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Virtual Reality in Neurological Rehabilitation: Coming of Age

F D Rose
Department of Psychology,
University of East London,
London E15 4LZ, UK
Voice/Message: +44 181-849-3651
FAX: +44 181-849-3697
Internet: f.d.rose@uel.ac.uk

Web Posted on: December 12, 1997


Virtual reality (VR), whether in its immersive or non-immersive form, is one of the most exciting developments within computer science in recent years.

One area with very considerable potential for VR applications is the area of neurological rehabilitation (Rose and Johnson, 1994; Rose et al 1996; Rizzo and Buckwalter, 1995; Pugnetti et al, 1995). However, if those involved in the development of VR are to be of help to the clinicians and therapists working in this area of rehabilitation it is important that they familiarise themselves with the clinicians' terminology and the detail of the problems they seek to address.

Traumatic brain damage has been labelled "the silent epidemic" (Klein, 1982). For the U.S.A. Frankowski, Annegers and Whitman (1985) reported an average incidence of 250 per 100,000 of the population. The need for effective rehabilitative strategies is therefore obvious.

The consequences of damage to the brain are usually described in terms of three concepts, impairments, disabilities and handicaps (World Health Organisation, 1980, p.27 - 29). The term "impairment simply labels the effect of the injury on the brain and its function. The term "disability" assesses the impairment due to the brain injury in terms of its effects on what would be considered a normal profile of activities for a fit person. Finally, the term "handicap" places the disability within the context of that particular person's previous abilities, expectations and aspirations.

Whilst the model is not universally accepted (Johnston, 1996) the terms "impairment", "disability", and "handicap" define a progression of consequences of traumatic brain injury which link the initial injury with eventual outcome and, most importantly, identify targets for rehabilitation strategies. Virtual Reality has a potential role in rehabilitation of all three consequences of brain damage. With an impairment the primary objective of VR rehabilitation would be to bring about clearly defined changes in brain structure or function; with a disability the objective in using VR would be to directly facilitate the learning process; and with a handicap the objective would be to use VR in a prosthetic manner.

However, before any rehabilitation can begin the person with brain injury must be carefully assessed. VR has a valuable role here also. Whilst the methodology for assessing sensory and motor capacities is well developed there is a continuing debate about how best to assess cognitive functions such as attention, memory and reasoning, and how what is measured under these headings relates to practical skills in real life settings. This is the issue of the "ecological validity" of measures. In the 1970s and 1980s laboratory based measures of cognitive function were seen as too narrow and artificial to give an accurate guide to cognitive function in real life situations and, in consequence, several tests of "everyday" cognitive function have been developed. However, in their turn these so-called "ecologically valid" measures have been criticised for a lack of rigorous control of the test situation (Banaji and Crowder, 1989).

Andrews et al (1995) suggested that a possible solution to the problem lies in measuring cognitive function within a VR environment. VR allows the measurement of cognitive function to be made in the context of interaction with a realistic everyday environment without sacrificing the opportunity to maintain strict control over every aspect of the test situation. Moreover, since interaction with a VR environment can be made contingent on a wide range of motor responses it is possible to measure cognitive function in an everyday situation in people whose motor disabilities restricts movement in the real world. Similarly, particular aspects of the sensory array which are presented to the patient can be artificially enhanced to help overcome partial sensory loss (Middleton, 1992).

Frequently, clinicians are confronted with patients whose level of responsiveness is so reduced that it is difficult to arrive at any reasonable estimate of their residual abilities. An extreme instance is persons who are in a persistent vegetative state (PVS). Recently there has been a great deal of debate about the ethical and legal problems raised by PVS (Jennett, 1993; Andrews, 1993) and understandable public concern about the adequacy of the methods available to assess the true cognitive function of such people. As Murphy (1995) has observed, neither brain scanning (CT/MRI) nor electroencephalography (EEG) can reliably predict or detect PVS and the label is ultimately applied on the basis of "clinical judgement". Fully immersive VR, in combination with suitable input/output devices to interface between the patient's behavioural and physiological responses (Knapp and Lusted, 1992), could be of great help here. VR would allow the person to be exposed to a sensory world of a complexity impossible to deliver in any other way. Sensory stimuli could be delivered singly, or in combination, without context or in meaningful and familiar contexts (the person's own home or workplace could easily be recreated), and over prolonged periods of time. Certainly VR has the potential to improve on existing assessments of sensory responsiveness (Freeman, 1993) in maximising the chance of identifying the right combination of stimuli and minimising the chance of missing a meaningful response.

As will be apparent from the definitions given above, the term impairment is used to refer primarily to compromised anatomy and physiology and its immediate functional consequences. Can VR be used to reduce impairments? Although as yet there is no direct evidence that it can, a case can certainly be made that it should.

A primary effect of most forms of neurological insult is a reduction in cerebral arousal - activation. This combines with other common neuropsychological impairments, for example in attention, memory and motivation, to result in significantly reduced levels of interaction between the brain damaged person and his/her environment whether at home or in a rehabilitation ward. Coexisting sensory and motor impairments, such as hemiplegia, typically restrict interaction still further.

Clinicians agree that this is undesirable and that environmental interaction is vital to the rehabilitation process. Moreover their clinical judgement is supported by an extensive scientific literature. Neuroplasticity, the brain's capacity to modify its structure and function in response to experience gained from interaction with the environment is no longer in doubt (Rose and Johnson, 1996). Animal studies have shown that increased levels of environmental interaction result in a more highly developed and more efficient brain (Renner and Rosenzweig, 1987) and enhance functional recovery following many types of brain damage in animals (Rose, 1988; Will and Kelche, 1992).

Conventional therapies in neurological rehabilitation (physiotherapy, occupational therapy and speech therapy) involve increased levels of interaction, of course. However, VR is also a powerful means of increasing levels of environmental interaction. Importantly it is generally a compelling experience, and largely inescapable, unlike more conventional computer based cognitive rehabilitation programmes (Bradley, Welch and Skilbeck, 1993). Moreover, as noted above, since interaction with a VR environment can be made contingent upon whatever motor capacity the person with brain damage has, and also take account of sensory impairments, this technology is eminently well suited to this therapeutic interaction.

The therapeutic role of environmental interaction in brain damaged animals is not yet fully understood. Moreover, there is always a question mark over the extent to which we can extrapolate from animals to humans. Nevertheless, it is possible that interaction with a virtual environment might have direct effects on damaged human brains, increasing their efficiency and, consequently, maximising their functional output. The possibility of success, given that VR is a non-invasive and low risk strategy, would certainly indicate further investigation.

As this particular application of VR to rehabilitation is developed it will be necessary to investigate the effects of exposure to VR on both nervous system structure and function and on behaviour. Already there have been reports of psychophysiological changes during interaction with a VR environment, Pugnetti, Mendozza, Cattaneo et al (1994) and Decety, Perani, Jeannerod et al (1994) have carried out PET scans following exposure to VR. However, as yet nervous system changes accompanying interaction with VR environments is a largely unexplored area.

The remedy for a failure to perform a normal activity in a normal manner (i.e. a disability) would most obviously seem to lie in the training process. In the specific context of neurological rehabilitation VR has great potential where training in real life situations is often made difficult because of the brain damaged person's sensory, motor and cognitive disabilities. Because the virtual training situation has been constructed to the computer programmer's specification, certain aspects or categories of sensory stimuli can be accentuated to offset partial sensory impairment. The salience of stimuli and the links between them can also be emphasised to offset some of the effects of cognitive impairments. Once again movement within the training situation can be precisely geared to whatever motor abilities the patient has. There are also other benefits. In terms of staff resources it is clearly less time consuming for training to be in a controlled and danger free VR environment than in a real life environment.

VR is currently being developed as a training aid in several neurological rehabilitation contexts. Emmett (1994), using the knowledge that despite their difficulty in walking Parkinson's patients will step over objects placed in their paths, presented visual obstacles via a head mounted display to achieve normal gait. VR has also been used to develop everyday living skills for children with severe learning disabilities (Brown and Wilson, 1995; Brown, Stewart and Wilson, 1995). Similarly, Mowafty and Pollack (1995) have described a VR training scheme to enable people with cognitive impairments to use public transport. In addition to these published examples there are ongoing attempts to use VR in training patients to overcome impairments in attention, incidental and spatial memory, visuospatial function and to correct contralateral neglect.

The arguments for applying VR specifically to the training of people with traumatic brain injuries have been rehearsed on several occasions (see, for example, Rizzo and Buckwalter, 1995: Rose et al, 1996). Without doubt VR embodies many of the characteristics of an ideal training medium (Darrow, 1995) and, in this respect, has significant advantages over traditional computer based cognitive rehabilitation formats (Bradley et al, 1993). However, as yet there appears to be no published empirical evidence of the efficacy of its use in this context (Darrow, 1995). Central to any claims of success for these training procedures is the demonstration that what is learned in VR transfers to real life situations. Whilst some have made such claims (Standen and Cromby, 1995; Wilson, 1993) others have not found any significant transfer (Foreman et al - personal communication; Kozac et al, 1993). For a fuller review of evidence on transfer from the virtual to the real world, see Rizzo and Buckwalter (1995). Certainly further systematic research is needed on this transfer of training issue.

The term handicap refers to the disadvantage, for a given individual, resulting from impairment or disability. It is a difficulty caused by the juxtaposition of impairments and disabilities, on the one hand, and that person's lifestyle and aspirations on the other. If everything possible is already being done to reduce impairments and disabilities and if life style and aspirations are not to be compromised more than necessary, the use of prosthetic devices is indicated. The addition of VR to the existing technologies employed in prosthetics promises to revolutionise the lives of the disabled. However, progress depends upon not only advances in VR technology but also in the development of input devices which interface between whatever response repertoire the person has (Knapp and Lusted, 1992) and the virtual world, and developments in robotics which allow the patient's actions in the virtual world to be translated into actions in the real world.

Of all the uses of VR in neurological rehabilitation this is the one which perhaps requires most development. But it is also one of the most exciting. Ultimately one can imagine a situation in which the disabled might be able to carry out tasks in their real world environments by operating within a linked virtual version of it. Recent work by Simsarian and Fahl (1995) investigates this possibility. Lasko-Harvill (1993) has claimed that: "In VR the distinction between people with and without disabilities disappears." Exaggeration for the sake of emphasis, perhaps. However, the combined resources of VR and robotics promises to empower the disabled to an extent undreamt of even a few years ago.

Remarkable as it is Virtual Reality (VR) is a technology which does seem to attract rather more than its fair share of hyperbole. If those who advocate the use of VR in rehabilitation are to be taken seriously by clinicians it is important to curb the temptation to "over-claim" its virtues. The realities of day to day life on a traumatic brain injury rehabilitation unit do not sit happily with such, as yet, unsupported promise. We should be mindful of the observation made in the National Academy of Sciences report (Durlach and Mavor, 1995), that so far for VR the "excitement to accomplishment ratio" remains high.

Clinicians will have other concerns as well. For example they may see cost and technical complexity as a barrier to the development of VR therapy. There is also an ethical question. VR based therapy is non-invasive and must be seen as a low risk strategy. However, there is evidence that exposure to VR, particularly immersive VR, can have side effects. These include visual disturbances and motion sickness.

Mon-Williams et al (1993) reported transient reduced binocular vision after wearing a head mounted display for just ten minutes. However, subsequent research (Rushton et al, 1994) found that 'new-generation' head-sets did not lead to changes in binocular function even after thirty minutes use. Nor did they cause significant changes in any other visual performance measures. Related to the question of visual symptoms is that of nausea following use of a head mounted display. In immersive VR environments the incongruity between visual and vestibular motion cues can produce "simulator sickness" which is similar to motion sickness. Regan (1995) found that 61% of subjects reported symptoms at some stage during a 20 minute immersion and 10 minute post- immersion period. However, Kolasinki (1995) has found considerable variability in the extent to which subjects in VR do suffer from this condition. No significant side effects have been reported with non immersive VR.

If VR is to be used clinically it is important that its effects on bodily systems be thoroughly investigated (Eberhart and Kizakevich, 1993) but, on the basis of research so far, side effects do not appear to represent a serious barrier to the use of VR in neurological rehabilitation. However, it is important to remain vigilant. For example, Middleton (1992) warns that immersion in VR can be quite disorienting for the hearing impaired or deaf and great caution seems advisable at this stage in using VR with people displaying psychiatric symptoms. As we develop VR as a therapy it is probable that we will discover still more exclusion criteria. Certainly they should not deter us from seeking to exploit the very considerable potential for VR in brain damage rehabilitation.

Although a relatively young technology the very great potential of VR to improving the lives of those with traumatic brain injury is not in dispute. However, in order to fulfil this potential we must invest great effort in research, development and evaluation. To this end we need to forge sound working relationships with our clinical colleagues and take their perspective and their aims as our starting point. We have just entered the second half of the "Decade of the Brain" (Goldstein, 1990). Let us hope that by the end of the decade VR therapy will be part of the clinician's armoury in tackling the problems of traumatic brain injury.


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