Inhibition and decision-processing speed are associated with performance on dynamic posturography in older adults

The association between dynamic balance and executive function: Which dynamic balance test has the strongest association with executive function? A systematic review and meta-analysis

AIM

The aging global population poses increasing challenges related to falls and dementia. Early identification of cognitive decline, particularly before noticeable symptoms manifest, is crucial for effective intervention. This review aims to determine the dynamic balance test most closely associated with executive function, potentially serving as a biomarker for cognitive decline.

RECENT FINDINGS

Based on recent reviews, inhibitory control, a component of executive function, holds significance in influencing balance performance. Studies suggest that the strength of the correlation between cognition and balance tends to be domain-specific and task-specific. Despite these findings, inconclusive evidence remains regarding the connection between executive function and various dynamic balance assessments. Our review identifies a significant association between all dynamic balance tests and executive function, albeit with varying strengths. Notably, a medium effect size is observed for the Timed Up and Go and Functional Reach Test, a small effect size for balance scales, and a strong effect size for postural sway. This review underscores a clear relationship between dynamic balance task performance and executive function. Dynamic posturography holds potential as a clinical biomarker for early detection of cognitive decline, with a note of caution due to observed heterogeneity and limited studies.

The Association Between Cognitive Domains and Postural Balance among Healthy Older Adults: A Systematic Review of Literature and Meta-Analysis

PURPOSE OF REVIEW

This review aims to explore which cognitive domain is more closely associated with which type of balance (static or dynamic).

RESENT FINDING

Based on recent reviews, inhibitory control, a part of cognition, plays a crucial role in balance performance. Previous reviews report significant links between cognition, mobility, and physical function in older adults. However, evidence regarding the relationship between cognition and balance scores remains inconclusive. The strength of association between cognition and balance appears to be domain-specific and task-specific. Executive function exhibits the strongest correlation with balance, while episodic memory shows a small link with dynamic balance. Processing speed and global cognition demonstrate moderate correlations. Additionally, there is a slight association between cognitive domains and static balance. Further research is needed to elucidate the underlying mechanisms and develop targeted interventions for managing balance-related concerns that are domain-specific and task-specific.

Exercise interventions, postural control, and prefrontal cortex activation in older adults

Improving postural control in older adults is necessary for reducing fall risk, and prefrontal cortex activation may also play a role. We sought to examine the impact of exercise interventions on postural control and prefrontal cortex activation during standing balance tasks. We hypothesized that balance would improve and prefrontal control would be reduced. We assessed a subset of participants enrolled in a randomized trial of two exercise interventions. Both groups completed strength and endurance training and the experimental treatment arm included training on timing and coordination of stepping. Postural control and prefrontal cortex activation were measured during dual-task standing balance tasks before and after the intervention. Eighteen participants in the standard strengthening and mobility training arm and 16 in the timing and coordination training arm were included. We examined pre- to post-intervention changes within each study arm, and compared them between interventions. Results did not show any pre- to post-intervention changes on standing postural control nor prefrontal cortex activation in either arm. In addition, there were no differences between the two intervention arms in either balance or prefrontal activation. While exercise interventions can improve mobility, we do not demonstrate evidence of improved standing balance or prefrontal control in standing.

Accelerometry applications and methods to assess standing balance in older adults and mobility-limited patient populations: a narrative review

Accelerometers provide an opportunity to expand standing balance assessments outside of the laboratory. The purpose of this narrative review is to show that accelerometers are accurate, objective, and accessible tools for balance assessment. Accelerometry has been validated against current gold standard technology, such as optical motion capture systems and force plates. Many studies have been conducted to show how accelerometers can be useful for clinical examinations. Recent studies have begun to apply classification algorithms to accelerometry balance measures to discriminate populations at risk for falls. In addition to healthy older adults, accelerometry can monitor balance in patient populations such as Parkinson's disease, multiple sclerosis, and traumatic brain injury. The lack of software packages or easy-to-use applications have hindered the shift into the clinical space. Lack of consensus on outcome metrics has also slowed the clinical adoption of accelerometer-based balance assessments. Future studies should focus on metrics that are most helpful to evaluate balance in specific populations and protocols that are clinically efficacious.

Mindfulness meditation and bimanual coordination control: study of acute effects and the mediating role of cognition

Introduction

Mindfulness meditation (MM) involves and benefits cognitive functioning, especially attention and inhibition processes, which are also implicated in the control of complex motor skills, such as bimanual coordination. Thus, MM practice could potentially enhance bimanual coordination control through its cognitive benefits. Accordingly, in this study, we investigated the acute effects of a brief MM session on bimanual coordination dynamics, attention, and inhibition abilities, as well as the mediation link between MM's cognitive and motor improvements.

Methods

Healthy meditation-naïve (novices, n = 29) and meditation-experienced participants (meditators, n = 26) were randomly assigned to either an active control intervention (attentive listening to a documentary podcast) or a MM intervention (breathing and open monitoring exercise), both lasting 15 min. In the motor domain, pre- and post-tests assessed participants' ability to intentionally maintain the anti-phase coordination pattern at maximal movement frequency and resist the spontaneous transition to the in-phase pattern. In the cognitive domain, the participants' attentional, perceptual inhibition and motor inhibition abilities were assessed.

Results

Following both interventions, meditators and novices improved the stability of their anti-phase coordination pattern (p = 0.034, η_p² = 0.10) and their attentional performance (p's < 0.001, η_p² > 0.40). Only following the MM intervention, meditators and novices improved their ability to intentionally maintain the anti-phase pattern by delaying or even suppressing the spontaneous transition to in-phase (p's < 0.05, η_p² ≥ 0.11), and improved concomitantly their motor inhibition scores (p = 0.011, η_p² = 0.13). No effects were found on perceptual inhibition. The increase in motor inhibition capacities did not however statistically mediate the observed acute effects of MM on bimanual coordination control.

Conclusion

We showed that a single MM session may have acute benefits in the motor domain regardless of the familiarity with MM practice. Although these benefits were concomitant to enhanced attentional and motor inhibition abilities, no formal mediation link could be established between the observed motor and cognitive benefits. This study paves the way for the investigation of the mechanisms underlying MM effects on motor control, as well as longer-term benefits.

Intentional maintenance of antiphase bimanual pattern at transition frequency: Is it associated with inhibition processes?

This study aimed at demonstrating the intentional modulation of bimanual coordination dynamics at transition frequency and determining whether it is associated with perceptual and/or motor inhibition capacities. Healthy adults (N = 29) performed in a random order: i) bimanual anti-phase (AP) movements at the maximal individual transition frequency, with the instruction to either let go, or intentionally maintain the initial movement pattern and oppose to the spontaneous transition to in-phase (IP) movements, and ii) The Motor and Perceptual Inhibition Test, giving separate scores for perceptual and motor inhibition. Results showed that in the intentional condition participants were able to delay (more movement cycles before the transition) and suppress (more trials without transition) the spontaneous transition from AP to IP. A statistically significant, though weak, correlation was found between motor performance and perceptual inhibition scores. We interpreted our findings as an indicator of the presence of an inhibitory mechanism underlying intentional dynamics that is partially associated to perceptual inhibition in healthy adults. This could have implications in populations with compromised inhibitory capacities, which might entail motor repercussions, and suggests the possibility of using bimanual coordination as means to stimulate both cognitive and motor capacities.

Viability, task switching, and fall avoidance of the simplest dynamic walker

Walking humans display great versatility when achieving task goals, like avoiding obstacles or walking alongside others, but the relevance of this to fall avoidance remains unknown. We recently demonstrated a functional connection between the motor regulation needed to achieve task goals (e.g., maintaining walking speed) and a simple walker's ability to reject large disturbances. Here, for the same model, we identify the viability kernel-the largest state-space region where the walker can step forever via at least one sequence of push-off inputs per state. We further find that only a few basins of attraction of the speed-regulated walker's steady-state gaits can fully cover the viability kernel. This highlights a potentially important role of task-level motor regulation in fall avoidance. Therefore, we posit an adaptive hierarchical control/regulation strategy that switches between different task-level regulators to avoid falls. Our task switching controller only requires a target value of the regulated observable-a "task switch"-at every walking step, each chosen from a small, predetermined collection. Because humans have typically already learned to perform such goal-directed tasks during nominal walking conditions, this suggests that the "information cost" of biologically implementing such controllers for the nervous system, including cognitive demands in humans, could be quite low.

The Effect of a Verbal Cognitive Task on Postural Sway Does Not Persist When the Task Is Over

Dual-task balance studies explore interference between balance and cognitive tasks. This study is a descriptive analysis of accelerometry balance metrics to determine if a verbal cognitive task influences postural control after the task ends. Fifty-two healthy older adults (75 ± 6 years old, 30 female) performed standing balance and cognitive dual-tasks. An accelerometer recorded movement from before, during, and after the task (reciting every other letter of the alphabet). Thirty-six balance metrics were calculated for each task condition. The effect of the cognitive task on postural control was determined by a generalized linear model. Twelve variables, including anterior-posterior centroid frequency, peak frequency and entropy rate, medial-later entropy rate and wavelet entropy, and bandwidth in all directions, exhibited significant differences between baseline and cognitive task periods, but not between baseline and post-task periods. These results indicate that the verbal cognitive task did alter balance, but did not bring about persistent effects after the task had ended. Traditional balance measurements, i.e., root mean square and normalized path length, notably lacked significance, highlighting the potential to use other accelerometer metrics for the early detection of balance problems. These novel insights into the temporal dynamics of dual-task balance support current dual-task paradigms to reduce fall risk in older adults.

Sensory integration abilities for balance in glaucoma, a preliminary study

The goal of this study was to quantify the association between sensory integration abilities relevant for standing balance and disease stage in glaucoma. The disease stage was assessed using both functional (visual field deficit) and structural (retinal nerve fiber layer thickness) deficits in the better and worse eye. Balance was assessed using an adapted version of the well-established Sensory Organization Test (SOT). Eleven subjects diagnosed with mild to moderate glaucoma stood for 3 min in 6 sensory challenging postural conditions. Balance was assessed using sway magnitude and sway speed computed based on center-of-pressure data. Mixed linear regression analyses were used to investigate the associations between glaucoma severity and balance measures. Findings revealed that the visual field deficit severity in the better eye was associated with increased standing sway speed. This finding was confirmed in eyes open and closed conditions. Balance was not affected by the extent of the visual field deficit in the worse eye. Similarly, structural damage in either eye was not associated with the balance measures. In summary, this study found that postural control performance was associated with visual field deficit severity. The fact that this was found during eyes closed as well suggests that reduced postural control in glaucoma is not entirely attributed to impaired peripheral visual inputs. A larger study is needed to further investigate potential interactions between visual changes and central processing changes contributing to reduced balance function and increased incidence of falls in adults with glaucoma.

Executive dysfunctions mediate between altered sensory processing and daily activity performance in older adults

BACKGROUND

Sensory processing is essential for the interaction with the environment and for adequate daily function. Sensory processing may deteriorate with aging and restrict daily activity performance. Aging may also affect Executive functions (EFs) which are critical for daily activity performance. Yet, most studies refer separately to the impacts of sensory processing or EFs and use clinical evaluations that do not necessarily reflect functional restrictions in real life. This study aims to describe the prevalence of altered sensory processing in the elderly as expressed in daily life scenarios and explore whether EFs mediate between altered sensory processing and daily activity performance in older adults.

METHODS

This cross-sectional study included 167 healthy independently functioning people aged 65 and above who were living in the community, had sufficient cognitive status and no symptoms of depression (based on the GDS and the MMSE). All participants completed a socio-demographic-health questionnaire, the Adolescent/Adult Sensory Profile, the Behavior Rating Inventory of Executive Function-Adult Version and the Daily Living Questionnaire.

RESULTS

Altered sensory processing, and mainly by the reduced ability to register and modulate sensory input from daily environment, were prevalent in older adults. Their impacts on daily activity performance were mediated by executive dysfunctions.

CONCLUSIONS

Executive dysfunctions may worsen the negative effects of altered sensory processing on daily activity performance in older adults. The interaction between EFs and sensory processing should receive growing attention in intervention and prevention programs for older adults, with the emphasis on their expressions and implications on peoples' function in real life context.

Relationship Between Chronic Conditions and Balance Disorders in Outpatients with Dizziness: A Hospital-Based Cross-Sectional Study

Background

Balance dysfunction is common in adult outpatients with dizziness, especially those who are older, which can lead to catastrophic outcomes such as falls. The aim of this study was to investigate the association between chronic conditions and balance disorders in patients with dizziness, especially those who are elderly.

Material/Methods

A cross-sectional study was conducted in adult outpatients diagnosed with dizziness referred to the Department of Otolaryngology at Beijing Tongren Hospital from September 2017 to August 2018. All of the patients completed a self-administered, structured questionnaire. Demographic data and information on history of chronic conditions were collected and the patients were divided into 2 groups based on whether their balance was normal or abnormal.

Results

Three hundred and thirty-two patients were included in this study, 168 in the normal balance group and 164 in the abnormal balance group. The incidence of chronic conditions, including hypertension and diabetes, in the abnormal balance group was higher than that in the normal balance group (all P<0.05). In subgroup analysis based on age, in those who were aged ≥60 years, the prevalence of chronic diseases was higher in the abnormal balance group than in the normal balance group (P=0.002), while there was no difference in age between the groups with abnormal and normal balance. Hypertension (OR: 2.268; 95%CI: 1.038–4.957; P<0.05) was a risk factor for balance disorders in elderly patients rather than those who were younger (P>0.05).

Conclusions

Our results show that chronic conditions are associated with balance function in older patients with dizziness. Thus, specialists should consider chronic conditions, especially hypertension, in elderly patients with dizziness.

Perceptual Inhibition Is Not a Specific Component of the Sensory Integration Process Necessary for a Rapid Voluntary Step Initiation in Healthy Older Adults

OBJECTIVES

We investigated whether performing step initiation during a proprioceptive perturbation would require greater perceptual or motor inhibitory control in older adults.

METHOD

Fifty-two healthy adults (young: n = 26, mean age 22.5 years vs. older: n = 26, mean age 70.1 years) performed a stepping reaction time task, with different inhibition requirements (i.e., perceptual vs. motor inhibitory conflict), with two proprioceptive configurations: with and without application of Achilles tendon vibrations.

RESULTS

Beyond a systematically greater stepping reaction time in older adults (p < .01), no difference was found between the perceptual versus motor inhibitory conflict resolution, regardless of age and proprioceptive configuration. Furthermore, slower reaction time was observed for young participants in the presence of Achilles tendon vibrations unlike older adults, who showed the same reactive stepping performance with or without vibrations (p < .05).

DISCUSSION

These findings show that perceptual inhibition cannot be considered as specifically involved in the central processing of proprioceptive signals, at least not in active older adults. Rather than motor system malfunctioning or a reduced amount of proprioceptive afference, we propose that cortical-proprioceptive processing in older adults remains as effective as in young adults, regardless of the high attentional requirements for step responses.

Impaired Multisensory Integration Predisposes the Elderly People to Fall: A Systematic Review

Background: This systematic review pooled all the latest data and reviewed all the relevant studies to look into the effect of multisensory integration on the balance function in the elderly.

Methods: PubMed, Web of Science and Scopus were searched to find eligible studies published prior to May 2019. The studies were limited to those published in Chinese and English language. The quality of the included studies was assessed against the Newcastle-Ottawa Scale or an 11-item checklist, as recommended by Agency for Healthcare Research and Quality (AHRQ). Any disagreement among reviewers was resolved by comparing notes and reaching a consensus.

Results: Eight hundred thirty-nine records were identified and 17 of them were included for systematic review. The result supported our assumption that multisensory integration works on balance function in the elderly. All the 17 studies were believed to be of high or moderate quality.

Conclusions: The systematic review found that the impairment of multisensory integration could predispose elderly people to fall. Accurate assessment of multisensory integration can help the elderly identify the impaired balance function and minimize the risk of fall. And our results provide a new basis for further understanding of balance maintenance mechanism. Further research is warranted to explore the change in brain areas related to multisensory integration in the elderly.

Optic flow and attention alter locomotion differently in the young and old

BACKGROUND

Optic flow is used in the control of walking speed and aids in navigation through space. However, the influence of attention on optic flow processing during locomotion is not known.

RESEARCH QUESTION

Does attentional focus influence the processing of optic flow during locomotion in young and older adults?

METHODS

Auditory and visual concurrent reaction time tasks were conducted while walking on a treadmill within an anterior-posterior modulating optic flow field in young and older adults. Optic flow was generated with full field back-projected scenes shown while walking on a treadmill under three conditions: a) optic flow consistent with the treadmill speed, b) slow sinusoidal modulation of the speed (SINE), and c) reversals of optic flow velocity from congruent with walking to the opposite direction (REV). Movement in response to the scenes along with reaction times were measured.

RESULTS

The optic flow perturbations altered movement on the treadmill. Older adults responded more than young adults during the slowly changing sinusoidal perturbations, but not to the rapid reversing scenes. Our main hypothesis that sensory modality of a concurrent cognitive task influences the processing of optic flow was confirmed for the reversing optic flow condition but not for the sinusoidal optic flow. The impact of optic flow conditions on reaction times was only found during the REV condition, with impact on visual RTs being greater than auditory RTs.

SIGNIFICANCE

Taken together, the results suggest attentional focus on sensory modality of concurrent tasks while walking can impact optic flow processing for navigation and control; however, the characteristics of the optic flow (e.g. perturbation speed) play an important role.