The Broken Brain: The Biological Revolution in Psychiatry
Brain, Mind, and Behavior
In 1895 Freud wrote his last work on the physiology of the nervous system. For the rest of his life he paid little attention to developments in neurobiology, a neglect characteristic of most modern therapists and psychologists. But recent work in the neurosciences has begun to challenge the separation of psychology from neurobiology. Mentally crippling diseases such as depression and schizophrenia (the latter considered by Freud beyond the reach of psychoanalysis) can now, in varying degrees, be relieved or controlled. Their physiological mechanisms, as well as those of other diseases, are beginning to be discerned. And the neuroanatomy and chemistry of moods and emotions are no longer complete mysteries. The observations of psychology and psychoanalysis are becoming part of a larger body of knowledge whose central questions concern the mechanisms and functions of the human brain.
But how “revolutionary” are the new discoveries in the neurosciences? Nancy Andreasen’s new book The Broken Brain gives an enthusiastic report on what she calls “the biological revolution in psychiatry.” The PBS television series The Brain and the books written to accompany it, Brain, Mind, and Behavior (an undergraduate textbook) and The Brain, more cautiously suggest that the remarkable findings of the past two decades may unravel the mysteries of the brain. Ornstein and Thompson, in The Amazing Brain, give a clear account of recent research without making undue claims about its consequences.
These works revise in some detail the popularizations of ten years ago. They retain the late-nineteenth-century view that the brain can be understood through studies of the local functioning of its separate parts and combine it with recent discoveries of the details of brain chemistry. Our ways of understanding the brain, however, have changed dramatically in the past decade and much of the excitement of that change has been missed by the authors and scriptwriters of these books and television programs.
Localization of function was the principal issue at the Seventh International Medical Congress, meeting in London in 1881. At that meeting, Frederick Goltz, a forty-seven-year-old professor of physiology at the University of Strasbourg, opened a suitcase and removed the damaged head of a dog. The dog, he explained, had survived four major operations on its brain before it had been killed, and its mental and physical functions had been badly impaired. But not a muscle of its body was paralyzed, not a spot on its hide was robbed of sensation. It was neither blind, nor had it lost the sense of smell.
Goltz’s purpose in demonstrating this damaged dog was to prove that brain function was not localized. Dogs might become imbeciles if they lost most of their brains, but they could still run, jump, hear, and smell.
David Ferrier, then a thirty-eight-year-old London physician who had been born near Aberdeen, had performed a series of experiments on monkeys at the West Riding Lunatic Asylum in 1873 and had come to a very different conclusion. At the same congress of 1881, Ferrier showed two monkeys from which he had carefully removed specific parts of the brain. One monkey had a paralysis of the right arm and leg. Ferrier’s other monkey was deaf, but otherwise quite “normal.” Ferrier concluded that different anatomical areas of the brain were associated with different functions.
A committee of experts then examined the brains of Ferrier’s monkeys and Goltz’s dog. The experts supported Ferrier’s claim, noting that the brain of Goltz’s dog showed considerably less damage than Goltz had stated. Localization of brain function had won the day at the Seventh International Medical Congress, and, except for a few dissenters, remained the guiding principle of brain research for more than fifty years.
At the same time scientists were trying to understand the workings of the nerve cells that made up all the brain’s functional units. Our understanding of brain chemistry began when they recognized that there were tiny spaces between nerve cells, gaps that the English neurophysiologist Charles Scott Sherrington in 1897 called synapses. Anatomists had long since identified pathways through which sensations pass back and forth between the nerve cells in the body and those in the brain. But how information passed from one nerve cell to another through synapses remained unknown until the 1920s when Otto Loewi discovered that when nerve cells are stimulated they release a chemical into the synaptic gap. Although some electrical transmission also takes place, chemical transmission seems far more important.
We now know a considerable amount about the chemical transmitters and the mechanisms by which they are released. When a nerve impulse reaches a synapse, tiny packets containing about a thousand neurotransmitter molecules release their contents into the synaptic gap. The molecules diffuse across to the connecting cell where they lock into molecules on the cell’s surface known as receptors. (See illustration on facing page.) In some cases, this results in the opening of channels into the nerve cell that permit the passage of electrically charged atoms (ions) that are constantly present in the fluid in and around the nerve cells. If enough neurotransmitters are released and if enough channels are opened, the recipient cell will in turn become stimulated, or inhibited. Until the 1950s only three neurotransmitters were known1 and nobody suspected that there were others yet to be discovered.
Then in 1949 Henri Laborit, a Paris surgeon, began looking for a chemical that would prevent surgical shock, the sudden and often fatal lowering of blood pressure during operations. Laborit hit on the idea of trying chemicals, called antihistamines, that are commonly used against allergic reactions. He not only succeeded in preventing shock, but he also noticed that the drugs had a dramatic calming effect on his patients both before and after the surgery. He suggested that they be tested for more general psychiatric use. His idea proved justified: for the first time in history a humane, relatively effective treatment had been found for the devastating mental disease of schizophrenia. By the late 1950s chlorpromazine and several other antipsychotic drugs were widely used throughout Europe and America. Schizophrenics, formerly put in straitjackets and confined to padded cells in mental institutions, were able to carry on relatively normal lives. Psychiatry had undergone a small revolution.
Treatment of psychiatric patients with antischizophrenic drugs frequently caused symptoms similar to those of Parkinson’s disease: tremors, a shuffling gait, difficulty in starting and stopping movements. During the late 1950s neurologists showed that Parkinson’s disease itself occurred in patients whose brains had low levels of a newly discovered neurotransmitter, dopamine. The neurologists subsequently suggested that schizophrenia was caused in part by an excess of dopamine or of dopamine receptors; and in fact the antischizophrenic drugs were eventually shown to be blocking the dopamine receptors in the brain. During the 1960s, L-dopa, a drug that is converted to dopamine in the brain, was found to relieve the symptoms of Parkinson’s disease, and it is still the most effective treatment. As with the antischizophrenic drugs, however, it remains a partial treatment. Observing a Parkinson’s patient in a recent TV program by Jonathan Miller, a critic wrote, “L-dopaâ€Śsmooths away with sinister ease the fearsome combination of rigidity and tremor. What replaces it, though, is a constant snaking movement throughout the body, which the patient cannot control. Which would you prefer: partly controllable tremor or uncontrollable sinuosity?”2
Depression is also connected with neurotransmitter imbalances, and therapies aimed at restoring the balances of neurotransmitters such as norepinephrine and serotonin have proved effective in relieving depressive symptoms. But once again, they often provide only a partial cure. This is not surprising since our knowledge of the underlying chemical imbalances in depression is incomplete, and today’s therapies can correct only some of those that are known.
That schizophrenia and other forms of mental illness result from chemical imbalances in the brain is clearly suggested, if not openly stated, in most recent writing about these diseases. Drug companies now spend enormous sums of money on research on drugs that can affect behavior. Of the works under review, Andreasen’s book makes the strongest claim for this position: “A large amount of evidence has been amassed suggesting that mental illness is caused by biochemical abnormalities, neuroendocrine abnormalities, structural brain abnormalities, and genetic abnormalities.”3
As neuroscientists concentrated their attention on the neurotransmitters, in the hope of unraveling the mysteries of the mind, they found more neurotransmitters than had ever been suspected. The original list of the 1950s has now grown to more than fifty, among them an important new group of chemicals called neuropeptides (peptides are strings of amino acids). Some of these were already known, but as hormones, released by nerve and other cells directly into the bloodstream, with specific effects on cells in organs such as the heart, the intestine, or the uterus. Research during the 1970s showed that neuropeptides also serve as neurotransmitters in the brain. While it was once claimed that each nerve cell releases only one kind of neurotransmitter, it is now known that this is not true. Many nerve cells apparently release neuropeptides as well as the “classical” transmitters. There may still be dozens if not hundreds of neuropeptides yet to be discovered and their function in the brain is far from certain. However, there is good evidence that some are associated, in some way, with a variety of emotional states and the perceptions of pleasure and pain.
This began to become clear during the early 1970s, when much excitement was produced by the discovery that the drug morphine, which is derived from opium, locks into specific receptors on nerve cells in particular areas of the brain. Scientists therefore suspected that morphine imitates the action of an as yet unknown neurotransmitter. By 1975 the brain’s “natural opiates”â€”the enkephalins (meaning “in the head”) and the endorphins (a morphine-like chemical in the brain)â€”were discovered. These are peptides that serve as neurotransmitters and that modulate painful stimuli. Since they are more powerful painkillers than morphine (and more addictive), their release within the brain may be the mechanism underlying the effectiveness of acupuncture and other unconventional treatments for chronic pain. Recently, it has been found that the endorphins and enkephalins also modulate our emotional reactions. As the authors of Brain, Mind, and Behavior note, people who suffer from claustrophobia, and therefore develop severe anxiety in elevators and other enclosed spaces, probably have some kind of endorphin malfunction. The same book summarizes some fascinating studies suggesting that in order for us to experience an emotion, both a physiological disturbance, such as a rapidly palpitating heart, and a psychological evaluation of that disturbance, such as fear, are necessary.
Endorphins may link these two mechanisms. People with spinal injuries (which may affect the release of endorphins in the brain), and who consequently have little sensation from their bodies, have claimed that their ability to “feel” emotions such as joy or grief diminished since their injuries. The release of endorphins within the brain may also provide the key to understanding “the ‘high’ experienced by most serious joggers,” we are told in The Amazing Brain.
They were acetylcholine, norepinephrine, and epinephrine, although most scientists probably thought acetylcholine the only important transmitter in the brain. (See the article by Solomon H. Snyder in Science, August 1980, pp. 976–983: "Until the 1960s the amines acetylcholine, norepinephrine, and serotonin were the only well-recognized transmitters." See also J. Glowinsky et al., "The mesocortico-prefrontal dopaminergic neurons" in Trends in Neuro-Sciences, November 1984, pp. 415–418.↩
See Julian Barnes's review of the BBC 2 Horizon program "Ivan" (The Observer, December 9, 1984). His description, of course, would not apply to many other patients using L-dopa. My thanks to the BBC for making available a tape of this film, which I hope will be shown in the US.↩
Restak wants to take a broader view:
At this point neuroscientists are still investigating the factors that may bring about excess dopamine activity within the brain. These influences could conceivably include thoughts, conversations, or fantasies. If such a correlation could ever be made between mental events and neurochemistry, it would, of course, put a permanent end to the artificial division that presently plagues those who seek to understand the human brain: "Mind" would no longer be set apart from brain.
However, "correlation" is a vague concept. We should want to know in what ways neurochemistry is responsible for mental events.↩
They were acetylcholine, norepinephrine, and epinephrine, although most scientists probably thought acetylcholine the only important transmitter in the brain. (See the article by Solomon H. Snyder in Science, August 1980, pp. 976–983: “Until the 1960s the amines acetylcholine, norepinephrine, and serotonin were the only well-recognized transmitters.” See also J. Glowinsky et al., “The mesocortico-prefrontal dopaminergic neurons” in Trends in Neuro-Sciences, November 1984, pp. 415–418.↩
See Julian Barnes’s review of the BBC 2 Horizon program “Ivan” (The Observer, December 9, 1984). His description, of course, would not apply to many other patients using L-dopa. My thanks to the BBC for making available a tape of this film, which I hope will be shown in the US.↩
Restak wants to take a broader view:
At this point neuroscientists are still investigating the factors that may bring about excess dopamine activity within the brain. These influences could conceivably include thoughts, conversations, or fantasies. If such a correlation could ever be made between mental events and neurochemistry, it would, of course, put a permanent end to the artificial division that presently plagues those who seek to understand the human brain: “Mind” would no longer be set apart from brain.
However, “correlation” is a vague concept. We should want to know in what ways neurochemistry is responsible for mental events.↩