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Mediolateral weight-shifting is an important aspect of postural control. As it is currently unknown whether a short training session of mediolateral weight-shifting in a virtual reality (VR) environment can improve weight-shifting, we investigated this question and also probed the impact of practice on brain activity. Forty healthy older adults were randomly allocated to a training (EXP, n = 20, age = 70.80 (65-77), 9 females) or a control group (CTR, n = 20, age = 71.65 (65-82), 10 females). The EXP performed a 25-min weight-shift training in a VR-game, whereas the CTR rested for the same period. Weight-shifting speed in both single- (ST) and dual-task (DT) conditions was determined before, directly after, and 24 h after intervention. Functional Near-Infrared Spectroscopy (fNIRS) assessed the oxygenated hemoglobin (HbO 2 ) levels in five cortical regions of interest. Weight-shifting in both ST and DT conditions improved in EXP but not in CTR, and these gains were retained after 24 h. Effects transferred to wider limits of stability post-training in EXP versus CTR. HbO 2 levels in the left supplementary motor area were significantly increased directly after training in EXP during ST (change < SEM), and in the left somatosensory cortex during DT (change > SEM). We interpret these changes in the motor coordination and sensorimotor integration areas of the cortex as possibly learning-related., (© 2023. The Author(s).)

Purpose: Postural control deteriorates with age, especially under dual-task conditions. It is currently unknown how a challenging virtual reality weight-shifting task affects lower back muscle activity. Hence, this study investigated erector spinae neuromuscular control during mediolateral weight-shifting as part of an exergame during single- (ST) and dual-task (DT) conditions in young and older adults., Methods: Seventeen young and 17 older adults performed mediolateral weight-shifts while hitting virtual wasps in a virtual environment with and without a serial subtraction task (DT). Center of mass position was recorded in real-time using 3D motion capturing. Electromyography recorded bilateral activation of the lumbar longissimus and iliocostalis muscles., Results: Weight-shifting (p < 0.03) and targeting the wasps (p < 0.005) deteriorated with age and DT. Relative muscle activation during both quiet stance and weight-shifting increased with age, while the DT-effect did not differ consistently between age-groups. However, bilateral muscle co-contraction decreased with DT in young adults only. When switching direction and targeting the wasps, variability of muscle activation increased with age and DT and proved related to worse targeting performance. These effects were mainly visible at the non-dominant body side., Conclusion: Older adults showed a higher erector spinae muscle contribution to perform weight-shifts with increased variability at the end of a shift, whereby muscle activity was modulated less well in older than in young adults in response to DT. Hence, the current findings point to the potential for developing postural training in which older adults learn to fine-tune trunk muscle activity to improve weight-shifting and reduce fall risk., Competing Interests: Declaration of competing interest None., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Significance: Functional near-infrared spectroscopy (fNIRS) is increasingly employed in studies requiring repeated measurements, yet test-retest reliability is largely unknown., Aim: To investigate test-retest reliability during a postural and a finger-tapping task with and without cap-removal., Approach: Twenty healthy older adults performed a postural and a finger-tapping task. The tasks were repeated twice in one session and once the next day. A portable fNIRS system measured cortical hemodynamics ( HbO 2 ) in five regions of interest for the postural task and in the hand motor region for finger-tapping., Results: Test-retest reliability without cap-removal was excellent for the prefrontal cortex (PFC), the premotor cortex (PMC) and the somatosensory cortex (SSC) (intraclass correlation coefficient ( ICC ) ≥ 0.78 ), and fair for the frontal eye fields (FEF) and the supplementary motor area (SMA) ( ICC ≥ 0.48 ). After cap-removal, reliability reduced for PFC and SSC ( ICC ≥ 0.50 ), became poor for SMA ( ICC = 0.01 ) and PMC ( ICC = 0.00 ) and remained good for FEF ( ICC = 0.64 ). Similarly, good reliability ( ICC = 0.66 ) was apparent for the hand motor region without cap-removal, which deteriorated after cap-removal ( ICC = 0.38 )., Conclusions: Test-retest reliability of fNIRS measurements during two separate motor tasks in healthy older adults was fair to excellent when the cap remained in place. However, removing the fNIRS cap between measurements compromised reliability., (© 2023 The Authors.)

Background: Postural control and cognition are affected by aging. We investigated whether cognitive distraction influenced neural activity differently in young and older adults during a game-like mediolateral weight-shifting task with a personalized task load. Methods: Seventeen healthy young and 17 older adults performed a balance game, involving hitting virtual wasps, serial subtractions and a combination of both (dual-task). A motion analysis system estimated each subject's center of mass position. Cortical activity in five regions was assessed by measuring oxygenated hemoglobin (HbO 2 ) with a functional Near-Infrared Spectroscopy system. Results: When adding cognitive load to the game, weight-shifting speed decreased irrespective of age, but older adults reduced the wasp-hits more than young adults. Accompanying these changes, older adults decreased HbO 2 in the left pre-frontal cortex (PFC) and frontal eye fields (FEF) compared to single-tasking, a finding not seen in young adults. Additionally, lower HbO 2 levels were found during dual-tasking compared to the summed activation of the two single tasks in all regions except for the right PFC. These relative reductions were specific for the older age group in the left premotor cortex (PMC), the right supplementary motor area (SMA), and the left FEF. Conclusion: Older adults showed more compromised neural activity than young adults when adding a distraction to a challenging balance game. We interpret these changes as competitive downgrading of neural activity underpinning the age-related deterioration of game performance during dual-tasking. Future work needs to ascertain if older adults can train their neural flexibility to withstand balance challenges during daily life activities., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 de Rond, Orcioli-Silva, Dijkstra, Orban de Xivry, Pantall and Nieuwboer.)

Postural instability is a strong risk factor for falls that becomes more prominent with aging. To facilitate treatment and prevention of falls in an aging society, a thorough understanding of the neural networks underlying postural control is warranted. Here, we present a systematic review of the functional neuroimaging literature of studies measuring posture-related neural activity in healthy subjects. Study methods were overall heterogeneous. Eleven out of the 14 studies relied on postural simulation in a supine position (e.g. motor imagery). The key nodes of human postural control involved the brainstem, cerebellum, basal ganglia, thalamus and several cortical regions. An activation likelihood estimation meta-analysis revealed that the anterior cerebellum was consistently activated across the wide range of postural tasks. The cerebellum is known to modulate the brainstem nuclei involved in the control of posture. Hence, this systematic review with meta-analysis provides insight into the neural correlates which underpin human postural control and which may serve as a reference for future neural network and region of interest analyses., Competing Interests: Declaration of Competing Interest None., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

There is controversy whether age-related neuroanatomical and neurophysiological changes in the central nervous system affect healthy old adults' abilities to acquire and retain motor skills. We examined the effects of age on motor skill acquisition and retention and potential underlying mechanisms by measuring corticospinal and intracortical excitability, using transcranial magnetic stimulation. Healthy young (n = 24, 22 years) and old (n = 22, 71 years) adults practiced a wrist flexion-extention visuomotor task or only watched the templates as an attentional control for 20 minutes. Old compared with young adults performed less well at baseline. Although the absolute magnitude of skill acquisition and retention was similar in the 2 age groups (age × intervention × time, p = 0.425), a comparison of baseline-similar age sub-groups revealed impaired skill acquisition but not retention in old versus young. Furthermore, the neuronal mechanisms differed as revealed by an opposite direction of associations in the age-groups between relative skill acquisition and intracortical facilitation during the task, and opposite changes during skill retention in corticospinal excitability at rest and during the task and intracortical inhibition during the task., (Copyright © 2016 Elsevier Inc. All rights reserved.)