Unveilling the cerebral and sensory contributions to automatic postural control during dual-task standing

Abstract

The postural control dual-task literature has demonstrated greater postural stability during dual-task in comparison to single task (i.e., standing balance alone through the examination of multiple kinetic and kinematic measures. This improve stability is thought to reflect an automatic mode of postural control during dual-task. Recently, sample entropy (SampEn) and wavelet discrete transform have supported the claim of automaticity, as higher SampEn values and a shift toward increased contributions from automatic sensory systems have been demonstrated in dual-task settings. In order to understand the cortical component of postural control, functional near-infrared spectroscopy has been used to measure cortical activation during postural control conditions. However, the neural correlates of automatic postural behaviour have yet to be fully investigated. Therefore, the purpose of this study is to confirm the presence of automatic postural control through static and dynamic balance measures, and to investigate the prefrontal cortex activation when concurrently performing quiet standing and the auditory cognitive tasks of varied difficulty. Eighteen healthy young adults (21.4±3.96yo), 12 females and 6 males, with no balance deficits were recruited. Participants were instructed to either quietly stand on a force platform (SM), perform three cognitive tasks while seated (SC) or perform both aforementioned tasks concurrently (DT). Results supported automatic postural control with lower area and standard deviation of center-of-pressure in DT conditions compared to SM. As for SampEn and the wavelet analysis, DT conditions demonstrated greater values than SM, and a shift from vision to a cerebellar contribution. For the most difficult cognitive task, the DNS task, a trend toward significantly lower right hemisphere prefrontal cortex activation compared to left hemisphere activation in DT was found, potentially representing a decrease in cognitive control, and the presence of automaticity. These findings suggest that the simultaneous performance of a difficult cognitive task and posture yields automatic postural behaviour, and provides insight into the neural correlates of automaticity.