to
make to get the job done.
Did you know? Animal research and “lazy eye”
One of the best examples of how animal studies can have unexpected benefits for human
medicine comes from research on visual development. Because the two eyes are in
different places on the head, they see the world from slightly different angles. This creates a
problem for brain development; to create a coherent view, the brain needs to match up the
information arriving in the two eyes that comes from the same part of the visual world. It
would be hard to specify this matching in advance, since everyone’s head is a different
size, and the distance between the eyes changes as the body grows. So the brain figures it
out by learning to match up information from locations in each eye that are active at the
same time, and so presumably are seeing the same place in the visual world. If an animal is
deprived of sight in one eye when it’s young, then this learning can’t happen, and almost all
the visual neurons in the brain end up carrying signals from just one eye. If an animal loses
sight in one eye at certain young ages (about the first month after birth in cats, longer for
people), its brain will learn to interpret information only from the other eye. This pattern
can’t be reversed later in life. David Hubel and Torsten Wiesel won the Nobel Prize for
discovering this process.
A friend of ours has a daughter with strabismus, what people used to call lazy eye,
which occurs in 5 percent of children. She has trouble controlling the movement of one eye,
leading it to wander off in a different direction from the other one. Twenty years ago, the
standard treatment for this problem would have been to keep a patch over the good eye (to
train
energy into changing your environment so that the available choices are healthy ones rather than
spending your mental energy trying to resist the urge to reach for that chocolate bar. Your brain will
thank you, and so will your waistline.
Part Two
Coming to Your Senses
Looking Out for Yourself: Vision
How to Survive a Cocktail Party: Hearing
Accounting for Taste (and Smell)
Touching All the Bases: Your Skin’s Senses
Chapter 6
Looking Out for Yourself: Vision
While skiing downhill one day, Mike May realized he was headed toward a huge dark object too
close to dodge. He was sure he was going to die. When he passed through the object, he realized it
was a shadow cast by the ski lift.
Such experiences are common in May’s life, ever since he had his sight restored by a corneal
transplant at age forty-three. May had been blind since a jar of lantern fuel exploded in his face when
he was three. However, blindness did not stop him from becoming an excellent skier. He had claimed
the world record for speed as a blind downhill skier, following his guide down the mountain at sixty-
five miles per hour. During his four decades of blindness, though, his brain had no experience of
natural vision. Now, with his vision restored, he has trouble interpreting what he sees. It’s especially
hard for him to distinguish two-dimensional objects from three-dimensional objects, an essential skill
when you are approaching a large two-dimensional shadow.
Your brain interprets many scenes without making you explicitly aware of what’s going on.
Because May learned to see late in life, the way you might learn a foreign language as an adult, his
brain is unable to accomplish many visual tasks correctly, such as figuring out that the large, dark,
featureless object in front of him was probably a shadow and not a rock. In general, it’s hard for him
to figure out which lines or colors are part of one object, and which are part of another object, or
even part of the background behind the objects. His case illustrates how difficult and important these
processes are in understanding how to see—and how many invisible assumptions your brain needs to
make to get the job done.
Did you know? Animal research and “lazy eye”
One of the best examples of how animal studies can have unexpected benefits for human
medicine comes from research on visual development. Because the two eyes are in
different places on the head, they see the world from slightly different angles. This creates a
problem for brain development; to create a coherent view, the brain needs to match up the
information arriving in the two eyes that comes from the same part of the visual world. It
would be hard to specify this matching in advance, since everyone’s head is a different
size, and the distance between the eyes changes as the body grows. So the brain figures it
out by learning to match up information from locations in each eye that are active at the
same time, and so presumably are seeing the same place in the visual world. If an animal is
deprived of sight in one eye when it’s young, then this learning can’t happen, and almost all
the visual neurons in the brain end up carrying signals from just one eye. If an animal loses
sight in one eye at certain young ages (about the first month after birth in cats, longer for
people), its brain will learn to interpret information only from the other eye. This pattern
can’t be reversed later in life. David Hubel and Torsten Wiesel won the Nobel Prize for
discovering this process.
A friend of ours has a daughter with strabismus, what people used to call lazy eye,
which occurs in 5 percent of children. She has trouble controlling the movement of one eye,
leading it to wander off in a different direction from the other one. Twenty years ago, the
standard treatment for this problem would have been to keep a patch over the good eye (to
train
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