Welcome to Your Brain (40 page)

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Authors: Sam Wang,Sandra Aamodt

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brain works, the bottom line is that it allows high-level commands from the cortex to get through more

clearly to the midbrain and spinal cord.

Deep brain stimulation treatment for Parkinson’s disease has, in turn, led to other discoveries,

often when doctors missed a surgical target, even by just a few millimeters. In one famous case, a

woman was being treated for Parkinson’s disease by deep brain stimulation. When her brain was

tickled at a site just two millimeters (one-tenth of an inch) away from the place that relieved her

motor symptoms, she became intensely depressed, weeping and saying things like “I’m disgusted with

life … Everything is useless, always feeling worthless, I’m scared in this world.” Fortunately, her

symptoms disappeared about a minute after the stimulation ended. In other patients, stimulating

another site, also just a few millimeters away, led to the opposite result: mania in the form of

euphoria, nonstop talking, grandiose delusions, and increased sexual drive, all of which lasted for

days. One of these patients asked repeatedly why he had not had the procedure done earlier. By the

way, the answer to your question is no, you may not have this operation. Not yet, anyway.

An unavoidable impression from all the neurosurgical case studies reported to date is that we

know very little about what many of these brain regions do. As we’ve pointed out before, structures

such as the brainstem and midbrain are incredibly crowded, consisting of regions with very different

functions piled next to one another cheek by jowl. Scientifically speaking, this can be considered a

lucky accident, since surgeons’ fortuitous discoveries in the middle of the brain would not be

permitted as planned research.

In some cases, deep brain stimulation is starting to be applied in a rational fashion. For instance,

surgery to treat obsessive-compulsives has focused on destroying a band of axons called the internal

capsule, but a newer approach is to try deep brain stimulation at this location, a less damaging

procedure. Another proposed therapy for depression is based on the observation that depressive

episodes are associated with activity in a thin strip of cortical tissue called the subgenual cingulate,

also known as area 25. Area 25 becomes less active in patients suffering from depression who

respond to antidepressant drugs. In a small study, deep brain stimulation of the white matter

underneath area 25 relieved symptoms in four of six patients with depression who could not be

helped by medication, electroconvulsive therapy, or psychotherapy.

Did you know? Interfaces between brains and machines

In the classic novel
The Count of Monte Cristo
, Alexandre Dumas describes Monsieur

Noirtier de Villefort, who after a stroke is alert and oriented to his surroundings, but is

mute and paralyzed. He is able to communicate with others only by moving and blinking his

eyes, and he conveys information using a list of letters. This disorder now has a name:

locked-in syndrome. Locked-in people still have active brains but cannot translate their

thoughts into actions. In addition to being caused by stroke, lock-in can result from

neurological disorders, such as amyotrophic lateral sclerosis or ALS, which afflicts

physicist Stephen Hawking. Spinal cord transection can also paralyze some or all of the

limbs but spare speech, as happened to the late Christopher Reeve in a horseback-riding

accident.

Researchers have been trying to design prosthetic mechanical limbs to help locked-in

people gain some control over their surroundings. The idea is to monitor brain activity in

the motor cortex to infer what movements patients are thinking of making. Such mind

reading is possible, at least at a crude level, since even tetraplegics, who do not have

control over any limb, show activity in the motor cortex when asked to think about

movement. Arrays of electrodes can measure brain activity in a monkey as it moves its arm

to play a video game, and researchers have used that activity to drive a mechanical arm.

The resulting movements resemble those made by the monkey’s own arm, albeit with a

certain flailing quality and occasional moves in unexpected directions. Comparable

progress has been made in an electrode array implanted into the brain of a human

tetraplegic.

This approach to treating depression may eventually replace some extreme current treatments. The

most effective therapy for major depression is electroconvulsive therapy, inducing seizures

throughout the entire brain, which can relieve symptoms for months (especially when paired with

cognitive behavioral therapy). A therapy that is less extreme but less effective, and just about as

mysterious, is stimulation of the vagus nerve, which helps one-third of persons suffering from

depression who do not respond to antidepressant drugs. The vagus nerve conveys information to the

brain about body systems, such as how fast the heart is beating, pain signals, and information from the

gut and stomach (for instance, whether the stomach is full). One hypothesis is that this treatment works

because feelings of well-being may depend on the interplay between body and brain signals. That is,

vagus nerve stimulation may send happy-body signals to the brain.

Someday, deep brain stimulation may be designed rationally based on the known functions of the

various parts of our brains. For the time being, though, we are limited by our basic knowledge about

brain function. Scientists claim that deep brain stimulation is useful in treating problems like

Tourette’s syndrome and epilepsy, in addition to the disorders of movement and mood discussed

above. It isn’t clear whether deep brain stimulation can reliably help these patients, but that should

become apparent if the treatment helps anyone as much as it helps parkinsonian patients. In the

meantime, reports of weird effects of probing the brain’s depths are a continuing source of evidence

that when it comes to understanding how our brains work, we have a long way to go.

A Note on the Authors

Sandra Aamodt
is the editor in chief of
Nature Neuroscience
, the leading scientific journal in the

field of brain research. She received her undergraduate degree in biophysics from Johns Hopkins

University and her doctorate in neuroscience from the University of Rochester. After four years of

postdoctoral research at Yale University, she joined
Nature Neuroscience
at its founding in 1998 and

became editor in chief in 2003. During her editorial career, she has read over three thousand

neuroscience papers and written dozens of editorials on neuroscience and science policy for the

journal. She has also given lectures at twenty universities, and attended forty-five scientific meetings

in ten countries. She enjoys motorcycling and is preparing to spend a year sailing in the South Pacific.

She lives with her husband, a professor of neuroscience, in California.

Sam Wang
is an associate professor of neuroscience and molecular biology at Princeton

University. He graduated with honor in physics from the California Institute of Technology at the age

of nineteen and holds a doctorate in neuroscience from Stanford University School of Medicine. He

has done research at Duke University Medical Center and at Bell Labs Lucent Technologies, and has

worked on science and education policy for the United States Senate. He has published over forty

articles on the brain in leading scientific journals, including
Nature
,
Nature Neuroscience
,

Proceedings of the National Academy of Sciences
, and
Neuron
. He is the recipient of a National

Science Foundation Young Investigator Award and is an Alfred P. Sloan Fellow and a W. M. Keck

Foundation Distinguished Young Scholar. He lives with his wife, a physician, and daughter in

Princeton, New Jersey.

Copyright © 2008 by Sandra Aamodt and Sam Wang

All rights reserved. No part of this book may be used or reproduced in any manner whatsoever without written permission from the

publisher except in the case of brief quotations embodied in critical articles or reviews. For information address Bloomsbury USA, 175

Fifth Avenue, New York, NY 10010.

Art credits:

Illustrations throughout by Lisa Haney. Page 5 courtesy of Michael MacAskill; page 17 (left) courtesy of Kenneth Catania; pages 17

(right), 19, 26, and 166 courtesy of Sam Wang; page 23 courtesy of Patrick Lane; page 43 courtesy of Edward Adelson, reprinted with

permission; page 44 reprinted with permission from P. Thompson “Margaret Thatcher: A New Illusion,†Perception 9 (1980):

483–84.

Published by Bloomsbury USA, New York

LIBRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA

Aamodt, Sandra.

Welome to your brain: why you lose your car keys but never forget how to drive and other puzzles of Everyday life / Sandra Aamodt and

Sam Wang.—1st U.S. ed.

p. cm.

ISBN-13: 978-1-59691-283-0 (hardcover)

ISBN-10: 1-59691-283-9 (hardcover)

1. Brain—Popular works. 2. Neurophysiology—Popular works. I. Wang, Sam, 1967– II. Title.

QP376.A222 2008

612.8'2—dc22

2007026739

First published in the U.S. by Bloomsbury in 2008

This e-book edition published in 2010

E-book ISBN: 978-1-59691-706-4

www.bloomsburyusa.com

Document Outline

 

Table of Contents

Acknowledgments

Quiz How Well Do You Know Your Brain?

Introduction Your Brain: A User’s Guide

Part 1—Your Brain and the World

Chapter 1 Can You Trust Your Brain?

Chapter 2 Gray Matter and the Silver Screen: Popular Metaphors of How the

Chapter 3 Thinking Meat: Neurons and Synapses

Chapter 4 Fascinating Rhythms: Biological Clocks and Jet Lag

Chapter 5 Bring Your Swimsuit: Weight Regulation

Part 2—Coming to Your Senses

Chapter 6 Looking Out for Yourself: Vision

Chapter 7 How to Survive a Cocktail Party: Hearing

Chapter 8 Accounting for Taste (and Smell)

Chapter 9 Touching All the Bases: Your Skin’s Senses

Part 3—How Your Brain Changes Throughout Life

Chapter 10 Growing Great Brains: Early Childhood

Chapter 11 Growing Up: Sensitive Periods and Language

Chapter 12 Rebels and Their Causes: Childhood and Adolescence

Chapter 13 An Educational Tour: Learning

Chapter 14 Reaching the Top of the Mountain: Aging

Chapter 15 Is the Brain Still Evolving?

Part 4—Your Emotional Brain

Chapter 16 The Weather in Your Brain: Emotions

Chapter 17 Did I Pack Everything? Anxiety

Chapter 18 Happiness and How We Find It

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