BRAIN IMAGING TIMELINE 1543: Artists in the painter Titian’s studio sketched detailed drawings of the brains of cadavers. This sketch appeared in a book by The Dana Dutch anatomist Andreas Vesalius, which revolutionized the study of anatomy. Sourcebook The Dana Sourcebook of Brain Science 1861: French surgeon Paul Broca of Brain Science identified the speech center in the brain through autopsies. 1911: Santiago Ramon y Cajal’s drawings and staining methods advanced those of Camillo Golgi for visualizing neurons, dendrites, and axons. Cajal promoted the “neuron theory,” the fundamental principle of modern neuroscience which holds that neurons are the basic unit of the central nervous system. More important, Cajal realized that neurons communicate across a small gap, or synapse. 1929: Electroencephalogram (EEG) introduced; measures and records minute wavelike electrical signals pro- duced by neurons as they “fire.” 1992: Functional magnetic resonance imaging Third Edition (fMRI) introduced; used to map brain activity by detecting variations in the response of hydrogen atoms when oxygen is present in the blood. Resources 1973: First computed tomogra- for Secondary and Post-Secondary phy (CT) camera; produces a com- posite image of the brain with a scanner that revolves around the Teachers and Students skull, taking thousands of x-rays. 1977: First magnetic resonance imaging 1975: First positron emission tomography (PET) cam- Third Edition (MRI) camera; produces images by subject- era; uses the principle that blood is rushed to busy areas ing the patient’s head to a strong magnetic of the brain to deliver oxygen and nutrients to the neu- field, followed by several pulses of radio rons. Patients are injected with radioactive glucose, then waves, producing three-dimensional com- scanned for the rays emitted as the solution metabolizes, puter-generated images. highlighting neuronal activity. 1489: Background: Sketch of the brain by Leonardo da Vinci. The brain: the most complex entity we know. The three-pound mass of pinkish-gray tissue is what makes us distinctively human. The brain encases 100 billion or more nerve cells and it can send signals to thousands of other cells at a rate of about 200 miles an hour. Because of its daunting complexity, the brain is the locus of many of our most serious remaining diseases and disorders—from Alzheimer’s to learning disabilities. An unexpectedly close genetic cousin. In a landmark event in biology, a team of international scientists in 2002 showed the genetic Does the brain reorganize itself? makeup of the common mouse to bear remarkable similarities to that These images suggest how the brain can reorganize itself to perform of humans. Because roughly 50% of our genes are devoted to devel- specific functions. The lines in image A represent the area of the brain oping and maintaining the brain and the central nervous system, examined by functional magnetic resonance imaging in two subjects: being able to compare two complete mammalian genomes for the In image B, a sighted person reads a one-syllable word by touch in first time should speed up efforts to understand brain-related Braille. In image C, a person with severe visual disability reads the diseases and disorders. same word in Braille. In the visually-disabled person, additional brain Positron emission tomography (PET) images reveal the activity occurs in the parietal, temporal, and occipital lobes—areas effects of drug addiction. that process visual information in sighted people—suggesting that the The images show dopamine receptor levels of a control brain of the visually-impaired person has reorganized its sensory subject (top) and a methamphetamine abuser (bottom). pathways. The graphs represented by D and E plot the data of the Chronic abuse of drugs such as methamphetamine appears experiment. to damage the brain’s dopamine system, which regulates the ability to sense pleasure. One in 100 billion—and a quadrillion connections. Here is an image of a single neuron taken from a rat brain, isolated in culture. The cell body is rep- resented by the large red area; the neuron’s axon sprouts from the left of the cell body. Other lines represent dendrites connecting to other neurons. Scientists estimate that there are more than 100 Computer technology opens a window on the living brain. A tiny worm with great potential to help explain the human nervous system. billion neurons in the human brain, and that there The worm C. elegans, shown here, was the first multicellular animal to have its com- Before the early 1970s, only neurosurgeons had seen a living human are about 1 quadrillion (1 with 15 zeroes) connec- About the cover: plete genetic code mapped. The blue dots in this image mark synapses that brain. Rapid advances in computer-generated imaging have allowed tions between neurons. brain scientists and doctors to go inside the head and examine the These images demonstrate, by Positron Emission Tomography permit motor movement. As in vertebrates, including humans, the C. elegans nervous structure and function of the brain in the living patient. Advances in (PET scanning), that certain areas of the brain activate as the system relies on neurotransmitters such as dopamine and serotonin, and it shares the next few decades are expected to allow scientists to investigate brain performs specific language tasks. other basic chemical structures as well. The 2002 Nobel Prize in Physiology or Medicine how brain circuits work, how one part of the brain modifies the func- honored three scientists who used C. elegans as an experimental model system to tions of other parts, and how these circuits adapt to new situations study genetic regulation of organ development and controlled elimination of cells (pro- or damage to existing circuits. grammed cell-death). “Every aspect of our lives depends on the normal functioning of our brains. Our education depends on it; the education of our children depends on it; our relation- ships to our fellow humans depend on it; our hopes and aspirations are all repre- sented in our brain. And all of these human qualities are at risk if something goes wrong with one’s brain.” —W. Maxwell Cowan, M.D., Ph.D., Neuroscientist, Educator (1931–2002) The Dana Sourcebook of Brain Science Resources for Secondary and Post-Secondary Teachers and Students Third Edition 1 From the Dana Foundation William Safire Chairman Edward F. Rover President Edward Bleier Wallace L. Cook Charles A. Dana III Ann McLaughlin Korologos LaSalle D. Leffall, Jr., M.D. Hildegarde E. Mahoney Donald B. Marron L. Guy Palmer II Herbert J. Siegel Clark M. Whittemore, Jr. Secretary-Treasurer Edward C. Andrews, Jr., M.D. Honorary Director Carlos Moseley Honorary Director Web site: www.dana.org The Dana Sourcebook of Brain Science Resources for Secondary and Post-Secondary Teachers and Students Third Edition This publication is provided by the Dana Foundation to participating schools. The Foundation is a private philanthropic organization with particular interests in science, health, and education. Please note: Access the online edition at www.dana.org. Copyright 2003 Dana Press David Balog, Editor A Dana Press publication Jane Nevins, Editor-in-Chief 2 Walter Donway, Director Table of Contents Scientific Lives 4 Revealing the Workings, the Wonder, of the Human Brain 6 Genes and the Brain 18 Stem Cells and Brain Research 23 Advances in Brain Research 25 Behind the Scenes in the Adolescent Brain 26 Neuroethics Weighs the Benefits or Potential Misuses of Brain Research 27 Neuroimmunology: Harnessing the Power of the Brain and the Immune System 28 Defining Stroke or Brain Attack 29 What Exactly Are Antidepressants? 31 The Developing Nervous System: Vision 32 The Science of Attracting Axons —The Final Key to Spinal Cord Regeneration? 33 Allostatic Load Scenario 4: Too Little Is as Bad as Too Much 34 Research and Future Treatments for Alzheimer’s Disease 35 The Workings of Memory 36 The Power of Emotions 37 Use It or Lose It 39 Imagine a World 40 Suggested Activities 49 The Great Brain Books 68 Great Literary Portrayals of Brain Disorders 85 Tracing Shakespeare’s Insights Through Modern Brain Science 99 ANote on Sources of Information on the Brain 109 A Glossary of Key Brain Science Terms 124 Maps of the Brain 134 Resources on the Web 140 Acknowledgments 150 Index 151 3 Scientific Lives Part One: be something inherently attractive to women in the A Life of Research, Advancing Our concepts of growth and repair.” Knowledge of How the Brain Works Writing in In Search of the Lost Cord: Solving the Mystery of Spinal Cord Regeneration, (Dana Press/ Editor’s note: One way to study the brain is to become Joseph Henry Press, 2001) author Luba Vikhanski a researcher, conducting experiments, analyzing data, publishing results, and teaching. A world-renowned describes Dr. Bernice Grafstein’s groundbreaking scientist and researcher on the development and regenera- work: “Unlike in mammals, regenerating nerve tion of nerve cells, Bernice Grafstein, Ph.D., is professor cells in fish and amphibians readily reconnect to of physiology and Vincent & Brooke Astor Distinguished their appropriate targets. Dr. Grafstein’s pioneering Professor of Neuroscience, Department of Physiology, studies with radioactive tracing showed that fish Weill Medical College of Cornell University. nerve cells undergo massive changes in metabo- Bernice Grafstein, Ph.D. lism when they regenerate, a finding that would A Leader in Spinal Cord Research and lead to many of the current studies on the activity for Women in Neuroscience of neuronal genes involved in regeneration.” Spinal cord injury remains one of our most Dr. Bernice Grafstein has a tragic, devastating medical conditions. It often particular interest in advancing strikes the young and can cause serious incapacita- the careers of young neurosci- tion for 40 years or more. As a scientist who has entists through her role as a been interested in development and regeneration of teacher of neuroscience and nerve cells for several decades, Dr.