Alzheimer's disease is a degenerative disease of unknown etiology, the incidence of which increases with advancing age. Neurons are affected in many brain regions, but the distribution of degenerative changes is not random. The hippocampus and amygdala, which are known to be involved in learning, and areas of the frontal, temporal, and parietal lobes known to be involved in language and related processes are typically affected intensely by the pathological process of Alzheimer's disease (Brun & Englund, 1981). Disorders of memory and language are accordingly clinical features of the disease, which is characterized by an insidiously progressive dementia. Patients consistently develop an impairment of naming, or anomia, as a prominent feature of their language disorder. In this chapter, the general features of Alzheimer's disease are described, followed by a discussion of the language disorder, emphasizing research on anomia and its associated cognitive deficits. The chapter concludes with presentation of an experimental investigation in which an effort was made to establish the importance of a visual, semantic, and word-retrieval deficits in accounting for anomia in Alzheimer's disease.

Neuropathological features of Alzheimer's disease

Although a presumptive diagnosis of Alzheimer's disease can be made clinically (McKhann et al., 1984), the diagnosis can be made definitively only by histopathological examination. Abundant intracellular tangles of neurofilaments and extracellular plaques composed of degenerating neuronal cell processes and deposits of amyloid protein are diagnostic of Alzheimer's disease.