Body and peripersonal space representations in chronic stroke patients with upper limb motor deficits

The remapping of peripersonal space after stroke, spinal cord injury and amputation: A PRISMA systematic review

Peripersonal space (PPS) is the body-centered area where interactions occur and objects can be reached. Its boundaries are dynamic, modulated by ongoing sensorimotor experiences: limb immobilization shrinks PPS, whereas tool use expands it. However, consistent clinical information on PPS alterations remains limited due to methodological heterogeneity, varying types and severities of sensorimotor disorders, and diverse experimental paradigms. This review explores the causal mechanisms of PPS processing by integrating findings from brain-lesioned patients and individuals with body deafferentation, such as amputees and spinal cord injury (SCI) patients. By comparing the effects of brain lesions and sensorimotor deafferentation, it clarifies how PPS is encoded, maintained, and reorganized following central nervous system damage, bodily changes, and the use of assistive devices. A systematic search of Scopus, Web of Science, and PubMed identified 17 studies: 4 on stroke patients (N = 100), 6 on SCI patients (N = 104), and 7 on amputees (N = 65). Risk of bias was assessed using the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. Despite the limited number of studies and methodological variability, findings consistently show that sensorimotor changes significantly affect PPS. Notably, a contraction of PPS around the affected limb was observed in stroke, SCI patients, and amputees. Assistive devices were able to restore PPS after training, or even immediately in the case of prosthesis use. A shared neurophysiological mechanism across these conditions may underlie PPS as an online construct, continuously updated to reflect the body's current state and its interaction with the environment.

Body Representation in Stroke Patients: A Systematic Review of Human Figure Graphic Representation

Background: Body representation is a complex process involving sensory, motor, and cognitive information. Frequently, it is disrupted after a stroke, impairing rehabilitation, emotional functioning, and daily functioning. The human figure graphic representation has emerged as a holistic tool to assess post-stroke outcomes. Objectives: This systematic review examines the methodologies of human figure representation tests and their application in assessing post-stroke body representation, emphasizing its role in bridging subjective patient experiences with objective metrics. Methods: This review follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. A literature search was conducted through the databases PubMed, Scopus, Embase, Web of Science, and Google Scholar, collecting publications eligible for qualitative analysis. We selected studies where patients drew human figures in the study design to assess body representation, involving exclusively the adult stroke population. The Newcastle-Ottawa Scale was used to assess the risk of bias. Results: Ten studies were analyzed. The tool demonstrated versatility in capturing unilateral spatial neglect, emotional disturbances, and functional independence. Qualitative metrics and quantitative indices correlated with cognitive deficits, mood disorders, and activities of daily living. Human figure representation also predicted rehabilitation outcomes, with improvements aligning with motor recovery. Innovations included digital quantification of evaluation metrics. Conclusions: Human figure graphic representation is a low-cost, adaptable tool bridging motor, cognitive, and emotional assessments in stroke survivors. While methodological variability persists, AI-driven analytics and standardized frameworks could enhance objectivity. Future research should prioritize validating parameters and developing hybrid models combining traditional qualitative insights with machine learning, thus advancing precision neurorehabilitation and personalized care.

Body ownership alterations in stroke emerge from reduced proprioceptive precision and damage to the frontoparietal network

BACKGROUND

Stroke patients often experience alterations in their subjective feeling of ownership for the affected limb, which can hinder motor function and interfere with rehabilitation. In this study, we aimed at disentangling the complex relationship between sensory impairment, body ownership (BO), and motor control in stroke patients.

METHODS

We recruited 20 stroke patients with unilateral upper limb sensory deficits and 35 age-matched controls. Participants performed a virtual reality reaching task with a varying displacement between their real unseen hand and a visible virtual hand. We measured reaching errors and subjective ownership ratings as indicators of hand ownership. Reaching errors were modeled using a probabilistic causal inference model, in which ownership for the virtual hand is inferred from the level of congruency between visual and proprioceptive inputs and used to weigh the amount of visual adjustment to reaching movements.

FINDINGS

Stroke patients were more likely to experience ownership over an incongruent virtual hand and integrate it into their motor plans. The model explained this tendency in terms of a decreased capability of detecting visuo-proprioceptive incongruences, proportionally to the amount of proprioceptive deficit. Lesion analysis further revealed that BO alterations, not fully explained by the proprioceptive deficit, are linked to frontoparietal network damage, suggesting a disruption in higher-level multisensory integration functions.

CONCLUSIONS

Collectively, our results show that BO alterations in stroke patients can be quantitatively predicted and explained in a computational framework as the result of sensory loss and higher-level multisensory integration deficits.

FUNDING

Swiss National Science Foundation (163951).

Efficacy of Body Representation Rehabilitation Training for Adults with Unilateral Brain Damage: A Preliminary Study

BACKGROUND/OBJECTIVES

Body representations (BRs) are essential for guiding movements, maintaining spatial awareness, and achieving effective interactions with the environment. Several studies suggest that BRs are frequently impaired following unilateral brain damage, emphasising the need for tailored rehabilitation interventions; however, there is a lack of studies evaluating the effectiveness of training specifically designed to improve different kinds of functional BRs after stroke. Therefore, the present study aimed to present and implement a specific rehabilitation training program for BR alterations and evaluate its effectiveness in a sample of adults with unilateral brain damage.

METHODS

Nine adults with unilateral brain damage and seven age- and education-matched healthy controls were recruited. Both groups underwent a neuropsychological assessment to evaluate BR (action- and nonaction-oriented). Additionally, functional autonomy and motor functioning were assessed in the patient group. Following an initial assessment (T0), the patients participated in a BR-specific rehabilitation intervention. At the end of the rehabilitation program (T1), both groups were re-evaluated with the same tasks used at T0.

RESULTS

At T0, the patient group performed worse on BR tasks than the controls. At T1, a significant improvement in the nonaction-oriented BR and functional autonomy was observed in the patient group.

CONCLUSIONS

This preliminary study suggests the effectiveness of a targeted rehabilitation intervention for BR in promoting enhanced body boundary awareness and greater accuracy in the perception of body part positions, possibly leading to increased functional autonomy. These findings highlight the importance of incorporating BR training in rehabilitation programs for adults with acquired brain damage, alongside motor rehabilitation.

Perception and control of a virtual body in immersive virtual reality for rehabilitation

PURPOSE OF REVIEW

This review explores recent advances in using immersive virtual reality to improve bodily perception and motor control in rehabilitation across musculoskeletal and neurological conditions, examining how virtual reality's unique capabilities can address the challenges of traditional approaches. The potential in this area of the emerging metaverse and the integration of artificial intelligence in virtual reality are discussed.

RECENT FINDINGS

In musculoskeletal rehabilitation, virtual reality shows promise in enhancing motivation, adherence, improving range of motion, and reducing kinesiophobia, particularly postsurgery. For neurological conditions like stroke and spinal cord injury, virtual reality's ability to manipulate bodily perceptions offers significant therapeutic potential, with reported improvements in upper limb function and gait performance. Balance and gait rehabilitation, especially in older adults, have also seen positive outcomes. The integration of virtual reality with brain-computer interfaces presents exciting possibilities for severe speech and motor impairments.

SUMMARY

Current research is limited by small sample sizes, short intervention durations, and variability in virtual reality systems. Future studies should focus on larger, long-term trials to confirm findings and explore underlying mechanisms. As virtual reality technology advances, its integration into rehabilitation programs could revolutionize treatment approaches, personalizing treatments, facilitating home training, and potentially improving patient outcomes across a wide variety of conditions.

Using a tablet to understand the spatial and temporal characteristics of complex upper limb movements in chronic stroke

Robotic devices are commonly used to quantify sensorimotor function of the upper limb after stroke; however, the availability and cost of such devices make it difficult to facilitate implementation in clinical environments. Tablets (e.g. iPad) can be used as devices to facilitate rehabilitation but are rarely used as assessment tools for the upper limb. The current study aimed to implement a tablet-based Maze Navigation Task to examine complex upper-limb movement in individuals with chronic stroke. We define complex upper-limb movement as reaching movements that require multi-joint coordination in a dynamic environment. We predicted that individuals with stroke would have more significant spatial errors, longer movement times, and slower speeds compared to controls with increasing task complexity. Twenty individuals with chronic stroke who had a variety of arm and hand function (Upper extremity Fugl-Myer 52.8 ± 18.3) and twenty controls navigated eight pseudorandomized mazes on an iPad using a digitizing stylus. The task was designed to elicit reaching movements engaging both the shoulder and elbow joints. Each maze became increasingly complex by increasing the number of 90° turns. We instructed participants to navigate each maze as quickly and accurately as possible while avoiding the maze's boundaries. Sensorimotor behavior was quantified using the following metrics: Error Time (time spent hitting or outside boundaries), Peak Speed, Average Speed, and Movement Time, Number of Speed Peaks. We found that individuals with stroke had significantly greater Error Time for all maze levels (all, p < 0.01), while both speed metrics, Movement Time and Number of Speed Peaks were significantly lower for several levels (all, p < 0.05). As maze complexity increased, the performance of individuals with stroke worsened only for Error Time while control performance remained consistent (p < 0.001). Our results indicate that a complex movement task on a tablet can capture temporal and spatial impairments in individuals with stroke, as well as how task complexity impacts movement quality. This work demonstrates that a tablet is a suitable tool for the assessment of complex movement after stroke and can serve to inform rehabilitation after stroke.

Influence of Impaired Upper Extremity Motor Function on Static Balance in People with Chronic Stroke

BACKGROUND

Stroke is a leading cause of disability, especially due to an increased fall risk and postural instability. The objective of this study was to analyze the impact of motor impairment in the hemiparetic UE on static balance in standing, in subject with chronic stroke.

METHODS

Seventy adults with chronic stroke, capable of independent standing and walking, participated in this cross-sectional study. The exclusion criteria included vestibular, cerebellar, or posterior cord lesions. The participants were classified based on their UE impairment using the Fugl-Meyer Assessment of Motor Recovery after Stroke (FMA-UE). A posturographic evaluation (mCTSIB) was performed in the standing position to analyze the center of pressure (COP) displacement in the mediolateral (ML) and anteroposterior (AP) axes and its mean speed with eyes open (OE) and closed (EC) on stable and unstable surfaces.

RESULTS

A strong and significant correlation (r = -0.53; p < 0.001) was observed between the mediolateral (ML) center of pressure (COP) oscillation and the FMA-UE, which was particularly strong with eyes closed [r(EO) = 0.5; r(EC) = 0.54]. The results of the multiple linear regression analysis indicated that the ML oscillation is influenced significantly by the FMA-Motor, and specifically by the sections on UE, wrist, coordination/speed, and sensation.

CONCLUSIONS

The hemiparetic UE motor capacity is strongly related to the ML COP oscillation during standing in individuals with chronic stroke, with a lower motor capacity associated with a greater instability. Understanding these relationships underpins the interventions to improve balance and reduce falls in people who have had a stroke.

Enhancing poststroke hand movement recovery: Efficacy of RehabSwift, a personalized brain-computer interface system

This study explores the efficacy of our novel and personalized brain-computer interface (BCI) therapy, in enhancing hand movement recovery among stroke survivors. Stroke often results in impaired motor function, posing significant challenges in daily activities and leading to considerable societal and economic burdens. Traditional physical and occupational therapies have shown limitations in facilitating satisfactory recovery for many patients. In response, our study investigates the potential of motor imagery-based BCIs (MI-BCIs) as an alternative intervention. In this study, MI-BCIs translate imagined hand movements into actions using a combination of scalp-recorded electrical brain activity and signal processing algorithms. Our prior research on MI-BCIs, which emphasizes the benefits of proprioceptive feedback over traditional visual feedback and the importance of customizing the delay between brain activation and passive hand movement, led to the development of RehabSwift therapy. In this study, we recruited 12 chronic-stage stroke survivors to assess the effectiveness of our solution. The primary outcome measure was the Fugl-Meyer upper extremity (FMA-UE) assessment, complemented by secondary measures including the action research arm test, reaction time, unilateral neglect, spasticity, grip and pinch strength, goal attainment scale, and FMA-UE sensation. Our findings indicate a remarkable improvement in hand movement and a clinically significant reduction in poststroke arm and hand impairment following 18 sessions of neurofeedback training. The effects persisted for at least 4 weeks posttreatment. These results underscore the potential of MI-BCIs, particularly our solution, as a prospective tool in stroke rehabilitation, offering a personalized and adaptable approach to neurofeedback training.

Evaluation of upper limb perception after stroke with the new Affected Limb Perception Questionnaire (ALPQ): a study protocol

BACKGROUND

Following a stroke, patients may suffer from alterations in the perception of their own body due to an acquired deficit in body representations. While such changes may impact their quality of life as well as recovery, they are not systematically assessed in clinical practice. This study aims at providing a better understanding of the rate, evolution, and impact on recovery of upper limb (UL) body perceptions (BPs) alterations following stroke. In addition, we will investigate associations among BPs alterations items, their associations with the sensorimotor functions, UL activity, damages in brain structure and connectivity.

METHODS

We developed a new tool named ALPQ (for Affected Limb Perception Questionnaire) to address the present study objectives. It assesses subjective alterations in the perception of the affected UL following stroke, by measuring several dimensions, namely: anosognosia for hemiplegia, anosodiaphoria for hemiplegia, hemiasomatognosia, somatoparaphrenia, personification of the affected limb, illusion of modification of physical characteristics (temperature, weight, length), illusory movements, super- or undernumerary limb, UL disconnection, misoplegia, and involuntary movement. This study combines a cross-sectional and longitudinal design. The completed data sample will include a minimum of 60 acute and 100 sub-acute stroke patients. When possible, patients are followed up to the chronic stage. Complementary evaluations are administered to assess patients' sensorimotor and cognitive functions as well as UL activity, and brain lesions will be analysed.

DISCUSSION

This study will provide a better understanding of BPs alterations following stroke: their rate and evolution, as well as their associations with sensorimotor deficit, cognitive profile and UL activity, brain lesions and recovery. Ultimately, the results could support the personalization of rehabilitation strategy according to patients' UL perception to maximize their recovery.

STUDY REGISTRATION

The protocol for this study has been pre-registered on the Open Science Framework on July the 7th, 2021: https://osf.io/p6v7f .

Neuroanatomical correlates of peripersonal space: bridging the gap between perception, action, emotion and social cognition

Peripersonal space (PPS) is a construct referring to the portion of space immediately surrounding our bodies, where most of the interactions between the subject and the environment, including other individuals, take place. Decades of animal and human neuroscience research have revealed that the brain holds a separate representation of this region of space: this distinct spatial representation has evolved to ensure proper relevance to stimuli that are close to the body and prompt an appropriate behavioral response. The neural underpinnings of such construct have been thoroughly investigated by different generations of studies involving anatomical and electrophysiological investigations in animal models, and, recently, neuroimaging experiments in human subjects. Here, we provide a comprehensive anatomical overview of the anatomical circuitry underlying PPS representation in the human brain. Gathering evidence from multiple areas of research, we identified cortical and subcortical regions that are involved in specific aspects of PPS encoding.We show how these regions are part of segregated, yet integrated functional networks within the brain, which are in turn involved in higher-order integration of information. This wide-scale circuitry accounts for the relevance of PPS encoding in multiple brain functions, including not only motor planning and visuospatial attention but also emotional and social cognitive aspects. A complete characterization of these circuits may clarify the derangements of PPS representation observed in different neurological and neuropsychiatric diseases.

The different impact of attention, movement, and sensory information on body metric representation

A growing body of research investigating the relationship between body representation and tool-use has shown that body representation is highly malleable. The nature of the body representation does not consist only of sensory attributes but also of motor action-oriented qualities, which may modulate the subjective experience of our own body. However, how these multisensory factors and integrations may specifically guide and constrain body reorientation's plasticity has been under-investigated. In this study, we used a forearm bisection task to selectively investigate the contribution of motor, sensory, and attentional aspects in guiding body representation malleability. Results show that the perceived forearm midpoint deviates from the real one. This shift is further modulated by a motor task but not by a sensory task, whereas the attentional task generates more uncertain results. Our findings provide novel insight into the individual role of movement, somatosensation, and attention in modulating body metric representation.

Multisensory peripersonal space: Visual looming stimuli induce stronger response facilitation to tactile than auditory and visual stimulations

Anticipating physical contact with objects in the environment is a key component of efficient motor performance. Peripersonal neurons are thought to play a determinant role in these predictions by enhancing responses to touch when combined with visual stimuli in peripersonal space (PPS). However, recent research challenges the idea that this visuo-tactile integration contributing to the prediction of tactile events occurs strictly in PPS. We hypothesised that enhanced sensory sensitivity in a multisensory context involves not only contact anticipation but also heightened attention towards near-body visual stimuli. To test this hypothesis, Experiment 1 required participants to respond promptly to tactile (probing contact anticipation) and auditory (probing enhanced attention) stimulations presented at different moments of the trajectory of a (social and non-social) looming visual stimulus. Reduction in reaction time as compared to a unisensory baseline was observed from an egocentric distance of around 2 m (inside and outside PPS) for all multisensory conditions and types of visual stimuli. Experiment 2 tested whether these facilitation effects still occur in the absence of a multisensory context, i.e., in a visuo-visual condition. Overall, facilitation effects induced by the looming visual stimulus were comparable in the three sensory modalities outside PPS but were more pronounced for the tactile modality inside PPS (84 cm from the body as estimated by a reachability judgement task). Considered together, the results suggest that facilitation effects induced by visual looming stimuli in multimodal sensory processing rely on the combination of attentional factors and contact anticipation depending on their distance from the body.

May Spasticity-Related Unpleasant Sensations Interfere with Daily Activities in People with Stroke and Traumatic Brain Injury? Secondary Analysis from the CORTOX Study

Background/Objectives: This study examined the impact of spasticity-related unpleasant sensations (pain, heaviness, stiffness) on various domains of the International Classification of Functioning, Disability, and Health (ICF) and psychosocial well-being in individuals affected by stroke or traumatic brain injury (TBI). The primary aim is to explore how these sensations affect daily activities, participation, and overall quality of life, guided by the comprehensive framework of the ICF. Methods: Utilizing a secondary analysis of data from a cohort undergoing Botulinum toxin type-A treatment for spasticity post-stroke or TBI, we developed and administered an ad-hoc questionnaire focusing on ICF domains such as body function, activities and participation, and psychosocial aspects such as mood, relationship, social life, motivation, and sleep quality. Spearman rho correlation was applied to assess the relationship between unpleasant sensations and functional as well as psychosocial outcomes among 151 participants. Results: This study identified significant correlations between the severity of unpleasant sensations and limitations in daily functioning, particularly in activities of daily living and mobility. Furthermore, an impactful association was identified between increased unpleasant sensations and deterioration in psychosocial well-being, notably in mood and sleep quality. Conclusions: These findings advocate for a person-centered approach in spasticity management, emphasizing the integration of sensory impairment strategies into rehabilitation to enhance functional outcomes and quality of life. Such an approach aims to improve functional outcomes and enhance the quality of life for individuals experiencing spasticity post-stroke or TBI. Future directions include targeted interventions to alleviate these sensations, support better rehabilitation results and improve patient experiences.

Feasibility and Validation of a Robotic-Based Multisensory Integration Assessment in Healthy Controls and a Stroke Patient

After experiencing brain damage, stroke patients commonly suffer from motor and sensory impairments that impact their ability to perform volitional movements. Visuo-proprioceptive integration is a critical component of voluntary movement, allowing for accurate movements and a sense of ownership over one's body. While recent studies have increased our understanding of the balance between visual compensation and proprioceptive deficits in stroke patients, quantitative methods for studying multisensory integration are still lacking. This study aimed to evaluate the feasibility of adapting a 3D visuo-proprioceptive disparity (VPD) task into a 2D setting using an upper-limb robotic platform for moderate to severe chronic stroke patients. To assess the implementation of the 2D task, a cohort of unimpaired healthy participants performed the VPD task in both a 3D and 2D environment. We used a computational Bayesian model to predict errors in visuo-proprioceptive integration and compared the model's predictions to real behavioral data. Our findings indicated that the behavioral trends observed in the 2D and 3D tasks were similar, and the model accurately predicted behavior. We then evaluated the feasibility of our task to assess post-stroke deficits in a patient with severe motor and sensory deficits. Ultimately, this work may help to improve our understanding of the significance of visuo-proprioceptive integration and aid in the development of better rehabilitation therapies for improving sensorimotor outcomes in stroke patients.

Preliminary Rasch analysis of the multidimensional assessment of interoceptive awareness in adults with stroke

PURPOSE

The Multidimensional Assessment of Interoceptive Awareness (MAIA) measures interoceptive body awareness, which includes aspects such as attention regulation, self-regulation, and body listening. Our purpose was to perform a preliminary validation of the MAIA in adults with stroke using Rasch Measurement Theory.

METHODS

The original MAIA has 32 items that measure interoceptive sensibility, which is an aspect of body awareness. We performed a preliminary analysis with Rasch Measurement Theory to evaluate the unidimensionality and structural validity of the scale. We investigated overall fit to assess unidimensionality, person and item fit, person separation reliability, targeting, local item dependence, and principal components analysis of residuals.

RESULTS

Forty-one adults with chronic stroke (average 3.8 years post-stroke, 13 women, average age 57±13 years) participated in the study. Overall fit (χ 2 = 62.26, p = 0.26) and item fit were obtained after deleting 3 items and rescoring 26 items. One participant did not fit the model (2.44%). There were no floor (0.00%) or ceiling effects (0.00%). Local item dependence was found in 42 pairs. The person separation reliability was 0.91, and the person mean location was 0.06±1.12 logits.

CONCLUSIONS

The preliminary structural validity of the MAIA demonstrated good targeting and reliability, as well as unidimensionality, and good item and person fit in adults with chronic stroke. A study with a larger sample size is needed to validate our findings.

A Quantitative, Digital Method to Analyze Human Figure Drawings as a Tool to Assess Body Representations Distortions in Stroke Patients

OBJECTIVE

Human figure drawings are widely used in clinical practice as a qualitative indication of Body Representations (BRs) alterations in stroke patients. The objective of this study is to present and validate the use of a new app called QDraw for the quantitative analysis of drawings and to investigate whether this analysis can reveal distortions of BRs in chronic stroke patients.

RESULTS

QDraw has proven to generate reliable data as compared to manual scoring and in terms of inter-rater reliability, as shown by the high correlation coefficients. Moreover, human figure drawings from chronic stroke patients demonstrated a distortion of upper limb perception, as shown by a significantly higher arm length asymmetry compared to legs, whereas no difference was found in healthy controls.

CONCLUSIONS

The present study supports the use of quantitative, digital methods (the QDraw app) to analyze human figure drawings as a tool to evaluate BRs distortions in stroke patients.

Social Context and Tool Use Can Modulate Interpersonal Comfort Space

Recent research has investigated whether the representation of space around the body, in terms of reach-action (imagining of reaching another person) and comfort-social (tolerance of the other's proximity) spaces, may reflect a shared sensorimotor basis. Some studies exploiting motor plasticity induced by tool use have not observed sensorimotor identity (i.e., the same mechanisms that underlie, based on sensory information, the representation of proximal space in terms of action possibilities, goal-directed motor actions, and anticipation of the sensorimotor consequences), whereas evidence to the contrary has also emerged. Since the data are not fully convergent, here we wondered whether or not the combination of motor plasticity induced by tool use and the processing of the role of social context might reflect a similar modulation in both spaces. To this end, we conducted a randomized control trial with three groups of participants (N = 62) in which reaching and comfort distances were measured in Pre- and Post-tool-use sessions. The tool-use sessions were conducted under different conditions: (i) in the presence of a social stimulus (determining the social context) (Tool plus Mannequin group); (ii) without any stimulus (Only Tool group); (iii) in the presence of a box (Tool plus Object group) as a control condition. Results showed an extension of comfort distance in the Post-tool session of the Tool plus Mannequin group compared with the other conditions. Conversely, the reaching distance was larger after tool use than at the Pre-tool-use session, independently of the experimental conditions. Our findings suggest that motor plasticity impacts reaching and comfort spaces to different degrees; while reaching space is markedly sensitive to motor plasticity, comfort space needs qualification of social context information.

Your brain is amazing: Let's keep it that way

Our editor discusses brain resilience and how it can be harnessed to prevent diseases that cause dementia.