Virtual Reality rehabilitation
Virtual reality is frequently used to describe rehabilitation treatment and occasionally assessments. But what does the term mean, or, more accurately, what does the user mean by it? Was ‘Return of the [space] Invaders’, released in 1984, virtual reality? It certainly engrossed thousands of people, including me! Knowing what the term means is crucial when undertaking systematic reviews and selecting virtual reality trials as a treatment. A Cochrane review on its use after stroke stated, “Key concepts related to virtual reality are immersion and presence.” yet the review included many studies where immersion and presence were almost certainly absent. Another review investigated the effects of virtual reality intervention on neural plasticity in stroke rehabilitation, suggesting it did change neural plasticity. In another post, I have emphasised that neural plasticity “is the physiological mechanism underpinning adaptation and learning.” The review suggests virtual reality may increase learning. The lack of clarity about virtual reality has consequences; if the term encompasses two or more interventions that differ in effectiveness, the results of a metanalysis may incorrectly conclude that an effective treatment is ineffective, or vice versa. This post explores this issue.
Table of Contents
Introduction
Films can now create entirely life-like images of people moving, talking, singing, etc, for example, people who have died or grown older and even creatures that no longer exist or never existed (e.g. Gollum in Lord of the Rings). These are genuinely virtual reality. Some modern computer games, such as Assassin’s Creed, develop worlds that, while not entirely realistic, are extraordinarily credible. Many training programmes, for example, for pilots and surgeons, are also sufficiently realistic to contribute to a person’s skills in complex situations.
In contrast, many commercial computer games are blatantly unrealistic. Minecraft and Fortnite are successful, engaging games but are not realistic portrayals of the world. At best, they create a different world with many objects and animals being crude representations. Nonetheless, the player adapts to this simplified different world.
At a lower level, some computer programs use a person’s movement to control an image on the screen, such as moving an object around a maze or hitting a moving image on the screen. As the developer of Space Invaders discovered, these games can be highly motivating.
Virtual reality is frequently used to describe low-level computer games that require a person to move to control something on the screen without any need for reality. This may be exploiting the motivational aspect of computer software rather than enabling direct feedback and learning of a specific skill.
Virtual reality definition.
Jonathan Abbas and colleagues reviewed the definitions of virtual reality used in healthcare literature. They found 105 definitions in 88 publications, 58 of which were published between 2017 and 2021. The first definition found was published in 2001. The most cited definition was published in 2001 and was only cited four times (by December 2021).
The striking feature was the variability in definitions, which covered a broad range with over 250 different phrases found in the definitions. The overlap of emerging subtypes such as Extended Reality, Augmented Reality, and Mixed Reality and the development of Head Mounted Displays all added to the mix of definitions.
The five most frequently occurring words were environment, computer, user, interactive, and simulation. In the first 15 years, computer was the most vital associated word. Between 2017 and 2021, environment, user, simulation, and interactive were added. Some definitions distinguish types, such as immersive reality from non-immersive reality.
The authors and the Virtual Reality Committee at Manchester developed an “appropriate up-to-date definition”:
“VR is a three-dimensional computer-generated simulated environment, which attempts to replicate real world or imaginary environments and interactions, thereby supporting work, education, recreation, and health.”
In a recent article, Jonathan Abbas and colleagues place virtual reality in a broader setting. He suggests the overarching concept is Extended Reality Technology, which has three subtypes:
- virtual reality,
- augmented reality (superimposing computer images on an actual scene), and
- mixed reality (anchoring the computer image to a fixed point in the real-world scene)
Virtual reality’s nature.
Two components are widely used to define virtual reality: immersion and presence or embodiment. Immersion describes how much the user perceives the environment as part of the actual (external) world; it measures how realistic the sensory experience is. Immersion will be more significant when sensory inputs are increased in range, such as vision, bodily sensations (e.g. touch, pressure), smell, hearing, etc.
Presence describes how much the user feels within the environment and how much they are embodied in the virtual environment. The contrast is between someone watching a film who knows they are an outsider looking at something that may be a faithful visual and auditory replication of an environment and someone who feels integrated into the perceived environment. This feeling will be enhanced when a person acts within the environment and immediately sees the effect of their action. Actions by a person will have no impact on the environment displayed.
The distinction is between the projected reality’s objective, externally verifiable fidelity and the participant’s subjective, unverifiable experience. You may read more about this here.
Other studies exist. Kim and Biocca (2018) discuss the representation of the person within the virtual environment (their avatar) and the influence that immersion and the nature of the avatar may have on embodiment. A recent study by Han et al. (2022) investigated the effect of first- and third-person perspectives on embodiment and empathy. A first-person perspective and a highly immersive environment induced the most empathy.
Last, Stefan Weber and colleagues (2021) highlight another facet of presence: perceived realism. They argue that presence has two components that jointly influence the degree of embodiment (Figure one in their paper shows this).
The first is what they term ‘being there’, and it is a cognitive phenomenon. It is influenced by the proportion of attention directed to the virtual world as opposed to the actual world. Attention is also influenced by the extent of the illusion, the person’s involvement in events in the virtual environment, their engagement, absorption, and perceptual immersion. The critical point is that the greater the subject’s attention to the virtual world, the more they will feel part of it.
However, they introduce a second factor, perceived realism, which is the participant’s judgement on the credibility of the environment and the effects of their actions on it. The concepts associated with this include the fidelity and coherence of the virtual world.
Virtual reality, like all healthcare interventions, carries risks. These have not been well studied, but Emil Høeg and colleagues studied system immersion in virtual reality-based rehabilitation of motor function in older adults. They noted that cybersickness (nausea) was commoner with more immersive systems.
They also suggested virtual reality programs should be described on two axes:
- the degree of immersion
- the specificity of the intervention, the degree to which it is tailored to focus on a particular skill
In summary, virtual reality is measured on two axes. First, how well does the virtual world’s representation of places, objects, and events reflect the actual world, not necessarily actual places or objects, but plausible places or objects based on the natural world? Second, how believable are the places, objects, and events to the participant; is the experience credible? Further, any programme should be classified on a third axis, measuring its specificity and the extent to which it is designed to increase a specific phenomenon.
Virtual Reality and Serious Games.
A game is typically an enjoyable activity; its purpose is to amuse. Naturally, games may also increase friendship, team cohesion, physical fitness, and so on, but they are designed to engage someone or a group in a non-productive pastime. Therefore, they are usually motivating.
Because they are motivating and because they will always depend on or increase some aspect of a person’s performance, they have been used in educational settings. However, even there, the design has focused on enjoyment and engagement, although its purpose may have been to improve pupils’ abilities.
The educational potential of games was recognised in 1970 by Clark C Abt, who coined Serious Games to refer to games that “have an explicit and carefully thought-out educational purpose and are not intended to be played primarily for amusement.” Rehabilitation is primarily an educational activity undertaken in a health context, so, unsurprisingly, serious games have been studied,
An Overview of Serious Games, published in 2014, summarised their development. For example, war games were used by the military during World War II and probably before. A computer-based simulation trainer for driving a tank based on an arcade game was first used in 1980. Combat games have burgeoned. Publications on serious games designed to educate grew slowly between 1980 and 2006 and have increased dramatically since. Many of the games are computer-based.
In a systematic review of serious game design and clinical improvement in physical rehabilitation, Catarina Viera and colleagues (2021) extracted data from 12 studies (512 patients) investigating patients with stroke, cerebral palsy, or multiple sclerosis; one study investigated ‘the elderly’. They examined the influence of the game’s development strategy, genre, and nature on effects.
The data suggested that customised games were more effective than commercial games, though commercial games were more motivating. They concluded that “custom-made casual games that resort to the first-person perspective, do not feature a visible player character, are played in single-player mode, and use non-immersive virtual reality attain the best results.”
Synthesis: computer-assisted treatment
Virtual reality’s meaning has expanded pari passu with the increasing power of digital computers and has been used to describe almost any therapeutic intervention involving a computer. Any systematic review selecting studies involving virtual reality will include a wide variety of interventions that are unlikely to be similar. Consequently, one cannot draw any conclusions unless the many different aspects of virtual reality have been investigated.
Computer use is central to virtual reality. Computers are also used to make games intended to be amusing and enjoyed without intending or being designed to achieve any more profound educational or therapeutic benefit. Although games preceded computers by many millennia, computers have become a common game medium. Some games are intended to educate or train people, which may be called serious games.
Thus, the range of virtual reality includes serious games, though a serious game based on a computer may be classified as virtual reality,
One way to consider this is as ‘computer-assisted treatment’. Treatments described as virtual reality, serious games, and extended reality treatment are all based on computers, and no valid classification yet exists because the beneficial mechanisms are often unknown.
There are three potential mechanisms:
- Motivation to undertake an activity.
The motivational aspect of computer-assisted treatments is apparent because many of the treatments are commercially produced and sell well. The games often involve motor and cognitive skills, such as playing tennis on Xbox. Benefits are likely to arise from a combination of the non-specific benefits of exercise and the specific effects of practising the skill. - Feedback on the activity.
Some programs give explicit feedback, sometimes called biofeedback, but are also classified as virtual reality; balance programs are one example. Other programmes will provide implicit feedback, primarily based on the person’s success in controlling something on a screen or in a virtual world. For example, a virtual tennis game will reflect hand-eye coordination and motor control success. - Psychological benefits.
Most people feel better when motivated and when they succeed. Computers can adjust task difficulty to increase the person’s chance of succeeding more consistently than a human. The combination of motivation and engagement in an enjoyable activity may elevate mood. A virtual environment may increase self-confidence and a sense of agency by allowing the person to practice safely and without risk.
The characteristics of the computer-aided intervention may vary significantly across many dimensions, as has been outlined. To recap, an intervention may be described on the following three axes:
- Being there, immersion.
This cognitive phenomenon manifests through the amount of attention the participant devotes to the virtual world in contrast to their place in the real world. It reflects the objective reality of the virtual world. - Perceived reality, credibility
This is a subjective judgement by the participant on how believable the presented virtual world is. - Specificity, tailoring and targeting
This describes the extent to which the programme is designed to influence a particular skill, function, or activity and how it might be customised to a patient’s situation.
Conclusion
Describing a rehabilitation intervention as virtual reality is too imprecise to be helpful. Systematic reviews that analyse all studies as a single group without identifying and analysing the potential mechanisms and nature of included studies will not be able to draw sound conclusions. I have suggested two aspects of any computer-assisted rehabilitation treatment, each measured on three axes. This is not a validated system and further work is needed. However, I am highlighting the need for a systematic analysis of any virtual reality intervention when undertaking any meta-analysis
Meta
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