Mysteries of the Brain--Technology Opens Windows

Shrouded in an armor of skull and spine and guarded by an intricate network of chemical processes, the central nervous system has been for centuries perhaps man’s most intriguing but bewildering scientific mystery.

A few decades ago, it was virtually unthinkable to explore the living brain for fear of permanent damage, paralysis or death. Today, however, numerous theoretical and technological advances in fields ranging from anatomy to molecular biology have placed the neurosciences--the study of the brain and behavior--on the cutting edge of modern science and medicine.

While genetic engineering techniques are allowing some scientists to map the precise structure of some mental illnesses, complex new imaging techniques are allowing other researchers to peer inside the human brain to see actual biochemical processes as they occur.

“We’re in the midst of as dramatic a transformation as has ever occurred in science,” David A. Hamburg, president of the Carnegie Corp., told a group of scientists gathered in Los Angeles on Wednesday for the annual meeting of the American Assn. for the Advancement of Science.

Hamburg, who is president of the association, noted that while the field was regarded with “extreme caution” only a few years ago, it is now “moving into the top category in all sciences.”

“The past 15 years have witnessed a dazzling growth of research laboratories, educational programs, membership in the unifying Society of Neuroscience, journal publications--and a kind of scientific migration involving not only young people but established scientists from other fields.”

Discoveries are happening at such a pace that only a sampling of research findings can be made available at any one time, said Floyd E. Bloom, director of the Division of Preclinical Neuroscience and Endocrinology at the Research Institute of Scripps Clinic in La Jolla.

“It is a field,” Bloom said, “that involves many disciplines, from the analysis of molecules to the study of the behavior of a whole person. . . . There are new and exciting ventures here beyond those in any other area of science.”

Perhaps more than in any other area of science, technology has helped to bring about some of the most significant discoveries in neuroscience.

For a number of years, scientists have had at their disposal the computerized axial tomography device, known as the CAT scanner, which takes much clearer pictures of internal anatomy than do X-ray machines. Only recently, however, have neuroscientists begun to make use of the positron emission tomography device, or PET scanner, which allows them to see biochemical processes as they actually happen inside the brain or other organs of the body.

By revealing the chemical workings of the brain, said Dr. Michael E. Phelps, chief of the division of nuclear medicine and biophysics at UCLA’s School of Medicine, this new technology can help doctors for the first time differentiate between Alzheimer’s disease and similar forms of dementia, one of which is treatable.

Although PET scanners are now used almost exclusively in research because of their high costs and limited supply, Phelps said UCLA has used them to examine patients with epilepsy and to identify which of the offspring of victims of Huntington’s disease are themselves at risk. One day, he said, the scanners will be available for routine examinations of patients with suspected mental disorders.

The new technology and research has revealed a network in the human nervous system of immense complexity--far more intricate than scientists had ever imagined, said Dr. Henry N. Wagner, professor of radiology and environmental health sciences and director of the divisions of nuclear medicine and education health sciences at Johns Hopkins University.

In the early 1970s, scientists understood only a few of the chief elements of the chemistry and structure of the neuron, a nerve cell that is the basic functional unit of the brain. Today there is a wealth of detail available about how substances travel through the neuron and how one neuron communicates with another. But there is still much to be learned.

The human brain has so many neurons--some estimate 10 billion--that no one has ever succeeded in actually counting them, Bloom told a symposium on advances in new technology sponsored by the Radiological Society of North America.

One of the most intriguing questions facing scientists in the field of neuroscience is precisely how the brain puts itself together.

What does a developing cell rely on in order to know what to become and what to do? “Does it sample its environment? Or does it turn internally to its own genealogy?” asked Dr. Karl Herrup, associate professor of human genetics at Yale University School of Medicine.

At a session on the frontiers of neuroscience, Herrup said that he and his colleagues at Yale have conducted genetic studies on inbred strains of mice and, although they have yet to collect all their data, they have found evidence that “strongly suggests cell lineage relationships are very important in development.”

While such basic research may not have any immediate, direct application to human health, it is the beginning of what Herrup believes is the solution to the “phenomenal puzzle” of the way the brain and central nervous system come to exist.

In essence, he said, “we are finding out why the brain of an elephant doesn’t develop in a mouse.”

Another important question to neuroscientists is how the cells of the brain communicate with one another.

Recent discoveries at the University of California, San Francisco, concerning the role of chemical transmitters in the brain may partly explain how living beings can maintain a state of attention or arousal--what is sometimes known as “quiet readiness.”

They found that two well-known neurotransmitters, norepinephrine and acetylcholine, keep some brain cells primed to “fire” in response to stimulation. This primed state facilitates transmission of signals when they arrive and thus allow a faster reaction time to anything from physical danger to the smell of food.

The San Francisco experiments involved the study of living slices of part of a rat’s brain known as the hippocampus, a region thought to play a key role in memory. Because one of the neurotransmitters involved in the study, acetylcholine, is also thought to be involved in memory, these findings may have implications for understanding such disorders as Alzheimer’s disease, in which acetylcholine pathways are lost.

Another group of studies that may have implications for patients who have severe neurological disorders was recently completed by researchers at the University of Wisconsin, Madison.

In one study, Richard J. Davidson, a professor of psychology, found that expression of emotion, once thought to be solely a function of the right side of the brain, actually emanates from both sides, with each side controlling opposite kinds of emotions.

By measuring the electrical activity in the frontal regions of the scalp, Richard J. Davidson, professor of psychology, found that regions of the left side of the brain control positive emotions such as happiness and euphoria, while parts of the right side process negative emotions such as sadness and disgust.

What is important for the future of the field, Hamburg said, is for scientists to be willing to move into areas that are now considered “marginal” and “controversial.”

In remarks prepared for a major address before the association Wednesday night, Hamburg told the scientists that it was time for them to move into an area of behavior that has too long been neglected: the reasons for human conflict and ways to stop it.

“How we come to have prejudice, the source of ethnocentrism, the ease with which we learn to hate each other. . . . There is still much prejudice against this kind of study. . . . But this is surely the greatest challenge that exists for scientists today.”

Moreover, he said, it is not an area of study that should be left just to the social scientists. “A deeper understanding of conflict and its resolution clearly involves the physical, biological, behavioral and social sciences, very often acting in collaborative ways. . . . The stakes are now so high that there is an urgent necessity for cooperative engagement with these problems over a wide range of scientific activity.”