It sets humans apart from all other species by allowing us to achieve the wonders of walking on the moon and composing masterpieces of literature, art and music. Throughout recorded time, the human brain—a spongy, three-pound mass of fatty tissue—has been compared to a telephone switchboard and a supercomputer.
But the brain is much more complicated than any of these devices, a fact scientists confirm almost daily with each new discovery. The extent of the brain’s capabilities is unknown, but it is the most complex living structure known in the universe.
This single organ controls all body activities, ranging from heart rate and sexual function to emotion, learning and memory. The brain is even thought to influence the response to disease of the immune system and to determine, in part, how well people respond to medical treatments. Ultimately, it shapes our thoughts, hopes, dreams and imagination. In short, the brain is what makes us human.
Neuroscientists have the daunting task of deciphering the mystery of this most complex of all machines: how as many as a trillion nerve cells are produced, grow and organize themselves into effective, functionally active systems that ordinarily remain in working order throughout a person’s lifetime.
The motivation of researchers is twofold: to understand human behavior better—from how we learn to why people have trouble getting along together—and to discover ways to prevent or cure many devastating brain disorders.
The more than 1,000 disorders of the brain and nervous system result in more hospitalizations than any other disease group, including heart disease and cancer. Neurological illnesses affect more than 50 million Americans annually at costs exceeding $400 billion. In addition, mental disorders, excluding drug and alcohol problems, strike 44 million adults a year at a cost of some $148 billion.
However, during the congressionally designated Decade of the Brain, which ended in 2000, neuroscience made significant discoveries in these areas:
■ Genetics. Key disease genes were identified that underlie several neurodegenerative disorders—including Alzheimer’s disease, Huntington’s disease, Parkinson’s disease and amyotrophic lateral sclerosis. This has provided new insights into underlying disease mechanisms and is beginning to suggest new treatments.
With the mapping of the human genome, neuroscientists will be able to make more rapid progress in identifying genes that either contribute to human neurological disease or that directly cause disease. Mapping animal genomes will aid the search for genes that regulate and control many complex behaviors.
■ Brain Plasticity. Scientists began to uncover the molecular bases of neural plasticity, revealing how learning and memory occur and how declines might be reversed. It also is leading to new approaches to the treatment of chronic pain.
■ New Drugs. Researchers gained new insights into the mechanisms of molecular neuropharmacology, which provides a new understanding of the mechanisms of addiction. These advances also have led to new treatments for depression and obsessive-compulsive disorder.
■ Imaging. Revolutionary imaging techniques, including magnetic resonance imaging and positron emission tomography, now reveal brain systems underlying attention, memory and emotions and indicate dynamic changes that occur in schizophrenia.
■ Cell Death. The discovery of how and why neurons die, as well as the discovery of stem cells, which divide and form new neurons, has many clinical applications. This has dramatically improved the outlook for reversing the effects of injury both in the brain and spinal cord. The first effective treatments for stroke and spinal cord injury based on these advances have been brought to clinical practice.
■ Brain Development. New principles and molecules responsible for guiding nervous system development now give scientists a better understanding of certain disorders of childhood. Together with the discovery of stem cells, these advances are pointing to novel strategies for helping the brain or spinal cord regain functions lost to diseases.
Federal neuroscience research funding of more than $4 billion annually and private support should vastly expand our knowledge of the brain in the years ahead.
This book only provides a glimpse of what is known about the nervous system, the disorders of the brain and some of the exciting avenues of research that promise new therapies for many neurological diseases.
Brain Facts : A Primer on the Brain and Nervous System