Interacting effects of cognitive load and adult age on the regularity of whole-body motion during treadmill walking.

Abstract

We investigated effects of concurrent cognitive task difficulty (n-back) on the regularity of whole-body movements during treadmill walking in women and men from 3 age groups (20 -30, 60 -70, and 70 -80 years old). Using principal component analysis of individual gait patterns, we separated main (regular) from residual (irregular) components of whole-body motion. Proportion of residual variance (RV) was used as an index of gait irregularity. The gait in all age groups became more regular (reduced RV) upon introduction of a simple cognitive task (1-back), relative to walking without a concurrent cognitive task. In contrast, parametrically increasing working memory load from 1-back to 4-back led to age-differential effects, with gait patterns becoming more regular in those 20 -30 years old, becoming less regular in those 70 -80 years old, and showing no significant effects in those 60 -70 years old. Our results support the dual-process account of sensorimotor-cognitive interactions (O. Huxhold, S.-C. Li, F. Schmiedek, and U. Lindenberger, 2006), with age-general effects of internal versus external attentional focus and age-specific effects of resource competition with increasing cognitive task difficulty.

Effects of aging on the relationship between cognitive demand and step variability during dual-task walking

“…Higher demands (forced attention conditions) overshadowed this beneficial effect, hindering gait control (i.e., increased variability) through attentional resource competition. However, although these findings support the dual-process account (Lövdén et al 2008;Verrel et al 2009), the fact that step variability in the most cognitively demanding FL condition did not exceed that in the control walking condition is counterintuitive in the framework of attentional resource competition. An explanation may be that walking alone already required attentional resources to not walk off the treadmill, the person regulating his/her gait by limiting deviations from a Bpreferred operating point^ (Dingwell et al 2010;Decker et al 2012;Dingwell and Cusumano 2015).…”

“…Inversely, there was a dual-task gain in the older adults with fewer errors while walking. Some previous studies already showed increased cognitive performance when walking was performed simultaneously with a concurrent cognitive task Schaefer et al 2010;Verrel et al 2009). This effect was interpreted in terms of a general increase in arousal induced by physical activity.…”

“…A dual-process account of cognitive-motor interactions including opposing effects of Bexternal focus of attention^and Battentional resource competition^on gait variability may account for the above mixed findings (Lövdén et al 2008;Verrel et al 2009). Simple cognitive tasks would shift the focus of attention away from gait control, thus reducing top-down cognitive (or attentional executive) control of gait (i.e., decreased gait variability).…”

“…However, empirical support for this model remains insufficient. Studies either failed to detect a clear trade-off between the two processes with increasing cognitive control demand in older adults (Lövdén et al 2008) or reported such tradeoff using gait parameters lacking of functional significance (Verrel et al 2009). …”

“…Besides its ecological validity, the strength of the dichotic listening task is twofold in the context of the dual-process account of cognitive-motor interactions Lövdén et al 2008;Schaefer et al 2015;Verrel et al 2009). First, the cognitive demand and effort parametrically increase from the NF to the FL condition (Hugdahl et al 2009).…”