Hockenbury Discovering Psychology 5th txtbk

268 CHAPTER 6 MemorydementiaProgressive deterioration and impairment ofmemory, reasoning, and other cognitivefunctions occurring as the result of a diseaseor a condition.Alzheimer’s disease (AD)A progressive disease that destroys thebrain’s neurons, gradually impairing memory,thinking, language, and other cognitivefunctions, resulting in the complete inabilityto care for oneself; the most common causeof dementia.Alzheimer’s DiseaseGradually Losing the Ability to RememberUnderstanding how the brain processes and stores memories has important implications.Dementia is a broad term that refers to the decline and impairment ofmemory, reasoning, language, and other cognitive functions. These cognitive disruptionsoccur to such an extent that they interfere with the person’s ability to carryout daily activities. Dementia is not a disease itself. Rather, it describes a group ofsymptoms that often accompanies a disease or a condition.The most common cause of dementia is Alzheimer’s disease (AD). It is estimatedthat about 5.3 million Americans suffer from AD. That number is expectedto dramatically escalate as the first of the “baby boomers” are just now reachingage 65. The disease usually doesn’t begin until after age 60, but the risk goes upwith age. About 5 percent of men and women in the 65–74 age group have AD.Among adults age 85 and older, about half may have Alzheimer’s disease(Alzheimer’s Association, 2009).Although the cause or causes of Alzheimer’s disease are still unknown, it is knownthat the brains of AD patients develop an abundance of two abnormal structures—beta-amyloid plaques and neurofibrillary tangles (Masliah, 2008; Meyer-Luehmann& others, 2008). The plaques are dense deposits of protein and other cell materialsFOCUS ON NEUROSCIENCEMapping Brain Changes in Alzheimer’s DiseaseThe hallmark of Alzheimer’s disease is its relentless, progressivedestruction of neurons in the brain, turning once-healthy tissueinto a tangled, atrophied mass. This progressive loss of braintissue is dramatically revealed in the MRI images shown below.Created by neuroscientist Paul Thompson and his colleagues(2003), these high-resolution “brain maps” represent compositeimages of the progressive effects of Alzheimer’s disease (AD)in 12 patients over the course of two years. In these color-codedimages, blue corresponds to normal tissue (no loss), red indicatesup to 10 percent tissue loss, and white indicates up to 20percent tissue loss.Thompson likens the progression of AD to that of molten lavaflowing around rocks—the disease leaves islands of brain tissueunscathed. The disease first attacks the temporal lobes, affectingareas involved in memory, especially short-term memory. Nextaffected are the frontal areas, which are involved in thinking,reasoning, self-control, and planning ahead. You can also seesignificant internal loss in limbic areas, which are involved in regulatingemotion. At this point in the progression of AD, there isvery little loss in sensory and visual brain areas. Eventually thedisease engulfs the entire brain. The photo to the right contrastsInitital diagnosis18 months latercross sections of a normal brain (top) and the brain of a personwho died of Alzheimer’s disease (bottom). In the normal brain,the temporal lobes are intact. The ventricles, which hold thecerebral spinal fluid, are slender. In the brain ravaged byAlzheimer’s, the gaping ventricles extend into the space left bythe death of brain cells in the temporal lobes.