Neuropsychology

Both age-related sensory acuity changes and response slowing can influence test performance, as can the physical limitations of such prevalent illnesses as arthritis. Changes in visual and auditory acuity with aging are well documented. Such sensory changes can affect neuropsychological test performance by making it more difficult for an older individual to accurately see test stimuli or hear the examiner's instructions. Reaction time shows progressive slowing from early through late adulthood. One obvious implication is that older adults will take longer than younger adults to complete various neuropsychological testing procedures.

Response slowing may also result in lower scores on tests that assign bonus points for faster performance. This underscores the need for age-appropriate normative data to which an individual's performance can be compared. Although healthy older people are unlikely to fatigue more rapidly than younger adults during average-length (e.g., two to three hours) testing sessions, older persons in poor health are likely to fatigue quickly. It may thus be necessary to take more frequent breaks during a neuropsychological examination session when evaluating older (particularly ill or frail) adults. Performance limitations imposed by physical disabilities (e.g., arthritis) may require modifications in testing procedures (e.g., allowing the person to work on a task beyond the standard time limits). Such departures from standardized test procedures require both caution and clinical experience when interpreting performance.

Even on neuropsychological tests that do not assign bonus points for faster performance, and for which age-related sensory changes do not likely contribute, performance is often poorer for older adults than for younger adults. This is particularly true for tests of memory and for tests of abstract reasoning and complex problem solving. There is both animal and human experimental data that suggests age-associated memory changes are due to cell loss and physiologic changes within the hippocampal complex, a deep brain region known to be important for establishing longer-lasting memories. Similarly, human experimental neuropsychological data has indicated that age-associated decreases in abstract reasoning and complex problem-solving ability likely reflect cellular and physiologic changes within the frontal lobes and deep brain structures to which they are interconnected. The frontal lobes and their interconnected brain structures are known to be important for a range of complex cognitive abilities that have been collectively termed executive functions.

However, it should be noted that there is greater variability in neuropsychological test performance among older (versus younger) individuals, with some older adults performing within the range of average younger persons. This observation has led to controversy over whether age-group differences in neuropsychological test performance should be thought of as reflecting necessary changes in brain structure and functioning with aging or as the manifestation of subtle age-associated neurological disease processes within a subgroup of older adults. The resolution of this controversy must await future research, particularly that employing longitudinal research designs in which persons are repeatedly examined (both neuropsychologically and with sophisticated brain imaging technologies) as they age.