FIGURE 4.2. Tangles of neural fibers and “plaques” in the brain are two of the well-known signs of Alzheimer's disease. 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. Source: R. Cook-Deegan, taken from archives of the Department of Neurology, University of Colorado.

those aged 85 or older. This profile does not appear to be linked to an American life-style; study populations from various parts of the world have produced similar figures.

Although Alzheimer's disease is widely recognized, the formal criteria for diagnosing it are still under debate. In 1984, a working group of the National Institute of Neurological and Communicative Disorders and Stroke –Alzheimer's Disease and Related Disorders Association, headed by Guy McKhann, director of the Krieger Mind/Brain Institute at Johns Hopkins University, published a report concluding that to diagnose Alzheimer's disease with confidence, the physician should rely on specific signs in the brain. Chief among these were tangled knots of fine neural fibers and so-called “senile plaques,” actu-

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