Cortical Engagement Metrics During Reactive Balance Are Associated With Distinct Aspects of Balance Behavior in Older Adults.

Jacqueline A Palmer,Michael R Borich,Aiden M Payne,Lena H Ting

doi:10.3389/fnagi.2021.684743

Abstract

Heightened reliance on the cerebral cortex for postural stability with aging is well-known, yet the cortical mechanisms for balance control, particularly in relation to balance function, remain unclear. Here we aimed to investigate motor cortical activity in relation to the level of balance challenge presented during reactive balance recovery and identify circuit-specific interactions between motor cortex and prefrontal or somatosensory regions in relation to metrics of balance function that predict fall risk. Using electroencephalography, we assessed motor cortical beta power, and beta coherence during balance reactions to perturbations in older adults. We found that individuals with greater motor cortical beta power evoked following standing balance perturbations demonstrated lower general clinical balance function. Individual older adults demonstrated a wide range of cortical responses during balance reactions at the same perturbation magnitude, showing no group-level change in prefrontal- or somatosensory-motor coherence in response to perturbations. However, older adults with the highest prefrontal-motor coherence during the post-perturbation, but not pre-perturbation, period showed greater cognitive dual-task interference (DTI) and elicited stepping reactions at lower perturbation magnitudes. Our results support motor cortical beta activity as a potential biomarker for individual level of balance challenge and implicate prefrontal-motor cortical networks in distinct aspects of balance control involving response inhibition of reactive stepping in older adults. Cortical network activity during balance may provide a neural target for precision-medicine efforts aimed at fall prevention with aging.

Highlights

The development of balance impairment with aging is common but poorly understood
Our results yield three main findings: (1) Similar to our previous findings in younger adults (Ghosn et al, 2020), perturbation-evoked beta oscillatory activity over central midline motor cortical regions was negatively correlated with balance ability in older adults, suggesting that perturbation-evoked cortical beta activity may provide a biomarker of individual level of balance challenge across the lifespan; (2) Individual older adults demonstrate a wide range of cortical engagement levels involving prefrontaland somatosensory-motor circuits during balance behavior; and (3) Greater perturbation-evoked prefrontal-motor cortical network connectivity was associated with greater decline in in a context-dependent manner to influence balance behavior
Our findings show that older adults engage individual circuitspecific cortical strategies during balance behavior that are linked to distinct aspects of balance control

Summary

Introduction

The development of balance impairment with aging is common but poorly understood. The neural mechanisms by which some individuals maintain high levels of activity while others suffer a debilitating loss of mobility and independence remain elusive. Previous studies have identified active cortical regions during continuous balance and walking tasks in older adults (Chang et al, 2016; Malcolm et al, 2020), but cortical oscillatory activity time-locked to destabilizing balance events, shown to be associated with balance ability in younger adults (Ghosn et al, 2020), or interactions between cortical regions reflecting information processing and integration during motor behavior have not been well investigated in older adults, who, as a group, have a higher risk for falling Such knowledge could identify effective neural control strategies during balancecorrecting behavior in high-functioning older adults and could be leveraged towards the development of precision medicine approaches for individualized fall prevention strategies among a heterogeneous older adult population. We aimed to characterize the neural dynamics of cortical oscillatory activity and interactions between cortical regions during balance reactions, and test the relationship between individual cortical engagement strategy during balance reactions and distinct aspects of balance behavior that are predictive of falls in older adults

Objectives

Methods

Results

Discussion

Conclusion