Hemodynamic responses of quiet standing simultaneously performed with different cognitive loads in older adults.

Postural control decrements with advancing age have been largely identified in the literature. Dual-task paradigms have been utilized to increase older adults' stability in order to direct the attention towards the completion of a secondary task, leaving the automatic motor control processes to modulate posture unconstrained. To the extent that older adults allocate greater attentional resources to maintain an upright posture, the present study aimed at replicating St-Amant et al. (2020) protocol to investigate automatic postural control and prefrontal cortex activation in older adults when simultaneously performing quiet standing wtih different attention-demanding cognitive tasks. Nineteen healthy older adults (71.47 ± 6.01 years) were recruited and self-reported no hearing, musculoskeletal and neurological problems. Older adults were required to perform three different cognitive loads while seated (SC), quietly standing on a force platform (SM), and performing both tasks simultaneously (DT). Static center-of-pressure measurements and wavelet discrete transform did not reveal postural automaticity in dual-task conditions. Conversely, sample entropy values were significantly greater when performing n-back compared to all other tasks in the medial-lateral direction, and significantly greater than SM in the anterior-posterior direction. The relative concentration of oxygenated hemoglobin (HbO) of the left hemisphere was significantly greater than the right when performing n-back, and significantly greater within the left hemisphere when performing n-back compared to double-number sequence. Collectively, our results do not support the presence of automatic postural control in dual-task conditions for older adults. The present study highlights the importance of using numerous variables when investigating posture in order to capture its complexity.