Visual Error Augmentation for Enhancing Motor Learning and Rehabilitative Relearning

We developed a real-time controller for a 2 degree-of-freedom robotic system using xPC Target. This system was used to investigate how different methods of performance error feedback can lead to faster and more complete motor learning in individuals asked to compensate for a novel visuo-motor transformation (a 30 degree rotation). Four groups of normal human subjects were asked to reach with their unseen arm to visual targets surrounding a central starting location. A cursor tracking hand motion was provided during each reach. For one group of subjects, deviations from the ideal compensatory hand movement (i.e. trajectory errors) were amplified with a gain of 2 whereas another group was provided visual feedback with a gain of 3.1. Yet another group was provided cursor feedback wherein the cursor was rotated by an additional (constant) offset angle. We compared the rates at which the hand paths converged to the steady-state trajectories. Our results demonstrate that error-augmentation can improve the rate and extent of motor learning of visuomotor rotations in healthy subjects. We also tested this method on straightening the movements of stroke subjects, and our early results suggest that error amplification can facilitate neurorehabilitation strategies in brain injuries such as stroke

Visual error amplification showed no benefit for non-naïve subjects in trunk-arm rowing

Motor learning is assumed to be a partly error driven process. Motor learning studies on simple movements have shown that skilled subjects benefit from training with error amplification. Findings of studies with simple movements do not necessarily transfer to complex sport movements. The goal of this work was to determine the benefit of visual error amplification for non-naïve subjects in learning a fast rowing movement.We conducted a study comparing non-naïve subjects receiving a fading, visual feedback with visual error amplification against a control group receiving the same visual feedback without error amplification. Separate outcome metrics were applied for the domains of spatial and velocity magnitude errors. Besides error metrics, variability metrics were evaluated for both domains, such that they could be interpreted in quantitative relation to each other.The implemented error amplification did not cause group differences in any variable. Subjects with or without error amplification reached similar absolute levels in error and variability. Possible reasons remain speculative. For implementing error amplification to the training of complex movements design decisions must be made for which an informative basis is missing, e.g. the error amplification gains

Learning to perform a new movement with robotic assistance: comparison of haptic guidance and visual demonstration

BACKGROUND: Mechanical guidance with a robotic device is a candidate technique for teaching people desired movement patterns during motor rehabilitation, surgery, and sports training, but it is unclear how effective this approach is as compared to visual demonstration alone. Further, little is known about motor learning and retention involved with either robot-mediated mechanical guidance or visual demonstration alone. METHODS: Healthy subjects (n = 20) attempted to reproduce a novel three-dimensional path after practicing it with mechanical guidance from a robot. Subjects viewed their arm as the robot guided it, so this "haptic guidance" training condition provided both somatosensory and visual input. Learning was compared to reproducing the movement following only visual observation of the robot moving along the path, with the hand in the lap (the "visual demonstration" training condition). Retention was assessed periodically by instructing the subjects to reproduce the path without robotic demonstration. RESULTS: Subjects improved in ability to reproduce the path following practice in the haptic guidance or visual demonstration training conditions, as evidenced by a 30–40% decrease in spatial error across 126 movement attempts in each condition. Performance gains were not significantly different between the two techniques, but there was a nearly significant trend for the visual demonstration condition to be better than the haptic guidance condition (p = 0.09). The 95% confidence interval of the mean difference between the techniques was at most 25% of the absolute error in the last cycle. When asked to reproduce the path repeatedly following either training condition, the subjects' performance degraded significantly over the course of a few trials. The tracing errors were not random, but instead were consistent with a systematic evolution toward another path, as if being drawn to an "attractor path". CONCLUSION: These results indicate that both forms of robotic demonstration can improve short-term performance of a novel desired path. The availability of both haptic and visual input during the haptic guidance condition did not significantly improve performance compared to visual input alone in the visual demonstration condition. Further, the motor system is inclined to repeat its previous mistakes following just a few movements without robotic demonstration, but these systematic errors can be reduced with periodic training

A Real-Time Haptic/Graphic Demonstration of How Error Augmentation Can Enhance Learning

We developed a real-time controller for a 2 degree-of-freedom robotic system using xPC Target. This system was used to investigate how different methods of performance error feedback can lead to faster and more complete motor learning in individuals asked to compensate for a novel visuo-motor transformation (a 30 degree rotation). Four groups of human subjects were asked to reach with their unseen arm to visual targets surrounding a central starting location. A cursor tracking hand motion was provided during each reach. For one group of subjects, deviations from the “ideal” compensatory hand movement (i.e. trajectory errors) were amplified with a gain of 2 whereas another group was provided visual feedback with a gain of 3.1. Yet another group was provided cursor feedback wherein the cursor was rotated by an additional (constant) offset angle. We compared the rates at which the hand paths converged to the steady-state trajectories. Our results demonstrate that error-augmentation can improve the rate and extent of motor learning of visuomotor rotations in healthy subjects. Furthermore, our results suggest that both error amplification and offset-augmentation may facilitate neuro-rehabilitation strategies that restore function in brain injuries such as stroke

Abnormal sensory integration affects balance control in hemiparetic patients within the first year after stroke

OBJECTIVE: Impairments in balance can be a consequence of changes in the motor, sensory, and integrative aspects of motor control. Abnormal sensory reweighting, i.e., the ability to select the most appropriate sensory information to achieve postural stability, may contribute to balance impairment. The Sensory Organization Test is a component of Computerized Dynamic Posturography that evaluates the impact of visual, vestibular, and somatosensory inputs, as well as sensory reweighting, under conditions of sensory conflict. The aim of this study is to compare balance control in hemiparetic patients during the first year post-stroke and in age-matched neurologically normal subjects using the Berg Balance Scale and Computerized Dynamic Posturography. METHODS: We compared the Berg Balance Scale and Sensory Organization Test scores in 21 patients with hemiparesis after first-ever ischemic stroke and in 21 age-matched, neurologically normal subjects. An equilibrium score was defined for each Sensory Organization Test condition. RESULTS: Berg Balance Scale scores were significantly lower in the patients than in the neurologically normal subjects. Equilibrium scores were significantly lower in the patients than in the neurologically normal subjects for those Sensory Organization Test conditions that did not provide appropriate somatosensory information and under conditions of sensory conflict. A history of falls was more frequent in patients with lower equilibrium scores. CONCLUSION: During the first year after a stroke, defective sensory reweighting significantly impacts balance control in hemiparetic patients. These results are important for the planning of effective rehabilitation interventions

The interplay between movement and perception: how interaction can influence sensorimotor performance and neuromotor recovery

openMovement and perception interact continuously in daily activities. Motor output changes the outside world and affect perceptual representations. Similarly, perception has consequences on movement. Nevertheless, how movement and perception influence each other and share information is still an open question. Mappings from movement to perceptual outcome and vice versa change continuously throughout life. For example, a cerebrovascular accident (stroke) elicits in the nervous system a complex series of reorganization processes at various levels and with different temporal scales. Functional recovery after a stroke seems to be mediated by use-dependent reorganization of the preserved neural circuitry. The goal of this thesis is to discuss how interaction with the environment can influence the progress of both sensorimotor performance and neuromotor recovery. I investigate how individuals develop an implicit knowledge of the ways motor outputs regularly correlate with changes in sensory inputs, by interacting with the environment and experiencing the perceptual consequences of self-generated movements. Further, I applied this paradigm to model the exercise-based neurorehabilitation in stroke survivors, which aims at gradually improving both perceptual and motor performance through repeated exercise. The scientific findings of this thesis indicate that motor learning resolve visual perceptual uncertainty and contributes to persistent changes in visual and somatosensory perception. Moreover, computational neurorehabilitation may help to identify the underlying mechanisms of both motor and perceptual recovery, and may lead to more personalized therapies.openXXXII CICLO - BIOINGEGNERIA E ROBOTICA - BIOENGINEERING AND ROBOTICS - Bioengineering and bioelectronicsSedda, Giuli

The effect of sensory-motor training on brain activation and functional recovery in chronic stroke survivors

Thesis (PhD)--Stellenbosch University, 2018.ENGLISH ABSTRACT: Introduction: Functional loss is greatly determined by postural control impairment in chronic stroke survivors causing reduced ability to execute activities of daily living, impaired mobility and increases the risk of falling. It is known that the basal ganglia network play an important role in postural control, however the effect of sensory-manipulated balance training on structural connectivity in chronic stroke survivors remains unknown. Objective: To assess the influence of sensory-manipulated balance training, i.e. sensory-motor training (SMT), on structural connectivity and functional recovery in chronic stroke survivors. Study design: Double-blind randomised controlled trial. Methods: Twenty-two individuals with chronic stroke (≥6 months post-stroke) were randomly divided into two groups, namely the sensory-motor training (SMT; n = 12) and attention-matched control group (CON; n = 10). The SMT group participated in task-specific balance training, which focused on manipulating the visual, vestibular and somatosensory systems, three times a week for 45 to 60-minute sessions, over an eight-week period. The CON group attended educational talks regarding various lifestyle topics for the same duration as the SMT group. Both interventions were delivered by experienced clinical exercise therapists and were executed in a group setting. Primary outcome measures included changes in structural connectivity strength (diffusion tensor magnetic resonance imaging (MRI) scan), postural sway and sensory dependency (modified Clinical Test for Sensory Interaction and Balance (m-CTSIB), as well as functional mobility (Timed-Up and Go (TUG). Structural connectivity strength was specifically investigated between the twosubcortical basal ganglia nuclei, caudate and lentiform nucleus, with other regions of interest. Furthermore, the m-CTSIB and TUG tests were executed with APDM’s Mobility LabTMbody-worn inertial sensors. Secondary outcome measures were health-related quality of life (Short Form Health Survey (SF-36)) and fall efficacy (Fall Efficacy Scale - International (FES-I)). Participants were tested pre- and post-intervention. Results: Diffusion tensor MRI results showed interaction effects for increased connectivity strength between the basal ganglia and sensory-motorfronto-parietal areas in the SMT group (n = 5; p<0.05), where as the CON group (n = 4 ) presented increased structural connectivity in the higher cognitive orbitotemporal and frontal lobe areas (p<0.05). For the behavioural outcome measures, interaction effects were found for turning performance(p = 0.02), perceived physical functioning (p = 0.005) and fall efficacy (p= 0.03). Moreover, the SMT group (n = 12) showed improved postural sway when standing on a foam pad with eyes open (p = 0.04, ES = 0.61M, 95% CI= -0.27 to 1.36), reduced somatosensory dependence (p = 0.02, ES = 0.63M,95% CI = -0.24 to 1.40), improved turning performance (p≤0.05) as well as improvements in perceived physical (p = 0.01, ES = 0.52M, 95% CI = -0.33to 1.29) and social functioning (p = 0.02, ES = 1.03L, 95% CI = 0.11 to 1.80)after participating in the SMT programme. Lastly, a group difference wasobserved for perceived physical (p = 0.003, ES = 0.90L, 95% CI = -0.05 to1.70) and social functioning (p = 0.02, ES = 1.01L, 95% CI = 0.04 to 1.81) at post-intervention. Conclusions: This study highlights postural control-related improvements induced by SMT, which may be associated with structural connectivity changes in chronic stroke survivors. Therefore, the preliminary results support the notion that the human brain has the ability to undergo activity-dependent neuroplasticity.AFRIKAANSE OPSOMMING: Inleiding: Funksionele verlies word grootliks bepaal deur aantasting van postuurbeheer in individue met kroniese beroerte, wat veroorsaak dat die vermoë om alledaagse aktiwiteite uit te voer verswak, mobiliteit aangetas word en valrisiko verhoog. Dit is bekend dat die basale ganglia ’n belangrike rol in postuurbeheer speel, maar die effek van sensories-gemanipuleerde balans-oefening op strukturele konnektiwiteit in individue met kroniese beroerte bly onbekend. Doelwit: Om die invloed van sensories-gemanipuleerde balansoefening, d.i. sensories-motoriese oefening (SMO), op strukturele konnektiwiteit en funksionele herstel te evalueer in individue met kroniese beroerte. Studie ontwerp: Dubbelblind ewekansige gekontroleerde proefneming. Metodes: Twee-en-twintig individue met kroniese beroerte (≥6 maandegelede) is ewekansig in twee groepe verdeel, naamlik die sensories-motorieseoefening (SMO; n = 12) en gelyke-aandag kontrolegroep (KON; n = 10). Die SMO-groep het drie keer per week in 45- tot 60 minuut sessies deelgeneem aan taak-spesifieke balansoefeninge, wat gefokus het op die manipulering van die visuele, vestibulêre en somato sensoriese stelsels oor ’n tydperk van agt weke. Die KON-groep het opvoedkundige praatjies met betrekking tot verskeie onderwerpe oor lewenstyl bygewoon vir dieselfde tydsduur as die SMO-groep. Beide intervensies was deur ervare kliniese oefenterapeute gelewer en in groepsverband uitgevoer. Primêre uitkomstes het die sterkte van strukturele konnektiwiteit (diffusion tensor magnetic resonance imaging (MRI) scan), postuurswaai en sensoriese afhanklikheid (modified Clinical Test for Sensory Interaction and Balance (m-CTSIB)), sowel as funksionele mobiliteit (Timed-Up and Go (TUG)) ingesluit. Die sterkte van strukturele konnektiwiteit was spesifiek ondersoek tussen die twee subkortikale basale ganglia kerne, koudaat en lensvormige kern, met ander areas van belang. Verder was diem-CTSIB en TUG-toetse uitgevoer met APDM se Mobility LabTM traagheidsensors. Sekondêre uitkomstes was gesondheidsverwante lewenskwaliteit (Short Form Health Survey (SF-36)) en valpersepsie (Fall Efficacy Scale - International (FES-I)).Deelnemers was voor- en na-intervensie getoets. Resultate: Diffusion tensor MRI resultate het interaksie effekte vir ver-hoogde konnektiwiteitsterkte tussen die basale ganglia en sensories-motoriesefronto-pariëtale areas in die SMO-groep (n = 5; p<0.05) getoon, terwyl die KON-groep (n = 4) verhoogde strukturele konnektiwiteit in die hoër orbito-temporale- en frontale lobareas (p<0.05) getoon het. Vir die gedragsuitkomste was interaksie effekte gevind vir omdraai-prestasie (p = 0.02), self-waargenome fisiese funksionering (p = 0.005) en valpersepsie (p = 0.03). Verder het die SMO-groep (n = 12) die volgende getoon: verbeterde postuurswaai wanneer daar op ’n sponsmat met oop oë gestaan word (p = 0.04, ES = 0.61M,95% CI = -0.27 to 1.36), verlaagde somatosensoriese afhanklikheid (p = 0.02,ES = 0.63M, 95% CI = -0.24 to 1.40), verbeterde omdraai-prestasie (p≤0.05) sowel as ’n verbetering in self-waargenome fisiese- (p = 0.01, ES = 0.52M,95% CI = -0.33 to 1.29) en sosiale funksionering (p = 0.02, ES = 1.03L,95% CI = 0.11 to 1.80) na deelname aan die SMO-program. Laastens was ’n groepsverskil opgemerk vir waargenome fisiese- (p = 0.003, ES = 0.90L,95% CI = -0.05 to 1.70) en sosiale funksionering (p = 0.02, ES = 1.01L, 95%CI = 0.04 to 1.81) na-intervensie. Gevolgtrekkings: Hierdie studie beklemtoon postuurbeheer verwante verbeteringe wat deur SMO geïnduseer is, en word geassosieer met veranderinge instrukturele konnektiwiteit in individue met kroniese beroerte. Die voorlopige resultate ondersteun daarom die idee dat die menslike brein die vermoë het om aktiwiteits-afhanklike neuroplastisiteit te ondergaan.Doctor

Pseudo-haptics survey: Human-computer interaction in extended reality & teleoperation

Pseudo-haptic techniques are becoming increasingly popular in human-computer interaction. They replicate haptic sensations by leveraging primarily visual feedback rather than mechanical actuators. These techniques bridge the gap between the real and virtual worlds by exploring the brain’s ability to integrate visual and haptic information. One of the many advantages of pseudo-haptic techniques is that they are cost-effective, portable, and flexible. They eliminate the need for direct attachment of haptic devices to the body, which can be heavy and large and require a lot of power and maintenance. Recent research has focused on applying these techniques to extended reality and mid-air interactions. To better understand the potential of pseudo-haptic techniques, the authors developed a novel taxonomy encompassing tactile feedback, kinesthetic feedback, and combined categories in multimodal approaches, ground not covered by previous surveys. This survey highlights multimodal strategies and potential avenues for future studies, particularly regarding integrating these techniques into extended reality and collaborative virtual environments.info:eu-repo/semantics/publishedVersio

Multiple roles of motor imagery during action observation

Over the last 20 years, the topics of action observation (AO) and motor imagery (MI) have been largely studied in isolation from each other, despite the early integrative account by Jeannerod (1994, 2001). Recent neuroimaging studies demonstrate enhanced cortical activity when AO and MI are performed concurrently (“AO+MI”), compared to either AO or MI performed in isolation. These results indicate the potentially beneficial effects of AO+MI, and they also demonstrate that the underlying neurocognitive processes are partly shared. We separately review the evidence for MI and AO as forms of motor simulation, and present two quantitative literature analyses that indeed indicate rather little overlap between the two bodies of research. We then propose a spectrum of concurrent AO+MI states, from congruent AO+MI where the contents of AO and MI widely overlap, over coordinative AO+MI, where observed and imagined action are different but can be coordinated with each other, to cases of conflicting AO+MI. We believe that an integrative account of AO and MI is theoretically attractive, that it should generate novel experimental approaches, and that it can also stimulate a wide range of applications in sport, occupational therapy, and neurorehabilitation