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

Palmer

et al. 2021

Front. Aging Neurosci.

Self Cite

The mechanisms underlying associations between cognitive set shifting impairments and balance dysfunction are unclear. Cognitive set shifting refers to the ability to flexibly adjust behavior to changes in task rules or contexts, which could be involved in flexibly adjusting balance recovery behavior to different contexts, such as the direction the body is falling. Prior studies found associations between cognitive set shifting impairments and severe balance dysfunction in populations experiencing frequent falls. The objective of this study was to test whether cognitive set shifting ability is expressed in successful balance recovery behavior in older adults with high clinical balance ability (N = 19, 71 ± 7 years, 6 female). We measured cognitive set shifting ability using the Trail Making Test and clinical balance ability using the miniBESTest. For most participants, cognitive set shifting performance (Trail Making Test B-A = 37 ± 20 s) was faster than normative averages (46 s for comparable age and education levels), and balance ability scores (miniBESTest = 25 ± 2/28) were above the threshold for fall risk (23 for people between 70 and 80 years). Reactive balance recovery in response to support-surface translations in anterior and posterior directions was assessed in terms of body motion, muscle activity, and brain activity. Across participants, lower cognitive set shifting ability was associated with smaller peak center of mass displacement during balance recovery, lower directional specificity of late phase balance-correcting muscle activity (i.e., greater antagonist muscle activity 200–300 ms after perturbation onset), and larger cortical N1 responses (100–200 ms). None of these measures were associated with clinical balance ability. Our results suggest that cognitive set shifting ability is expressed in balance recovery behavior even in the absence of profound clinical balance disability. Specifically, our results suggest that lower flexibility in cognitive task performance is associated with lower ability to incorporate the directional context into the cortically mediated later phase of the motor response. The resulting antagonist activity and stiffer balance behavior may help explain associations between cognitive set shifting impairments and frequent falls.

Section: Discussionmentioning

confidence: 99%

Lower Cognitive Set Shifting Ability Is Associated With Stiffer Balance Recovery Behavior and Larger Perturbation-Evoked Cortical Responses in Older Adults

Palmer

et al. 2021

Front. Aging Neurosci.

Self Cite

“…Increased synchronization between prefrontal and motor cortical areas during balance recovery with aging may explain associations between cognitive function and balance control in older adults. For example, we recently showed that beta coherence between motor and prefrontal cortical areas during balance recovery in older adults is associated with cognitive dual task interference in walking (Palmer et al, 2021). A better understanding of the mechanisms linking balance and cognitive function in aging could reveal new therapeutic targets for rehabilitation and enable a more targeted exploration of the effects of cognitive training on balance rehabilitation (Smith-Ray et al, 2015;Hagovska and Olekszyova, 2016).…”

Section: Discussionmentioning

confidence: 99%

Lower cognitive set shifting ability is associated with stiffer balance recovery behavior and larger perturbation-evoked cortical responses in older adults

Palmer

et al. 2021

Preprint

Self Cite

The mechanisms underlying associations between cognitive set shifting impairments and balance dysfunction are unclear. Cognitive set shifting refers to the ability to flexibly adjust behavior to changes in task rules or contexts, which could be involved in flexibly adjusting balance recovery behavior to different contexts, such as the direction the body is falling. Prior studies found associations between cognitive set shifting impairments and severe balance dysfunction in populations experiencing frequent falls. The objective of this study was to test whether cognitive set shifting ability is expressed in successful balance recovery behavior in older adults with high clinical balance ability (N=19, 71 ± 7 years, 6 female). We measured cognitive set shifting ability using the Trail Making Test and clinical balance ability using the miniBESTest. For most participants, cognitive set shifting performance (Trail Making Test B-A = 37 ± 20s) was faster than normative averages (46s for comparable age and education levels), and balance ability scores (miniBESTest = 25 ± 2 / 28) were above the threshold for fall risk (23 for people between 70-80 years). Reactive balance recovery in response to support-surface translations in anterior and posterior directions was assessed in terms of body motion, muscle activity, and brain activity. Across participants, lower cognitive set shifting ability was associated with smaller peak center of mass displacement during balance recovery, lower directional specificity of late phase balance-correcting muscle activity (i.e., greater antagonist muscle activity 200-300ms after perturbation onset), and larger cortical N1 responses (100-200ms). None of these measures were associated with clinical balance ability. Our results suggest that cognitive set shifting ability is expressed in balance recovery behavior even in the absence of profound clinical balance disability. Specifically, our results suggest that lower flexibility in cognitive task performance is associated with lower ability to incorporate the directional context into the cortically-mediated later phase of the motor response. The resulting antagonist activity and stiffer balance behavior may help explain associations between cognitive set shifting impairments and frequent falls.

“…While studies in older populations have been limited, older adults generally have smaller and later cortical N1s (Duckrow et al 1999;Ozdemir et al 2018), with changes in temporal characteristics including the appearance of multiple component peaks in some individuals with reduced mobility (Duckrow et al 1999). We recently reported associations between larger N1 amplitudes, lower cognitive set shifting ability, stiffer balance recovery behavior, and increased antagonist muscle activity in older adults (Payne et al 2021), further implicating the cortical N1 in the relationship between balance and cognitive problems with aging. We now investigate the cortical N1 responses in a population of older adults with Parkinson's disease, who have both balance and cognitive impairments.…”

Section: Introductionmentioning

confidence: 89%

“…Additionally, N1 amplitude in younger adults is associated with lower balance ability (Payne and Ting 2020a), a hallmark of Parkinson's disease (Bloem 1992;Grimbergen et al 2004;Koller et al 1989). Further, in older adults N1 amplitude is associated with lower cognitive set shifting ability and greater antagonist muscle activity (Payne et al 2021), both of which are associated with balance impairment in Parkinson's disease (Lang et al 2019;McKay et al 2018). All of these associations in unimpaired populations suggest the N1 would be larger in Parkinson's disease, related to greater cortical engagement to compensate for balance impairments, but there are also reasons to suspect the N1 might be reduced in Parkinson's disease.…”

Section: Introductionmentioning

confidence: 99%

The cortical N1 response to balance perturbation is associated with balance and cognitive function in different ways between older adults with and without Parkinson’s disease

Ting

2022

Preprint

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Mechanisms underlying associations between balance and cognitive impairments in older adults with and without Parkinson's disease (PD) are poorly understood. Balance disturbances evoke a cortical N1 response that is associated with both balance and cognitive abilities in unimpaired populations. We hypothesized that the N1 response reflects a neural mechanism that is shared between balance and cognitive function, and would therefore be associated with both balance and cognitive impairments in PD. Although N1 responses did not differ at the group level they showed distinct associations with balance and cognitive function in the PD vs. control (noPD) groups. In noPD, higher N1 amplitudes were correlated with lower cognitive set shifting ability and lower balance confidence. However, in PD, higher N1 amplitudes were correlated with lower overall cognitive function, while earlier and narrower N1 peaks were correlated with more severe PD and balance impairments. Our results show that balance and cognitive impairments are dissociable and associated with distinct features of the N1 response, suggesting that the N1 response reflects coordination of distinct mechanisms for balance and cognitive function. Identifying coordinated but dissociable mechanisms underlying balance and cognitive processes may reveal potential targets for rehabilitation of comorbid balance and cognitive impairments.