Cognitive and motor cortices activity during complex stepping tasks in older people at high risk of falling
P. Pelicioni (1, 2), S. Lord (1, 2), Seng N. (3), B. Halmy (1), D. Sturnieks (1, 4), R. Liu (1, 3) and J. Menant (1, 2)
Falls, Balance and Injury Research Centre, Neuroscience Research Australia, Sydney, New South Wales, Australia
School of Public Health and Community Medicine, University of New South Wales, Sydney, New South Wales, Australia
School of Medicine, University of New South Wales, Sydney, New South Wales, Australia
School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
Background and aim
Impaired stepping and reduced cognitive are fall risk factors in older people. Understanding neural mechanisms may assist in elucidating mechanisms underpinning these relationships. The aim of this study was to investigate cognitive and motor cortices activity during complex stepping tasks using fNIRS (functional near-infrared spectroscopy) in older people. We hypothesised those with a high risk of falling would display greater cortical activation when performing a complex stepping task (stroop stepping task – SST).
Fifty-nine older adults first undertook a fall risk assessment; the Physiological Profile Assessment (PPA) which includes five sensorimotor and balance tests (simple reaction time, proprioception, knee muscle strength, visual contrast sensitivity and postural sway), and for which a weighted summary score provides a composite measure of fall risk. Participants who reported 1+ fall in the past year or a PPA score > 1 were classified as high fall risk (n=27). Cortical activation in cognitive and motor brain areas was determined as relative changes in deoxygenated haemoglobin levels during the SST.
A group comparison revealed that the high fall risk group exhibited significantly decreased activity in the supplementary motor area and premotor cortex (p<0.05) during the SST. The high fall group also showed slower stepping response, as well as larger postural sway and lower limb weakness (p<0.05).
Surprisingly, individuals at high fall risk had decreased cortical activity in the supplementary motor area and premotor cortex when performing the SST. This may indicate that the falls in these individuals are due to: (i) physiological impairments (lower limb weakness and greater postural sway) associated with worse stepping response; (ii) reduced capacity to recruit motor neurons to perform challenging balance tasks; (iii) reduced capacity to make appropriated motor planning to perform controlled tasks, such as stepping; (iv) poor anticipatory postural adjustments.