Virtual Reality Feedback Research Articles

Controlling an avatar by thought using real-time fMRI

Objective. We have developed a brain–computer interface (BCI) system based on real-time functional magnetic resonance imaging (fMRI) with virtual reality feedback. The advantage of fMRI is the relatively high spatial resolution and the coverage of the whole brain; thus we expect that it may be used to explore novel BCI strategies, based on new types of mental activities. However, fMRI suffers from a low temporal resolution and an inherent delay, since it is based on a hemodynamic response rather than electrical signals. Thus, our objective in this paper was to explore whether subjects could perform a BCI task in a virtual environment using our system, and how their performance was affected by the delay. Approach. The subjects controlled an avatar by left-hand, right-hand and leg motion or imagery. The BCI classification is based on locating the regions of interest (ROIs) related with each of the motor classes, and selecting the ROI with maximum average values online. The subjects performed a cue-based task and a free-choice task, and the analysis includes evaluation of the performance as well as subjective reports. Main results. Six subjects performed the task with high accuracy when allowed to move their fingers and toes, and three subjects achieved high accuracy using imagery alone. In the cue-based task the accuracy was highest 8–12 s after the trigger, whereas in the free-choice task the subjects performed best when the feedback was provided 6 s after the trigger. Significance. We show that subjects are able to perform a navigation task in a virtual environment using an fMRI-based BCI, despite the hemodynamic delay. The same approach can be extended to other mental tasks and other brain areas.

Virtual reality feedback cues for improvement of gait in patients with Parkinson's disease.

BackgroundOur aim was to study the effects of visual feedback cues, responding dynamically to patient's self-motion and provided through a portable see-through virtual reality apparatus, on the walking abilities of patients with Parkinson's disease.MethodsTwenty patients participated. On-line and residual effects on walking speed and stride length were measured.ResultsAttaching the visual feedback device to the patient with the display turned off showed a negligible effect of about 2%. With the display turned on, 56% of the patients improved either their walking speed, or their stride length, or both, by over 20%. After device removal, and waiting for 15 minutes, the patients were instructed to walk again: 68% of the patients showed over 20% improvement in either walking speed or stride length or both. One week after participating in the first test, 36% of the patients showed over 20% improvement in baseline performance with respect to the previous test. Some of the patients reported that they still walked on the tiles in their minds.DiscussionImprovements in walking abilities were measured in patients with Parkinson's disease using virtual reality visual feedback cues. Residual effects suggest the examination of this approach in a comprehensive therapy program.

Virtual Reality Feedback Cues for Improvement of Gait in Patients with Parkinson’s Disease

<strong>Background:</strong> Our aim was to study the effects of visual feedback cues, responding dynamically to patient’s self-motion and provided through a portable seethrough virtual reality apparatus, on the walking abilities of patients with Parkinson’s disease. <strong>Methods:</strong> Twenty patients participated. On-line and residual effects on walking speed and stride length were measured. <strong>Results:</strong> Attaching the visual feedback device to the patient with the display turned off showed a negligible effect of about 2%. With the display turned on, 56% of the patients improved either their walking speed, or their stride length, or both, by over 20%. After device removal, and waiting for 15 minutes, the patients were instructed to walk again: 68% of the patients showed over 20% improvement in either walking speed or stride length or both. One week after participating in the first test, 36% of the patients showed over 20% improvement in baseline performance with respect to the previous test. Some of the patients reported that they still walked on the tiles in their minds. <strong>Discussion:</strong> Improvements in walking abilities were measured in patients with Parkinson’s disease using virtual reality visual feedback cues. Residual effects suggest the examination of this approach in a comprehensive therapy program.

Visuomotor Gain Distortion Alters Online Motor Performance and Enhances Primary Motor Cortex Excitability in Patients With Stroke

Determine if ipsilesional primary motor cortex (M1) in stroke patients processes online visuomotor discordance in gain between finger movement and observed feedback in virtual reality (VR). Chronic stroke patients flexed (N= 7) or extended (N= 1) their finger with real-time feedback of a virtual hand presented in VR. Virtual finger excursion was scaled by applying a low-gain (G(0.25) ), high-gain (G(1.75) ), or veridical (G(1.00) ) scaling factor to real-time data streaming from a sensor glove. Effects of visuomotor discordance were assessed through analysis of movement kinematics (joint excursion, movement smoothness, and angular velocity) and amplitude of motor evoked potentials (MEPs) elicited with transcranial magnetic stimulation applied to ipsilesional M1. Data were analyzed with a repeated-measures analysis of variance (significance set at 0.05). G(0.25) discordance (relative to veridical) leads to significantly larger joint excursion, online visuomotor correction evidenced by decreased trajectory smoothness, and significantly facilitated agonist MEPs. This effect could not be explained by potential differences in motor drive (background electromyographic) or by possible differences related to joint angle or angular velocity, as these variables remained invariant across conditions at the time of MEP assessment. M1 was not significantly facilitated in the G(1.75) condition. MEPs recorded in an adjacent muscle that was not involved in the task were unaffected by visual feedback in either discordance condition. These data suggest that the neuromodulatory effects of visuomotor discordance on M1 were relatively selective. Visuomotor discordance may be used to alter movement performance and augment M1 excitability in patients following stroke. Our data illustrate that visual feedback may be a robust way to selectively modulate M1 activity. These data may have important clinical implications for the development of future VR training protocols.

The Short-Term Effects of Real-Time Virtual Reality Feedback on Motor Learning in Dance

Does virtual reality (VR) represent a useful platform for teaching real-world motor skills? In domains such as sport and dance, this question has not yet been fully explored. The aim of this study was to determine the effects of two variations of real-time VR feedback on the learning of a complex dance movement. Novice participants (n = 30) attempted to learn the action by both observing a video of an expert's movement demonstration and physically practicing under one of three conditions. These conditions were: full feedback (FULL-FB), which presented learners with real-time VR feedback on the difference between 12 of their joint center locations and the expert's movement during learning; reduced feedback (REDUCED-FB), which provided feedback on only four distal joint center locations (end-effectors); and no feedback (NO-FB), which presented no real-time VR feedback during learning. Participants' kinematic data were gathered before, immediately after, and 24 hr after a motor learning session. Movement error was calculated as the difference in the range of movement at specific joints between each learner's movement and the expert's demonstrated movement. Principal component analysis was also used to examine dimensional change across time. The results showed that the REDUCED-FB condition provided an advantage in motor learning over the other conditions: it achieved a significantly greater reduction in error across five separate error measures. These findings indicate that VR can be used to provide a useful platform for teaching real-world motor skills, and that this may be achieved by its ability to direct the learner's attention to the key anatomical features of a to-be-learned action.

Mirrored feedback in virtual reality enhances corticospinal excitability

Mirrored feedback in virtual reality enhances corticospinal excitability

Assessing range of motion to evaluate the adverse effects of ill-fitting cervical orthoses

Background context Although previous studies have primarily focused on testing the effectiveness of cervical orthoses under properly fit conditions, this study focuses on analyzing the effects of an ill-fitted cervical orthosis (Miami J). This may have significance to health-care providers in understanding the effects of an improperly fitted neck brace. Purpose The aims of this study were threefold: first, to apply virtual reality (VR) feedback control to repeatedly measure orthoses effectiveness in the primary motions; second, to use this control methodology to test the orthoses ability to restrict flexion/extension (FE) as a function of axial rotation (AR); third, to test the effects of an ill-fitting Miami J on cervical motion. Study design/setting This study combines six degrees of freedom electromagnetic trackers and VR feedback to analyze the effectiveness of common cervical orthoses under less than optimal conditions. Patient sample Twelve healthy male subjects aged 21 to 35 (mean 29.44 years, SD 6.598) years with no previous spinal cord injuries or current neck pain participated in the study. Outcome measures Cervical range of motion (CRoM) measurements were used to determine the amount of motion restriction for each of the fitted (too small, correct size, and too big) Miami J orthoses. Methods One Nest of Birds (NOB) electromagnetic sensor (Ascension Technology) was placed on the head and another on the upper back to measure motion of the head relative to the torso. The VR goggles (i-O Display Systems) were worn so that real-time feedback was available to the subject for motion control. The subject executed the primary motions of FE, AR, and lateral bending (LB) in separate sets of five trials each. Next, in combined motion, the subject axially rotated to a set point and then FE to his maximums. This entire set of motions was repeated for each (soft collar, Miami J, Miami J with chest extension, Sternal Occipital Mandibular Immobilizer (AliMed, Inc.), (SOMI and Halo) as well as the Miami J (one size too small and one size too big); the fitting of each brace was done by a board certified orthotist. A repeated measures analysis of variance was used to determine differences between the tested states (∗p=.05). Results For the validation test, the primary motions recorded for subjects wearing each cervical brace, which demonstrated that the various orthoses all restricted CRoM. The soft collar restricted less motion than the other devices, whereas the Halo restricted the most motion throughout. For the ill-fitting cervical collar comparison, motion in the correct size collar was normalized to 1.0, and the correct size allowed less motion than either the too big or too small braces. In FE, the too big brace tended to allow more motion than the too small, but only the too big brace in extension was significantly different from the correct size. In AR, the too small brace seemed to allow more motion than the too big. Both the too big and too small braces were significantly different than the correct size in both left and right AR. In LB, the too big brace and too small brace were very similar in the amount of motion they were able to restrict. Both braces were significantly different than the correct size in right LB, whereas only the too small brace was significantly different from the correct size in left LB. In the combined motion data, both the too big and too small braces allowed more motion than the correct size. The too small brace seemed to allow more FE at all degrees of AR except for extreme right AR. Conclusions To our knowledge, the effects of improperly fitted cervical orthoses on CRoM are still unknown. Using the NOB electromagnetic tracking system combined with VR feedback, we were able to consider the motion restriction of ill-fitting Miami J orthoses for both primary and combined motions. For both motion types, increased motion was possible when the subject was improperly fitted with the Miami J. If not considered, these excessive motions could potentially have detrimental effects on patient satisfaction, clinical outcomes, or even lead to increased secondary injury.

Interaction with co-located haptic feedback in virtual reality

This paper outlines a study into the effects of co-location (the term `co-location' is used throughout to refer to the co-location of haptic and visual sensory modes, except where otherwise specified) of haptic and visual sensory modes in VR simulations. The study hypothesis is that co-location of these sensory modes will lead to improved task performance within a VR environment. Technical challenges and technological limitations are outlined prior to a description of the implementation adopted for this study. Experiments were conducted to evaluate the effect on user performance of co-located haptics (force feedback) in a 3D virtual environment. Results show that co-location is an important factor, and when coupled with haptic feedback the performance of the user is greatly improved.

A REVIEW OF HAPTIC FEEDBACK IN VIRTUAL REALITY FOR MANUFACTURING INDUSTRY

This paper discusses the application of haptic feedback in Virtual Reality to enhance user performance in manufacturing industry. Haptic interfaces have the potential to enhance communication and interaction via the computer enabling affective expressive interpersonal communication and enriching interaction by haptic feedback. The aim of this study was to investigate and develop a better understanding of using haptic feedback in manufacturing. Keywords: Virtual Reality, haptic, manufacturing doi: 10.3329/jme.v40i1.3476 Journal of Mechanical Engineering, Vol. ME40, No. 1, June 2009 68-71