Functional rating scales and psychometric assessment in Alzheimer's disease: applications in pharmacological trials.

New findings on cognitive aging show that decline in brain functions is not part of a general decline of functioning in old age. We know now that with increasing age there is a differentiation of cognitive functions into two independent dimensions (fluid and crystallized functions). This two-dimensional model allows a more precise description of the cognitive aging process and of pathological changes. While crystallized cognitive abilities can be improved by training till late in life, fluid cognitive functions are subject to a progressive decrease starting as early as age 30, becoming most evident in cases of organic mental disorders. Thus, pathological aging is not necessarily accompanied by global loss of functions. Different abilities undergo changes in different ways, a fact taken into consideration by modern methods of psychometric evaluation. Beyond the aging processes mentioned previously, cognitive and behavioral changes in the elderly may be considered to be early indicators of organic mental disorders. The Nuremberg Self-Evaluation List seems to be a promising approach to diagnosis.