Aging, time scales, and sensorimotor variability.

It is well established that there is an increased amount of intraindividual variability with aging in a variety of behavioral contexts. Here, we elaborate from a self-organization and dynamic systems framework to investigate the relevant time scales of variability as a function of aging and their relation to the changes in the amount and structure (frequency and time domains) of movement and postural variability. In particular, we examine evidence for the general hypotheses that (a) there is a reduction or even loss of shorter time scales in the control of movement with aging and (b) the shorter the time scale in motor output variability, the more sensitive the measure is as a biomarker to revealing the onset and early influence of aging and disease. The dynamic analysis of the time scales of variability distinguishes the distinctive roles of stability and noise in the increased amount of intraindividual variability with aging.