Contribution of muscle proprioception to limb movement perception and proprioceptive decline with ageing

Developing a Multi-Directional Lower-Limb Training System Toward Aging in Place Rehabilitation: A Preliminary Feasibility Study on Healthy Individuals

Not only improving muscle strength but also improving muscle power and neuromuscular control are important factors in improving lower limb function. In this study, a multi-directional lower-limb training system for aging -in-place rehabilitation was developed. The training system offers four distinct modes: muscle power training, pivoting neuromuscular training, muscle strength training using eccentric contractions, and proprioception training with evaluation. The feasibility of the training system was assessed through experiments conducted on healthy adults. Parameters such as mean of electromyography (EMG) peaks and pivoting instability during stepping tasks, and proprioceptive acuity in terms of pivoting angle error were tested using the system. By incorporating these diverse training modes, the training system can potentially be used to support clinicians in delivering tailored and effective subject-specific interventions for individuals with musculoskeletal and/or neuromuscular abnormalities toward aging-in-place rehabilitation.

Movement control of the cervical spine declines with aging: a cross-sectional study

BACKGROUND

Previous studies suggest that cervical spine position sense declines with age, while the relationship between aging and cervical spine movement control remains unknown.

OBJECTIVE

To investigate the relationship between age and cervical spine movement control in asymptomatic adults.

METHODS

One hundred five asymptomatic adults (21-79 years old) were included. The Butterfly test (performed with an inertial measurement unit) was used to assess movement control of the cervical spine, in which participants tracked an unpredictable moving target with active head and neck movements at three different movement path difficulty levels (3 repetitions each). The determined parameters were amplitude accuracy (AA), time on target (ToT), undershoot (U) and overshoot (O). Spearman's rank correlation coefficient and simple linear regression analysis were used to assess the relationship between age and each parameter.

RESULTS

A significant relationship was demonstrated between advancing age and the AA, ToT and U parameters for all three movement path difficulty levels (p ≤ .001), but not for the O parameter (p > .05). Advancing age explained 19.8-30.4%, 24.5-30.8% and 33.7-37.2% of the variance in the AA, ToT, and U parameters, respectively.

CONCLUSION

The results suggest that cervical spine movement control declines with aging in an asymptomatic population. Clinicians may need to monitor potential deficits in cervicocephalic kinesthesia in older asymptomatic adults, as these impairments may have a considerable impact on their functional abilities.

[Static delay exercises for improvement of proprioception and movements control in children with impaired intelligence (on the example of walking pattern correction)]

Children with mental retardation, due to the inertia of cortical processes, have changes in the motor sphere development, which are reflected in both mechanisms of motion control and postural disorders of the musculoskeletal system.

OBJECTIVE

To evaluate the effectiveness of static delay exercises in improving motor control and development of proprioception in children with mental retardation.

MATERIAL AND METHODS

The study involved 80 children aged 12-14 years. For comparison, 4 groups of 20 patients in each were formed: the 1st, the 2nd groups - children with a mild degree of impaired intelligence; the 3rd, the 4th groups - healthy children. Completion of two courses of exercises throughout the academic year was proposed to experimental groups. The emphasis of static exercises performed with rubber expander was focused on strengthening the core muscles as a main segment, providing the body's stability and participation in locomotions.

RESULTS

Significant differences in the changes of the indicators of dynamic and biomechanical disorders of movement patterns in children with impaired intelligence, primarily related to the improvement of movement coordination and motor act regulation mechanisms were identified.

CONCLUSION

Static delay exercises are effective for improving proprioception and movements control in children with impaired intelligence. Correctional work should be continued.

The Relationship Between Reduced Hand Dexterity and Brain Structure Abnormality in Older Adults

BACKGROUND

Hand dexterity is affected by normal aging and neuroinflammatory processes in the brain. Understanding the relationship between hand dexterity and brain structure in neurotypical older adults may be informative about prodromal pathological processes, thus providing an opportunity for earlier diagnosis and intervention to improve functional outcomes.

METHODS

this study investigates the associations between hand dexterity and brain measures in neurotypical older adults (≥65 years) using the Nine-Hole Peg Test (9HPT) and magnetic resonance imaging (MRI).

RESULTS

Elastic net regularized regression revealed that reduced hand dexterity in dominant and non-dominant hands was associated with an enlarged volume of the left choroid plexus, the region implicated in neuroinflammatory and altered myelination processes, and reduced myelin content in the left frontal operculum, the region implicated in motor imagery, action production, and higher-order motor functions. Distinct neural mechanisms underlying hand dexterity in dominant and non-dominant hands included the differences in caudate and thalamic volumes as well as altered cortical myelin patterns in frontal, temporal, parietal, and occipital regions supporting sensorimotor and visual processing and integration, attentional control, and eye movements. Although elastic net identified more predictive features for the dominant vs. non-dominant hand, the feature stability was higher for the latter, thus indicating higher generalizability for the non-dominant hand model.

CONCLUSIONS

Our findings suggest that the 9HPT for hand dexterity might be a cost-effective screening tool for early detection of neuroinflammatory and neurodegenerative processes. Longitudinal studies are needed to validate our findings in a larger sample and explore the potential of hand dexterity as an early clinical marker.

Aging increases proprioceptive error for a broad range of movement speed and distance estimates in the upper limb

Previous work has identified age-related declines in proprioception within a narrow range of limb movements. It is unclear whether these declines are consistent across a broad range of movement characteristics that more closely represent daily living. Here we aim to characterize upper limb error in younger and older adults across a range of movement speeds and distances. The objective of this study was to determine how proprioceptive matching accuracy changes as a function of movement speed and distance, as well as understand the effects of aging on these accuracies. We used an upper limb robotic test of proprioception to vary the speed and distance of movement in two groups: younger (n = 20, 24.25 ± 3.34 years) and older adults (n = 21, 63 ± 10.74 years). The robot moved one arm and the participant was instructed to mirror-match the movement with their opposite arm. Participants matched seven different movement speeds (0.1-0.4 m/s) and five distances (7.5-17.5 cm) over 350 trials. Spatial (e.g., End Point Error) and temporal (e.g., Peak Speed Ratio) outcomes were used to quantify proprioceptive accuracy. Regardless of the speed or distance of movement, we found that older controls had significantly reduced proprioceptive matching accuracy compared to younger control participants (p ≤ 0.05). When movement speed was varied, we observed that errors in proprioceptive matching estimates of spatial and temporal measures were significantly higher for older adults for all but the slowest tested speed (0.1 m/s) for the majority of parameters. When movement distance was varied, we observed that errors in proprioceptive matching estimates were significantly higher for all distances, except for the longest distance (17.5 cm) for older adults compared to younger adults. We found that the magnitude of proprioceptive matching errors was dependent on the characteristics of the reference movement, and that these errors scaled increasingly with age. Our results suggest that aging significantly negatively impacts proprioceptive matching accuracy and that proprioceptive matching errors made by both groups lies along a continuum that depends on movement characteristics and that these errors are amplified due to the typical aging process.

Quantifying body ownership information processing and perceptual bias in the rubber hand illusion

Bodily illusions have fascinated humankind for centuries, and researchers have studied them to learn about the perceptual and neural processes that underpin multisensory channels of bodily awareness. The influential rubber hand illusion (RHI) has been used to study changes in the sense of body ownership - that is, how a limb is perceived to belong to one's body, which is a fundamental building block in many theories of bodily awareness, self-consciousness, embodiment, and self-representation. However, the methods used to quantify perceptual changes in bodily illusions, including the RHI, have mainly relied on subjective questionnaires and rating scales, and the degree to which such illusory sensations depend on sensory information processing has been difficult to test directly. Here, we introduce a signal detection theory (SDT) framework to study the sense of body ownership in the RHI. We provide evidence that the illusion is associated with changes in body ownership sensitivity that depend on the information carried in the degree of asynchrony of correlated visual and tactile signals, as well as with perceptual bias and sensitivity that reflect the distance between the rubber hand and the participant's body. We found that the illusion's sensitivity to asynchrony is remarkably precise; even a 50 ms visuotactile delay significantly affected body ownership information processing. Our findings conclusively link changes in a complex bodily experience such as body ownership to basic sensory information processing and provide a proof of concept that SDT can be used to study bodily illusions.

Age-Related Decline in Cervical Proprioception and Its Correlation with Functional Mobility and Limits of Stability Assessed Using Computerized Posturography: A Cross-Sectional Study Comparing Older (65+ Years) and Younger Adults

Cervical proprioception and its implications on postural stability are crucial in older adults. Understanding their relationship is important in understanding and preventing falls in older adults. This research aims to evaluate the proprioceptive, functional mobility, and limits of stability (LOS) variables among two age groups: individuals aged 65 and above and those below 65. A secondary goal of the study is to analyze the relationship between cervical proprioception, functional mobility, and the LOS.

METHODS

In this cross-sectional study, 100 participants each were included in the older and younger groups. Researchers employed the target reposition technique to assess cervical proprioception and measured the joint position error (JPE) in degrees. Functional mobility was estimated using the Berg balance scale (BBS) and timed up-and-go test (TUG). In addition, dynamic posturography was utilized to evaluate variables related to the LOS, including reaction time, maximum excursion, and directional control.

RESULTS

The magnitudes of the mean cervical JPE are larger (p < 0.001), and functional mobility (p < 0.001) and the LOS (p < 0.001) are impaired in older individuals compared to the younger ones. The cervical proprioception is significantly associated with functional mobility (p < 0.001), and the LOS (p < 0.001).

CONCLUSION

In older adults aged above 65 years, cervical proprioception, functional mobility, and the LOS are impaired. Older adults with greater cervical JPE had more impaired functional mobility and LOS parameters. When evaluating or treating older adults with problems with their balance or falls, these factors should be considered.

Precision control for a flexible body representation

Adaptive body representation requires the continuous integration of multisensory inputs within a flexible 'body model' in the brain. The present review evaluates the idea that this flexibility is augmented by the contextual modulation of sensory processing 'top-down'; which can be described as precision control within predictive coding formulations of Bayesian inference. Specifically, I focus on the proposal that an attenuation of proprioception may facilitate the integration of conflicting visual and proprioceptive bodily cues. Firstly, I review empirical work suggesting that the processing of visual vs proprioceptive body position information can be contextualised 'top-down'; for instance, by adopting specific attentional task sets. Building up on this, I review research showing a similar contextualisation of visual vs proprioceptive information processing in the rubber hand illusion and in visuomotor adaptation. Together, the reviewed literature suggests that proprioception, despite its indisputable importance for body perception and action control, can be attenuated top-down (through precision control) to facilitate the contextual adaptation of the brain's body model to novel visual feedback.