“(The] brain is an enchanted loom where millions of flashing shuttles weave a dissolving pattern.”
— Sir Charles Sherrington
Welcome to the 1990s—the "Decade of the Brain"—where scientists are plotting a functional map of our thought processes, a sort of scientific Rand McNally that will enable us to locate the precise areas of language, thought and mathematic abilities—perhaps even the essence of our human selves.
For a long time we’ve known that who and what we are depends on that wrinkled orb in our head. But if personality—even what we think of as our soul—is dependent on neural circuit breakers and chemical bytes, is the human being just a machine? Are we HAL or human?
Researchers at the University of Washington and around the nation are exploring our vast, uncharted neural jungles, hoping to find the clues to how the brain makes us what we are.
Understanding the workings of consciousness begins with looking at the physical structure of the brain. Thanks to evolution, our rotund little heads hold up to three pounds of the most intricate circuitry in the body.
Traveling from the brainstem at the base of your neck to your frontal lobes is like going from the Stone Age villages of prehistory to the World Trade Center in New York City. The “lower” areas, such as the hindbrain and brainstem, contain the survival gear which controls heartbeat, breathing and other vital functions.
The next major way station is the midbrain. Here are structures that move us a little further up the evolutionary trail, playing roles in memory, emotions and sensory input.
Then we get to the cerebral cortex, almost literally the frosting on the cake. Enveloped in its creamy folds are all the so-called higher functions, the ones that allow us to enjoy Beethoven or the B-52s, “Nova” or “Studs.”
In a sense, the cerebral cortex is just a thin veneer of civilization. Only a quarter of an inch thick, the cortex consists of two hemispheres (the right and left), each composed of four distinct lobes and coordinated by a fibrous conduit called the corpus callosum. Yet, researchers hypothesize, this slender layer is responsible for producing the crowning achievements of humanity—poetry, music, art, science, philanthropy. And, some argue, this is what we mean when we talk about the mind.
“The mind doesn't exist; it's an illusion. To chase it is like chasing a cloud.”
UW Neuroanatomist John Sundsten
In the past, researchers studied brain function by looking at diseased or damaged brains. Scientists would determine which areas of the brain had been affected and would attempt to match the damage to a corresponding dysfunctional behavior.
The trend in neuroscience now is to look at the normal cerebral cortex. With the advent of new imaging technology, such as positron emission tomography (PET), scientists can watch a living color picture of the functioning brain. You probably don’t think of your brain as your most colorful organ, but when images of the brain are projected on a computer screen, our nondescript gray matter becomes a brilliant rainbow.
PET permits precise identification of the various structures involved in different tasks. It works by tracking blood flow, a key indicator of neuronal activity. Computers translate blood flow data into three-dimensional color images.
Researchers such as Dr. Marcus Raichle, a 1964 graduate of the UW School of Medicine, use PET to track the interplay of neurons during complex tasks such as learning, language and memory. Raichle, whose work was featured in the April 20 issue of Newsweek, is a professor of neurology and radiology working in the Mallinckrodt Institute of Radiology at the Washington University School of Medicine in St. Louis.
One of his experiments revealed that the brain has different areas for learning a new skill and practicing the skill. Volunteers had to match common nouns with appropriate verbs. For example, a volunteer would rapidly view words like “hammer” and respond with “hit.” As a control, the brain scans of this group were compared to scans from a group that spoke the words without matching them.
When volunteers began their matching exercises, different areas of the brain were initially engaged in the task; the prefrontal cortex, the cingulate cortex, the temporal cortex and the cerebellum lit up like fireworks on the scanner. However, after about 15 minutes of practice, those areas were no longer visible. After the practice time, the brain activity of the volunteers appeared no different than the control group who simply repeated the words.
“It’s as if the brain has two different circuits to handle the processing of words, ” Raichle says, “a conscious, non-automatic pathway and an automatic pathway for well-practiced tasks. ”
At the University of Washington, scientists in every field from biochemistry to psychiatry are exploring the terra incognita of the consciousness. This soup-to-nuts approach has been furthered by the creation of interdisciplinary research centers, such as the Keck Center for Advanced Studies of Neural Signalling. With a $2.7-million grant from the William M. Keck Foundation, researchers are exploring everything from a molecule for memory to the nervous systems of genetically altered mice.
UW neurosurgeons have pioneered the use of brain mapping for distinguishing tumors from critical motor and speech areas of the brain. More recently, Dr. Mitchel Berger and his colleagues have used brain mapping to identify “seizure foci tissue,” tissue surrounding brain tumors that appears normal but can continue to be a source of post-operative seizures.
UW researchers led by Biological Structure Chair Cornelius Rosse have developed a three-dimensional computer atlas of the brain that has been transcribed to laser disk and is offered through the Health Sciences Educational Resource Center. This 3-D mapping has been paired with an intensely focused “blade” of energy to form a high-tech type of scalpel. The scalpel can treat previously inoperable tumors and potentially deadly neurological conditions.
Advanced computer technology also allows physicians at Harborview Medical Center and the UW Medical Center to monitor and treat patients who have life-threatening neurological conditions, such as inoperable brain tumors.
Harborview has the nation’s first transcranial Doppler ultrasound monitor, which allows researchers to look beneath the dense bone of the skull and observe blood flow deep within the brain. The device is so sensitive physicians can use it to detect and locate blood clots in the brain before the clots block arteries and cause strokes.
But for all the sophisticated razzle-dazzle of research and its clinical applications, the origin of the mind still eludes us. In all of us there exists a sense of self, an internal narrator, the I, the ego. As they map the functions of the brain, will these researchers find the terra incognita of the mind?
“The mind doesn’t exist; it’s an illusion, ” says UW Neuroanatomist John Sundsten. Sundsten, a professor in the Department of Biological Structure and co-developer of the 3-D computer atlas of the brain, views the search for the seat of the mind as a quixotic adventure.
“To chase it is like chasing a cloud,” he continues. “You aren’t going to find the mind in a structure or a set of neurons. We’re desperate to set ourselves apart, but it’s a mistake to try to explain the mind by the mechanisms of the brain.
“You see, the brain generates all kinds of stuff and attempts to put a name on it. The mind is the way the brain has of talking about itself—it’s a concept—a powerful concept—and we use it because it’s helpful for survival.”
But most neuroscientists concede that a model for how the brain works can be useful for finding “workarounds ” (alternate circuits) when it malfunctions, or for developing ways to boost the power of our minds.
William Calvin
“We’re always trying to develop metaphors to imagine how the mind works,” says Dr. William Calvin, UW affiliate associate professor of psychiatry and behavioral sciences, and author of The Ascent of the Mind, The River that Flows Uphill and The Cerebral Symphony. “Descartes used a plumbing analogy; in the early 20th century we used telephone exchanges as a way of explaining function. We use a brain-as-a-computer analogy now. But that is still a sloppy, imprecise way of looking at the brain. It doesn’t take into account the amazing plasticity of the brain or the effects of experience and memories.”
Calvin’s goal is to develop a better theory of the mind and how it works, with the hope that it will lead to ways of treating mental dysfunctions. He envisions a system that will better explain psychiatric disorders and enable people with developmental disorders to devise “work-arounds” for a more enriching life.
”I’d like to see us devise a way to make creative thought more possible,” he says, “to learn the process of creativity.”
Calvin, whose previous work, The Cerebral Symphony, examined the phenomenon of the narrator self, is currently working with UW Neurological Surgery Professor George Ojemann on a new book tentatively titled In Search of the Brain’s Voice.
According to Calvin, self-consciousness and the development of self may simply be a byproduct of evolution. There are no selection pressures that appear to enhance its development.
Calvin makes a persuasive argument that the increasingly bigger brain allowed early humans to adapt to the environmental pressures of the Ice Ages and exploit the “boom times” when the glaciers retreated. These extra neuronal circuits kept humming even when, and perhaps especially when, the heat was on. These surplus circuits, he hypothesizes, didn’t just sit around twiddling neuronal thumbs during the easy years. They kept busy by inventing language, music and other skills that, he surmises, are the byproducts of hunting. During this time, our narrator “self’ emerged as well.
“The brain’s voice, the narrator, is not found in any one place in the cerebral cortex,” explains Calvin. “Even if the narrator is impaired by a lesion of some kind, a sense of self persists.”
This narrator comes along at an early age, usually between 18 and 24 months. After we begin to acquire language, we become self-aware, conscious of our separateness from other people and our ability to act independently. About this time, words like I, me, mine, become firmly embedded in our vocabulary.
This sense of self, what we might call our mind, may not be a single voice, but rather a rich chorus of neurons and synapses all singing the same melody. And, we like to believe, each song is unique, a product of genes, history, experience and expectations, a cantata that continues to develop as the choir adds the voices of new learning and memories, a melody that grows richer and more complex as we age. Our self, or some might say, our soul, continually emerges from the grand unity of billions of cells that somehow collaborate to hold our past and invent our future, our magnificent, private evolution.
What’s 18 million brain cells per year, more or less? That, my friend, is the number of brain cells you lost last year, and what you can expect to lose every year till you die.
So why aren’t you braindead yet? Because, as Carl Sagan would say, you have “billions and billions ” of brain cells at your disposal, 100 billion or so. In fact, you had more brain cells as a fetus than you will at any other time of your life. A notorious process called “neuronal pruning ” carved large chunks of “unnecessary ” neural interconnections out of the way before you hit puberty.
Not every part of the brain loses cells at the same rate. The brainstem regions lose the least, while our poor cerebral cortex is taxed at a rate of about 50,000 cells per day. The worst isn’t over either; along with brain cells, we suffer the loss of nerve cell connections and a decrease in the amounts of essential neurotransmitters.
Of course, these losses are just the ordinary events in a normally aging brain. People afflicted with neuronal diseases associated with aging—such as Alzheimer’s disease—undergo much more severe brain cell damage and loss. In our aging society (by the year 2010, one out of every six people in the United States will be 65 years or older), it is sobering to think that 10 percent of the people over 65 and 20 percent of those over 80 will suffer from significant dementia related to aging. About 50 to 60 percent of the cases of dementia will be the result of Alzheimer’s disease; another 20 percent will result from stroke or other causes of interrupted blood flow to the brain and subsequent cell death.
But the news isn’t all bad. For instance, the brain makes full use of the principles of plasticity and redundancy. Plasticity is your brain’s ability to create new connections with fewer neurons. Undamaged brain cells in the aging brain can grow more dendrites. Redundancy is simply the fact that the brain has quite a lot of brain cells to begin with, so that the loss of a million cells or so every two weeks won’t make a huge dent in our brain power for quite a while.
You can continue to strengthen and develop your neuronal connections throughout your life. Researchers have found in aging rats that an increase in the complexity and number of learning experiences creates a greater number of synapses. Researchers believe that a stimulating environment can offset and even reverse late brain aging. People who continue to seek challenges and new experiences will continue to develop their brains’ capacities. As the saying goes: use it or lose it. The mind is a terrible thing to waste.