Discovering the Brain (1992) / Chapter Skim
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4 The Role of the Brain in Mental Illness
4 The Role of the Brain in Mental Illness
Pages 46-66
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From page 46... ...
Early Christian thought located mental functions in the ventricles of the brain, along a progression from the front of the head toward the back: sensation and imagination in the anterior ventricle, reason and intellect in the third ventricle, and memory, as the most selective mental faculty, in the rearmost ventricle. In the eighteenth and nineteenth centuries, the popular science of phrenology sought to assign every conceivable trait of personaTity to its own specific location on the cerebral cortex, as if the mind were a physical entity like the brain.
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From page 47... ...
~W ~,~,~_ Calm 47 .i''2~} 't\/ $.~Q,l ~ ../ ~1 ~( MAP FIGURE 4.1. The medical basis of mental illness was under study as long ago as the fifteenth century, in Persia.
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From page 48... ...
Current work in the laboratory and in clinical practice builds on the basic research and clinical practice of the past, offering better prospects than before for alleviating a number of mental disorders. Multidisciplinary efforts have also made considerable progress toward untangling the factors at the root of some mental illnesses, bringing closer the goal of early detection or even of prevention to some degree, by interrupting a chain of factors.
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From page 49... ...
The treatment for bipolar disorder nowadays is usually administered in the form of the common salt lithium carbonate; this compound appears to reduce the intensity of both the manic and the depressive phases, producing something of an evening out of mood. Just how the one compound could inhibit both extremes is unclear.
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From page 50... ...
Certain drugs or injuries to the head have been known, however, to bring on compulsive behavior. Moreover, family studies show a significant rate of concordance for the illness in identical twins, regardless of whether they are brought up together or separately.
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From page 51... ...
For example, if a particular compound or class of drugs was found to block Panic anxiety sne- r -- -- -- -- -- -- -- -a -rcifically and consistently, this response could be used as a criterion for diagnosing the disorder. Certain antidepressant medications appeared indeed to work this way, as did several minor tranquilizers; this combination of effects set panic anxiety apart from less intense chronic anxiety and from transient feelings of panic, states that are unaffected by antidepressant drugs.
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From page 52... ...
, by substances that block the action of the "stress hormone" epinephrine, by at least one compound that facilitates the uptake of serotonin, and by inhalation of high concentrations of carbon dioxide. At the cellular level, PET scans uncover a striking feature of panic disorder (see Plate 61.
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From page 53... ...
i ~ , ~ 1ne result is to hyperpolarize the cell membrane, thereby reducing the excitability of the neuron; this brings about a lower level of response to stimuli, which is experienced as a sedating or tranquilizing effect. This mechanism in turn points back toward panic disorder, In which some patients apparently have a lower than usual sensitivity in their receptors to the benzodiazepines and an increased sensitivity to substances that block the action of those compounds.
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From page 54... ...
The plaques are lesions that contain a protein known as amyloid; their actual role in the course of the disease is still under debate. In this microscopic view of tissue from the cerebral cortex of a patient with Alzheimer's disease, the plaques appear as black knots against the gray background of the more healthy cells.
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From page 55... ...
Excitatory amino acids can indeed cause severe deficits in the brain, including loss of memory. A dramatic illustration came recently from eastern Canada, where a number of people
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From page 56... ...
The theory that the presence of metal in the brain specifically, aluminum—produces a toxic effect attracted lively interest when it was first advanced in the early 1970s. Evidence of aluminum in the neural tangles was plentiful and striking, and the theory circulated widely, to the point that the public began to wonder about the prudence of using aluminum cookware, for example.
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From page 57... ...
Genetic factors currently offer an exciting line of research into Alzheimer's disease. Recent success in locating the genetic region for another degenerative neurological disease, Huntington's chorea, has fostered the hope of a similar discovery for Alzheimer's.
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From page 58... ...
The administration of nerve growth factor has been a newsworthy step in laboratory attempts to prevent degeneration of the nerve fiber tracts known as the cholinergic pathways. In animals, nerve growth factor successfully protects the neurons of the hippocampus from dying, which should in turn preserve the workings of short-term memory.
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From page 59... ...
Another advance in epidemiology would be to gather study populations whose health factors are thoroughly known and homogeneous, to address satisfactorily the two-sided question of what brings on dementia with increasing age and what permits increasing age without dementia. Many specialists in this area feel that the current position of research on Alzheimer's disease resembles that of work on Parkinson's disease about 15 years ago, when the cause and some effective therapies were just about to come to light.
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From page 60... ...
:V negative and served as control subjects. At the beginning, the study involved psychological testing and neurological examination; a smaller group underwent nuclear magnetic resonance imaging, electroencephalography, and a spinal tap at regular intervals, and they continue to volunteer for these painful and arduous tests as investigations proceed today with this same cohort.
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From page 61... ...
Johnson, director of the neurology department at Johns Hopkins Medical School. Close examination of the tissues of the brain reveals some frayed white matter, often containing macrophages, and occasionally an abnormally large cell that appears to contain viral antigen, but in general no striking appearance of disease.
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From page 62... ...
For example, what are the special health risks associated with the AIDS virus in intravenous drug users or the ways the virus affects women differently from men or children differently from adults? Research in this field has taken shape quickly, moving in less than 10 years from the earliest observations of nervous system disease to focused molecular biological studies of the disease-causing virus.
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From page 63... ...
Nor has it been established that the biochemical factors lead to or in any sense cause the drop in mood, energy, motivation, or enjoyment that characterizes depression. Several drugs that are effective in treating depression apparently act by influencing, in different ways, the levels of norepinephrine and serotonin available to receptors.
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From page 64... ...
ChIorpromazine, as well as several other drugs that relieve schizophrenic symptoms, works by blocking the brain's receptor sites for dopamine, particularly in the prefrontal cortex. More specifically, experiments at the National Institute of Mental Health anct in Scandinavia in which schizophrenic patients were asked to perform cognitive tasks showed that these individuals have abnormally low activity in that area of the brain.
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From page 65... ...
and sudden urgent feelings of anger or fear can all be traced, at least in neurophysiological theory, to misfiring synapses in one area or another of the sensory association cortex or of the limbic system, which controls moocl. Another point in favor of this line of thinking is that the frontal lobe contains the highest concentration of dopamine fibers in the cerebrum, and the specific clopamine receptor that is the primary site of action of antipsychotic drugs is known to reside in this area.
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From page 66... ...
Observations from clinical practice, laboratory study of the mechanisms of disease and the ability of chemical compounds to harm or help, and genetic analysis of family history all build on one another, offering the prospect of more efficacious treatments and of theoretical accounts that grow more solid as new details are filled in. While neuroscience looks more closely at the brain, it continues to enlarge our options for treating the mind.
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