Visual feedback improves movement illusions induced by tendon vibration after chronic stroke

Background Illusion of movement induced by tendon vibration is commonly used in rehabilitation and seems valuable for motor rehabilitation after stroke, by playing a role in cerebral plasticity. The aim was to study if congruent visual cues using Virtual Reality (VR) could enhance the illusion of movement induced by tendon vibration of the wrist among participants with stroke. Methods We included 20 chronic stroke participants. They experienced tendon vibration of their wrist (100 Hz, 30 times) inducing illusion of movement. Three VR visual conditions were added to the vibration: a congruent moving virtual hand (Moving condition); a static virtual hand (Static condition); or no virtual hand at all (Hidden condition). The participants evaluated for each visual condition the intensity of the illusory movement using a Likert scale, the sensation of wrist’s movement using a degree scale and they answered a questionnaire about their preferred condition. Results The Moving condition was significantly superior to the Hidden condition and to the Static condition in terms of illusion of movement (p < 0.001) and the wrist’s extension (p < 0.001). There was no significant difference between the Hidden and the Static condition for these 2 criteria. The Moving condition was considered the best one to increase the illusion of movement (in 70% of the participants). Two participants did not feel any illusion of movement. Conclusions This study showed the interest of using congruent cues in VR in order to enhance the consistency of the illusion of movement induced by tendon vibration among participants after stroke, regardless of their clinical severity. By stimulating the brain motor areas, this visuo-proprioceptive feedback could be an interesting tool in motor rehabilitation. Record number in Clinical Trials: NCT04130711, registered on October 17th 2019 (https://clinicaltrials.gov/ct2/show/NCT04130711?id=NCT04130711&draw=2&rank=1).

Influence of virtual reality visual feedback on the illusion of movement induced by tendon vibration of wrist in healthy participants

Introduction Illusion of movement induced by tendon vibration is an effective approach for motor and sensory rehabilitation in case of neurological impairments. The aim of our study was to investigate which modality of visual feedback in Virtual Reality (VR) associated with tendon vibration of the wrist could induce the best illusion of movement. Methods We included 30 healthy participants in the experiment. Tendon vibration inducing illusion of movement (wrist extension, 100Hz) was applied on their wrist during 3 VR visual conditions (10 times each): a moving virtual hand corresponding to the movement that the participants could feel during the tendon vibration (Moving condition), a static virtual hand (Static condition), or no virtual hand at all (Hidden condition). After each trial, the participants had to quantify the intensity of the illusory movement on a Likert scale, the subjective degree of extension of their wrist and afterwards they answered a questionnaire. Results There was a significant difference between the 3 visual feedback conditions concerning the Likert scale ranking and the degree of wrist’s extension (p<0.001). The Moving condition induced a higher intensity of illusion of movement and a higher sensation of wrist’s extension than the Hidden condition (p<0.001 and p<0.001 respectively) than that of the Static condition (p<0.001 and p<0.001 respectively). The Hidden condition also induced a higher intensity of illusion of movement and a higher sensation of wrist’s extension than the Static condition (p<0.01 and p<0.01 respectively). The preferred condition to facilitate movement’s illusion was the Moving condition (63.3%). Conclusions This study demonstrated the importance of carefully selecting a visual feedback to improve the illusion of movement induced by tendon vibration, and the increase of illusion by adding VR visual cues congruent to the illusion of movement. Further work will consist in testing the same hypothesis with stroke patients.

Acquired nystagmus

Nystagmus is the repetitive to and fro movement of the eyes, which may be physiological or pathological. The movements can be horizontal, vertical, torsional or a combination of these movements. It starts by a slow movement of the eye away from the visual target. The second movement brings the eye back to the visual target. If this second movement is quick, the nystagmus is called jerk nystagmus. If the second movement is slow, the nystagmus is said to be pendular. Maintaining steady gaze is dependent upon visual fixation, the vestibulo-ocular reflex and the gaze-holding neural integrator system. Pathological nystagmus typically presents with the symptom of oscillopsia, which is the illusory movement of the surrounding environment. Nystagmus that develops outside of early infancy is termed acquired nystagmus. There may be serious underlying pathology that will require further investigation and management. This article reviews the terminology, pathophysiology, causes and treatment of acquired nystagmus.

Imagination der Bewegung durch Vibrationsreize – ein neuer Ansatz in der Frühmobilisation auf der Intensivstation?

Zusammenfassung Die Optimierung der motorischen Leistung und die Einbindung und Vernetzung bisher nicht verwendeter motorischer Einheiten sowie die vermehrte Ausschüttung neurotropher Faktoren sind zentrale Mechanismen der Vibrationswirkung, die therapeutisch auf einzelne Körperteile oder den gesamten Körper angewendet werden können. Eine Möglichkeit, die Frühmobilisation bei kritisch kranken Patienten effektiver zu gestalten und immobilitätsbedingten Veränderungen vorzubeugen, könnte die Verwendung des Vibramoov™-Systems sein. Gezielt programmierte Vibrationssequenzen stimulieren hier das Nervensystem mit sensorischen Informationen, die die Empfindung einer Bewegung nachahmen (z. B. des Gehens) und somit Regenerations- und Reor-ganisationsprozesse im zentralen Nervensystem unterstützen können. Von Bedeutung ist dieser Therapieansatz vor allem bei Patienten, bei denen aufgrund ihres Zustandes konventionelle Maßnahmen nicht oder nur eingeschränkt durchgeführt werden können. Da bisher keine Erfah-rungen zur Anwendung bei intensivpflichtigen Patienten verfügbar sind, wurde eine Pilotstudie durchgeführt mit der Fragestellung, ob diese Therapieform sicher ist und im normalen Betrieb auf der Intensivstation verwendet werden kann. Die Ergebnisse der Pilotstudie mit fünf Patienten zei-gen, dass die Anwendung von Vibramoov™ zu keiner wesentlichen Veränderung kardiopulmo-naler Parameter im Sinne einer Non-Toleranz führte und im klinischen Setting gut umsetzbar war. Schlüsselwörter: Frührehabilitation, Imagination von Bewegung, Intensivstation, Vibramoov™ Imagination of movement through vibrational stimuli – a new approach to early mobilization in intensive care units? A pilot study Abstract The optimization of motor performance and the integration and networking of previously unused motor units, as well as the increased release of neurotrophic factors, are central mechanisms related to the vibration effect that can be applied therapeutically to individual parts of the body or to the entire body. One way to make early mobilization more effective in critically ill patients and to prevent changes due to immobility could be rehabilitation with functional proprioceptive stimulation, also known as “illusory movement”. Specifically programmed vibration sequences stimulate the nervous system with sensory information that mimics the sensation of movement (e. g., walking) and can thus support regeneration and reorganization processes in the central nervous system. This therapeutic approach is particularly important for patients who, due to their condition, cannot – or only to a limited extent – carry out conventional measures. Since no experience has so far been available for use in intensive care patients, we carried out a pilot study to answer the question of whether this form of therapy can be used safely and in normal operations in the intensive care unit. The results of the pilot study with 5 patients showed that the use of Vibramoov™ did not lead to any significant change in cardiopulmonary parameters in terms of non-tolerance and was easy to implement in a clinical setting. Keywords: early rehabilitation, illusory movements, ICU, functional proprio-ceptive stimulation

Optimal visuotactile integration for velocity discrimination of self-hand movements

Illusory hand movements can be elicited by a textured disk or a visual pattern rotating under one's hand, while proprioceptive inputs convey immobility information (Blanchard C, Roll R, Roll JP, Kavounoudias A. PLoS One 8: e62475, 2013). Here, we investigated whether visuotactile integration can optimize velocity discrimination of illusory hand movements in line with Bayesian predictions. We induced illusory movements in 15 volunteers by visual and/or tactile stimulation delivered at six angular velocities. Participants had to compare hand illusion velocities with a 5°/s hand reference movement in an alternative forced choice paradigm. Results showed that the discrimination threshold decreased in the visuotactile condition compared with unimodal (visual or tactile) conditions, reflecting better bimodal discrimination. The perceptual strength (gain) of the illusions also increased: the stimulation required to give rise to a 5°/s illusory movement was slower in the visuotactile condition compared with each of the two unimodal conditions. The maximum likelihood estimation model satisfactorily predicted the improved discrimination threshold but not the increase in gain. When we added a zero-centered prior, reflecting immobility information, the Bayesian model did actually predict the gain increase but systematically overestimated it. Interestingly, the predicted gains better fit the visuotactile performances when a proprioceptive noise was generated by covibrating antagonist wrist muscles. These findings show that kinesthetic information of visual and tactile origins is optimally integrated to improve velocity discrimination of self-hand movements. However, a Bayesian model alone could not fully describe the illusory phenomenon pointing to the crucial importance of the omnipresent muscle proprioceptive cues with respect to other sensory cues for kinesthesia.