Development of upper limb proprioceptive accuracy in children and adolescents

Placebo and nocebo interventions impact perceived but not actual proprioceptive accuracy

Changes in performance caused by positive and negative expectations (i.e., placebo and nocebo responses) were found to play an important role in many aspects of motor performance. This study aimed to test the impact of placebo/nocebo responses and the assumed moderating role of dispositional optimism and anxiety on proprioceptive accuracy, an essential aspect of motor functions. 78 undergraduate university students completed questionnaires assessing dispositional optimism, state anxiety, and motivation to cooperate, then were randomly assigned to three experimental groups. A sham subliminal electric stimulation was applied with claimed positive (placebo group, n = 26), negative (nocebo group, n = 26) or neutral (control group, n = 26) impact on proprioceptive accuracy. Proprioceptive accuracy was measured with active and passive versions of the Joint Position Reproduction task before and after the intervention. Expected and perceived changes in performance were also assessed; changes in state anxiety, optimism, and motivation to cooperate were used as control variables (covariates). Mixed analyses of variance indicated that the experimental manipulation did not affect actual proprioceptive accuracy but impacted expected and perceived performance. Adding the covariates to the models did not substantially change the results. Further, no significant association emerged between actual and perceived change in performance in the active test, and only a weak correlation was found in the passive test. Expected performance did not predict actual performance but predicted perceived performance in both tasks. The results suggest that only perceived (subjective) aspects of proprioceptive accuracy are susceptible to placebo and nocebo interventions.

Effects of Video-Based Exercises and Conventional Physiotherapy on Upper Extremity Functionality, Selective Motor Control, and Proprioception in Unilateral Cerebral Palsy: A Randomized Controlled Trial

Objective: The present study was conducted to evaluate the effects of video-based exercises added to conventional physiotherapy (CPT) on upper extremity functionality, selective motor control, and proprioception in individuals with unilateral cerebral palsy (UCP). Materials and Methods: Thirty patients with UCP were randomized into two groups: the intervention group (15 individuals with a mean age of 9.2 ± 3.8 years) and the control group (15 individuals with a mean age of 8.3 ± 4.1 years). The intervention group received 8 weeks of video-based exercises, and the control group received 8 weeks of conventional physiotherapy. Upper extremity functional abilities, upper extremity selective motor control, proprioception, and entertainment levels were evaluated before and after the intervention for all groups. Results: While a significant change was observed in the mean scores of the ABILHAND-Kids, Selective Control of the Upper Extremity Scale right-left scores, shoulder flexion, shoulder abduction, and elbow flexion proprioception angles after the video-based exercises in the intervention group (P < 0.05), a significant change was observed only in the 60-degree flexion angle in the control group (P = 0.001). In the comparison between the groups, there were significant differences in post-intervention value only in shoulder flexion and abduction angles, whereas there was no difference between the groups in elbow flexion angles (P > 0.05). Conclusion: Incorporating video-based exercises into the upper extremity rehabilitation processes of individuals with UCP is beneficial in terms of upper extremity functionality, selective motor control, and proprioception.

Keeping up with ourselves: Multimodal processes underlying body ownership across the lifespan

The sense of a bodily self is thought to depend on adaptive weighting and integration of bodily afferents and prior beliefs. While the physical body changes in shape, size, and functionality across the lifespan, the sense of body ownership remains relatively stable. Yet, little is known about how multimodal integration underlying such sense of ownership is altered in ontogenetic periods of substantial physical changes. We aimed to study this link for the motor and the tactile domain in a mixed-realty paradigm where participants ranging from 7 to 80 years old saw their own body with temporally mismatching multimodal signals. Participants were either stroked on their hand or moved it, while they saw it in multiple trials with different visual delays. For each trial, they judged the visuo-motor/tactile synchrony and rated the sense of ownership for the seen hand. Visual dependence and proprioceptive acuity were additionally assessed. The results show that across the lifespan body ownership decreases with increasing temporal multisensory mismatch, both in the tactile and the motor domain. We found an increased sense of ownership with increasing age independent of delay and modality. Delay sensitivity during multisensory conflicts was not consistently related to age. No effects of age were found on visual dependence or proprioceptive accuracy. The results are at least partly in line with an enhanced weighting of top-down and a reduced weighting of bottom-up signals for the momentary sense of bodily self with increasing age.

A pilot study: effect of somatosensory loss on motor corrections in response to unknown loads in a reaching task by chronic stroke survivors

Despite recent studies indicating a significant correlation between somatosensory deficits and rehabilitation outcomes, how prevailing somatosensory deficits affect stroke survivors' ability to correct their movements and recover overall remains unclear. To explore how major deficits in somatosensory systems impede stroke survivors' motor correction to various external loads, we conducted a study with 13 chronic stroke survivors who had hemiparesis. An inertial, elastic, or viscous load, which was designed to impose perturbing forces with various force profiles, was introduced unexpectedly during the reaching task using a programmable haptic robot. Participants' proprioception and cutaneous sensation were also assessed using passive movement detection, finger-to-nose, mirror, repositioning, and Weinstein pressure tests. These measures were then analyzed to determine whether the somatosensory measures significantly correlated with the estimated reaching performance parameters, such as initial directional error, positional deviation, velocity deviations, and speed of motor correction were measured. Of 13 participants, 5 had impaired proprioception, as they could not recognize the passive movement of their elbow joint, and they kept showing larger initial directional errors even after the familiarization block. Such continuously found inaccurate initial movement direction might be correlated with the inability to develop the spatial body map especially for calculating the initial joint torques when starting the reaching movement. Regardless of whether proprioception was impaired or not, all participants could show the stabilized, constant reaching movement trajectories. This highlights the role of proprioception especially in the execution of a planned movement at the early stage of reaching movement.

Proprioceptive Acuity Influences Speech Motor Control in Healthy Adult Talkers

PURPOSE

Somatosensory feedback, including proprioception, is important for speech production. This study evaluates proprioceptive acuity of the tongue using a position-matching task and determining if proprioceptive acuity impacts speech motor control in healthy adult talkers.

METHOD

Twenty-five young adults with no history of speech, language, or hearing disorders had their tongue movements recorded with an electromagnetic articulograph while completing a position-matching task. Participants were also asked to repeat two sentences that differed in the somatosensory feedback obtained. One sentence provided both tactile and proprioceptive feedback, whereas the other primarily provided proprioceptive feedback.

RESULTS

Participants ranged in proprioceptive acuity as measured by the position-matching task. Talkers with smaller position-matching errors and, therefore, higher proprioceptive acuity had smaller movements and slower speeds for both sentences. Talkers with lower proprioceptive acuity had reduced speech movement stability for the sentence that primarily provides proprioceptive feedback.

CONCLUSION

Proprioceptive acuity of the tongue can be evaluated using a position-matching task, and acuity is associated with more efficient speech movements and greater speech movement stability, particularly when producing utterances that provide less tactile feedback.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.24293740.

Adolescents running in conventional running shoes have lower vertical instantaneous loading rates but greater asymmetry than running barefoot or in partial-minimal shoes

Footwear may moderate the transiently heightened asymmetry in lower limb loading associated with peak growth in adolescence during running. This repeated-measures study compared the magnitude and symmetry of peak vertical ground reaction force and instantaneous loading rates (VILRs) in adolescents during barefoot and shod running. Ten adolescents (age, 10.6 ± 1.7 years) ran at self-selected speed (1.7 ± 0.3 m/s) on an instrumented treadmill under three counter-balanced conditions; barefoot and shod with partial-minimal and conventional running shoes. All participants were within one year of their estimated peak height velocity based on sex-specific regression equations. Foot-strike patterns, peak vertical ground reaction force and VILRs were recorded during 20 seconds of steady-state running. Symmetry of ground reaction forces was assessed using the symmetry index. Repeated-measures ANOVAs were used to compare conditions (α=.05). Adolescents used a rearfoot foot-strike pattern during barefoot and shod running. Use of conventional shoes resulted in a lower VILR (P < .05, dz = 0.9), but higher VILR asymmetry (P < .05) than running barefoot (dz = 1.5) or in partial-minimal shoes (dz = 1.6). Conventional running shoes result in a lower VILR than running unshod or in partial-minimal shoes but may have the unintended consequence of increasing VILR asymmetry. The findings may have implications for performance, musculoskeletal development and injury in adolescents.

Lower extremity proprioception and its association with activity and participation in children with unilateral spastic cerebral palsy

OBJECTIVE

This cross-sectional study aimed to assess lower extremity proprioception and investigate its relationship to activity and participation levels in children with unilateral spastic cerebral palsy (USCP).

METHODS

A total of 22 children with USCP between the ages of 5 and 16 years participated in this study. Lower extremity proprioception was evaluated with a protocol that consisted of verbal and location identification, unilateral and contralateral limb matching, and static and dynamic balance tests performed with the impaired and less impaired lower extremities under eyes-open and eyes-closed conditions. Furthermore, the Functional Independence Measure (WeeFIM) and Pediatric Outcomes Data Collection Instrument (PODCI) were used to evaluate the independence levels in daily living activities and participation levels.

RESULTS

Children demonstrated proprioceptive loss, as evidenced by an increase in matching errors under the eyes-closed condition compared to the eyes-open condition (p<0.05). Also, the impaired extremity had greater proprioceptive loss than the less impaired extremity (p<0.05). The 5-6-year age group experienced greater proprioceptive deficits than did the 7-11 and 12-16 age groups (p<0.05). Children's lower extremity proprioceptive deficit was moderately associated with their activity and participation levels (p<0.05).

CONCLUSIONS

Our findings suggest that treatment programs based on comprehensive assessments, including proprioception, may be more effective in these children.

Typical Development of Finger Position Sense From Late Childhood to Adolescence

Finger position sense is a proprioceptive modality highly important for fine motor control. Its developmental time course is largely unknown. This cross-sectional study examined its typical development in 138 children (8-17 years) and a group of 14 healthy young adults using a fast and novel psychophysical test that yielded objective measures of position sense acuity. Participants placed their hands underneath a computer tablet and judged the perceived position of their unseen index finger relative to two visible areas displayed on a tablet following a two-forced-choice paradigm. Responses were fitted to a psychometric acuity function from which the difference between the point-of-subjective-equality and the veridical finger position (ΔPSE) was derived as a measure of position sense bias, and the uncertainty area (UA) as a measure of precision. The main results are: First, children under 12 exhibited a significantly greater UA than adults while adolescent children (13-17 years) exhibited no significant differences when compared to adults. Second, no significant age-related differences in ΔPSE were found across the age range of 8-17 years. This implies that the typical development of finger position sense from late childhood to adulthood is characterized as an age-dependent increase in proprioceptive precision and not as a decrease in bias.

Reliable and Valid Robotic Assessments of Hand Active and Passive Position Sense in Children With Unilateral Cerebral Palsy

Impaired hand proprioception can lead to difficulties in performing fine motor tasks, thereby affecting activities of daily living. The majority of children with unilateral cerebral palsy (uCP) experience proprioceptive deficits, but accurately quantifying these deficits is challenging due to the lack of sensitive measurement methods. Robot-assisted assessments provide a promising alternative, however, there is a need for solutions that specifically target children and their needs. We propose two novel robotics-based assessments to sensitively evaluate active and passive position sense of the index finger metacarpophalangeal joint in children. We then investigate test-retest reliability and discriminant validity of these assessments in uCP and typically developing children (TDC), and further use the robotic platform to gain first insights into fundamentals of hand proprioception. Both robotic assessments were performed in two sessions with 1-h break in between. In the passive position sense assessment, participant's finger is passively moved by the robot to a randomly selected position, and she/he needs to indicate the perceived finger position on a tablet screen located directly above the hand, so that the vision of the hand is blocked. Active position sense is assessed by asking participants to accurately move their finger to a target position shown on the tablet screen, without visual feedback of the finger position. Ten children with uCP and 10 age-matched TDC were recruited in this study. Test-retest reliability in both populations was good (intraclass correlation coefficients (ICC) >0.79). Proprioceptive error was larger for children with uCP than TDC (passive: 11.49° ± 5.57° vs. 7.46° ± 4.43°, p = 0.046; active: 10.17° ± 5.62° vs. 5.34° ± 2.03°, p < 0.001), indicating discriminant validity. The active position sense was more accurate than passive, and the scores were not correlated, underlining the need for targeted assessments to comprehensively evaluate proprioception. There was a significant effect of age on passive position sense in TDC but not uCP, possibly linked to disturbed development of proprioceptive acuity in uCP. Overall, the proposed robot-assisted assessments are reliable, valid and a promising alternative to commonly used clinical methods, which could help gain a better understanding of proprioceptive impairments in uCP, facilitating the design of novel therapies.

Elbow Joint Position and Force Senses in Young and Adult Untrained People and Gymnasts

Joint position (JPS) and force senses (FS) are the proprioception modalities. While the development of JPS was investigated both in children/adult and athlete/untrained conditions, there is a lack of insight into the development of FS. Overall, 28 gymnasts and 25 untrained controls underwent proprioception testing. They were divided into two groups: 9 to 11-year-old boys (13 gymnasts and 10 non-athletes) and 18 to 25-year-old adults (15 gymnasts and 15 non-athletes). The testing was performed at an isokinetic dynamometer and included elbow JPS and FS (20% and 50% maximal voluntary contraction) tasks. Children had two times higher error in JPS (p < 0.01) and 50% higher errors in FS of both flexor (p < 0.001) and extensor muscles (p < 0.05) in comparison with adults. Only in the 50% maximal voluntary contraction task, gymnasts showed 33% lower error than the controls (p < 0.01). Untrained boys presented 54%, 132%, and 169% higher error for elbow flexor performance than young gymnasts, untrained adults, and adult gymnasts, respectively (p < 0.01). The 9 to 11-year-old participants were characterized by a lower precision of JPS and FS performance in comparison with adults. Gymnastic training can possibly accelerate the development of FS when higher loads are considered.

Simple and Reliable Position Sense Assessment under Different External Torques: Toward Developing a Post-stroke Proprioception Evaluation Device

Evaluation of position sense post-stroke is essential for rehabilitation. Position sense may be an output of a process needing position information, external torque, and the sense of effort. Even for healthy individuals, it is unclear whether external torque affects position sense. Thus, evaluation of position sense under different external torques in clinical settings is strongly needed. However, simple devices for measuring position sense under different external torques in clinical settings are lacking. Technologically advanced devices that may evaluate the elbow position sense under different torques were reported to be infeasible clinically because of device complexity and the need for technical experts when analyzing data. To address the unmet need, in this study, a simple and light elbow position sense measurement device was developed that allows clinicians to measure elbow position sense under different external torques in the form of position matching error objectively without any technical difficulties. The feasibility of the device, including intra-session intra-rater reliability and test-retest reliability over two consecutive days, was verified to be clinically applicable using tests with 25 healthy subjects. Thanks to its ease of use, high reliability, and ease of data analysis, it is expected that the device can help to evaluate the position sense post-stroke comprehensively.

Neonatal brachial plexus palsy and hand representation in children and young adults

AIM

To assess the impact of neonatal brachial plexus palsy (NBPP) on higher-order hand representation.

METHOD

Eighty-two left-handed children and adolescents with and without right-sided NBPP were recruited. Thirty-one participants with NBPP (mean age [SD] 11y 4mo [4y 4mo]; age range 6y 2mo-21y 0mo; 15 females; C5-6, n=4, C5-7, n=12, C5-T1, n=11, C5-T1 with Horner sign, n=4) were assessed along with 30 controls (mean age 11y 5mo [4y 4mo]; age range 6y 7mo-21y 7mo; 14 females). Participants' estimated hand size and shape on measure of implicit and explicit hand representation was assessed. A linear mixed model (LMM) was used to investigate the effect of condition, sensorimotor impairment, and age.

RESULTS

Individuals with NBPP showed a significant difference in implicit hand representation between affected and non-affected hands. LMM confirmed a significant influence of the severity of sensorimotor injury. Only the estimated implicit hand representation was associated with age, with a significant difference between 6- to 8-year-olds and 9- to 10-year-olds.

INTERPRETATION

The effect of sensorimotor impairment on central hand representation in individuals with NBPP is specific due to its implicit component and is characterized by finger length underestimation in the affected hand compared to the characteristic underestimation in the unaffected hand. Neither NBPP nor age impacted the explicit hand estimate. This study confirms the importance of sensorimotor contribution to the development of implicit hand representation.

Identification of Proprioceptive Thalamocortical Tracts in Children: Comparison of fMRI, MEG, and Manual Seeding of Probabilistic Tractography

Studying white matter connections with tractography is a promising approach to understand the development of different brain processes, such as proprioception. An emerging method is to use functional brain imaging to select the cortical seed points for tractography, which is considered to improve the functional relevance and validity of the studied connections. However, it is unknown whether different functional seeding methods affect the spatial and microstructural properties of the given white matter connection. Here, we compared functional magnetic resonance imaging, magnetoencephalography, and manual seeding of thalamocortical proprioceptive tracts for finger and ankle joints separately. We showed that all three seeding approaches resulted in robust thalamocortical tracts, even though there were significant differences in localization of the respective proprioceptive seed areas in the sensorimotor cortex, and in the microstructural properties of the obtained tracts. Our study shows that the selected functional or manual seeding approach might cause systematic biases to the studied thalamocortical tracts. This result may indicate that the obtained tracts represent different portions and features of the somatosensory system. Our findings highlight the challenges of studying proprioception in the developing brain and illustrate the need for using multimodal imaging to obtain a comprehensive view of the studied brain process.

Active Joint Position Sense in Children With Unilateral Cerebral Palsy

Objective

The aim of the study was to examine the differences in joint position sense at the elbow joint between 15 children with unilateral cerebral palsy (CP) and 15 typically developing (TD) controls without neurological or other health deficits.

Methodology

Joint position sense, a major proprioceptive component, was evaluated actively using a Kin Com 125 AP isokinetic dynamometer (Chattanooga Group, Chattanooga, TN).

Results

A significant interaction was found (p<0.05) between disability and side, with respect to the active reproduction movement scores. Post-hoc independent t-tests, with Bonferroni adjustments, revealed significant differences for the dominant (t=-3.63, p=0.001) and non-dominant sides respectively (t=-6.19, p=0.000). Repeated measures t-test revealed wider errors with the non-dominant (affected side) in the active reproduction test, compared to the dominant (nonaffected) side for the CP group of children (t=-4.73, p=0.000). A positive correlation was evident between the level of spasticity and joint position sense (Rho=0.71, p=0.003).

Conclusions

Based on our findings, joint position sense is impaired at the elbow joint in children with spastic hemiplegia. The proprioceptive deficit is present at both the affected and unaffected sides and is related to the level of spasticity.

Immersive virtual reality interferes with default head-trunk coordination strategies in young children

The acquisition of postural control is an elaborate process, which relies on the balanced integration of multisensory inputs. Current models suggest that young children rely on an 'en-block' control of their upper body before sequentially acquiring a segmental control around the age of 7, and that they resort to the former strategy under challenging conditions. While recent works suggest that a virtual sensory environment alters visuomotor integration in healthy adults, little is known about the effects on younger individuals. Here we show that this default coordination pattern is disrupted by an immersive virtual reality framework where a steering role is assigned to the trunk, which causes 6- to 8-year-olds to employ an ill-adapted segmental strategy. These results provide an alternate trajectory of motor development and emphasize the immaturity of postural control at these ages.

Development of eye-hand coordination in typically developing children and adolescents assessed using a reach-to-grasp sequencing task

Eye-hand coordination is required to accurately perform daily activities that involve reaching, grasping and manipulating objects. Studies using aiming, grasping or sequencing tasks have shown a stereotypical temporal coupling pattern where the eyes are directed to the object in advance of the hand movement, which may facilitate the planning and execution required for reaching. While the temporal coordination between the ocular and manual systems has been extensively investigated in adults, relatively little is known about the typical development of eye-hand coordination. Therefore, the current study addressed an important knowledge gap by characterizing the profile of eye-hand coupling in typically developing school-age children (n = 57) and in a cohort of adults (n = 30). Eye and hand movements were recorded concurrently during the performance of a bead threading task which consists of four distinct movements: reach to bead, grasp, reach to needle, and thread. Results showed a moderate to high correlation between eye and hand latencies in children and adults, supporting that both movements were planned in parallel. Eye and reach latencies, latency differences, and dwell time during grasping and threading, showed significant age-related differences, suggesting eye-hand coupling becomes more efficient in adolescence. Furthermore, visual acuity, stereoacuity and accommodative facility were also found to be associated with the efficiency of eye-hand coordination in children. Results from this study can serve as reference values when examining eye and hand movement during the performance of fine motor skills in children with neurodevelopmental disorders.

Gymnastics Experience Enhances the Development of Bipedal-Stance Multi-Segmental Coordination and Control During Proprioceptive Reweighting

Performance and control of upright bipedal posture requires a constant and dynamic integration of relative contributions of different sensory inputs (i. e., sensory reweighting) to enable effective adaptations as individuals face environmental changes and perturbations. Children with gymnastic experience showed balance performance closer to that of adults during and after proprioceptive alteration than children without gymnastic experience when their center of pressure (COP) was analyzed. However, a particular COP sway can be achieved through performing and coordinating different postural movements. The aim of this study was to assess how children and adults of different gymnastic experience perform and control postural movements while they have to adjust balance during and after bilateral tendon vibration. All participants were equipped with spherical markers attached to their skin and two vibrators strapped over the Achilles tendons. Bipedal stance was performed in three 45-s trials in two visual conditions (eyes open, EO, and eyes closed, EC) ordered randomly in which vibration lasted 10 s. Posture movements were analyzed by a principal component analysis (PCA) calculated on normalized and weighted markers coordinates. The relative standard deviation of each principal movement component (principal position, PP-rSTD) quantified its contribution to the whole postural movements, i.e., quantified the coordinative structure. The first (principal velocities, PV-rSTD) and second (principal accelerations, PA-rSTD) time-derivatives characterized the rate-dependent sensory information associated with and the neuromuscular control of the postural movements, respectively. Children without gymnastic experience showed a different postural coordinative structure and different sensory-motor control characteristics. They used less ankle movements in the anterior-posterior direction but increased ankle movements in medio-lateral direction, presented larger hip and trunk velocities, and exhibited more hip actions. Gymnastic experience during childhood seemed to benefit the development of proprioceptive reweighting processes in children, leading to a more mature form of coordinating and controlling posture similarly to adults.

Neurodevelopment of Posture-movement Coordination from Late Childhood to Adulthood as Assessed From Bimanual Load-lifting Task: An Event-related Potential Study

In a bimanual task, proprioception provides information about position and movement of upper arms. Developmental studies showed improvement of proprioceptive accuracy and timing adjustments of muscular events from childhood to adulthood in bimanual tasks. However, the cortical maturational changes related to bimanual coordination is not fully understood. The aim of this study was to investigate cortical correlates underlying motor planning and upper limb stabilization performance at left (C3) and right (C4) sensorimotor cortices using event-related potential (ERP) analyses. We recruited 46 participants divided into four groups (12 children: 8-10 years, 13 early adolescents: 11-13 years, 11 late adolescents: 14-16 years and 10 young adults: 20-35 years). Participants performed a bimanual load-lifting task, where the left postural arm supported the load and the right motor arm lifted the load. Maximal amplitude of elbow rotation (MA%) of the postural arm, reaction time (RT) and EMG activity of biceps brachii bilaterally were computed. Laplacian-transformed ERPs of the electroencephalographic (EEG) signal response-locked to motor arm biceps EMG activity onset were analyzed over C3 and C4. We found a developmental effect for behavioral and EEG data denoted by significant decrease of MA% and RT with age, earlier inhibition of the biceps brachii of the postural arm in adults and earlier EEG activation/inhibition onset at C3/C4. Amplitude of the negative wave at C4 was higher in children and early adolescents compared to the other groups. In conclusion, we found a maturational process in cortical correlates related to motor planning and upper limb stabilization performance with interhemispheric lateralization appearing during adolescence. Findings may serve documenting bimanual performance in children with neurodevelopmental disorders.

Upper limb proprioception and fine motor function in young pianists

BACKGROUND

This study investigated if intensive piano training may be associated with improved motor and somatosensory function. We systematically examined upper limb proprioception, which is known to play an essential role in skill movements, and motor function in young pianists.

METHOD

Forty-four typically developing children who either regularly played piano for more than six years (N = 16) or had no experience playing musical instruments (N = 28) participated. Elbow and wrist joint proprioceptive acuity was assessed using a manipulandum. The wrist/elbow was passively flexed to a target with participants actively trying to match the just experienced target position. Motor function was assessed using the Movement Assessment Battery for Children (MABC-2).

RESULTS

First, children in the pianist group exhibited significantly lower position sense bias (systematic error) at both the elbow and wrist when compared to controls. Position sense precision (random error) was not different between groups. Second, the piano group exhibited enhanced fine motor function as shown by higher manual dexterity MABC-2 scores. Performance in other motor domains (aiming and catching or balance) was not improved in young pianists. Third, a lower position sense bias was correlated with a higher level of manual dexterity.

CONCLUSION

This study documents that children who regularly play the piano have superior upper limb position sense acuity. Specifically, smaller position sense bias, i.e., less systematic error. Superior upper position sense acuity in young pianists is associated with higher fine motor functions.

Hand size representation in healthy children and young adults

Whereas we experience our body as a coherent volumetric object, the brain appears to maintain highly fragmented representations of individual body parts. Little is known about how body representations of hand size and shape are built and evolve during infancy and young adulthood. This study aimed to investigate the effect of hand side, handedness, and age on the development of central hand size representation. The observational study with comparison groups was conducted with 90 typically developing Belgian school children and young adults (48 male and 42 female; age range = 5.0-23.0 years; 49 left-handed and 41 right-handed). Participants estimated their hand size and shape using two different tasks. In the localization task, participants were verbally cued to judge the locations of 10 anatomical landmarks of an occluded hand. An implicit hand size map was constructed and compared with actual hand dimensions. In the template selection task, the explicit hand shape was measured with a depictive method. Hand shape indexes were calculated and compared for the actual, implicit, and explicit conditions. Participants were divided into four age groups (5-8 years, 9-10 years, 11-16 years, and 17-23 years). Implicit hand maps featured underestimation of finger length and overestimation of hand width, which is already present in the youngest children. Linear mixed modeling revealed no influence of hand side on finger length underestimation; nonetheless, a significant main effect of age (p = .001) was exposed. Sinistrals aged 11 to 16 years showed significantly less underestimation (p = .03) than dextrals of the same age. As for the hand shape, the implicit condition differed significantly with the actual and explicit conditions (p < .001). Again, the implicit shape index was subjected to handedness and age effects, with significant differences being found between sinistrals and dextrals in the age groups of 9 and 10 years (p = .029) and 11 to 16 years (p < .001). In conclusion, the implicit metric component of the hand representation in children and young adults is misperceived, featuring shortened fingers and broadened hands since a very young age. Crucially, the finger length underestimation increases with age and shows a different developmental trajectory for sinistrals and dextrals. In contrast, the explicit hand shape is approximately veridical and seems immune from age and handedness effects. This study confirms the dual character of somatoperception and establishes a point of reference for children and young adults.

Wrist proprioceptive acuity is linked to fine motor function in children undergoing piano training

Playing the piano involves rapid and precise upper limb movements, which require seamless integration of the proprioceptive and motor systems. In this study, we comprehensively assessed active and passive proprioception and different domains of motor function in young pianists, aiming to understand how their proprioceptive and motor functions are improved. Fifty-seven participants, including seventeen 11- to 12-yr-old (young) pianists, 20 children, and 20 adults, were included. The children in the pianist group had received piano training for 6 yr, whereas the children and adults in the control groups had no previous experience with instrumental training. All participants performed a psychophysical discrimination threshold hunting task and an ipsilateral joint position reproduction task, both of which measured the position sense acuity of the wrist. Their motor function was evaluated by the Movement Assessment Battery for Children, 2nd edition. The results revealed that the young pianists showed a significantly lower position sense discrimination threshold (31%) and fewer joint position reproduction errors (49%) than the nontrained children. Second, a higher level of manual dexterity, but not of ball skills or balance, was found in the young pianist group. Third, a higher proprioceptive acuity (i.e., decreased position sense discrimination threshold) significantly correlated with higher manual dexterity. This study documents that a high wrist position sense is a common characteristic among young pianists. The increased upper limb position sense acuity is correlated with better manual dexterity, suggesting that piano practice may benefit untrained fine motor skills in children.NEW & NOTEWORTHY We document that improved proprioceptive acuity is a common feature in young pianists. This proprioceptive improvement is associated with both proprioceptive processing and proprioceptive-motor integration. Higher wrist proprioceptive acuity in young pianists is linked to enhanced manual dexterity, which suggests that intensive piano training may improve untrained fine motor skills.

Robotic Assessments of Proprioception and the Impact of Age

We examined different methods of robotic proprioception assessment and provided comparison with the wrist position sense test gold standard assessment. The aim is to determine which of the assessments are the most reliable and would be acceptable for clinical evaluation. 31 children between six and sixteen participated in a pilot assessment trial and completed all four of the assessments. The assessments included the manual and robotic versions of the wrist position sense test, the joint position matching assessment and the psychometric threshold determination assessment. There was not a significant difference between the manual and robotic wrist position sense tests but there were significant differences with the other assessments. The study also examined the effect of age on the different assessments and found that three of the assessments, excluding the joint position matching assessment, can differentiate between children of different ages. This study concludes that the significant differences between the assessments indicates that proprioception in the wrist is complex and multifaceted. Further studies will likely need to include multiple assessments to gain a more complete understanding of proprioception.

Physiological Profile Assessment of Posture in Children and Adolescents with Autism Spectrum Disorder and Typically Developing Peers

A sound postural system requires sensorimotor integration. Evidence suggests that individuals with Autism Spectrum Disorder (ASD) present sensorimotor integration impairments. The Physiological Profile Assessment (PPA) can be used to evaluate postural capacity assessing five physiological subsets (i.e., vision, reaction time, peripheral sensation, lower limb strength, balance); however, no studies applied the PPA in young individuals. Therefore, this study aimed to investigate the PPA in children and adolescents with ASD compared with age-matched typically developing (TD) individuals and examine the relationship between the PPA subset within the ASD and TD participants according to different age groups. Percentiles from the PPA were obtained from the TD children and adolescents (n = 135) for each test. Performances of the individuals with ASD (n = 18) were examined relative to the TD percentiles. ASD participants' scores were above the 90th percentile (i.e., poor performance) in most sensory, motor and balance parameters. Performance in most of the PPA tests significantly improved with older age in the TD group but not in the ASD group. The study findings support the use of the PPA in TD children and adolescents while further research should investigate postural capacity in a larger ASD sample to enhance the understanding of sensorimotor systems contributing to compromised postural control.

The Developing Bodily Self: How Posture Constrains Body Representation in Childhood

Adults' body representation is constrained by multisensory information and knowledge of the body such as its possible postures. This study (N = 180) tested for similar constraints in children. Using the rubber hand illusion with adults and 6- to 7-year olds, we measured proprioceptive drift (an index of hand localization) and ratings of felt hand ownership. The fake hand was either congruent or incongruent with the participant's own. Across ages, congruency of posture and visual-tactile congruency yielded greater drift toward the fake hand. Ownership ratings were higher with congruent visual-tactile information, but unaffected by posture. Posture constrains body representation similarly in children and adults, suggesting that children have sensitive, robust mechanisms for maintaining a sense of bodily self.

Proprioceptive accuracy in Immersive Virtual Reality: A developmental perspective

Proprioceptive development relies on a variety of sensory inputs, among which vision is hugely dominant. Focusing on the developmental trajectory underpinning the integration of vision and proprioception, the present research explores how this integration is involved in interactions with Immersive Virtual Reality (IVR) by examining how proprioceptive accuracy is affected by Age, Perception, and Environment. Individuals from 4 to 43 years old completed a self-turning task which asked them to manually return to a previous location with different sensory modalities available in both IVR and reality. Results were interpreted from an exploratory perspective using Bayesian model comparison analysis, which allows the phenomena to be described using probabilistic statements rather than simplified reject/not-reject decisions. The most plausible model showed that 4-8-year-old children can generally be expected to make more proprioceptive errors than older children and adults. Across age groups, proprioceptive accuracy is higher when vision is available, and is disrupted in the visual environment provided by the IVR headset. We can conclude that proprioceptive accuracy mostly develops during the first eight years of life and that it relies largely on vision. Moreover, our findings indicate that this proprioceptive accuracy can be disrupted by the use of an IVR headset.

To have and to hold: embodied ownership is established in early childhood

We investigated whether embodied ownership is evident in early childhood. To do so, we gifted a drinking bottle to children (aged 24-48 months) to use for 2 weeks. They returned to perform reach-grasp-lift-replace actions with their own or the experimenter's bottle while we recorded their movements using motion capture. There were differences in motor interactions with self- vs experimenter-owned bottles, such that children positioned self-owned bottles significantly closer to themselves compared with the experimenter's bottle. Age did not modulate the positioning of the self-owned bottle relative to the experimenter-owned bottle. In contrast, the pattern was not evident in children who selected one of the two bottles to keep only after the task was completed, and thus did not 'own' it during the task (Experiment 2). These results extend similar findings in adults, confirming the importance of ownership in determining self-other differences and provide novel evidence that object ownership influences sensorimotor processes from as early as 2 years of age.

The Strength of the Movement-related Somatosensory Cortical Oscillations Differ between Adolescents and Adults

Adolescents demonstrate increasing mastery of motor actions with age. One prevailing hypothesis is that maturation of the somatosensory system during adolescence contributes to the improved motor control. However, limited efforts have been made to determine if somatosensory cortical processing is different in adolescents during movement. In this study, we used magnetoencephalographic brain imaging to begin addressing this knowledge gap by applying an electrical stimulation to the tibial nerve as adolescents (Age = 14.8 ± 2.5 yrs.) and adults (Age = 36.8 ± 5.0 yrs.) produced an isometric ankle plantarflexion force, or sat with no motor activity. Our results showed strong somatosensory cortical oscillations for both conditions in the alpha-beta (8–30 Hz) and gamma (38–80 Hz) ranges that occurred immediately after the stimulation (0–125 ms), and a beta (18–26 Hz) oscillatory response shortly thereafter (300–400 ms). Compared with the passive condition, all of these frequency specific cortical oscillations were attenuated while producing the ankle force. The attenuation of the alpha-beta response was greater in adolescents, while the adults had a greater attenuation of the beta response. These results imply that altered attenuation of the somatosensory cortical oscillations might be central to the under-developed somatosensory processing and motor performance characteristics in adolescents.

Quantifying Age-Related Differences of Ankle Mechanical Properties Using a Robotic Device

A deep analysis of ankle mechanical properties is a fundamental step in the design of an exoskeleton, especially if it is to be suitable for both adults and children. This study aims at assessing age-related differences of ankle properties using pediAnklebot. To achieve this aim, we enrolled 16 young adults and 10 children in an experimental protocol that consisted of the evaluation of ankle mechanical impedance and kinematic performance. Ankle impedance was measured by imposing stochastic torque perturbations in dorsi-plantarflexion and inversion-eversion directions. Kinematic performance was assessed by asking participants to perform a goaldirected task. Magnitude and anisotropy of impedance were computed using a multipleinput multiple-output system. Kinematic performance was quantified by computing indices of accuracy, smoothness, and timing. Adults showed greater magnitude of ankle impedance in both directions and for all frequencies, while the anisotropy was higher in children. By analyzing kinematics, children performed movements with lower accuracy and higher smoothness, while no differences were found for the duration of the movement. In addition, adults showed a greater ability to stop the movement when hitting the target. These findings can be useful to a proper development of robotic devices, as well as for implementation of specific training programs.

Age-related changes in proprioception of the ankle complex across the lifespan

BACKGROUND

Ankle complex proprioceptive ability, needed in active human movement, may change from childhood to elderly adulthood; however, its development across all life stages has remained unexamined. The aim of the present study was to investigate the across-the-lifespan trend for proprioceptive ability of the ankle complex during active ankle inversion movement.

METHODS

The right ankles of 118 healthy right-handed participants in 6 groups were assessed: children (6-8 years old), adolescents (13-15 years old), young adults (18-25 years old), middle-aged adults (35-50 years old), old adults (60-74 years old), and very old adults (75-90 years old). While the participants were standing, their ankle complex proprioception was measured using the Active Movement Extent Discrimination Apparatus.

RESULTS

There was no significant interaction between the effects of age group and gender on ankle proprioceptive acuity (F (5, 106) = 0.593, p = 0.705, η² _p = 0.027). Simple main effects analysis showed that there was a significant main effect for age group (F (5, 106) = 22.521, p < 0.001, η ² _p = 0.515) but no significant main effect for gender (F (1,106) =  2.283, p = 0.134, η ² _p = 0.021) between the female (0.723 ± 0.092, mean ± SD) and the male (0.712 ± 0.083) participants. The age-group factor was associated with a significant linear downward trend in scores (F (1, 106) = 10.584, p = 0.002, η ² _p = 0.091) and a strong quadratic trend component (F (1,106) = 100.701, p < 0.001, η ² _p = 0.480), producing an asymmetric inverted-U function.

CONCLUSION

The test method of the Active Movement Extent Discrimination Apparatus is sensitive to age differences in ankle complex proprioception. For proprioception of the ankle complex, young adults had significantly better scores than children, adolescents, old adults, and very old adults. The middle-aged group had levels of ankle proprioceptive acuity similar to those of the young adults. The scores for males and females were not significantly different. Examination of the range of the scores in each age group highlights the possible level that ankle complex movement proprioceptive rehabilitation can reach, especially for those 75-90 years of age.

Age-related Declines in Sensorimotor Proficiency are Specific to the Tested Motor Skill Component

This study utilized a 3-degree of freedom robotic device (Wristbot) to examine wrist proprioception and eye-hand coordination in a cross-sectional sample of sixty-three young adults (19-29 years), 20 older young adults (30-49), and 17 older adults (50 years and older). Results indicated differences in the emergence of age-related declines in sensorimotor functioning depending on the tested motor skill component. While young adults exhibited smaller matching error and lower variability compared to older young adults and older adults on the proprioception task, we observed lower times-on-target and higher Linearity indices for participants older than 50 years of age compared to both young adults and older young adults. The present results provide necessary quantitative information on sensorimotor function in adulthood, and have implications for the early diagnosis and effective management of sensorimotor dysfunction in clinical settings using a commercially available robotic device.

Practice modulates motor-related beta oscillations differently in adolescents and adults

KEY POINTS

Magnetoencephalography data were acquired during a leg force task in pre-/post-practice sessions in adolescents and adults. Strong peri-movement alpha and beta oscillations were mapped to the cortex. Following practice, performance improved and beta oscillations were altered. Beta oscillations decreased in the sensorimotor cortex in adolescents after practice, but increased in adults. No pre-/post-practice differences were detected for alpha oscillations.

ABSTRACT

There is considerable evidence that there are motor performance and practice differences between adolescents and adults. Behavioural studies have suggested that these motor performance differences are simply due to experience. However, the neurophysiological nexus for these motor performance differences remains unknown. The present study investigates the short-term changes (e.g. fast motor learning) in the alpha and beta event-related desynchronizations (ERDs) associated with practising an ankle plantarflexion motor action. To this end, we utilized magnetoencephalography to identify changes in the alpha and beta ERDs in healthy adolescents (n = 21; age = 14 ± 2.1 years) and middle-aged adults (n = 22; age = 36.6 ± 5 years) after practising an isometric ankle plantarflexion target-matching task. After practice, all of the participants matched more targets and matched the targets faster, and had improved accuracy, faster reaction times and faster force production. However, the motor performance of the adults exceeded what was seen in the adolescents regardless of practice. In conjunction with the behavioural results, the strength of the beta ERDs across the motor planning and execution stages was reduced after practice in the sensorimotor cortices of the adolescents, but was stronger in the adults. No pre-/post-practice changes were found in the alpha ERDs. These outcomes suggest that there are age-dependent changes in the sensorimotor cortical oscillations after practising a motor task. We suspect that these noted differences might be related to familiarity with the motor task, GABA levels and/or maturational differences in the integrity of the white matter fibre tracts that comprise the respective cortical areas.

Ability of individuals with chronic hemiparetic stroke to locate their forearms during single-arm and between-arms tasks

Background

According to between-arms assessments, more than 50% of individuals with stroke have an impaired position sense. Our previous work, which employed a clinical assessment and slightly differing tasks, indicates that individuals who have a deficit on a between-forearms position-localization task do not necessarily have a deficit on a single-forearm position-localization task.

Objective

Our goal here was to, using robotics tools, determine whether individuals with stroke who have a deficit when matching forearm positions within an arm also have a deficit when mirroring forearm positions between arms, independent of the arm that leads the task.

Methods

Eighteen participants with chronic hemiparetic stroke and nine controls completed a single-arm position-matching experiment and between-arms position-mirroring experiment. For each experiment, the reference forearm (left/right) passively rotated about the elbow joint to a reference target location (flexion/extension), and then the participant actively rotated their same/opposite forearm to match/mirror the reference forearm’s position. Participants with stroke were classified as having a position-matching/-mirroring deficit based on a quantitative threshold that was derived from the controls’ data.

Results

On our single-arm task, one participant with stroke was classified as having a position-matching deficit with a mean magnitude of error greater than 10.7° when referencing their paretic arm. Position-matching ability did not significantly differ for the controls and the remaining seventeen participants with stroke. On our between-arms task, seven participants with stroke were classified as having a position-mirroring deficit with a mean magnitude of error greater than 10.1°. Position-mirroring accuracy was worse for these participants with stroke, when referencing their paretic arm, than the controls.

Concluding remark

Findings underscore the need for assessing within-arm position-matching deficits, in addition to between-arms position-mirroring deficits when referencing each arm, to comprehensively evaluate an individual’s ability to locate their forearm(s).

New functions for the proprioceptive system in skeletal biology

Muscle spindles and Golgi tendon organs (GTOs) are two types of sensory receptors that respond to changes in length or tension of skeletal muscles. These mechanosensors have long been known to participate in both proprioception and stretch reflex. Here, we present recent findings implicating these organs in maintenance of spine alignment as well as in realignment of fractured bones. These discoveries have been made in several mouse lines lacking functional mechanosensors in part or completely. In both studies, the absence of functional spindles and GTOs produced a more severe phenotype than that of spindles alone. Interestingly, the spinal curve phenotype, which appeared during peripubertal development, bears resemblance to the human condition adolescent idiopathic scoliosis. This similarity may contribute to the study of the disease by offering both an animal model and a clue as to its aetiology. Moreover, it raises the possibility that impaired proprioceptive signalling may be involved in the aetiology of other conditions. Overall, these new findings expand considerably the scope of involvement of proprioception in musculoskeletal development and function.This article is part of the Theo Murphy meeting issue 'Mechanics of development'.

Assessing body sensations in children: Intra-rater reliability of assessment and effects of age

Introduction

This article examines the effect of age and gender on somatosensory capacity for children and adolescents, and provides preliminary normative data and reliability for the SenScreen© Kids, a new standardised measure of touch, wrist position sense and haptic object recognition.

Method

A cross-sectional study of 88 typically developing children aged 6–15 years (mean 10.3 years; SD 2.6 years) was used to determine the developmental effects of age and gender on somatosensory capacity. Intra-rater reliability was assessed in 22 of the 88 participants at two time points (mean 8.8 years; SD 2.6 years).

Results

Statistically significant differences were observed between age groups for tactile discrimination, wrist position sense and haptic object recognition, but not for touch registration for which all except one participant achieved a maximum score. There was no effect of gender. Three of four SenScreen Kids subtests demonstrated good intra-rater agreement between time points.

Conclusions

Somatosensory capacity increased with age for typically developing children aged 6–15 years. Three subtests of the SenScreen Kids demonstrated good intra-rater reliability with typically developing children. Further investigation of reliability is required, and all subtests require psychometric testing with clinical populations.

Development of Right-hemispheric Dominance of Inferior Parietal Lobule in Proprioceptive Illusion Task

Functional lateralization can be an indicator of brain maturation. We have consistently shown that, in the adult brain, proprioceptive processing of muscle spindle afferents generating illusory movement of the right hand activates inferior frontoparietal cortical regions in a right-side dominant manner in addition to the cerebrocerebellar motor network. Here we provide novel evidence regarding the development of the right-dominant use of the inferior frontoparietal cortical regions in humans using this task. We studied brain activity using functional magnetic resonance imaging while 60 right-handed blindfolded healthy children (8-11 years), adolescents (12-15 years), and young adults (18-23 years) (20 per group) experienced the illusion. Adult-like right-dominant use of the inferior parietal lobule (IPL) was observed in adolescents, while children used the IPL bilaterally. In contrast, adult-like lateralized cerebrocerebellar motor activation patterns were already observable in children. The right-side dominance progresses during adolescence along with the suppression of the left-sided IPL activity that emerges during childhood. Therefore, the neuronal processing implemented in the adult's right IPL during the proprioceptive illusion task is likely mediated bilaterally during childhood, and then becomes right-lateralized during adolescence at a substantially later time than the lateralized use of the cerebrocerebellar motor system for kinesthetic processing.

Age and gymnastic experience effects on sensory reweighting processes during quiet stand

BACKGROUND

The relative contribution of sensory inputs to control balance while standing is dynamically adjusted. These sensory reweighting processes could be impacted by age and sport expertise capabilities, especially when the sport emphasizes equilibrium like artistic gymnastics.

RESEARCH QUESTION

The aim of this study was to explore the sensory reweighting processes to adjust standing posture in children and adults with different gymnastic expertise (gymnasts, G, and non-gymnast, NG).

METHODS

All participants were asked to stand quietly on a force plate in two visual conditions (eyes open, EO, and eyes closed, EC). Within a trial, proprioception was altered with two vibrators strapped at the Achilles tendon level. The center of pressure (COP) displacements in the anterior-posterior and medio-lateral directions were calculated and normalized by the base of support. The effect of vibration application was characterized by the COP speed, maximal posterior displacement and the time when it occurred. The effect of vibration removal was depicted by the time between the motor switched off and the achievement of balance values similar to baseline and the COP speed and movement units performed during this time.

RESULTS

G children presented shorter posterior displacement during vibrations, needed less time to recover initial balance, and produced less movements units than NG children. In general, adults and EO showed better reweighting responses than children and EC, respectively.

SIGNIFICANCE

These results suggest that age could have a positive effect on reweighting processes and that gymnastic experience may benefit the development of proprioceptive reweighting processes in children but not in adults.

Protracted Development of the Proprioceptive Brain Network During and Beyond Adolescence

Proprioceptive processing is important for appropriate motor control, providing error-feedback and internal representation of movement for adjusting the motor command. Although proprioceptive functioning improves during childhood and adolescence, we still have few clues about how the proprioceptive brain network develops. Here, we investigated developmental changes in the functional organization of this network in early adolescents (n = 18, 12 ± 1 years), late adolescents (n = 18, 15 ± 1), and young adults (n = 18, 32 ± 4), by examining task-evoked univariate activity and patterns of functional connectivity (FC) associated with seeds placed in cortical (supramarginal gyrus) and subcortical (dorsal rostral putamen) regions. We found that although the network is already well established in early adolescence both in terms of topology and functioning principles (e.g., long-distance communication and economy in wiring cost), it is still undergoing refinement during adolescence, including a shift from diffuse to focal FC and a decreased FC strength. This developmental effect was particularly pronounced for fronto-striatal connections. Furthermore, changes in FC features continued beyond adolescence, although to a much lower extent. Altogether, these findings point to a protracted developmental time course for the proprioceptive network, which breaks with the relatively early functional maturation often associated with sensorimotor networks.

The Proprioceptive System Regulates Morphologic Restoration of Fractured Bones

Successful fracture repair requires restoration of bone morphology and mechanical integrity. Recent evidence shows that fractured bones of neonatal mice undergo spontaneous realignment, dubbed "natural reduction." Here, we show that natural reduction is regulated by the proprioceptive system and improves with age. Comparison among mice of different ages revealed, surprisingly, that 3-month-old mice exhibited more rapid and effective natural reduction than newborns. Fractured bones of null mutants for transcription factor Runx3, lacking functional proprioceptors, failed to realign properly. Blocking Runx3 expression in the peripheral nervous system, but not in limb mesenchyme, recapitulated the null phenotype, as did inactivation of muscles flanking the fracture site. Egr3 knockout mice, which lack muscle spindles but not Golgi tendon organs, displayed a less severe phenotype, suggesting that both receptor types, as well as muscle contraction, are required for this regulatory mechanism. These findings uncover a physiological role for proprioception in non-autonomous regulation of skeletal integrity.

The effects of age and amplitude on wrist proprioceptive acuity

This study examined wrist proprioception in a cross-sectional sample of 44 children aged between 8-to 14-years and a control group of 10 neurologically and physically healthy adults. Using a 3-degrees of freedom robotic device, participants performed an ipsilateral joint position matching task in which target amplitude (40% or 80% functional range of motion [fRoM]) and degrees-of-freedom (Flexion/Extension [FE], Radial/Ulnar deviation [RUD], Pronation/Supination [PS]) were manipulated. Results indicated that proprioceptive function became more accurate and consistent over the developmental spectrum, but that the ability to utilize proprioceptive feedback did not reach adult levels till the age of 10-11 years. Furthermore, proprioceptive acuity was influenced by target amplitude, such that movements were more accurate for the 80% fROM compared to the 40% fROM target for both the RUD and PS DoFs, independently of age. The present results provide critical information about the typical development of wrist proprioception that will enable clinicians to chart the course of development and dysfunction in neurological disorders in children, and help establish protocols for the robotic diagnosis and assessment of neurodevelopmental disorders.

Neural predictors of motor control and impact of visuo-proprioceptive information in youth

For successful motor control, the central nervous system is required to combine information from the environment and the current body state, which is provided by vision and proprioception respectively. We investigated the relative contribution of visual and proprioceptive information to upper limb motor control and the extent to which structural brain measures predict this performance in youth (n = 40; age range 9-18 years). Participants performed a manual tracking task, adopting in-phase and anti-phase coordination modes. Results showed that, in contrast to older participants, younger participants performed the task with lower accuracy in general and poorer performance in anti-phase than in-phase modes. However, a proprioceptive advantage was found at all ages, that is, tracking accuracy was higher when proprioceptive information was available during both in- and anti-phase modes at all ages. The microstructural organization of interhemispheric connections between homologous dorsolateral prefrontal cortices, and the cortical thickness of the primary motor cortex were associated with sensory-specific accuracy of tracking performance. Overall, the findings suggest that manual tracking performance in youth does not only rely on brain regions involved in sensorimotor processing, but also on prefrontal regions involved in attention and working memory. Hum Brain Mapp 38:5628-5647, 2017. © 2017 Wiley Periodicals, Inc.

How does the body representation system develop in the human brain?

Exploration of the body representation system (BRS) from kinaesthetic illusions in fMRI has revealed a complex network composed of sensorimotor and frontoparietal components. Here, we evaluated the degree of maturity of this network in children aged 7-11 years, and the extent to which structural factors account for network differences with adults. Brain activation following tendon vibration at 100Hz ('illusion') and 30Hz ('no illusion') were analysed using the two-stage random effects model, with or without white and grey matter covariates. The BRS was already well established in children as revealed by the contrast 'illusion' vs 'no illusion', although still immature in some aspects. This included a lower level of activation in primary somatosensory and posterior parietal regions, and the exclusive activation of the frontopolar cortex (FPC) in children compared to adults. The former differences were related to structure, while the latter difference reflected a functional strategy where the FPC may serve as the 'top' in top-down modulation of the activity of the other BRS regions to facilitate the establishment of body representations. Hence, the development of the BRS not only relies on structural maturation, but also involves the disengagement of an executive region not classically involved in body processing.

Movement quality of conventional prostheses and the DEKA Arm during everyday tasks

BACKGROUND

Conventional prosthetic devices fail to restore the function and characteristic movement quality of the upper limb. The DEKA Arm is a new, advanced prosthesis featuring a compound, powered wrist and multiple grip configurations.

OBJECTIVES

The purpose of this study was to determine if the DEKA Arm improved the movement quality of upper limb prosthesis users compared to conventional prostheses.

STUDY DESIGN

Case series.

METHODS

Three people with transradial amputation completed tasks of daily life with their conventional prosthesis and with the DEKA Arm. A total of 10 healthy controls completed the same tasks. The trajectory of the wrist joint center was analyzed to determine how different prostheses affected movement duration, speed, smoothness, and curvature compared to patients' own intact limbs and controls.

RESULTS

Movement quality decreased with the DEKA Arm for two participants, and increased for the third. Prosthesis users made slower, less smooth, more curved movements with the prosthetic limb compared to the intact limb and controls, particularly when grasping and manipulating objects.

CONCLUSION

The effects of one month of training with the DEKA Arm on movement quality varied with participants' skill and experience with conventional prostheses. Future studies should examine changes in movement quality after long-term use of advanced prostheses. Clinical relevance Movement quality with the DEKA Arm may depend on the user's previous experience with conventional prostheses. Quantitative analyses are needed to assess the efficacy of novel prosthetic devices and to better understand how to train people to use them effectively.

Does somatosensation change with age in children and adolescents? A systematic review

BACKGROUND

Somatosensory modalities, such as touch, proprioception and haptic ability, greatly influence the achievement of developmental milestones for children. Describing somatosensory impairment, natural variability and typical or expected developmental changes across age groups will help establish frameworks for intervention in clinical populations. This systematic review aimed to determine how different somatosensory modalities develop across childhood into adolescence to use as a point of reference for children at risk of somatosensory impairment.

METHODS

Searches of five electronic databases were undertaken through EBSCO-host (MEDLINE, CINAHL, PsycINFO, SPORTDiscus and ERIC) for studies measuring at least one somatosensory modality in typically developing individuals between birth and 18 years and analysed by age. Characteristics of studies were collected including country of origin, sample size, demographics and outcome measure used. Quality assessment and data extraction were performed by two independent reviewers.

RESULTS

Twenty three cross-sectional studies were included from a total of 188 articles retrieved: 8 examined aspects of touch, 5 proprioception and 10 haptic ability. Variability of study designs and variation in assessment tools precluded any formal meta-analysis.

CONCLUSIONS

Somatosensation matures through childhood into adolescence; however, the present review found the pattern of somatosensory development varied depending on the assessment tool used and the aspect of somatosensation being measured, making it difficult to describe typical performance. There is a need for comprehensive assessment batteries to measure the somatosensation, including touch, proprioception and haptic ability, of children at risk of somatosensory impairment to aid in the development of effective interventions.

Development of Proprioceptive Acuity in Typically Developing Children: Normative Data on Forearm Position Sense

This study mapped the development of proprioception in healthy, typically developing children by objectively measuring forearm position sense acuity. We assessed position sense acuity in a cross-sectional sample of 308 children (5–17 years old; M/F = 127/181) and a reference group of 26 healthy adults (18–25 years old; M/F = 12/14) using a body-scalable bimanual manipulandum that allowed forearm flexion/extension in the horizontal plane. The non-dominant forearm was passively displaced to one of three target positions. Then participants actively matched the target limb position with their dominant forearm. Each of three positions was matched five times. Position error (PE), calculated as the mean difference between the angular positions of the matching and reference arms, measured position sense bias or systematic error. The respective standard deviation of the differences between the match and reference arm angular positions (SDP_diff) indicated position sense precision or random error. The main results are as follows: First, systematic error, measured by PE, did not change significantly from early childhood to late adolescence (Median PE at 90° target: −2.85° in early childhood; −2.28° in adolescence; and 1.30° in adults). Second, response variability as measured by SDP_diff significantly decreased with age (Median SDP_diff at 90° target: 9.66° in early childhood; 5.30° in late adolescence; and 3.97° in adults). The data of this large cross-sectional sample of children document that proprioceptive development in typically developing children is characterized as an age-related improvement in precision, not as a development or change in bias. In other words, it is the reliability of the perceptual response that improves between early childhood and adulthood. This study provides normative data against which position sense acuity in pediatric patient populations can be compared. The underlying neurophysiological processes that could explain the observed proprioceptive development include changes in the tuning of muscle spindles at the spinal level, the maturation of supraspinal somatosensory pathways and the development of interhemispheric callosal connections responsible for the transfer of somatosensory information.

Sensorimotor Control Impairment in Young Adults With Idiopathic Scoliosis Compared With Healthy Controls

OBJECTIVE

It has been hypothesized that the impaired sensorimotor control observed in adolescents with idiopathic scoliosis (IS) may be related more to the onset of scoliosis than to the maturation of sensory systems or sensorimotor control mechanisms. The objective of this study was to assess sensorimotor control in adults diagnosed with IS in adolescence versus healthy controls.

METHODS

The study included 20 young adults 20 to 24 years of age (10 healthy controls and 10 diagnosed with adolescent IS but not treated for it). Binaural bipolar galvanic vestibular stimulation (GVS) was delivered to assess sensorimotor control. Vertical forces under each foot and upper body kinematics along the frontal plane were measured before GVS (2-second window), during GVS (2-second window), immediately after the cessation of GVS (1-second window), and during the following 2 seconds. Balance control was assessed by calculating the root mean square values of vertical forces and upper body kinematics.

RESULTS

Compared with healthy controls, the IS group showed greater body sway upon GVS; the amplitude of this sway was even greater immediately after the cessation of GVS-an outcome requiring sensorimotor control.

CONCLUSION

Compared with normal controls, adults who had been diagnosed with IS in adolescence showed altered balance control immediately following GVS. This finding suggests that dysfunctional sensorimotor control may be related to the onset of scoliosis rather than to a transient suboptimal development of the sensory systems or sensorimotor control mechanisms.

Proprioceptive ability at the lips and jaw measured using the same psychophysical discrimination task

In the human face, the muscles and joints that generate movement have different properties. Whereas the jaw is a conventional condyle joint, the facial musculature has neither distinct origin nor insertion points, and the muscles do not contain muscle spindle proprioceptors. This current study aims to compare the proprioceptive ability at the orofacial muscles with that of the temporomandibular joint (TMJ) in 21 neuro-typical people aged between 18 and 65 years. A novel psychophysical task was devised for use with both structures that involved a fixed 30.5 mm start separation followed by closure onto stimuli of 5, 6, 7, 8 mm diameter. The mean proprioceptive score when using the lips was 0.84 compared to 0.79 at the jaw (p < 0.001), and response error was lower by 0.1 mm. The greater accuracy in discrimination of lip movement is significant because, unlike the muscles controlling the TMJ, the orbicularis oris muscle controlling the lips inserts on to connective tissue and other muscle, and contains no muscle spindles, implying a different more effective, proprioceptive mechanism. Additionally, unlike the lack of correlation previously observed between joints in the upper and lower limbs, at the face the scores from performing the task with the two different structures were significantly correlated (r = 0.5, p = 0.018). These data extend the understanding of proprioception being correlated for the same left and right joints and correlated within the same structure (e.g. ankle dorsiflexion and inversion), to include use-dependant proprioception, with performance in different structures being correlated through extended coordinated use. At the lips and jaw, it is likely that this arises from extensive coordinated use. This informs clinical assessment and suggests a potential for coordinated post-injury training of the lips and jaw, as well as having the potential to predict premorbid function via measurement of the uninjured structure, when monitoring progress and setting clinical rehabilitation goals.