Estimating age-related changes in psychomotor function: influence of practice and of level of caloric intake in different genotypes.

This article presents a discussion of some key considerations in the measurement of age-related changes in psychomotor function of mice. We illustrate that "standard" measures of psychomotor performance, such as running speed on a rotorod task, are highly sensitive to practice effects. Examples are cited in which failure to assess practice effects can influence conclusions regarding the magnitude and rate of change in psychomotor capacity as a function of age. A second set of examples is focused on estimating the effect of an experimental intervention, caloric restriction, on age-related changes in psychomotor performance. These examples show that psychomotor performance at a given age may vary directly, and reversibly, with the level of caloric intake. Independent of such reversible effects, the level of caloric intake can also modulate the rate of change in capacity as a function of age. It is concluded that reversible, short-term effects must be considered in estimating the effect of an experimental intervention on the rate of age-associated change in psychomotor function.