Body schema building during childhood and adolescence: A neurosensory approach

Alteration of body representation in typical and atypical motor development

Developmental coordination disorder (DCD) impacts the quality of life and ability to perform coordinated actions in 5% of school-aged children. The quality of body representations of individuals with DCD has been questioned, but never assessed. We hypothesize that children with DCD have imprecise body representations in the sensory and motor domains. Twenty neurotypical children, seventeen children with DCD (8-12 years old) and twenty neurotypical adults (25-45 years old) performed both sensory and motor body representation tasks: a limb identification and a limb movement task. We observed lower accuracy in the sensory task but not in the motor task. In both tasks, we observe a larger amplitude of errors, or synkinesis, in children with DCD than in neurotypical children. In neurotypical children, accuracy was lower than in neurotypical adults in the motor and sensory task, and the amplitude of sensory errors and synkinesis was higher than in neurotypical adults. Using a linear regression model, we showed that sensory accuracy is a good predictor of synkinesis production, and that synkinesis production is a good predictor of sensory accuracy, as can be expected by the perception-action loop. Results support the hypothesis of an imprecision of body representation in DCD. We suggest that this imprecision arises from noise in the body representation used at the level of internal models of action. Future studies may assess whether slower plasticity of body representations, initial imprecision, or both may account for this observation. At the clinical level, prevention strategies targeting body representation in early childhood are strategically important to limit such impairments. RESEARCH HIGHLIGHTS: Body representation is impaired in children with DCD and has a significant cost in terms of the accuracy of sensory identification of body parts and associated movements. Inaccuracies in the body representation measured in perception and in action (error amplitude and synkinesis) are related in both NT children and adults. In typical development, we provide evidence of a strong link between body schema and body image.

Finding Stability-A Case Report on the Benefits of Adapted Kata Training for Children with Autism Spectrum Disorder

This study investigated the efficacy of an Adapted Kata Training Program (AKTP) in enhancing balance for a 10-year-old child with Autism Spectrum Disorder (ASD), employing a mixed-model approach for data collection. Over 12 weeks, the AKTP demonstrated significant improvements in the child's balance abilities, with an 11% increase in static balance, 8% in proprioceptive, 12% in horizontal, and 14% in vertical balance performance. These improvements persisted in a follow-up assessment after four weeks. Observations by the child's mother corroborated the above findings. Consequently, this research suggests the AKTP as a valuable non-pharmacological intervention to improve balance in children with ASD. However, further studies are necessary to validate these results and explore the impact on additional developmental domains, such as cognitive and motor skills.

A conceptual framework on body representations and their relevance for mental disorders

Many mental disorders are accompanied by distortions in the way the own body is perceived and represented (e.g., eating disorders, body dysmorphic disorder including muscle dysmorphia, or body integrity dysphoria). We are interested in the way these distortions develop and aim at better understanding their role in mental health across the lifespan. For this purpose, we first propose a conceptual framework of body representation that defines this construct and integrates different perspectives (e.g., cognitive neuroscience, clinical psychology) on body representations. The framework consists of a structural and a process model of body representation emphasizing different goals: the structural model aims to support researchers from different disciplines to structure results from studies and help collectively accumulate knowledge about body representations and their role in mental disorders. The process model is reflecting the dynamics during the information processing of body-related stimuli. It aims to serve as a motor for (experimental) study development on how distorted body representations emerge and might be changed. Second, we use this framework to review the normative development of body representations as well as the development of mental disorders that relate to body representations with the aim to further clarify the potential transdiagnostic role of body representations.

Atopic Dermatitis and Self-Image Design: A Real-Life Study in Children Using Drawings

Background: Atopic dermatitis (AD) induces alterations of external appearance and self-esteem, with impact on the personal development of the children. However, tools for estimating such suffering are lacking. We aimed to assess how children with AD represent themselves through their drawings. Methods: In this retrospective study, we included children (<18 years) suffering from AD who followed the instruction "draw yourself with and without eczema" at the end of a routine follow-up consultation. Drawings were interpreted with the child and then classified in different analysis groups by 5 independent evaluators. Results: A total of 64 children (41 [64.1%] girls and 23 [35.9%] boys, median [range] age 8 [3-7] years) made 64 drawings. Five groups of drawing were identified: "amputee" (n = 8, 12.5%), "identical" (n = 18, 28.1%), "sad" (n = 19, 29.7%), "complex" (n = 11, 17.2%), and "other" (n = 8, 12.5%). Univariate analysis found that age was differently distributed among the different drawing groups (P = 0.0047), as was the predominance of light colors (P = 0.038). The distribution of the other variables (gender, investigator global assessment score, active AD, and duration of activity) was not different among drawing groups. Conclusions: The drawing allows a majority of the AD children to express their self-image with and without eczema, as well as their feelings and their interactions with the environment and with their entourage. The visual tool proposed herein could be used during consultations, to (a) become aware of the need to treat AD, (b) better evaluate the impact of AD burden in childhood, and (c) adjust appropriately AD treatment.

Planet earth calling: unveiling the brain's response to awe and driving eco-friendly consumption

Eco-friendly consumption is important for solving climate crisis and moving humanity toward a better future. However, few consumers are willing to pay premiums for eco-friendly products. We investigated the psychological and neural factors that can increase eco-friendly consumption. We propose an experience of awe, in which the individual self is temporarily attenuated as the importance of beings other than oneself increases. Behavioral (Study 1) and functional magnetic resonance imaging (fMRI; Study 2) experiments were conducted to explore the awe mechanisms through which climate crisis messages lead to eco-friendly consumption. In Study 1, we found participants felt awe when exposed to climate crisis messages, and their choice of eco-friendly consumption increased. In Study 2, we found that when individuals were exposed to messages depicting the climate crisis (as opposed to a control stimulus), their brains exhibited a lower level of activation in the self-awareness processing and a higher level of activation in external attention processing areas. These results suggest that the awe experience plays an important role in promoting eco-friendly consumption. Marketing must evolve from satisfying basic individual needs to a high level for the well-being of humanity, the planet, and the biosphere. This study sheds light on our understanding of human perceptions of the climate crisis and suggests an effective communication strategy to increase individuals' eco-friendly actions.

Does visual experience influence arm proprioception and its lateralization? Evidence from passive matching performance in congenitally-blind and sighted adults

In humans, body segments' position and movement can be estimated from multiple senses such as vision and proprioception. It has been suggested that vision and proprioception can influence each other and that upper-limb proprioception is asymmetrical, with proprioception of the non-dominant arm being more accurate and/or precise than proprioception of the dominant arm. However, the mechanisms underlying the lateralization of proprioceptive perception are not yet understood. Here we tested the hypothesis that early visual experience influences the lateralization of arm proprioceptive perception by comparing 8 congenitally-blind and 8 matched, sighted right-handed adults. Their proprioceptive perception was assessed at the elbow and wrist joints of both arms using an ipsilateral passive matching task. Results support and extend the view that proprioceptive precision is better at the non-dominant arm for blindfolded sighted individuals. While this finding was rather systematic across sighted individuals, proprioceptive precision of congenitally-blind individuals was not lateralized as systematically, suggesting that lack of visual experience during ontogenesis influences the lateralization of arm proprioception.

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.

Relating different Dimensions of Bodily Experiences: Review and proposition of an integrative model relying on phenomenology, predictive brain and neuroscience of the self

How we mentally experience our body has been studied in a variety research domains. Each of these domains focuses in its own ways on different aspects of the body, namely the neurophysiological, perceptual, affective or social components, and proposes different conceptual taxonomies. It is therefore difficult to find one's way through this vast literature and to grasp the relationships between the different dimensions of bodily experiences. In this narrative review, we summarize the existing research directions and present their limits. We propose an integrative framework, grounded in studies on phenomenal consciousness, self-consciousness and bodily self-consciousness, that can provide a common basis for evaluating findings on different dimensions of bodily experiences. We review the putative mechanisms, relying on predictive processes, and neural substrates that support this model. We discuss how this model enables a conceptual assessment of the interrelationships between multiple dimensions of bodily experiences and potentiate interdisciplinary approaches.

Paradoxical decrease of imitation performance with age in children

Imitation development was studied in a cross-sectional design involving 174 primary-school children (aged 6-10), focusing on the effect of actions' complexity and error analysis to infer the underlying cognitive processes. Participants had to imitate the model's actions as if they were in front of a mirror ('specularly'). Complexity varied across three levels: movements of a single limb; arm and leg of the same body side; or arm and leg of opposite body sides. While the overall error rate decreased with age, this was not true of all error categories. The rate of 'side' errors (using a limb of the wrong body side) paradoxically increased with age (from 9 years). However, with increasing age, the error rate also became less sensitive to the complexity of the action. This pattern is consistent with the hypothesis that older children have the working memory (WM) resources and the body knowledge necessary to imitate 'anatomically', which leads to additional side errors. Younger children might be paradoxically free from such interference because their WM and/or body knowledge are insufficient for anatomical imitation. Yet, their limited WM resources would prevent them from successfully managing the conflict between spatial codes involved in complex actions (e.g. moving the left arm and the right leg). We also found evidence that action side and content might be stored in separate short-term memory (STM) systems: increasing the number of sides to be encoded only affected side retrieval, but not content retrieval; symmetrically, increasing the content (number of movements) of the action only affected content retrieval, but not side retrieval. In conclusion, results suggest that anatomical imitation might interfere with specular imitation at age 9 and that STM storages for side and content of actions are separate.

Upper crossed syndrome in secondary school students: A mixed-method study

Objective

The study objectives were to identify the prevalence of upper crossed syndrome (UCS) and its associated factors in a population of Spanish adolescents, and to explore these associations through focus groups.

Methods

The study used a sequential explanatory mixed method design. The quantitative phase consisted of a cross-sectional study in which 45 students underwent photogrammetry measurements and evaluations with the Kiddo-KINDL and VISA-TEEN questionnaires. Subsequently, several focus groups were conducted to discuss the quantitative results.

Results

The results indicated a 37.8% prevalence of UCS, a 48.9% prevalence of forward head posture (FHP) and an 80% prevalence of forward shoulder posture (FSP). A positive FSP was indicated by an angle represented by the intersection of the line between the midpoint of the humerus and the spinous process of C7 of <52°. FSP was significantly higher in boys (mean [M] = 43.59, standard deviation [SD] = 6.9) than in girls (M = 47.98, SD = 6.33; p < 0.05). Boys showed significant moderate associations of FSP with body mass index (BMI) (r = -0.48, p < 0.05) and hygiene habits (r = -0.46, p < 0.05), and of FHP with worse use of technology (r = 0.53, p < 0.05). Those with UCS showed significant differences in school performance (M = 47.22, SD = 8.33, p < 0.05). Analysis of the qualitative results led to the identification of 33 codes and five categories.

Conclusions

UCS was associated with factors such as BMI, school performance, use of technology and physical activity. Correcting posture in adolescence was generally believed to be necessary. Physical exercise and postural health were considered highly important among adolescents.

Posturographic Standards for Optimal Control of Human Standing Posture

Static posturography is a simple non-invasive technique commonly used in contemporary labs and clinics to quantify the central nervous system adaptive mechanisms involved in the control of posture and balance. Its diagnostic value, however, is quite limited due to the lack of posturographic standards for stable posture. To solve this problem, in this research, we aimed to establish reference values for the stable human posture using our novel parameters of static posturography including the sway anteroposterior directional index (DIAP), the mediolateral directional index (DIML), the stability vector amplitude (SVamp), and the stability vector azimuth (SVaz). Towards this end, in a population of young (mean age 22 yrs), healthy able-bodied volunteers (50 males and 50 females), trajectories of postural sway, based upon the center-of-pressure (COP), were assessed. The experiment consisted of ten 60s trials that were carried out 5 times while subjects were standing quietly on the force plate with eyes open (EO test) and 5 times with eyes closed (EC test). Results showed that in young healthy subjects, regardless of gender, the basic variables of COP remained at the following levels: SVamp = 9.2 ± 1.6 mm/s, SVaz = 0.9 ± 0.1 rad, and directional indices DIAP = 0.7 ± 0.05, DIML = 0.56 ± 0.06. Some of the measures were sensitive to visual input (EC trials) and showed a weak to moderate correlation with anthropometric features. These measures can be recommended as reference values that characterize the most stable erect posture.

Self/other distinction in adolescents with autism spectrum disorder (ASD) assessed with a double mirror paradigm

BACKGROUND

Self/other distinction (SOD), which refers to the ability to distinguish one's own body, actions, and mental representations from those of others, is an essential skill for effective social interaction. A large body of clinical evidence suggests that disruptions in SOD may be key to social communication deficits in individuals with autism spectrum disorders (ASD). In particular, egocentric biases have been found in cognitive, affective, behavioural, and motor domains. However, research in this area is scarce and consists of recognition paradigms that have used only static images; these methods may be insufficient for assessing SOD, given the increasing role of embodiment in our understanding of the pathophysiology of ASD.

METHOD

A single-centre, prospective pilot study was carried out to investigate, for the first time, self-recognition and SOD in seven adolescents with ASD compared with matched, typically developing controls (TDCs) using the "Alter Ego"TM double mirror paradigm. The participants viewed a double mirror in which their own face was gradually morphed into the face of an unfamiliar other (self-to-other sequence) or vice versa (other-to-self sequence); participants were instructed to indicate at which point the morph looked more like their own face than the other's face. Two judgement criteria were used: 1) M1: the threshold at which subjects started to recognize their own face during the other-to-self morphing sequence; 2) M2: the threshold at which subjects started to recognize the other's face during the self-to-other morphing sequence.

RESULTS

Consistent with the predictions, the results showed that the participants with ASD exhibited earlier self-recognition in the other-to-self sequence and delayed other-recognition in the self-to-other sequence, suggesting an egocentric bias. SOD impairments were also marginally correlated with ASD severity, indicating earlier face recognition in more severely affected individuals. Furthermore, in contrast with that of TDCs, the critical threshold for switching between self and other varied with the direction of morphing in ASD participants. Finally, these differences in face recognition and SOD using mirrors, unlike previous research using static images, support the central place of bodily self-consciousness in SOD impairments.

CONCLUSIONS

Although additional research is needed to replicate the results of this preliminary study, it revealed the first behavioural evidence of altered SOD in ASD individuals on an embodied, semiecological face-recognition paradigm. Implications for understanding ASD are discussed from a developmental perspective, and new research and therapeutic perspectives are presented.

Tactile sensory processing as a precursor of executive attention: Toward early detection of attention impairments and neurodevelopmental disorders

Recent studies in developmental neuroscience tend to show the existence of neural attention networks from birth. Their construction is based on the first sensory experiences that allow us to learn the patterns of the world surrounding us and preserve our limited attentional resources. Touch is the first sensory modality to develop, although it is still little studied in developmental psychology in contrast to distal modalities such as audition or vision. Atypical tactile sensory processing at an early age could predict later attention dysfunction, both of them being part of the symptomatology of neurodevelopmental disorders (NDD). We review the state of knowledge on tactile sensory processing and its links with attention, executive attention (EA) in particular, and propose that abnormal tactile sensory processing at an early age could provide markers of EA dysfunctions, contributing to the early detection of NDD. This article is categorized under: Psychology > Attention.

Age-related changes in the activation timing of postural muscles to the prime mover muscle for bilateral arm flexion during standing

Background

We aimed to obtain the standard values of age-related changes in the activation timing of postural muscles to the prime mover muscle (anterior deltoid [AD]) for bilateral arm flexion during standing.

Methods

The study participants were 276 children (aged 3–14 years) and 32 adults (aged 20–26 years). In response to a visual stimulus, participants raised both arms from a fully extended position as quickly as possible, stopped their arms voluntarily at a horizontal level at the shoulder, and maintained that position for 2 s. Ten test trials were performed. By using surface electromyography, the duration from the burst onset of the postural muscles to that of AD was measured as the starting time of the postural muscles (rectus abdominis [RA], erector spinae [ES], rectus femoris [RF], biceps femoris [BF], tibialis anterior [TA], gastrocnemius medialis [GcM], and soleus [SOL]). The starting time was presented as a negative value when the burst onset of the postural muscles preceded that of AD, which was defined as the preceding activation. A positive value for the starting time was defined as delayed activation.

Results

In adults, the burst onsets of ES and BF significantly preceded that of AD. In ES, the starting time preceded the onset of AD in those aged ≥ 5–6 years; no difference with adults was found at age 13–14 years. On the other hand, in BF, significant delayed activation was found at ages 3–4 to 11–12 years. While the starting time decreased with age, no significant preceding activation similar to adults was found, even at age 13–14 years. In TA, no significant difference with the onset of AD was found at age 3–6 years, and significant delayed activation was found at age ≥ 7–8 years. Significant delayed activation in GcM, SOL, RA, and RF was observed in all age groups, and no age-related changes were observed in children.

Conclusion

These findings could provide standard values from childhood to adolescence for age-related changes in anticipatory postural muscle activity during voluntary movement while standing and contribute to applications in the fields of sports and rehabilitation.

Body representation underlies response of proprioceptive acuity to repetitive peripheral magnetic stimulation

Proprioceptive acuity is of great significance in basic research exploring a possible neural mechanism of fine motor control and in neurorehabilitation practice promoting motor function recovery of limb-disabled people. Moreover, body representation relies on the integration of multiple somatic sensations, including proprioception that is mainly generated in muscles and tendons of human joints. This study aimed to examine two hypotheses: First, different extension positions of wrist joint have different proprioceptive acuities, which might indicate different body representations of wrist joint in the brain. Second, repetitive peripheral magnetic stimulation (rPMS) applied peripherally to the forearm radial nerve and extensors could change proprioceptive acuity at the wrist joint. Thirty-five healthy participants were recruited then randomly divided into the real stimulation group (n = 15) and the sham stimulation group (n = 20). The participants’ non-dominant side wrist joint position sense was tested at six extension positions within the physiological joint motion range (i.e., 10°, 20°, 30°, 40°, 50°, 60°) both before stimulation and after stimulation. Results showed that proprioceptive bias (arithmetic difference of target position and replicated position) among six extension positions could be divided into lower-extension position (i.e., 10°, 20°, 30°) and higher-extension position (i.e., 40°, 50°, 60°). One session rPMS could influence proprioceptive bias in lower-extension position but not in higher-extension position. However, proprioceptive precision (standard deviation within lower-extension position and higher-extension position) was not influenced. To conclude, proprioceptive bias may vary between different wrist extension positions due to different hand postures being related to changes in body representation, and different functions relating to proprioceptive bias and proprioceptive precision may underlie two aspects of body representation.

Witness as Victim: Clinical Encounters with Children Who Observed Violence

In the spring months of 2022, Human Rights Watch, the international humanitarian group, released stunning details of the carnage in the regions around Chernihiv and Kyiv that Russia left behind. In a report released from May 2022, Human Rights Watch stated that it was currently investigating 22 potential summary executions, nine other unlawful killings, six possible kidnappings, seven cases of torture and 21 reported incidents of other forms of “unlawful confinement in inhuman and degrading conditions” carried out by Russian forces against civilians. But even this report doesn’t take into account traumatic impact on witnesses. Having witnessed the crime once, the witness continues to see the world through the prism of the observed violence

Specific Learning Disorder in Children and Adolescents, a Scoping Review on Motor Impairments and Their Potential Impacts

Mastering motor skills is important for children to achieve functional mobility and participate in daily activities. Some studies have identified that students with specific learning disorders (SLD) could have impaired motor skills; however, this postulate and the potential impacts remain unclear. The purpose of the scoping review was to evaluate if SLD children have motor impairments and examine the possible factors that could interfere with this assumption. The sub-objective was to investigate the state of knowledge on the lifestyle behavior and physical fitness of participants with SLD and to discuss possible links with their motor skills. Our scoping review included preregistration numbers and the redaction conformed with the PRISMA guidelines. A total of 34 studies published between 1990 and 2022 were identified. The results of our scoping review reflected that students with SLD have poorer motor skills than their peers. These motor impairments are exacerbated by the complexity of the motor activities and the presence of comorbidities. These results support our sub-objective and highlight the link between motor impairments and the sedentary lifestyle behavior of SLDs. This could lead to deteriorating health and motor skills due to a lack of motor experience, meaning that this is not necessarily a comorbidity. This evidence emphasizes the importance of systematic clinical motor assessments and physical activity adaptations.

A Study on the Correlation between Intelligence and Body Schema in Children Who Practice Chess at School

The role of intelligence in chess is crucial because the game involves a situation of adversity between two players whose goal is to checkmate the opponent’s king. Due to the complex nature of the game and the huge amount of information needed to become a professional chess player, the ability to receive, analyze, sort and use abstract notions is essential. A total of 67 children from the third grade were selected and tested twice, initially and finally, to establish the level of body schema and intelligence. The Raven test was used to numerically quantify their intelligence and the Goodenough test was conducted for the body schema. We used the paired samples T-test to highlight the statistical difference between the results and performed a simple linear regression to see if the level of intelligence is a predictor of the body schema. There is a linear relationship between intelligence and body schema, and we can use the first one to predict the evolution of the second. In conclusion, body schema can be educated through chess lessons, and this will lead to better psychomotor development.

Sex differences in the association of postural control with indirect measures of body representations

Besides anthropometric variables, high-order body representations have been hypothesised to influence postural control. However, this has not been directly tested before. Moreover, some studies indicate that sex moderates the relationship of anthropometry and postural control. Therefore, as a proof of concept we investigated the association of body representations with postural control as well as the influence of participants’ sex/gender. Body image measures were assessed with a figural drawing task. Body schema was tested by a covert and an overt task. Body sway was measured during normal bipedal quiet standing with eyes closed (with/without neck extended). Statistical analysis consisted of hierarchical multiple linear regressions with the following regression steps: (1) sensory condition, (2) sex/gender, (3) age, (4) anthropometry, (5) body schema, (6) body image, (7) sex/gender-interactions. Across 36 subjects (19 females), body schema was significantly associated with body sway variability and open-loop control, in addition to commonly known influencing factors, such as sensory condition, gender, age and anthropometry. While in females, also body image dissatisfaction substantially was associated with postural control, this was not the case in males. Sex differences and possible causes why high-order body representations may influence concurrent sensorimotor control of body sway are discussed.

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.

A perception bias of the gravitational vertical is confirmed in Adolescent Idiopathic Scoliosis

PURPOSE

Adolescent Idiopathic Scoliosis (AIS) is the most frequent spine deformity in adolescence. The cause of AIS remains unknown. Several studies show that AIS can be associated with a perception bias of gravitational vertical. In particularly, AIS patients with a right thoracic convexity exhibit deviation of the Subjective Postural Vertical. The origin of this disturbance could be located in trunk proprioceptive graciveptors. We wanted to verify this result with a population of lumbar and thoracolumbar AIS with left convexity.

METHODS

It was a multicenter, cross-sectional case-control study. Thirty adolescents with left lumbar or thoraco-lumbar AIS (age 14.3 ± 1.7 years; Cobb angle 27.6° ± 6.1°) and 30 controls matched for age (14.0 ± 1.5 years), were compared for Subjective Visual Vertical (SVV) measured in static and dynamic (optokinetic stimulation) conditions, and Subjective Postural Vertical (SPV).

RESULTS

For SVV, there was no difference in the two groups, for static and dynamic conditions. The SPV was significantly different between the two groups (p < 0.0001). The SPV was shifted to the left for most of the AIS patients (med - 2.4°[- 3.6; - 1.7]) compared with controls (med 0°[- 0.5; 1.7]). Adolescents with AIS perceived verticality with significant greater uncertainty in postural modality than controls (p = 0.017).

CONCLUSION

Our study confirms a significant directional bias in the orientation of SPV in left lumbar or thoraco-lumbar AIS. This confirmation paves the way to a new physiopathological model focused on trunk proprioception.

LEVEL OF EVIDENCE

III.

Is self-image, in reference to the gravitational vertical, altered in adolescent idiopathic scoliosis? A multicenter, single-blind, case-control study

PURPOSE

Adolescent idiopathic scoliosis (AIS) is associated with perturbation of orthostatic postural control. In humans, orthostatic postural control is organized around the gravitational vertical (GV). Perception of the GV involves a bottom-up process (central integration of multisensorial information) and a top-down process that uses cognitive mechanisms relying on body image. This study hypothesized that AIS would be associated with an erroneous central representation of verticality. The objective was to demonstrate an altered top-down process of sense of verticality in AIS.

METHODS

This multicenter, single-blind, case-control study evaluated 63 adolescent girls with AIS divided into two groups (major AIS (n = 31) and minor AIS (n = 32)) and 30 matched non-scoliotic adolescents. Participants scored their perception of trunk appearance in an upright position using a pictographic scale. The outcome measure was the difference between perception score and real trunk deformity.

RESULTS

Participants with major AIS presented with misperception of their trunk appearance in an upright position when compared with those with minor AIS or controls.

CONCLUSION

Adolescents with major AIS underestimate their trunk deformity in an upright position. This suggests an altered representation of body image, affecting top-down control of sense of verticality.

A sensorimotor representation impairment in dyslexic adults: A specific profile of comorbidy

Sensorimotor disorders have been frequently reported in children and adults with dyslexia over the past 30 years. The present study aimed to determine the impact of sensorimotor comorbidity risks in dyslexia by investigating the functional links between phonological and sensorimotor representations in young dyslexic adults. Using 52 dyslexic participants and 58 normo-readers, we investigated whether the underlying phonological deficit, which is reported in the literature, was associated with a general impairment of sensorimotor representations of articulatory and bodily actions. Internal action representations were explored through motor imagery tasks, consisting of measuring and comparing the durations of performed or imagined actions chosen from their current repertoire of daily life activities. To detect sensorimotor deficits, all participants completed the extended version of the M-ABC 2, as a reference test. We found sensorimotor impairments in 27% of the young adult dyslexics, then considered as sensorimotor comorbid, as opposed to much less in the normo-reader group (5%). While motor slowdown, reflecting motor difficulty, was present in all dyslexic adults, motor imagery performance was impacted only in the specific dyslexic subgroup with sensorimotor impairments. Moreover, in contrast with slowness, only the comorbid subgroup showed an increased variability in execution durations. The present study highlights the importance of the quality of perception-action coupling, questions the relevance of investigating sensorimotor impairment profiles beyond phonological deficits and provides new arguments supporting the perspective of multiple deficits approaches in dyslexia.

Body schema plasticity is altered in Developmental Coordination Disorder

Developmental Coordination Disorder (DCD) is a pathological condition characterized by impaired motor skills. Current theories advance that a deficit of the internal models is mainly responsible for DCD children's altered behavior. Yet, accurate movement execution requires not only correct movement planning, but also integration of sensory feedback into body representation for action (Body Schema) to update the state of the body. Here we advance and test the hypothesis that the plasticity of this body representation is altered in DCD. To probe Body Schema (BS) plasticity, we submitted a well-established tool-use paradigm to seventeen DCD children, required to reach for an object with their hand before and after tool use, and compared their movement kinematics to that of a control group of Typically Developing (TD) peers. We also asked both groups to provide explicit estimates of their arm length to probe plasticity of their Body Image (BI). Results revealed that DCD children explicitly judged their arm shorter after tool use, showing changes in their BI comparable to their TD peers. Unlike them, though, DCD did not update their implicit BS estimate: kinematics showed that tool use affected their peak amplitudes, but not their latencies. Remarkably, the kinematics of tool use showed that the motor control of the tool was comparable between groups, both improving with practice, confirming that motor learning abilities are preserved in DCD. This study thus brings evidence in favor of an alternative theoretical account of the DCD etiology. Our findings point to a deficit in the plasticity of the body representation used to plan and execute movements. Though not mutually exclusive, this widens the theoretical perspective under which DCD should be considered: DCD may not be limited to a problem affecting the internal models and their motor functions, but may concern the state of the effector they have to use.

From Neural Command to Robotic Use: The Role of Symmetry/Asymmetry in Postural and Locomotor Activities

This article deepens a reflection on why and how symmetry/asymmetry affects the motor and postural behavior from the neural source, uterine development, child maturation, and how the notion of symmetry/asymmetry has been applied to walking robot design and control. The concepts of morphology and tensegrity are also presented to illustrate how the biological structures have been used in both sciences and arts. The development of the brain and the neuro-fascia-musculoskeletal system seems to be quite symmetric from the beginning of life through to complete maturity. The neural sources of movements (i.e., central pattern generators) are able to produce both symmetric or asymmetric responses to accommodate to environmental constraints and task requirements. Despite the fact that the human development is mainly symmetric, asymmetries already regulate neurological and physiological development. Laterality and sports training could affect natural musculoskeletal symmetry. The plasticity and flexibility of the nervous system allows the abilities to adapt and compensate for environmental constraints and musculoskeletal asymmetries in order to optimize the postural and movement control. For designing humanoid walking robots, symmetry approaches have been mainly used to reduce the complexity of the online calculation. Applications in neurological retraining and rehabilitation should also be considered.

Impaired postural control of axial segments in children with cerebral palsy

BACKGROUND

Sensorimotor control of axial segments, which develops during childhood and is not mature until adolescence, is essential for the development of balance control during motor activities. Children with cerebral palsy (CP) have deficits in postural control when standing or walking, including less stabilization of the head and trunk which could affect postural control.

RESEARCH QUESTION

Is dynamic stabilization of axial segments during an unstable sitting task deficient in children with CP compared to typically developing children? Is this deficit correlated with the deficit of postural control during standing?

METHOD

Seventeen children with CP (GMFCS I-II) and 17 typically-developing children from 6 to 12 years old were rated on the Trunk Control Measurement Scale (TCMS). In addition, posturography was evaluated in participants while they maintained their balance in stable sitting, unstable sitting, and quiet standing, under "eyes open" and "eyes closed" conditions. In sitting tasks, the participants had to remain stable while being prevented from using the lower and upper limbs (i.e. to ensure the involvement of axial segments alone).

RESULTS

Children with CP compared to TD children had significantly larger surface area, mean velocity and RMS values of CoP displacements measured during the unstable sitting task and the standing task, under both "eyes open" and "eyes closed" conditions. No significant group effects were observed during the stable sitting task. The TCMS total score was significantly lower, indicating trunk postural deficit, in the CP group than in the TD group and was significantly correlated with postural variables in the sitting and standing tasks.

SIGNIFICANCE

Children with CP indeed have a specific impairment in the postural control of axial segments. Since the postural control of axial segments is important for standing and walking, its impairment should be taken into account in rehabilitation programs for children with CP.

The long developmental trajectory of body representation plasticity following tool use

Humans evolution is distinctly characterized by their exquisite mastery of tools, allowing them to shape their environment in more elaborate ways compared to other species. This ability is present ever since infancy and most theories indicate that children become proficient with tool use very early. In adults, tool use has been shown to plastically modify metric aspects of the arm representation, as indexed by changes in movement kinematics. To date, whether and when the plastic capability of updating the body representation develops during childhood remains unknown. This question is particularly important since body representation plasticity could be impacted by the fact that the human body takes years to achieve a stable metric configuration. Here we assessed the kinematics of 90 young participants (8-21 years old) required to reach for an object before and after tool use, as a function of their pubertal development. Results revealed that tool incorporation, as indexed by the adult typical kinematic pattern, develops very slowly and displays a u-shaped developmental trajectory. From early to mid puberty, the changes in kinematics following tool use seem to reflect a shortened arm representation, opposite to what was previously reported in adults. This pattern starts reversing after mid puberty, which is characterized by the lack of any kinematics change following tool use. The typical adult-like pattern emerges only at late puberty, when body size is stable. These findings reveal the complex dynamics of tool incorporation across development, possibly indexing the transition from a vision-based to a proprioception-based body representation plasticity.

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.

EFFECT OF EXTREME CONDITIONING TRAINING ON BODY PERCEPTION

ABSTRACT Introduction Extreme conditioning training (ECT) has become a popular method, characterized by a wide variety of exercises. For good technical performance, practitioners must have good perception of the different parts of the body; however, it is not known whether this perception differs between practitioners and non-practitioners of ECT. Objective To analyze the perception of body dimensions among subjects submitted to an ECT session. Methods Adult men were divided into TRAINED (n = 10) and UNTRAINED (n = 10). All subjects were submitted to a combination of high-effort multiarticular exercises for a set period of nine minutes (“the largest possible number of repetitions” [AMRAP]). For the procedure of marking the body pattern, the subjects were scored in terms of acromioclavicular joints, waist and trochanter. Results Regarding the general perception of body size, the TRAINED and UNTRAINED groups were classified as adequate for each stage. In the dimension of body segments, there was an overestimation of the shoulder region in both groups (TRAINED Pre = 105.2 ± 8.37; Post = 117.23 ± 22.11 [ES = 0.79]; 30 min = 101.34 ± 14.21 [ES = 0.34] and UNTRAINED Pre = 96.72 ± 12.79; Post = 99.47 ± 12.17 [ES = 0.22]; 30 min = 111.05 ± 11.06 [ES = 1.27]). The perception of the waist region improved significantly after training (TRAINED Pre = 114.11 ± 16.4; Post = 117.7 ± 20.16 [ES = 0.20]; 30 min = 104.59 ± 11.46 [ES = 0.68] and UNTRAINED Pre = 114.66 ± 9.88; Post = 104.64 ± 12.87; [ES = 0.88]; 30 min = 108.36 ± 12.32 [ES = 0.57]). Conclusion ECT can promote better perception of body dimensions. In addition, the assessment of body size in active, but untrained individuals showed a better body perception, albeit a transitory effect. Level of evidence II; Therapeutic studies - investigation of treatment results.

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.

Functional properties of extended body representations in the context of kinesthesia

A person's internal representation of his/her body is not fixed. It can be substantially modified by neurological injuries and can also be extended (in healthy participants) to incorporate objects that have a corporeal appearance (such as fake body segments, e.g. a rubber hand), virtual whole bodies (e.g. avatars), and even objects that do not have a corporeal appearance (e.g. tools). Here, we report data from patients and healthy participants that emphasize the flexible nature of body representation and question the extent to which incorporated objects have the same functional properties as biological body parts. Our data shed new light by highlighting the involvement of visual motion information from incorporated objects (rubber hands, full body avatars and hand-held tools) in the perception of one's own movement (kinesthesia). On the basis of these findings, we argue that incorporated objects can be treated as body parts, especially when kinesthesia is involved.

Imagining handwriting movements in a usual or unusual position: effect of posture congruency on visual and kinesthetic motor imagery

Motor imagery has been used in training programs to improve the performance of motor skills. Handwriting movement may benefit from motor imagery training. To optimize the efficacy of this kind of training, it is important to identify the factors that facilitate the motor imagery process for handwriting movements. Several studies have shown that motor imagery is more easily achieved when there is maximum compatibility between the actual posture and the imagined movement. We, therefore, examined the effect of posture congruency on visual and kinesthetic motor imagery for handwriting movements. Adult participants had to write and imagine writing a sentence by focusing on the evocation of either the kinesthetic or visual consequences of the motion. Half the participants performed the motor imagery task in a congruent posture (sitting with a hand ready for writing), and half in an incongruent one (standing with arms crossed behind the back and fingers spread wide). The temporal similarity between actual and imagined movement times and the vividness of the motor imagery were evaluated. Results revealed that temporal similarity was stronger in the congruent posture condition than in the incongruent one. Furthermore, in the incongruent posture condition, participants reported greater difficulty forming a precise kinesthetic motor image of themselves writing than a visual image, whereas no difference was observed in the congruent posture condition. Taken together, our results show that postural information is taken into account during the mental simulation of handwriting movements. The implications of these findings for guiding the design of motor imagery training are discussed.

How do children aged 6 to 11 stabilize themselves on an unstable sitting device? The progressive development of axial segment control

Postural control continues to develop during middle childhood as shown by the decrease in body sway in stance between the ages of 5 and 11. Although head and trunk control is crucial for balance control during both static and dynamic activities, evaluating its specific development and its contribution to overall postural control is methodologically challenging. Here, we used an unstable sitting device adapted to ensure that only the axial segments could control the balance of the device and thus the balance of the upper body. This study aimed to assess the development of the postural stabilization of axial body segments during middle childhood. Thirty-six children (in three age groups: 6-7yo, 8-9yo, and 10-11yo) and 11 adults sat on the unstable sitting device and had to stabilize their axial segments under several conditions: a moderate vs. high level of balance challenge, and eyes open vs. eyes closed. Upper-body postural sway (area, mean velocity and root mean square (RMS) of the center of pressure (CoP) displacement) decreased progressively with age (6-7yo > 8-9yo > 10-11yo > adults), and this effect was accentuated when the balance challenge was high (for CoP area) or in the "eyes closed" condition (for CoP area and RMS). The stabilization strategies were assessed by anchoring indexes computed from three-dimensional kinematics. A progressive shift was showed, from an "en bloc" pattern at 6-7 years of age toward a more articulated (i.e. adult-like) pattern at 10-11. A head-on-space stabilization strategy first emerged at the age of 8-9. Middle childhood is an important period for the development of axial segment stabilization, which continues to mature until adulthood. This development might be related to the introduction and progressive mastery of feedforward sensorimotor processes and might contribute strongly to the development of overall postural control.

Brain activity associated with the rubber foot illusion

The internal representation of the body is constantly updated by sensory information based on interactions with the environment. The internal representation of the hand can be experimentally manipulated with the rubber hand illusion (RHI) paradigm. Brain activity during the RHI provides insight into the neural mechanisms underpinning the reconstruction of the internal representation of the hand. Recently, the RHI paradigm has been employed for the lower limb, revealing that the illusion is also induced in the lower limb (rubber foot illusion; RFI). However, the neural correlates of the RFI remain unknown. We used functional magnetic resonance imaging (fMRI) to examine brain activity during the RFI. Forty-four healthy volunteers participated in the fMRI experiment. Significant increases in activation were observed in the bilateral medial and middle frontal gyri, left supplemental motor area, bilateral inferior parietal lobuli, precunei, calcarine cortices, and cerebellar hemispheres; and in the vermis and bilateral thalami during the right RFI. During the left RFI, significant increases in activation were observed in the bilateral medial, middle, and superior frontal gyri; left inferior frontal gyrus and supplemental motor area, bilateral inferior parietal lobuli and middle temporal gyri, and in the left cerebellar hemisphere, vermis, and bilateral thalami. Conjunction analysis revealed that the prefrontal cortex including the bilateral medial and middle frontal gyri, parietal cortex including the bilateral inferior parietal lobuli, and cerebellum including the bilateral cerebellar hemispheres and vermis were conjointly activated during the right and left RFIs. The distribution of co-activated brain areas during the RFI was similar to the previously reported distribution of brain areas activated during the RHI. Co-activation of these brain areas may be associated with the reconstruction of the internal representation of the body. The fact that these areas are activated both in the RFI and RHI will have implications for the treatment of patients with disturbed internal bodily representation.

The Berg balance scale for assessing dynamic stability and balance in the adult spinal deformity (ASD) population

Background

Adult spinal deformity (ASD) is a prevalent condition in individuals over the age of 65; leading to impaired standing balance and abnormal gait patterns. This functional impairment may be due to the fixed sagittal or coronal malalignment; associated spinal stenosis or deconditioning. The Berg balance scale (BBS) was developed to measure balance by assessing the performance of functional tasks. The purpose of this study is to determine if BBS is a useful metric for evaluating functional status in ASD patients.

Methods

ASD patients who required fusion from the thoracic spine to the pelvis from 2014 to 2016 were enrolled and asked to complete the BBS prior to and six months after surgery. BBS were obtained by a certified physical therapist. Standard demographic; radiographic and surgical data were collected. The Oswestry disability index (ODI), EuroQOL-5D and numeric rating scales (0 to 10) for back and leg pain were assessed at baseline and post-intervention.

Results

Of 21 patients enrolled; 19 completed pre- and post-surgery BBS. The mean age was 59.8±13.3 years with 14 females. There was a statistically significant improvement in all outcome scores and radiographic parameters after surgery; but no difference in BBS. Only one patient had a BBS score low enough to be considered a medium fall risk. There was no difference in the pre-op BBS scores in the four patients that had revision surgery compared to those that did not.

Conclusions

In this small pilot study; BBS did not appear to be associated with measures of clinical and radiographic improvement in ASD patients. The test was also potentially problematic in that it has a ceiling effect and required significant time with a trained physical therapist for administration. Continued effort to identify a viable measure of balance dysfunction in ASD patients is warranted.

Evaluation of balance in young adults with idiopathic scoliosis

Objectives

This study aims to evaluate the relation of scoliosis with coronal and sagittal balance parameters and the effect of postural balancing in young adults with idiopathic scoliosis.

Patients and methods

Between April 2017 and June 2017, a total of 24 patients (7 males, 24 females; mean age 20.3±2 years; range 17 to 24) who were diagnosed with scoliosis and 65 age- and sex-matched healthy controls (20 males, 45 females; mean age 20.3±1.6 years; range 19 to 25) were included in the study. The Cobb angle, sagittal balance, coronal balance, and truncal shift were measured with radiographs in the patient group. The Biodex Balance System (BBS) was used to assess the general stability index, anterior- posterior and medial-lateral stability index, and fall risk.

Results

All balance parameters were significantly worse in the patient group than in the control group (p<0.05). The static balance was mostly associated with sagittal balance, followed by coronal balance. In the patients with left scoliosis, sagittal balance was 93% negative and 67% of the patients gave their weight to the back. Coronal balance was negative in 60% of the patients and 93.3% of the patients were weighted to the right side. In 89% of the patients with right scoliosis, sagittal balance was negative and 89% of the patients gave their weight to the back. Coronal balance was 44% neutral and 78% of the patients gave their weight to the right side.

Conclusion

In patients with scoliosis, the static balance is worse than healthy individuals. Static balance is mostly related to sagittal balance and also to coronal balance. While the coronal balance tends to be in the direction of the curve, both right and left scoliosis give more weight to the right.

Head-neck rotational movements using DidRen laser test indicate children and seniors' lower performance

Sensorimotor control strategies during cervical axial rotation movements have been previously explored in narrow age ranges but never concurrently in Children and Seniors during a well-standardized task. However, the lifespan developmental approach provides a framework for research in human sensorimotor control of the head-neck complex. A cross-sectional design was used to investigate the influence of age on head-neck dynamic performance adopted by asymptomatic Children, Adults and Seniors using a standardized task (DidRen Laser test). Participants performed 5 cycles of left/right head-neck complex fast rotational movements toward 3 targets with 30° of angular separation. Dynamic performances were computed from total execution time of the test and kinematic variables derived from rotational motion of head measured by an optoelectronic system. Eighty-one participants, aged 8–85 yrs, were stratified in four groups: Children, Younger adults, Older adults and Seniors. Children were significantly slower than Younger (p<0.001) and Older adults (p<0.004) and Seniors slower than Younger adults (p<0.017) to perform the test. Children adopted a lower average speed compared to Younger (p<0.001) and Older adults (p<0.008). Children reached the peaks speed significantly later than Younger (p<0.004) and Older adults (p<0.04) and acceleration significantly later than Younger (p<0.001) and Older adults (p<0.013). From the peak acceleration, Children reached end of the cycle significantly slower than Younger (p<0.008) and Older adults (p<0.008). Children significantly differed from all other groups for rotational kinetic energy, with smaller values compared to Younger adults (p<0.001), Older adults (p<0.005) and Seniors (p<0.012). Variability was also significantly higher for Seniors and Children. In conclusion, age influences head-neck visually elicited rotational dynamics, especially in Children. These results suggest that age should be taken into account when establishing normative data and assessing dynamic head-neck sensorimotor control of patients with neck pain.

Barbie's new look: Exploring cognitive body representation among female children and adolescents

The original Barbie doll’s unrealistic body shape can negatively affect young girls’ body image. Mattel produced new Barbie dolls with “tall”, “curvy”, and “petite” body types, yet how girls perceive and evaluate the three new Barbie body types remains unknown. This study investigated whether young girls engage in an automatic “self-other matching” process when viewing the different Barbie doll representations. Female children and adolescents (N = 38; M_age = 10; 6–14 years old; SD = 2.24 years) completed a body-part compatibility task to provide an index of how they implicitly relate cognitive representations of their own body to the different doll images. Significant (p < .05) body-part compatibility effects emerged for the original, curvy and petite dolls, but not for the tall Barbie. These findings indicate that girls engage in a self-other body matching process when viewing Barbie, but that the strength of this matching is influenced by the doll’s body type. Results provide new evidence on the underlying cognitive mechanisms that occur when girls are exposed to physique-salient toys, and may have implications for young girls’ body image development and use of appearance-based social comparisons.

Age-related kinematic performance should be considered during fast head-neck rotation target task in individuals aged from 8 to 85 years old

Kinematic behavior during fast cervical rotations is a useful parameter for assessing sensorimotor control performances in neck-pain patients. However, the influence of age in asymptomatic individuals from children to older people still needs to be explored. Our aim was to assess the impact of age on sensorimotor control performance of the head-neck with execution time and kinematic variables (time of task, mean speed/acceleration/deceleration, overshoots (OSs), minimum/maximum speed) during standardized fast rotation target task using the DidRen Laser test. A total of 80 volunteers were stratified in four different age-groups: Children (8–14 years): n = 16; Young Adults (18–35 years): n = 29; Old Adults (36–64 years): n = 18; Seniors (65–85 years): n = 17. Results showed that to perform the test, Children were slower (69.0 (60.6–87.3)s) compared to Young Adults (49.6 (45.6–55.6)s) with p < 0.001, and Old Adults (51.7 (48.4–55.8)s) with p < 0.001. It was also slower in Seniors (57 (52.3–67.6)s) compared to Young Adults with p < 0.013. Mean speed was slower in Children (9.4 ± 2.3 °s⁻¹) and Seniors (10.6 ± 2.4 °s⁻¹) compared to Young Adults (13.7 ± 1.9 °s⁻¹) with p < 0.001 and Old Adults (13.3 ± 2.4 °s⁻¹) with p < 0.001. Mean acceleration was slower for Children (8.4(7.6–10.2) °s⁻²) compared to Young Adults (11.1 (8.8–15.3) °s⁻²) with p < 0.016, and Old Adults (12.0(8.4–15.3) °s⁻²) with p < 0.015. Mean deceleration was slower for Children (−1.9(−2.6–1.4) °s⁻²) compared to Young Adults (−2.9(−3.7–2.5) °s⁻²) with p < 0.001 and Old Adults (−3.2(−3.7–2.3) °s⁻²) with p < 0.003. The DidRen Laser test allows us to discriminate age-specific performances for mean speed, acceleration and deceleration. Seniors and Children needed to be slower to become as precise as Young Adults and Old Adults. No difference was observed for OSs which assesses accuracy of movement. Age should therefore be considered as a key parameter when analyzing execution time and kinematic results during DidRen Laser test. These normative data can therefore guide clinicians in the assessment of subjects with neck pain.

Do Adolescents With Idiopathic Scoliosis Have an Erroneous Perception of the Gravitational Vertical?

STUDY DESIGN

Multicenter, case-control study.

OBJECTIVES

Demonstrate altered perception of verticality in AIS compared with matched controls.

SUMMARY OF BACKGROUND DATA

The cause of adolescent idiopathic scoliosis (AIS) remains to be found. AIS is associated with neurosensorial anomalies, in particular, altered control of orthostatic posture. During kinetic activity, the upright posture, in humans, is determined in reference to the gravitational vertical (GV). We hypothesized that in AIS, there is a discordance in the perception of the GV and the true GV. In AIS, the longitudinal axis of the body would thus be misoriented because of an erroneous perception of the GV.

METHODS

Thirty adolescents with right thoracic AIS (age 14.23 ± 1.75 years; Cobb angle 31.97°± 12.83°) and 30 controls matched for age (13.93 ± 1.85 years), body mass index, Tanner stage, and handedness were compared for subjective visual vertical (SVV) measured in static and dynamic (optokinetic stimulation) conditions, and subjective postural vertical (SPV).

RESULTS

There was no difference in the two groups, AIS and controls, for SVV. The SPV was significantly different between the two groups (p = .00023). The SPV was shifted to the right for most of the AIS patients (2.13°± 2.22°) compared with controls (-0.08°±1.40°). There was a significant correlation between SPV and clinical frontal tilt in the AIS patients.

CONCLUSION

Our findings demonstrate that patients with right thoracic AIS have an erroneous perception of the GV. In most AIS patients, SPV was shifted to the right, with no alteration of the SVV. AIS might be the consequence of a reoriented longitudinal body axis aligned with an erroneous vertical reference. The underlying mechanism might involve dysfunction of trunk graviceptors. The primary or secondary nature of this dysfunction remains an open question.

Clinical balance tests, proprioceptive system and adolescent idiopathic scoliosis

PURPOSE

Adolescent idiopathic scoliosis (AIS) is a three-dimensional deformity of the spinal column of unknown etiology. Multiple factors could be involved, including neurosensory pathways and, potentially, an elective disorder of dynamic proprioception. The purpose of this study was to determine whether routine balance tests could be used to demonstrate an elective alteration of dynamic proprioception in AIS.

METHODS

This was a multicentre case-control study based on prospectively collected clinical data, in three hospitals pediatric, with spine consultation, from January 2013 through April 2015. From an original population of 547 adolescents, inclusion and non-inclusion criteria indentified 114 adolescents with right thoracic AIS (mean age 14.5 ± 1.9 years, Cobb angle 35.7 ± 15.3°) and 81 matched adolescents without scoliosis (mean age 14.1 ± 1.9 years). Participants performed three routine clinical balance tests to assess the static and dynamic proprioception: the Fukuda-Utenberger stepping test (angle of rotation in degrees and distance of displacement in cm) to assess dynamic balance; the sharpened Romberg test and the unipedal stance test (eyes closed) to assess static balance.

RESULTS

There was no significant difference between AIS subjects and controls for the static tests, but there was a significant difference for the dynamic test for both measures: distance of displacement (p < 0.01) and angle of rotation (p < 0.0001). This result confirms our initial these: the dynamic proprioception is altered electively in AIS.

CONCLUSION

These findings confirm recent AIS studies. Our results might be related to immature central integration of dynamic proprioceptive input leading to a poorly adapted motor response, particularly for postural control of the, in AIS. These balance tests can be performed in routine practice. Their validity as a biomarker for screening and monitoring purposes should be assessed.

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.