Contributions of delayed visual feedback and cognitive task load to postural dynamics.

In this experiment, we examined the extent to which postural control is influenced by visual and cognitive task performance. Fourteen healthy young participants performed a balance task in eyes-open (EO) and delayed visual feedback (DVF) conditions. DVF was presented at delays ranging from 0 to 1200ms in 300ms increments. Cognitive load was implemented by a simple, serial arithmetic task. High and low-pass filtering (f(c)=0.3Hz) distinguished LOW and HIGH frequency components, which were used to compute the variability of Anteroposterior (AP) Center of Pressure (COP) trajectories on fast (>0.3Hz) and slow (<0.3Hz) times cales. Imposed visual delay increased sway variability at both LOW and HIGH components. Cognitive task performance, however, influenced only the variability of fast (HIGH) sway components. Our results support distinct timescale mechanisms for postural control, but also demonstrate that vision predominantly influences low frequency components of postural sway. Moment-to-moment COP fluctuations are dependent on cognitive performance during delayed visual feedback postural control.