General and specific cognitive dysfunctions in patients with Alzheimer's disease.

The purpose of the present study was to investigate the effect of Alzheimer's disease (AD) on general and specific neuropsychological function. Thirty-five subjects diagnosed with AD were compared to 30 medically normal aging control subjects using measures from the Halstead-Reitan Battery (HRB). All AD subjects were classified as "probable" AD (NINCDS-ADRDA) and found to be in the "late confusional" to "early dementia" stages of the disease (Global Deterioration Scale, GDS = 4-5). The AD group performed significantly worse than the controls on all measures of general neuropsychological function and almost all measures of specific functions. However, no differences were found between groups on motor abilities or many simple sensory functions. The findings demonstrate dramatic brain-behavior changes involving both general and specific cognitive functions which go beyond memory dysfunction even in the earlier stages of the disease. The neuropsychological pattern found may be the basis of a useful clinical-behavioral AD pattern in the earlier stages of the disease.