Abstract
Sensory information from our eyes, skin and muscles helps guide and correct balance. Less appreciated, however, is that delays in the transmission of sensory information between our eyes, limbs and central nervous system can exceed several 10s of milliseconds. Investigating how these time-delayed sensory signals influence balance control is central to understanding the postural system. Here, we investigate how delayed visual feedback and cognitive performance influence postural control in healthy young and older adults. The task required that participants position their center of pressure (COP) in a fixed target as accurately as possible without visual feedback about their COP location (eyes-open balance), or with artificial time delays imposed on visual COP feedback. On selected trials, the participants also performed a silent arithmetic task (cognitive dual task). We separated COP time series into distinct frequency components using low and high-pass filtering routines. Visual feedback delays affected low frequency postural corrections in young and older adults, with larger increases in postural sway noted for the group of older adults. In comparison, cognitive performance reduced the variability of rapid center of pressure displacements in young adults, but did not alter postural sway in the group of older adults. Our results demonstrate that older adults prioritize vision to control posture. This visual reliance persists even when feedback about the task is delayed by several hundreds of milliseconds.
Highlights
We can stand on a crowded bus with little difficulty, standing balance involves complex interactions between our body and the environment, sensory information from our eyes, skin and muscles, and control by distributed neural circuitry
This study demonstrated that even in human postural control, which receives rich input from interacting sensory systems, a simple change in visual feedback alters the frequency composition of center of pressure (COP) signals
Post hoc analysis revealed that increased feedback delays reduced the time that older adults spent in the postural target (F (2.52, 32.75) = 6.97, p,0.01; 900,600, 300, 0 ms, and eyes open (EO), all p’s,0.05)
Summary
We can stand on a crowded bus with little difficulty, standing balance involves complex interactions between our body and the environment, sensory information from our eyes, skin and muscles, and control by distributed neural circuitry. A number of studies have shown that the sensory receptors that monitor body orientation are less sensitive in older adults (see [4]; [5] for a review) This reduced sensitivity has been linked to falling [6] and overreliance on visual feedback [7,8,9], which can disrupt postural control when visual inputs are altered or unreliable [10,11,12]. In addition to reductions in sensory reliability, delays in the transmission of feedback from the lower limb can exceed several tens of milliseconds [13] These feedback delays may be problematic because the neural circuitry engaged in postural control must rely on information from the past to correct balance errors [14,15]. Despite evidence that sensory delays increase during aging [16,17], it is unclear how these additional feedback delays affect standing balance
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