AUTHOR=Fraser Sarah A. , Dupuy Olivier , Pouliot Philippe , Lesage Frédéric , Bherer Louis 

TITLE=Comparable Cerebral Oxygenation Patterns in Younger and Older Adults during Dual-Task Walking with Increasing Load

JOURNAL=Frontiers in Aging Neuroscience

VOLUME=Volume 8 - 2016

YEAR=2016

URL=https://www.frontiersin.org/journals/aging-neuroscience/articles/10.3389/fnagi.2016.00240

DOI=10.3389/fnagi.2016.00240

ISSN=1663-4365

ABSTRACT=The neuroimaging literature on dual-task gait clearly demonstrates increased prefrontal cortex (PFC) involvement when performing a cognitive task while walking. However, findings from direct comparisons of the cerebral oxygenation patterns of younger (YA) and older (OA) adults during dual-task walking are mixed and it is unclear how YA and OA respond to increasing cognitive load (difficulty) while walking. This functional near infra-red (fNIRS) study examined cerebral oxygenation of YA and OA during self-paced dual-task treadmill walking at two different levels of cognitive load (auditory n-back). Changes in accuracy (%) as well as oxygenated (HbO) and deoxygenated (HbR) hemoglobin were examined. For the HbO and HbR measures, eight regions of interest (ROIs) were assessed: the anterior and posterior dorsolateral and ventrolateral PFC (aDLPFC, pDLPFC, aVLPFC, pVLPFC) in each hemisphere. Nineteen YA (M = 21.83 yrs) and 14 OA (M = 66.85 yrs) walked at a self-selected pace while performing auditory 1-back and 2-back tasks. Walking alone (single motor: SM) and performing the cognitive tasks alone (single cognitive: SC) were compared to dual-task walking (DT = SM + SC). In the behavioural data, participants were more accurate in the lowest level of load (1-back) compared to the highest (2-back; p ˂ .001). YA were more accurate than OA overall (p = .009), and particularly in the 2-back task (p = .048). In the fNIRS data, both younger and older adults had task effects (SM < DT) in specific ROIs for ∆HbO (3 YA, 1 OA) and ∆HbR (7 YA, 8 OA). After controlling for walk speed differences, direct comparisons between YA and OA did not reveal significant age differences, but did reveal a difficulty effect in HbO in the left aDLPFC (p = .028) and significant task effects (SM < DT) in HbR for 6 of the 8 ROIs. Findings suggest that YA and OA respond similarly to manipulations of cognitive load when walking on a treadmill at a self-selected pace.