Motor rehabilitation using virtual reality

Negative viscosity can enhance learning of inertial dynamics

We investigated how learning of inertial load manipulation is influenced by movement amplification with negative viscosity. Using a force-feedback device, subjects trained on anisotropic loads (5 orientations) with free movements in one of three conditions (inertia only, negative viscosity only, or combined), prior to common evaluation conditions (prescribed circular pattern with inertia only). Training with Combined-Load resulted in lower error (6.89±3.25%) compared to Inertia-Only (8.40±4.32%) and Viscosity-Only (8.17±4.13%) according to radial deviation analysis (% of trial mean radius). Combined-Load and Inertia-Only groups exhibited similar unexpected no-load trials (8.38±4.31% versus 8.91±4.70% of trial mean radius), which suggests comparable low-impedance strategies. These findings are remarkable since negative viscosity, only available during training, evidently enhanced learning when combined with inertia. Modeling analysis suggests that a feedforward after-effect of negative viscosity cannot predict such performance gains. Instead, results from Combined-Load training are consistent with greater feedforward inertia compensation along with a small increase in impedance control. The capability of the nervous system to generalize learning from negative viscosity suggests an intriguing new method for enhancing sensorimotor adaptation.

Interactive computer play in rehabilitation of children with sensorimotor disorders: a systematic review

The aim of this review was to examine systematically the evidence for the application of interactive computer play in the rehabilitation of children with sensorimotor disorders. A literature search of 11 electronic databases was conducted to identify articles published between January 1995 and May 2008. The review was restricted to reports of intervention studies evaluating the impact of interactive computer play on motor rehabilitation in children. For each study the quality of the methods and the strength of the evidence were assessed by two independent reviewers using the guidelines of the American Academy for Cerebral Palsy and Developmental Medicine. A total of 74 articles were identified, of which 16 met the inclusion criteria. Three studies were randomized controlled trials (RCTs) and half were case series or case reports. Areas investigated were movement quality, spatial orientation and mobility, and motivational aspects. Thirteen studies presented positive findings. Two of the three RCTs investigating movement quality and one level III study examining spatial orientation showed no significant improvements. Interactive computer play is a potentially promising tool for the motor rehabilitation of children but the level of evidence is too limited to assess its value fully. Further and more convincing research is needed.

Technology-assisted training of arm-hand skills in stroke: concepts on reacquisition of motor control and therapist guidelines for rehabilitation technology design

Background

It is the purpose of this article to identify and review criteria that rehabilitation technology should meet in order to offer arm-hand training to stroke patients, based on recent principles of motor learning.

Methods

A literature search was conducted in PubMed, MEDLINE, CINAHL, and EMBASE (1997–2007).

Results

One hundred and eighty seven scientific papers/book references were identified as being relevant. Rehabilitation approaches for upper limb training after stroke show to have shifted in the last decade from being analytical towards being focussed on environmentally contextual skill training (task-oriented training). Training programmes for enhancing motor skills use patient and goal-tailored exercise schedules and individual feedback on exercise performance. Therapist criteria for upper limb rehabilitation technology are suggested which are used to evaluate the strengths and weaknesses of a number of current technological systems.

Conclusion

This review shows that technology for supporting upper limb training after stroke needs to align with the evolution in rehabilitation training approaches of the last decade. A major challenge for related technological developments is to provide engaging patient-tailored task oriented arm-hand training in natural environments with patient-tailored feedback to support (re) learning of motor skills.

Sensorimotor training in virtual reality: a review

Recent experimental evidence suggests that rapid advancement of virtual reality (VR) technologies has great potential for the development of novel strategies for sensorimotor training in neurorehabilitation. We discuss what the adaptive and engaging virtual environments can provide for massive and intensive sensorimotor stimulation needed to induce brain reorganization.Second, discrepancies between the veridical and virtual feedback can be introduced in VR to facilitate activation of targeted brain networks, which in turn can potentially speed up the recovery process. Here we review the existing experimental evidence regarding the beneficial effects of training in virtual environments on the recovery of function in the areas of gait,upper extremity function and balance, in various patient populations. We also discuss possible mechanisms underlying these effects. We feel that future research in the area of virtual rehabilitation should follow several important paths. Imaging studies to evaluate the effects of sensory manipulation on brain activation patterns and the effect of various training parameters on long term changes in brain function are needed to guide future clinical inquiry. Larger clinical studies are also needed to establish the efficacy of sensorimotor rehabilitation using VR in various clinical populations and most importantly, to identify VR training parameters that are associated with optimal transfer to real-world functional improvements.

Use of a low-cost, commercially available gaming console (Wii) for rehabilitation of an adolescent with cerebral palsy

BACKGROUND AND PURPOSE

The purpose of this retrospective and prospective case report is to describe the feasibility and outcomes of using a low-cost, commercially available gaming system (Wii) to augment the rehabilitation of an adolescent with cerebral palsy.

PATIENT AND SETTING

The patient was an adolescent with spastic diplegic cerebral palsy classified as GMFCS level III who was treated during a summer session in a school-based setting.

INTERVENTION

The patient participated in 11 training sessions, 2 of which included other players. Sessions were between 60 and 90 minutes in duration. Training was performed using the Wii sports games software, including boxing, tennis, bowling, and golf. He trained in both standing and sitting positions.

OUTCOMES

Three main outcome measures were used: (1) visual-perceptual processing, using a motor-free perceptual test (Test of Visual Perceptual Skills, third edition); (2) postural control, using weight distribution and sway measures; and (3) functional mobility, using gait distance. Improvements in visual-perceptual processing, postural control, and functional mobility were measured after training.

DISCUSSION AND CONCLUSION

The feasibility of using the system in the school-based setting during the summer session was supported. For this patient whose rehabilitation was augmented with the Wii, there were positive outcomes at the impairment and functional levels. Multiple hypotheses were proposed for the findings that may be the springboard for additional research. To the authors' knowledge, this is the first published report on using this particular low-cost, commercially available gaming technology for rehabilitation of a person with cerebral palsy.

Observing virtual arms that you imagine are yours increases the galvanic skin response to an unexpected threat

Multi-modal visuo-tactile stimulation of the type performed in the rubber hand illusion can induce the brain to temporarily incorporate external objects into the body image. In this study we show that audio-visual stimulation combined with mental imagery more rapidly elicits an elevated physiological response (skin conductance) after an unexpected threat to a virtual limb, compared to audio-visual stimulation alone. Two groups of subjects seated in front of a monitor watched a first-person perspective view of slow movements of two virtual arms intercepting virtual balls rolling towards the viewer. One group was instructed to simply observe the movements of the two virtual arms, while the other group was instructed to observe the virtual arms and imagine that the arms were their own. After 84 seconds the right virtual arm was unexpectedly “stabbed” by a knife and began “bleeding”. This aversive stimulus caused both groups to show a significant increase in skin conductance. In addition, the observation-with-imagery group showed a significantly higher skin conductance (p<0.05) than the observation-only group over a 2-second period shortly after the aversive stimulus onset. No corresponding change was found in subjects' heart rates. Our results suggest that simple visual input combined with mental imagery may induce the brain to measurably temporarily incorporate external objects into its body image.

Motor control learning in chronic low back pain

STUDY DESIGN

A randomized prospective cohort study of participants with chronic low back pain, seeking physical therapy, with follow-up at weeks 6 and 28. Effects of conventional physiotherapy and physiotherapy with the addition of postural biofeedback were compared.

OBJECTIVE

To evaluate the benefits of postural biofeedback in chronic low back pain participants.

SUMMARY OF BACKGROUND DATA

Biofeedback using electromyographic signals has been used in chronic low back pain with mixed results. Postural feedback had not been previously used.

METHODS

Demographic and psychological baseline data along with range of motion were analyzed from a sample of 47 chronic participants with low back pain randomized into conventional physiotherapy with or without the addition of postural biofeedback.

RESULTS

After 6 months, there were 21 dropouts. The participants with biofeedback had markedly improved status in visual analog pain scales, short form-36, and range of motion.

CONCLUSION

The study strongly suggests that postural feedback is a useful adjunct to conventional physiotherapy of chronic low back pain participants.

Novel design of interactive multimodal biofeedback system for neurorehabilitation

A previous design of a biofeedback system for Neurorehabilitation in an interactive multimodal environment has demonstrated the potential of engaging stroke patients in task-oriented neuromotor rehabilitation. This report explores the new concept and alternative designs of multimedia based biofeedback systems. In this system, the new interactive multimodal environment was constructed with abstract presentation of movement parameters. Scenery images or pictures and their clarity and orientation are used to reflect the arm movement and relative position to the target instead of the animated arm. The multiple biofeedback parameters were classified into different hierarchical levels w.r.t. importance of each movement parameter to performance. A new quantified measurement for these parameters were developed to assess the patient's performance both real-time and offline. These parameters were represented by combined visual and auditory presentations with various distinct music instruments. Overall, the objective of newly designed system is to explore what information and how to feedback information in interactive virtual environment could enhance the sensorimotor integration that may facilitate the efficient design and application of virtual environment based therapeutic intervention.

Interactive priming enhanced by negative damping aids learning of an object manipulation task

We investigated how free interaction with an object influences the formation of motor planning. Subjects controlled a force-feedback planar manipulandum that presented simulated anisotropic inertial forces. As a performance evaluation, subjects made circular movements about a prescribed track. In order to investigate potential enhancement of motor planning, we introduced negative damping during an "interactive priming" phase prior to task performance. As a control, we presented a second subject group with normal interactive priming. Our results showed significantly greater reduction in maximum curvature error for the subject group that received enhanced priming (two-tailed T-test, p=1.86e-6) compared to the control group. Group-I demonstrated a 34.8% reduction in error while Group-II achieved 5.78% reduction. We also observed that the presentation of enhanced priming evidently caused a greater sensitivity to catch trials compared to the control. Group-I demonstrated a larger increase (92.0%) in maximum curvature error in catchtrials (with respect to baseline), compared to Group-II (50.8%) during early training (two-tailed T-test, p=1.9e-3). These results suggest that some forms of augmentation to task dynamics - leading to the exploration of a broader state space -can help the accelerate the learning of control strategies suitable for an unassisted environment. The finding is also consistent with the hypothesis that subjects can decompose the environment impedance into acceleration and velocity dependent elements.

Virtual reality-based approaches to enable walking for people poststroke

Several approaches have been developed and implemented to use virtual reality for rehabilitation of walking for people poststroke. The purpose of this article is to compare and contrast these approaches by describing the virtual reality technology and evaluating the evidence to support its use. Early findings are encouraging but await verification, refinement, and extension.

Evaluation of virtual shopping in the VMall: comparison of post-stroke participants to healthy control groups

OBJECTIVE

To investigate the potential use of the VMall as an evaluation tool for rehabilitation by (1) describing its use with 14 post-stroke participants and (2) by comparing performance within the VMall of the post-stroke participants to healthy control participants.

DESIGN

Criterion standard.

SETTING

University of Haifa and the Chaim Sheba Medical Center.

PARTICIPANTS

Fourteen post-stroke participants and 93 healthy participants from three age groups (children, young adults and older adults).

PROCEDURE

The participants experienced the VMall and shopped for four grocery items and then completed feedback questionnaires.

MAIN OUTCOME MEASURES

The experience of the stroke participants is described in detail. The duration and number of mistakes made during a four-item shopping task within the VMall, overall feedback, and perceived exertion.

RESULTS

Significant differences were found between each of the three healthy groups and the stroke group for the mean total time to shop (F(3,97) = 23.28, P < 0.000). The participants' overall feedback on the VMall was positive with no differences between the groups.

CONCLUSIONS

The VMall as used with the four-item shopping task was found to significantly differentiate between healthy to stroke participants. The shopping task was challenging for the stroke participants which have positive implications for treatment effectiveness.

Development and user evaluation of a virtual rehabilitation system for wobble board balance training

We have developed a prototype virtual reality-based balance training system using a single inertial orientation sensor attached to the upper surface of a wobble board. This input device has been interfaced with Neverball, an open source computer game to create the balance training platform. Users can exercise with the system by standing on the wobble board and tilting it in different directions to control an on-screen environment. We have also developed a customized instruction manual to use when setting up the system. To evaluate the usability our prototype system we undertook a user evaluation study with twelve healthy novice participants. Participants were required to assemble the system using an instruction manual and then perform balance exercises with the system. Following this period of exercise VRUSE, a usability evaluation questionnaire, was completed by participants. Results indicated a high level of usability in all categories evaluated.

Effects of visually simulated roll motion on vection and postural stabilization

Background

Visual motion often provokes vection (the induced perception of self-motion) and postural movement. Postural movement is known to increase during vection, suggesting the same visual motion signal underlies vection and postural control. However, self-motion does not need to be consciously perceived to influence postural control. Therefore, visual motion itself may affect postural control mechanisms. The purpose of the present study was to investigate the effects of visual motion and vection on postural movements during and after exposure to a visual stimulus motion.

Methods

Eighteen observers completed four experimental conditions, the order of which was counterbalanced across observers. Conditions corresponded to the four possible combinations of rotation direction of the visually simulated roll motion stimulus and the two different visual stimulus patterns. The velocity of the roll motion was held constant in all conditions at 60 deg/s. Observers assumed the standard Romberg stance, and postural movements were measured using a force platform and a head position sensor affixed to a helmet they wore. Observers pressed a button when they perceived vection. Postural responses and psychophysical parameters related to vection were analyzed.

Results

During exposure to the moving stimulus, body sway and head position of all observers moved in the same direction as the stimulus. Moreover, they deviated more during vection perception than no-vection-perception, and during no-vection-perception than no-visual-stimulus-motion. The postural movements also fluctuated more during vection-perception than no-vection-perception, and during no-vection-perception than no-visual-stimulus-motion, both in the left/right and anterior/posterior directions. There was no clear habituation for vection and posture, and no effect of stimulus type.

Conclusion

Our results suggested that visual stimulus motion itself affects postural control, and supported the idea that the same visual motion signal is used for vection and postural control. We speculated that the mechanisms underlying the processing of visual motion signals for postural control and vection perception operate using different thresholds, and that a frame of reference for body orientation perception changed along with vection perception induced further increment of postural sway.

Relationships between sensory stimuli and autonomic nervous regulation during real and virtual exercises

BACKGROUND

Application of virtual environment (VE) technology to motor rehabilitation increases the number of possible rehabilitation tasks and/or exercises. However, enhancing a specific sensory stimulus sometimes causes unpleasant sensations or fatigue, which would in turn decrease motivation for continuous rehabilitation. To select appropriate tasks and/or exercises for individuals, evaluation of physical activity during recovery is necessary, particularly the changes in the relationship between autonomic nervous activity (ANA) and sensory stimuli.

METHODS

We estimated the ANA from the R-R interval time series of electrocardiogram and incoming sensory stimuli that would activate the ANA. For experiments in real exercise, we measured vehicle data and electromyogram signals during cycling exercise. For experiments in virtual exercise, we measured eye movement in relation to image motion vectors while the subject was viewing a mountain-bike video image from a first-person viewpoint.

RESULTS

For the real cycling exercise, the results were categorized into four groups by evaluating muscle fatigue in relation to the ANA. They suggested that fatigue should be evaluated on the basis of not only muscle activity but also autonomic nervous regulation after exercise. For the virtual exercise, the ANA-related conditions revealed a remarkable time distribution of trigger points that would change eye movement and evoke unpleasant sensations.

CONCLUSION

For expanding the options of motor rehabilitation using VE technology, approaches need to be developed for simultaneously monitoring and separately evaluating the activation of autonomic nervous regulation in relation to neuromuscular and sensory systems with different time scales.

Virtual reality in stroke rehabilitation: still more virtual than real

PURPOSE

To assess the utility of virtual reality (VR) in stroke rehabilitation.

METHOD

The Medline, Proquest, AMED, CINAHL, EMBASE and PsychInfo databases were electronically searched from inception/1980 to February 2005, using the keywords: Virtual reality, rehabilitation, stroke, physiotherapy/physical therapy and hemiplegia. Articles that met the study's inclusion criteria were required to: (i) be published in an English language peer reviewed journal, (ii) involve the use of VR in a stroke rehabilitation setting; and (iii) report impairment and/or activity oriented outcome measures. Two assessors independently assessed each study's quality using the American Academy for Cerebral Palsy and Developmental Medicine (AACPDM) grading system.

RESULTS

Eleven papers met the inclusion criteria: Five addressed upper limb rehabilitation, three gait and balance, two cognitive interventions, and one both upper and lower limb rehabilitation. Three were judged to be AACPDM Level I/Weak, two Level III/Weak, three Level IV/Weak and three Level V quality of evidence. All articles involved before and after interventions; three randomized controlled trials obtained statistical significance, the remaining eight studies found VR-based therapy to be beneficial. None of the studies reported any significant adverse effects.

CONCLUSION

VR is a potentially exciting and safe tool for stroke rehabilitation but its evidence base is too limited by design and power issues to permit a definitive assessment of its value. Thus, while the findings of this review are generally positive, the level of evidence is still weak to moderate, in terms of research quality. Further study in the form of rigorous controlled studies is warranted.

Virtual reality for mobility devices: training applications and clinical results: a review

Virtual reality technology is an emerging technology that possibly can address the problems encountered in training (elderly) people to handle a mobility device. The objective of this review was to study different virtual reality training applications as well as their clinical implication for patients with mobility problems. Computerized literature searches were performed using the MEDLINE, Cochrane, CIRRIE and REHABDATA databases. This resulted in eight peer reviewed journal articles. The included studies could be divided into three categories, on the basis of their study objective. Five studies were related to training driving skills, two to physical exercise training and one to leisure activity. This review suggests that virtual reality is a potentially useful means to improve the use of a mobility device, in training one's driving skills, for keeping up the physical condition and also in a way of leisure time activity. Although this field of research appears to be in its early stages, the included studies pointed out a promising transfer of training in a virtual environment to the real-life use of mobility devices.

Assessing mechanisms of recovery during robot-aided neurorehabilitation of the upper limb

OBJECTIVE

The present study aimed to qualify and quantify the different components of motor recovery in a group of stroke patients treated by robot-aided techniques. In addition, the learning model of each motor recovery component was analyzed.

METHODS

Two groups of poststroke patients were treated with the use of an elbow-shoulder manipulator, respectively, within (recent) and after (chronic) the first 6 months of their cerebrovascular accident. Both groups were evaluated by means of standard clinical assessment scales and a robot-measured evaluation method.

RESULTS

These findings confirm that motor training consisting of voluntary movements assisted by the robot device led to significant improvements in motor performance in terms of the kinematic and dynamic components of the arm movements. This corresponded to improvement of impairment as confirmed by the clinical scale results.

CONCLUSIONS

Knowledge of the recovery components and of the associated performance acquisition model may be useful in assessing and training stroke patients and should make it possible to precisely plan and, if necessary, modify the rehabilitation strategies.

Aging and selective sensorimotor strategies in the regulation of upright balance

Background

The maintenance of upright equilibrium is essentially a sensorimotor integration task. The central nervous system (CNS) has to generate appropriate and complex motor responses based on the selective and rapid integration of sensory information from multiple sources. Since each sensory system has its own coordinate framework, specific time delay and reliability, sensory conflicts may arise and represent situations in which the CNS has to recalibrate the weight attributed to each particular sensory input. The resolution of sensory conflicts may represent a particular challenge for older adults given the age-related decline in the integrity of many postural regulating systems, including musculoskeletal and sensory systems, as well as neural processing and conduction of information. The effects of aging and adaptation (by repeated exposures) on the capability of the CNS to select pertinent sensory information and resolve sensory conflicts were thus investigated with virtual reality (VR) in the present study.

Methods

Healthy young and older adults maintained quiet stance while immersed in a virtual environment (VE) for 1 hour during which transient visual and/or surface perturbations were randomly presented. Visual perturbations were induced by sudden pitch or roll plane tilts of the VE viewed through a helmet-mounted display, and combined with or without surface perturbations presented in a direction that was either identical or opposite to the visual perturbations.

Results

Results showed a profound influence of aging on postural adjustments measured by electromyographic (EMG) responses and displacements of the center of pressure (COP) and body's center of mass (COM) in the recovery of upright stance, especially in the presence of sensory conflicts. Older adults relied more on vision as compared to young adults. Aging affects the interaction of the somatosensory and visual systems on the control of equilibrium during standing and the ability of CNS to resolve sensory conflicts. However, even with a one-hour immersion in VE and exposure to sensory conflicts, it is possible for the CNS to recalibrate and adapt to the changes, while improving balance capability in older adults.

Conclusion

Preventive and rehabilitation programs targeting postural control in older adults should take into account the possible impairment of sensory organization or sensorimotor integration and include VE training under conditions of sensory conflicts.

A kinematic analysis of a haptic handheld stylus in a virtual environment: a study in healthy subjects

Background

Virtual Reality provides new options for conducting motor assessment and training within computer-generated 3 dimensional environments. To date very little has been reported about normal performance in virtual environments. The objective of this study was to evaluate the test-retest reliability of a clinical procedure measuring trajectories with a haptic handheld stylus in a virtual environment and to establish normative data in healthy subjects using this haptic device.

Methods

Fifty-eight normal subjects; aged from 20 to 69, performed 3 dimensional hand movements in a virtual environment using a haptic device on three occasions within one week. Test-retest stability and standardized normative data were obtained for all subjects.

Results

No difference was found between test and retest. The limits of agreement revealed that changes in an individual's performance could not be detected. There was a training effect between the first test occasion and the third test occasion. Normative data are presented.

Conclusion

A new test was developed for recording the kinematics of the handheld haptic stylus in a virtual environment. The normative data will be used for purposes of comparison in future assessments, such as before and after training of persons with neurological deficits.

Functional balance and dual-task reaction times in older adults are improved by virtual reality and biofeedback training

Virtual reality (VR) training has been used successfully to rehabilitate functional balance and mobility in both traumatic brain injury (TBI) survivors and elderly subjects. Similarly, computer-based biofeedback (BF) training has resulted in decreased sway during quiet stance and decreased reaction times during a dual-task reaction time paradigm in elderly subjects. The objective of this study was to determine the effect of VR and BF training on balance and reaction time in older adults. Two groups of twelve healthy older adults completed 10-week training programs consisting of two 30-min sessions per week. VR training required that participants lean sideways to juggle a virtual ball. Participants in the BF group viewed a red dot representing their center of gravity on a screen and were required to move the dot to the four corners of the monitor. Measures of functional balance and mobility (Community Balance and Mobility Scale [CB&M]), sway during quiet stance, and reaction time during a dual task paradigm were recorded before training, as well as 1 week and 1 month after the end of the program. Both groups showed significant improvements on the CB&M, as well as decreased reaction times with training. Postural sway during quiet stance did not change significantly.

Field of view and base of support width influence postural responses to visual stimuli during quiet stance

We explored the destabilizing effect of visual field motion as the base of support (BOS) and the field of view (FOV) were narrowed. Visual field motion was achieved using an immersive virtual environment (scene) that moved realistically with head motion (natural motion) and translated sinusoidally at 0.1Hz in the fore-aft direction (augmented motion). Natural motion was presented in stereo while augmented motion was presented in both stereo and non-stereo. Subjects viewed scene motion under wide (90 degrees and 55 degrees in the horizontal and vertical directions) and narrow (25 degrees in both directions) FOV conditions while standing flatfooted (100% BOS) and on two blocks (45% and 35% BOS). Head and whole body center of mass (COM) and ankle angle root mean square (RMS) were determined as were head, whole body, and shank COM FFTs. During natural motion, the primary effect emerged in the head RMS which was significantly smaller with a 35% BOS and the wide FOV compared to the narrow FOV. However, the primary effect of augmented motion emerged in the power analysis of head and whole body COM which significantly increased with the wide FOV for a 35% BOS compared to 100% BOS. Statistical analysis indicated an effect of BOS on depth perception for head and whole body RMS; however, post hoc comparisons revealed no significant differences between stereo and non-stereo augmented motion. We conclude that reducing the BOS increased reliance on peripheral visual information to stabilize the head in space even when the augmented visual motion promoted postural instability.

Head-Mounted Displays for Clinical Virtual Reality Applications: Pitfalls in Understanding User Behavior while Using Technology

The use of virtual environments with head-mounted displays (HMDs) offers unique assets to the evaluation and therapy of clinical populations. However, research examining the effects of this technology on clinical populations is sparse. Understanding how wearers interact with the HMD is vital. Discomfort leads to altered use of the HMD that could confound performance measures; the very measures which might be used as tools for clinical decision making. The current study is a post-hoc analysis of the relationship between HMD use and HMD comfort. The analysis was conducted to examine contributing factors for a high incidence of simulator sickness observed in an HMD-based driving simulator. Pearson correlation analysis was used to evaluate objective and subjective measures of HMD performance and self-reported user comfort ratings. The results indicated weak correlations between these variables, indicating the complexity of quantifying user discomfort and HMD performance. Comparison of two case studies detailing user behavior in the virtual environment demonstrates that selected variables may not capture how individuals use the HMD. The validity and usefulness of the HMD-based virtual environments must be understood to fully reap the benefits of virtual reality (VR) in rehabilitation medicine.

Recent developments in biofeedback for neuromotor rehabilitation

The original use of biofeedback to train single muscle activity in static positions or movement unrelated to function did not correlate well to motor function improvements in patients with central nervous system injuries. The concept of task-oriented repetitive training suggests that biofeedback therapy should be delivered during functionally related dynamic movement to optimize motor function improvement. Current, advanced technologies facilitate the design of novel biofeedback systems that possess diverse parameters, advanced cue display, and sophisticated control systems for use in task-oriented biofeedback. In light of these advancements, this article: (1) reviews early biofeedback studies and their conclusions; (2) presents recent developments in biofeedback technologies and their applications to task-oriented biofeedback interventions; and (3) discusses considerations regarding the therapeutic system design and the clinical application of task-oriented biofeedback therapy. This review should provide a framework to further broaden the application of task-oriented biofeedback therapy in neuromotor rehabilitation.