Short-Term Fluctuations in Elderly People’s Sensorimotor Functioning Predict Text and Spatial Memory Performance: The MacArthur Successful Aging Studies

Abstract

Background: While age-related increases of between-person variability in a variety of cognitive measures are commonly reported in cross-sectional studies, the nature of short-term intraindividual fluctuation in elderly people’s performance is relatively unexplored. Objective: The goal of the present study is to examine short-term fluctuations in elderly people’s sensorimotor functioning and their relations to individual differences in verbal and spatial memory. Methods: Fluctuations in old adults’ (mean = 75.71 years, SD = 6.93 years) sensorimotor performance were investigated by biweekly measurements spanning approximately 7 months. Sensorimotor performance was measured by three walking tasks, including the duration and the number of steps taken to walk a 360-degree circle and to walk 10 feet both at normal and fast pace. Performances of verbal and spatial memory were assessed by weekly measurements of digit memory span, memory for short text and spatial recognition. Results: The magnitude of intraindividual fluctuation in most sensorimotor and memory tasks examined was at least half as great as the level of individual differences across persons. In addition, intraindividual fluctuation in sensorimotor performance is a relatively stable individual attribute, which correlates positively with age and negatively with the levels of sensorimotor, text and spatial memory performance. Although a substantial amount of individual differences in intraindividual fluctuation was shared with mean performance level, variance component and hierarchical regression analyses showed that intraindividual fluctuation in walking steps added significant independent contribution over and above that given by level of performance in predicting text and spatial memory. Conclusion: Taking these results together, we suggest that intraindividual fluctuations in elderly people’s performance should not be ignored or simply treated as measurement error; rather, they are potentially important empirical variables for understanding sensory and cognitive aging and the nature of intraindividual response variations in general.

Aging cognition: from neuromodulation to representation

“…A shift to cross-level paradigms generates more opportunities for hypothesis generation and testing across levels. For instance, neuromodulation might not only influence aging-related increases in intraindividual performance variability within individuals 53,54 , but also inter-individual diversity at the group level. Future animal pharmacological studies could directly examine the effects of dopamine agonists and antagonists on intra-individual fluctuations and their effects on inter-individual diversity.…”

Dual-tasking postural control: Aging and the effects of cognitive demand in conjunction with focus of attention

“…At the same time, impaired cognitive capacities and the associated losses in prefrontal working memory and attention functions commonly found in older adults (e.g., [15,49,57]) may, in turn, impair the successful employment of attentional resources for effective postural control [25,30]. Such reciprocal influences between attenuated sensory integration, sensorimotor functions' greater reliance on cognitive processes, and more limited cognitive capacity in later adulthood probably contribute to increased couplings between cognitive and sensorimotor processes (e.g., [3,20,24,25]). In summary, parallel declines in various levels of brain mechanisms as well as cognitive and sensorimotor processes during aging has motivated researchers to investigate the relations between neurocognitive mechanisms underlying attention and postural control (see [21], for review).…”

Relations between aging sensory/sensorimotor and cognitive functions

“…Salthouse et al [52] reached similar conclusions with three independent samples, using tests of near visual acuity, working memory, associative learning, and concept identification. Similarly, Li et al [32] have added to this view by demonstrating a relationship between short-term fluctuations in walking ability and short-term verbal and spatial memory in a healthy sample of residents aged 64 -86 years. The degree of sensorimotor fluctuation increased with age, and correlated negatively with level of cognitive performance, again suggesting a possible common factor such as neurological deterioration that takes on increasing importance with advancing adult age [33,34].…”

“…In addition, both the shared resource and common cause models, though plausible, are flexible and must be approached carefully to enhance falsifiability [47,54]. We propose a multi-level approach, along the lines of that proposed by Li et al [32,34], that attempts to delineate cause and effect more clearly. The onset of age-related cognitive and sensory declines occurs in early adulthood, and possibly sooner for sensory abilities [54].…”

“…This multi-level perspective on sensory, sensorimotor, and cognitive changes in aging also has methodological implications, as it puts much emphasis on the study of intraindividual change and variability [32]. To better study the sequence of events leading to age differences in 'functional cerebral space' [30] including loss-induced, behaviorally initiated neural plasticity, existing correlational and experimental designs should be complemented by multivariate, replicated, single-subject, repeated-measures designs in which individual subjects are followed over time in a variety of experimental conditions [28].…”