VREs can even propose to replace the own body with a virtual representation. The illusion of having i. For instance, manipulations of the bodily self can be used to examine the brain mechanisms that support body perception and integration in healthy subjects [ 26 ] and in the context of diverse pathologies, ranging from eating disorders [ 27 ] to neuropathic pain in paraplegia [ 28 ].
This sense of embodiment has been suggested to consist of three illusory components: the sense of self-location, the sense of agency, and the sense of body ownership [ 29 ].
The Virtual Embodied
Several conceptual models have been proposed to address how our nervous system decides to accept a fake e. A combination of Bayesian models characterizing bottom-up and top-down neural processes seems to explain bodily illusions obtained via VREs [ 26 , 30 , 31 ]. While the illusion of presence can be easily generated by simply exposing the participant to an immersive virtual environment, the illusions related to the own body our physical link to the outside world require higher levels of sensorimotor contingencies.
Plausibility, place and virtual embodiment illusions together are probably the key differentiation elements of VREs versus other existing media and experiences. Although virtual embodiment i. Therefore, the occurrence of embodiment presupposes a certain level of presence, sensorimotor contingencies and plausibility illusion. Indeed, while high levels of presence can be achieved with none or low embodiment level, e.
Strategies to measure the quality and strength of VREs and their components are currently shifting from subjective scales usually questionnaires to more objective behavioral and neurophysiological measures. For instance, event-related brain potentials have been suggested as a non-subjective measure of virtual embodiment [ 33 ]. In that study, brain activity in the motor cortex and readiness potential negativity were observed when an embodied virtual hand was threatened but not the real hand , which was associated with the intention of the participant to move away the threatened virtual hand to avoid harm.
Other examples of bodily responses used to measure the illusions generated in VREs include changes in electro-dermal activity galvanic skin response , pupil dilation or skin temperature see summary in [ 34 ]. However, all these measures mostly represent indirect measures of the assessed element, as illusions like presence or body illusions are subjective experiences qualia arising from multisensory stimulation, which cannot be directly measured [ 17 ].
Historically, goggles or HMDs, motion capture and haptic gloves have been considered the identification signs for virtual reality. Gonzalez-Franco and Lanier recently suggested that the minimum instrumentation requirements to support illusory VREs should include continuously updated multisensory feedback at least visual with congruent sensorimotor contingencies to prevent violations of brain expectations [ 22 ].
Although stereoscopic 3D images displayed in highly immersive HMD are more effective in generating a strong and continuous VRE, wearing an HMD or 3D goggles does not guarantee having strong VREs unless the other components interaction, sensorimotor contingencies, illusions also take place. Conversely, VREs can also be experienced on flat screens despite their lower level of immersion.
Indeed, the recent new boom of virtual reality starting in is related to the mass-market arrival of two technologies initially developed for virtual reality applications: HMDs and, to a lesser extent, motion capture systems. The gaming industry is particularly taking advantage of both technologies, in a field where interaction has been traditionally two-dimensional and non-natural either with a simple mouse or with game controllers.
In return, low-cost 3D motion tracking systems that were originally developed for gaming Microsoft Kinect and computer interaction LeapMotion are populating todays VRS, underlining an increasing confluence of these related fields. By adding different VRS elements, the user can interact with the environment and its content including persons to increase the number and strength of sensorimotor contingencies. To integrate new interactions and sensorimotor contingencies into VREs, new tools are continuously widening the list of VRS components.
Indeed, VRS have also borrowed advanced tools from other fields ranging from human- and brain-computer interaction, e.
The Virtual Embodied: Practice, Presence, Technology - Google Books
These signals can be used to measure different aspects of the VRE or to control exposure to adaptive virtual environments, e. Slater and colleagues have recently published a guide with the technical and experimental building blocks required to generate powerful VREs, in particular embodiment illusions, ranging from motion capture to brain-computer interfaces [ 34 ].
VREs enclose many advantages for healthcare applications, in particular for neurorehabilitation.
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VREs can deliver sensorimotor training able to engage brain motor and perceptual areas as body-related visual feedback alone or in combination with other multisensory stimulation, e. VREs using embodied feedback allow for manipulations of a virtual body that could have implications for neurorehabilitation [ 37 ].
Indeed, a critical ability of VREs is the possibility to promote changes in the perception of the own body by means of an illusion of ownership of a virtual body. For instance, illusions based on multisensory correlations can be extremely useful to apply VRE-based mirror visual feedback [ 38 ] and action-observation therapy for motor rehabilitation post stroke [ 39 ]. A recent study has shown that chronic stroke participants are more sensitive to embodiment illusions than healthy controls, i.
This augmented sensitivity in stroke patients opens the space to further manipulations, which may not fully correspond with reality. For instance, the visual amplification of the movement of the paretic limb seems to promote its use in chronic stroke patients [ 41 ], which also translated to changes in clinical outcomes [ 42 ]. In a preliminary study with 18 healthy subjects, fMRI data recorded during exercising with a VRE-based rehabilitation system providing embodied feedback has revealed activation in brain regions associated with motor control and consistent with those related to the human mirror neuron system [ 43 ].
Authors observed activations of the left supplementary motor area, the inferior parietal lobe and the inferior frontal gyrus, which have been shown to be active during execution, imitation, observation or motor imagery of goal-directed movements using action observation [ 44 ]. Concerning the evaluation of effectiveness of VRE-based interventions post stroke, one of the main issues is that often standard clinical scales are inappropriate because they cannot disentangle true recovery from just compensation [ 45 , 46 ].
In this regard, inherent components of VRS e. For instance, in a study with chronic stroke, Kitago and colleagues observed no improvement in motor control features mainly arm and wrist trajectory analysis and errors captured by a robotic system after intensive constraint-induced movement therapy despite standard clinical outcomes Action Research Arm Test and Fugl-Meyer Assessment reported significant improvements [ 47 ]. The accumulating evidence over the last decade has had its echo in the recently formed Stroke Recovery and Rehabilitation Roundtable, which is working on defining standards for stroke recovery and rehabilitation research.
A field that is frequently confused or mixed up with virtual reality is that of videogames. A videogame in virtual reality, e. Indeed, the gaming industry has been the major driving force of virtual reality for its popularization. The main advantage of videogames is their inherent capacity to motivate and enhance learning [ 49 ]. Videogames can foster learning at multiple levels cognitive, navigation, concentration, physical in both clinical and non-clinical populations [ 50 ].
When adapted for healthcare purposes, videogames — often called serious video- games — can help improve motor and cognitive conditions in different clinical populations [ 51 , 52 ]. Particularly in motor rehabilitation, game-based interventions usually rely on exergames, i. It is worth nothing that not all VRS qualify for this purpose, even though they may be eligible to create interactive VRE.
Interestingly, playing videogames can make structural changes in the brain, including gray matter increase and hippocampal formation, which could be used to counteract known risk factors in neurological disorders [ 55 ]. In addition, action videogames have been shown to be beneficial for a range of mental skills including attention, faster processing of information, task switching and mental rotation in healthy participants [ 56 ], and to improve visual acuity in the amblyopic eye [ 57 ].
VREs often incorporate gamification elements e. And vice versa, more and more innovative videogames integrate VRS initially developed for VREs, typically HMDs, motion tracking technology or, more recently, physiological information as in so-called neurogames, which use brain or muscle signals to control basic game features [ 59 , 60 ]. However, VRE-intrinsic illusions like plausibility and virtual embodiment are usually lacking in standard videogames. In the particular case of neurorehabilitation, exergames provided through standard off-the-shelf console games, where subjects can for instance use their own movements and gestures to control the movements of a virtual character, does not necessarily deliver a VRE.
The fact of using VRS elements e. And vice versa, an application that does not use motion tracking or HMD may still deliver a strong VRE provided that some of the illusions listed above take place. In other words, the fact of using an HMD, or other peripheral such as haptic devices, does not make the Pong or a soccer videogame a VRE. However, if they do not provide active interaction mechanisms, their contribution to generate strong plausibility illusion and sensorimotor contingencies would be rather limited to the moments where the soccer ball comes out of the screen towards the position of the observer the user.
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This illusion will break as soon as they try to hit it. Another category is 3D animated films such as Avatar.
Even if we could imagine an immersive experience by exploring the computer-generated imaginary world using HMD and head tracking, it would not necessarily deliver a VRE per se, unless spectators can interact with it. Then, the conceptual boundaries between videogames, films and VREs may disappear towards highly immersive, gamified and embodied VREs. In summary, in this short paper I have reviewed similarities, differences and synergies of VREs virtual reality experiences , VRS virtual reality systems and videogames, with emphasis on neurorehabilitation.
Despite the increasing link between VRS and videogames, distinction between VREs and videogames should be made when categorizing the kind of intervention.
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This is important for databases searches when looking for specific studies or building metareviews. Hence, I recommend a purposeful use of the term Virtual Reality Experience when the experience involves illusions, specially plausibility and virtual embodiment, irrespectively whether the experience is gamified or not. Finally, VRS fall under a different category than VREs and videogames: while the latter refer to the generated experience and content, VRS refer to the technology mainly hardware used to create those experiences and content.
This disambiguation should help reduce confusion in a field where large univariable and well-controlled clinical trials are scarce. The author thanks Prof. Mel Slater, Prof. Andrea Serino and Gangadhar Garipelli for their feedback on the manuscript. DPM is a Senior Scientist investigating on neurotechnologies for healthcare, with special focus on virtual reality-based rehabilitation after brain damage.
Exergame: A game that involves physical exercise and that integrate motion-tracking technology e. Immersion: Deep mental involvement in something [ 61 ]. In the context of virtual reality, and in a technical acceptation of the term, immersion is achieved by removing as many real-world sensations as possible and substituting these with the sensations corresponding to the virtual reality experience [ 62 ]. Plausibility illusion: The illusion that the scenario being depicted is actually occurring [ 17 ].
The level of presence is usually proportional to the level of immersion provided. Also referred to as Place Illusion [ 17 ]. Videogame: A game played by electronically manipulating images produced by a computer program on a monitor or other display [ 48 ]. Virtual embodiment: The illusion of having i.
The Virtual Embodied: Practice, Presence, Technology: Practices, Theories and the New Technologies
Virtual reality experience: An experience on a virtual reality medium and composed of a set of qualities, including immersion, interaction, sensorimotor contingencies, and illusions. Virtual reality system: A set of physical solutions or means to generate virtual reality experiences.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. National Center for Biotechnology Information , U. Journal List J Neuroeng Rehabil v. J Neuroeng Rehabil. Published online Nov Daniel Perez-Marcos. Author information Article notes Copyright and License information Disclaimer. Daniel Perez-Marcos, Email: hc. The dangers of virtual reality, he believes, call for serious engagement with its potential abuse. This watch would measure a romantic moment as much longer than the wait to board a plane.