Read Welcome to Your Brain Online
Authors: Sam Wang,Sandra Aamodt
Tags: #Neurophysiology-Popular works., #Brain-Popular works
As in other sensory systems, areas of the brain that analyze touch information are organized into
maps, in this case, maps of the body surface. The size of a given brain area depends on the number of
receptors in each part of the body, rather than on the size of that body part, so that the part of the
brain’s map that receives information from the face is larger than the area that receives information
from the entire chest and legs. Along the same lines, in a cat’s brain, a large area is occupied by
neurons that respond to the whiskers.
Responses to painful stimuli are carried by separate receptors and analyzed by brain areas
distinct from those that carry information about regular touch. One family of pain receptors detects
heat and cold, while another family of receptors detects painful touch.
Practical tip: Does acupuncture work?
Having needles stuck into your skin doesn’t sound like much fun, but a lot of people
swear by it. The therapeutic use of needles, called acupuncture, is routine in Asia and has
become increasingly common in the West over the past three decades. Roughly 3 percent of
the U.S. population and 21 percent of the French population have tried it. About 25 percent
of medical doctors in the U.S. and U.K. endorse acupuncture for some conditions.
The scientific evidence for medical benefits from acupuncture is mixed and very
controversial. Many of the studies are done and evaluated by people with a vested interest
in proving or disproving its effectiveness—making it difficult to know who you should
listen to. In our reading of the scientific literature, the best evidence suggests that
acupuncture is more effective than no treatment at all for some conditions, notably chronic
pain and nausea. For most people, acupuncture seems to be about as effective as
conventional treatments for these conditions, but there is little or no evidence that it’s
effective for other conditions, such as headache or drug addiction.
Traditional practitioners believe that acupuncture improves the flow of
qi
—a Chinese
word that, roughly, means
energy
—circulating in pathways of the body. To unblock the
energy flow, needles are inserted along these pathways, though different authors disagree
on the exact locations, number of pathways, and acupuncture points. Attempts to identify
these pathways in terms of the body’s electrical or other physical properties have not been
successful.
However, acupuncture definitely has some effect on the brain. Functional imaging of
brain activity shows that acupuncture has specific effects on particular brain areas. For
instance, an acupuncture point in the foot traditionally related to vision has been reported to
activate the brain’s visual cortex, while stimulation at other sites nearby do not. However,
a follow-up study reported a different result, creating considerable uncertainty about this
conclusion. Brain areas that control pain are activated by acupuncture—but also by the
expectation of pain relief or by sham acupuncture at incorrect sites.
This brings up a major problem with evaluating any medical treatment (and especially
acupuncture): a lot of patients feel better just because someone is paying attention to their
problem. This is the reason that more than half of the patients in many studies report
improvements in their conditions after taking sugar pills. Scientists solve this problem by
doing double-blind studies, in which neither the patients nor the health care providers know
who’s receiving the real treatment and who’s getting the fake one.
Of course, it’s tough to keep patients guessing about whether needles are being stuck in
them or not. Some researchers have used sham acupuncture, inserting needles into incorrect
locations. Sham acupuncture is often found to be as effective as real acupuncture, but it’s
easy to believe that sham acupuncture might have some therapeutic effect in its own right. A
few studies have used a telescoping probe that retracts as it approaches the skin, feeling
like a needle to people who haven’t experienced real acupuncture. This solves half the
problem, but the practitioners still know whether they are giving real or fake treatments,
which may lead them to behave differently with patients in the two groups and therefore
influence their responses. Telescoping-probe studies have given mixed results. Most of
them show real and sham acupuncture to be equally effective, but a large minority find real
acupuncture to be more effective.
At the end of the day, you probably don’t care why you’re feeling better, as long as you
are, and there’s no reason not to try acupuncture if you’re interested. In the hands of a
qualified practitioner, it’s pretty safe, causing serious problems for fewer than one in two
thousand patients. Even if many of the details of the process turn out to be folklore, as we
expect that they will, acupuncture does seem to have practical value in treating certain
conditions.
Prediction is hard, especially of the future.
—Unknown
If you’ve ever touched a hot stove, you know that many pain receptors can activate reflex
pathways that allow you to make a very rapid response to sensations that indicate the possibility of
immediate danger to your body. However, these reflexes—and all responses to pain—are very
strongly influenced by the person’s interpretation of the painful situation. Indeed, there is an entire set
of brain areas that influences activity in the direct pain-sensing parts of the brain based on context and
expectation. This effect can be as powerful as a near-complete lack of pain in a soldier with a serious
injury on the battlefield. More commonly, we’ve all seen the opposite effect—the sudden
intensification of pain in a small child when his mother approaches.
These responses are often called psychological, but that doesn’t mean they’re not real: people’s
expectations and beliefs create physical changes in the brain. If people are given a pill or an injection
that contains no active drug but are told that it will relieve their pain, activity increases in the parts of
the brain that are normally involved in modulating pain. When people are told that a cream will
reduce the pain of an upcoming electric shock or heat stimulus, they not only show increased activity
in pain-controlling regions, they also show reduced activity in parts of the brain that receive pain
signals. In addition, pain relief from such placebo treatments can be blocked by naloxone, a drug that
prevents morphine from acting on its receptors. From these results, we can conclude that when
patients are told that their pain will be reduced, the brain responds by releasing natural chemicals that
reduce pain, which are called endorphins. Even a saltwater injection, the most innocuous treatment
possible, can lead to pain relief—and also the release of endorphins.
Practical tip: Referred pain
Have you ever had pain caused by indigestion that made it feel like your chest was
hurting? This sort of confusion happens because all the nerves that sense pain in the internal
organs send signals through the same pathways in the spinal cord that carry information
from the body surface. This convergence leaves the brain uncertain about what’s wrong.
Pain felt in a place other than its true source is called referred pain.
For this reason, doctors learn that when patients complain about pain in their left arm, it
may indicate a heart attack. Similarly, pain from a kidney stone may feel like a
stomachache, gallbladder pain may be felt near the collarbone, and pain from appendicitis
may hurt near your bellybutton. If you have persistent pain without an apparent cause in any
of these areas (but especially the left arm), you should see a doctor as soon as possible.
Endorphins act on the same receptors that respond to morphine and heroin. The existence of
endorphins is the reason that your body has receptors that respond to these drugs. Endorphins may
allow pain relief when the brain decides that it’s more important for the body to be able to go on
(perhaps to escape from continuing danger) than it is to protect the injury from further damage.
Scientists at Stanford have been trying to use brain imaging to train people to activate pain-
controlling areas of their own brains. If it works, this technique could allow people with chronic pain
to reduce their own discomfort without needing fake pills or creams or injections. The scientists use
functional imaging to detect activity in the target region of the brain. Subjects can see on a computer
display whether they are achieving the desired effect. Using this technique, people have been able to
gain voluntary control over the activity in one area of their brains—though it remains to be seen
whether this approach will lead to pain relief in patients.
How Your Brain Changes Throughout Life
Growing Great Brains: Early Childhood
Growing Up: Sensitive Periods and Language
Rebels and Their Causes: Childhood and Adolescence
Reaching the Top of the Mountain: Aging
Growing Great Brains: Early Childhood
When we were kids, our parents tried to keep us safe and stop us from running with scissors. As
far as we can remember, that was enough to keep their hands full. Today, middle-class family life has
become a far more complicated affair. Daily activities are a blur of flash cards and baby aerobics.
Magazines say that you can increase your children’s intelligence by playing Mozart for them when
they’re young—or even before they’re born. Parents worry that if little Emma doesn’t attend the right
preschool, she’ll never get into a decent college. Every few years, another expert piles on more
anxiety by explaining how a child’s experiences in early life determine intelligence and success later
on.
Our own parents had very different philosophies of child rearing. Sam spent hours each day
watching television and can still recite the plot of almost every episode of
Star Trek
and
The Brady
Bunch
. Sandra was five years old before friends at school let her in on the secret that there were
other channels on TV besides PBS. Since her parents never watched anything else, she spent her early
years with
Sesame Street
and other carefully designed educational fare. Yet Sam seems to have made
up for any possible brain damage, and, indeed, as a university professor, is now even responsible for
the training of younger minds.
It’s true that the early environment influences how a child’s brain grows, but you rarely need to
worry that your child isn’t getting enough stimulation. There’s no question that childhood deprivation
can interfere with brain development. To start with an extreme example, children who spent their
early years in Romanian orphanages often have lifelong problems. But these poor kids were left alone
in a crib for years, visited only by a caretaker who came along every so often to change diapers.
Unless you’re locking your kid in a closet (in which case, you should stop doing that right away), you
don’t have to worry about how this sort of serious deprivation affects brain development.
Myth: Listening to Mozart makes babies smarter
One of the most persistent brain myths is that playing classical music to babies
increases their intelligence. There’s no scientific evidence for this idea, but it’s proven
amazingly persistent, probably because it allows parents to address their anxiety about their
children’s intellectual development—and because sellers of classical music for children
encourage the belief every chance they get.
This myth began with a 1993 report in the scientific journal
Nature
that listening to a
Mozart sonata improved the performance of college students on a complex spatial
reasoning task. The researchers summarized the effect as equivalent to an eight- to nine-
point gain on the Stanford-Binet IQ scale. Journalists didn’t find this result immediately
fascinating; they reported it about as much as any other science story published in the same
journal that year.
The idea really took off after the 1997 publication of
The Mozart Effect
by Don