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Albert A. Rizzo Ph.D.
1629 Steinhart Ave.
Redondo Beach, Ca. 90278
J. Galen Buckwalter Ph.D.
Andrus Gerontology Center at USC
University Park MC-0191
Los Angeles, Ca. 90089
Within one year, two and a half million Americans will have a traumatic head injury resulting in significant brain damage. In fact, every 15 seconds someone in the United States will suffer a head injury requiring some hospitalization. Of the survivors of head injury, approximately 90,000 will experience an enduring loss of function due to the resulting brain damage. Although the popular media have recently taken notice of the significance of this form of disability, the relative lack of awareness in this area has led the National Head Injury Foundation to refer to traumatic brain injury as “The Silent Epidemic”.
Brain injuries consequent to physical head trauma can occur from a variety of sources including motor vehicle accidents, falls, bullet wounds, sports injuries, physical assaults, industrial accidents, etc. Additionally, brain damage can often be the result of disease processes such cerebral vascular accidents--commonly called strokes, tumors, infections, oxygen deprivation, hydrocephaly, toxic exposure, and metabolic disorders. As a result of these various forms of neurological trauma, individuals may suffer varying degrees of functional impairment. This impairment is often seen within the physical, cognitive, emotional, social, and vocational domains of human functioning. While Virtual Reality (VR) technology can undoubtedly be of some use in the rehabilitation of all of these areas, the present paper will focus specifically on the potential applications within the domain of cognitive functioning or thinking abilities.
In the past twenty years, professionals in the areas of special education and neuropsychology have found that cognitive rehabilitation can benefit individuals with brain injuries. Sohlberg and Mateer (1989) define cognitive rehabilitation as "the therapeutic process of increasing or improving an individual's capacity to process and use incoming information so as to allow increased functioning in everyday life." These methods may be applied with the goal of restoration of cognitive function by retraining new functional systems in the brain to take over for areas of lost cognitive function, or by teaching compensation skills which will allow the individual to perform a task by using alternative preserved abilities. Cognitive rehabilitative methods have been applied to a wide range of thinking abilities from the most basic processes of attention training to the higher mental functions of logical reasoning. Generally, the most often addressed cognitive areas include attentional abilities, memory, visual and auditory processing, language, spatial skills, executive functioning (planning, organizational, and goal-oriented behaviors), logical reasoning, problem solving, and critical thinking. The use of VR technology for the rehabilitation of individuals with acquired brain injury offers considerable promise for both the restorative and compensatory approaches for the improvement of cognitive functioning.
Implied within both the restorative and compensatory approaches to cognitive rehabilitation are differential primary goals. The restorative approach places as the primary objective the attempt to retrain individuals on how to think, whereas the primary emphasis of the compensatory approach is to teach individuals how to do. While most rehabilitation programs provide a mixture of techniques from both of these orientations, the issues surrounding the relative pragmatic value of each are often hotly debated.
An example of the differential emphasis contained within these approaches can be seen in the area of memory rehabilitation. The restorative approach would emphasize a "drill and practice" method in which the person would be required to remember increasingly more difficult pieces of information over time, and hence, memory is expected to improve much like a muscle gets stronger with increased exercise. Stimuli that can be gradually increased in difficulty level such as lists of letters, numbers, words, sentences, geometric designs, etc. are presented to the person and they are required to recall or recognize the test materials over increased periods of time, contingent upon prior successes. Other restorative techniques require the person to remember an activity to perform at a later time and as the person begins to demonstrate success after brief time periods, the time interval to perform is gradually lengthened. It is believed that by having a person practice "storing and holding" information for increased time intervals, that they will "build" a "stronger" memory. One often cited criticism of these methods is that they rely on test materials or tasks that are essentially artificial and have little relevance to real-world functional memory challenges. This criticism holds that "memorizing" lists of words or activities within a training environment does not guarantee that the memory ability will generalize to the person's real- world situation.
By contrast, compensatory approaches generally focus on the activities of daily living (ADL's), such as remembering a sequence of events to prepare for work in the morning or a set of structured steps for completing day-to-day functional activities (meal preparation, job tasks, grooming routines, etc). Compensatory methods include teaching a person to use a variety of memory aids that fall into two categories: external and internal. An external aid would include memory notebook systems, electronic memory devices, alarms, calendars, reminders posted in different positions around the house, standardized locations for storing regularly needed items (car keys on a hook by the front door). Internal aids usually consist of learning mnemonic strategies, such as acronyms, peg word systems, and associative imagery. Criticism of compensatory methods include foremost, that the learning of standard stereotyped behaviors to accomplish ADL's assumes that the person lives in a static world where life demands do not change and that the person will not need to creatively adjust, and think through these changing circumstances.
It is proposed that the application of VR technology for the rehabilitation of cognitive deficits could serve to remedy the major weaknesses of both the restorative and compensatory approaches and actually produce a systematic treatment method which would integrate the best features from both methods. In essence, it may be possible for a VR application to provide systematic restorative training within the context of functionally relevant simulated environments which optimize the degree of transfer or generalization of learning to the person's real world environment.
Overall, the minimum requirements appear to include:
As for the compensatory approach, the basic requirement is that the training activity should actually be an end in itself. By this, it is necessary for the training activity to closely resemble the activity required in the person's day-to-day environment. Therefore, training in meal preparation should be conducted in a kitchen that is very similar to most kitchens within which the person would be likely to function and should include standard tools and appliances found in most kitchens.
Regarding the criteria for the restorative approach, it appears that at the current state of VR technology, these requirement could be met. Criterion one is limited only by the designers knowledge of persons current type and level of impairment and the rehabilitative relevancy of the task. Criterion two can be addressed by adjusting factors including speed of presentation, quantity of required activity, number of distractions, and complexity of stimuli. Criterion three can be addressed via data storage of all responses within the simulated environment. Criterion four is especially addressed in that a computer- generated environment offers the potential for consistent task presentation, on demand with little demand on staffing. Criterion five is also possible by simply programming in a feedback component following responses performed within the virtual environment. And finally, the major criterion for the compensatory approach is only limited by the creativity of the program designer and the available state of technology. In light of this analysis, it appears that useful cognitive rehabilitative tasks using VR technology are realistically possible and what remains is to delineate the specific approaches necessary for each of the cognitive functions.
In discussing the possible VR applications for the rehabilitation of deficits following acquired brain injury, it is important to first focus on some of the recent findings pertaining to preserved memory abilities following brain trauma. A number of studies have shown that in persons suffering memory loss, following a brain injury, certain memory abilities often remain intact. Procedural or skill memory is one such cognitive operation (Cohen and Squire, 1980; Carness, Milberg, and Alexander, 1988). This type of memory ability concerns the capacity to learn rule-based or automatic procedures including motor skills, certain kinds of rule based puzzles, and sequences for running or operating things (Solhberg and Mateer, 1989). Procedural memory is seen in contrast to declarative or fact-based memory which is usually more impaired and less susceptible to rehabilitative improvement. Also persons with brain injuries often demonstrate an ability to perform rule-based procedural tasks without any recollection of the actual training sessions. This is commonly referred to as implicit memory (Graf and Schacter, 1985) and it's presence is indicative of a preserved ability to process and retain new material without the person's conscious awareness of when or where the learning occurred. These observations provide support for the idea that VR technology has the potential to provide training environments which could maximize cognitive improvement by focussing on the person's preserved procedural abilities. Hence, VR could provide settings where cognitive skills are restored via procedures practiced repetitively within an environment which resembles real-world demands. Whether the person could recall the actual training episodes is irrelevant as long as the learned skill is shown to generalize to functional situations. The real challenge would then be to translate complicated declarative tasks into procedural activities with the goal being the restoration of complex reasoning abilities.
A set of cognitive processes that would serve as a logical starting point for a comprehensive VR delivered cognitive rehabilitation system is in the area of attention. This area would have value for a number of reasons. First, attentional difficulties are frequently cited as the chief disability in brain-injured individuals (Posner and Rafal, 1987). These sorts of cognitive deficits occur with injuries to a variety of brain areas including the parietal lobes, frontal lobes, midbrain structures, and the brainstem. Attentional problems may also result from lack of oxygen to the brain, secondary to cardiovascular problems including strokes and myocardial infarctions. Second, attentional abilities are the necessary foundation for future rehabilitative work on higher cognitive processes such as memory, perceptual processing, executive functions, and problem-solving. Third, even if higher processes are unable to be remediated, some level of attentional ability is essential for vocational and quality of life pursuits.
One useful system for conceptualizing attentional processes is presented by Sohlberg and Mateer (1989). In their model, they outline hierarchically organized levels of attention which are:
Standard methods applied for the cognitive rehabilitation of attention usually include pencil and paper techniques (sometimes with taped audio distractions), motor reaction time tasks in response to various signalling stimuli, and computerized training tasks. Within a VR setting, a person could be systematically challenged on attentional tasks which incorporated settings and response requirements that would simulate real-world functional environments beyond what currently exists. Simulated environments in which a hierarchical drill and practice method could be applied include factories, offices, home settings, and are limited only by the creativity of the programmer and the knowledge of what is relevant to the person's rehabilitative needs. Also, with the addition of voice recognition technology, verbal responding could be included with motor movement to further replicate the demands of real-world functional environments. It is believed that cognitive rehabilitation using a VR approach would offer the potential to build stronger attentional abilities by exercising the preserved procedural memory capabilities of the person. Some examples of how this could be done with attentional skills are the following:
Divided Attention - The person would motorically and/or verbally respond to simulated presentations of numbered, colored, or labeled boxes rolling off an assembly line contingent upon the additional changing requests of a "supervisor" presented via the auditory and visual channels. The "supervisor" would consist of a person that is conversing with another co-worker in the background while intermittently adding a request for an additional set of boxes to be removed from the assembly line via motor movements or verbal responses. The divided attention component is "worked" as the person needs to monitor the visual display while at the same time keeping track of the changing verbal commands that are enmeshed within ambient background conversation. As can be readily seen, any combination of gauges, meters, clocks, and instruments, etc. can be used in place of the assembly line stimuli and the difficulty level of the tasks can be easily adjusted by varying the stimulus/response complexity (i.e., changing the rate of stimulus presentation, etc.) The task can also be changed to challenge other specific attentional skills simply by reversing the sensory mode of stimulus presentation. This could be done by presenting visual commands using language or coded symbols, alone or in combination with auditory commands, with similar response requirements outlined above.
Alternating Attention - On these tasks the patient would be required to alternate between two or more activities. For example, the person could be required adjust the level of heat on a virtual representation of a stove in order to boil water, and upon completion of that task, would need to go to a representation of a cupboard and remove a certain color cup that was requested on the auditory channel. Upon returning to the water, the person receives a signal that it has cooled and that the stove needs to be relit. Tasks such as these could be designed that target many everyday activities in the home, at school, and at the work place. Representations of temperature and oil pressure gauges on a piece of machinery that needs to be monitored and adjusted periodically, and can be cued auditorily, could also provide many variations on this theme. Also, the scenario described in the divided attention example above could be used. In this case, the commands from the "supervisor" regarding which types of boxes are to be removed are alternately changed requiring the patient to shift from one set of targets to another.
Selective Attention - These tasks would require the person to selectively pick out a target stimulus from a variety of information presented within a three dimensional environment. This could be done with visual inputs such as gauges or meters in some type of "control room" where the patient could respond verbally or with some motor action when the target signals an overload in this simulated setting. Another method would be to present the name of a type of tool auditorily and the person would be required to respond when the targeted tool is found in the virtual "toolshed". In a sensory reversal of this last method, the person can receive a visual "memo" within an office setting which instructs him to answer a phone only when it rings twice in rapid succession. Once again, settings designed for the higher attentional levels could be used at this level with modifications to reduce the cognitive demands.
Sustained Attention - These vigilance tasks would require the patient to respond to stimuli over extended periods of time. One example would be to have patients "work" at a train crossing and their job would be to initiate the safety gate motorically or verbally upon the imminent arrival of the train that is signalled either visually or auditorily. Basic adaptations of the stimuli used for the higher level attention training could also be used at this beginning level.
Focussed Attention - Being the most basic level of orientation, persons working on these tasks would simply need to respond to the presence of any stimuli--possibly repeating auditorily presented material or making some type of movement upon stimulus presentation. Probably anyone who couldn't do this would not be at a level of orientation where cognitive rehabilitation could progress in a meaningful way at that time.
As with the attentional training settings described above, it is also possible to design VR approaches which could rehabilitate memory abilities systematically within a simulated functional environment. For example, in any of the situations described for attention training, the person could be helped to gradually remember locations of tools, settings on gauges, responses which need to occur at certain times, sequences of behaviors to accomplish tasks, etc. with the assistance of cues or prompts which could be systematically faded as memory skills are gradually acquired. Another method might involve having the person practice organizing household items and storing them in various locations within a simulated home with the purpose of recalling the items location at a later time. This sort of exercise might help develop better "pre-memory" organizational skills which could improve procedural learning of activities of daily living, even if memory performance was seen to have leveled off.
Sensory Processing: Visual and Auditory
Individuals who suffer brain trauma can manifest problems with sensory and perceptual processing in any of the five senses. While the senses of touch, smell, and taste are important to the experience of living, problems in the areas of vision and audition are especially relevant for day-to-day functioning. These areas could be potentially addressed within a VR environment. Within the type of VR settings already described, a person could actively practice the visual skills of object recognition, scanning, and organization in a systematic manner. One example, might involve having a person with impaired visual-spatial abilities practice navigating through progressively more complex virtual buildings. Along the way, the person could be presented with tips and cues by a therapist, within a shared virtual environment, which might aid the person in learning effective tactics for this task and learning could possibly generalize to real-life situations. It may be possible to adapt the technology for this from currently existing architectural walk-through programs. Auditory processing might also be addressed within a VR simulation. For example, methods for enhancing sound localization could utilize VR advancements in 3-D sound to create stimuli linked with visual inputs to gradually retrain this ability.
Higher Cognitive Functions
While it is beyond the scope of this paper to fully address these areas, it can stated that rehabilitation of the higher cognitive functions (executive functioning, organizational and conceptual thinking, logical reasoning, problem-solving, and critical thinking, etc.) could theoretically be possible via similar tactics proposed for the more basic thinking activities. Surely military personnel develop some of these skills in the process of VR flight simulation and tank operation training! Probably the biggest challenge for the field of cognitive rehabilitation will be in the translation of declarative information into discrete procedural steps which can be presented within a VR setting. Ideas for this process can be readily seen in the stepwise presentation of these functions currently found in a variety of college level critical thinking textbooks.
One group of researchers have begun the work of developing a VR system specifically designed for the assessment and cognitive rehabilitation of higher cognitive functions in persons with acquired brain injuries (Pugnetti, Mendozzi, Motta, Cattaneo, Barbieri, Brancotti, & Cazzullo, 1995). In a very ambitious approach, their work has initially focused on the development of a system designed to address the cognitive processes referred to as "Executive Functions". Executive functions, as these authors have defined them includes, "...control cognitive abilities that are crucial for successful adaptation to new situations and environments. Concept formation, conceptual reasoning, planning of behaviour, inhibition of impulse, categorisation, sustained voluntary attention, (and) selection of priorities,..." (Pugnetti et.al., 1994). Having used a standard tool of neuropsychological assessment as a model (Wisconsin Card Sorting Test--WCST), these researchers have created a virtual building which requires the person to utilize environmental clues in the selection of appropriate choices (doorways) in order to navigate through the building. The doorway choices can vary according to the categories of shape, color, and number of portholes and the person is required to refer back to the previous doorway for clues as to the appropriate next choice. When the choice criteria is changed, the person is then required to shift cognitive set, analyze clues, and devise a new choice strategy. The parameters of this system are fully adjustable so that training applications can follow initial standardized assessments. In light of the large body of literature that exists on the WCST (Robinson, Heaton, Lehman, & Stilson, 1980), it's choice as a model for this initial VR application is potentially quite useful. Results from case study reports using this system seem encouraging (Pugnetti, et.al. 1995), and it's developers (Cyberfunk/Italy-Medical Division) are commended for this ambitious ground-breaking effort. Additionally, programs are being developed by this group to address attention, memory, visuomotor, and visuospatial cognitive functions, and results from this work are highly anticipated.
Side Effects Assessment
Short of developing Virtual Reality systems specifically directed for cognitive rehabilitation applications, certain feasibility issues could currently be investigated. One of these issues involves the potential for adverse side effects (visually induced motion sickness, disorientation, headaches,etc.) that could occur for persons with brain injuries when using VR. Studies with non-brain injured populations have reported a wide range of percentages regarding the occurrence of these side effects (DiZio and Lackner, 1992; Hettinger, 1992; Kennedy, et.al.,1992; Regan and Price, 1994;). Variability in the reported occurrence of these symptoms may be contingent upon such factors as the type of VR program used, the length of exposure time, the person's prior experience using VR, and the construction of the actual self-report rating scale used to assess occurrence. In one recent study (Regan and Price, 1994), 61% of 146 healthy subjects reported "symptoms of malaise" (i.e., dizziness, stomach awareness, headaches, eyestrain, lightheadedness, and severe nausea) at some point during a 20-min immersion and 10-min postimmersion period. The "side effect" issue is of particular importance when considering the use of VR with the brain injured population, some of whom display residual equilibrium, balance, and orientation difficulties. In the only report to date which addresses this issue, Pugnetti, et. al. (1995) compared 11 neurological patients with 41 non-neurological subjects regarding self-reported prevalence of "cybersickness". The authors tested subjects in their ARCANA1 system which is specifically designed for the diagnosis and rehabilitation of executive cognitive functioning following brain injury. The results suggested a reduced occurrence of VR related side effects compared to past studies with an overall prevalence rate of 17% for the total sample. The authors also reported that the neurological subjects appeared to be at no greater risk for developing "cybersickness" than the non-neurological group. While these initial findings are encouraging, further work is necessary to specifically assess how the factors of, type and severity of neurological trauma, prior VR exposure, length of time within the VR environment, and characteristics of the specific VR program, influence the occurrence of side effects. This is an essential step in determining the conditions where VR would be of practical value in the area of brain injury assessment and rehabilitation.
Transfer of Learning
Another fundamental issue which has important implications regarding the feasibility of a VR approach applied to cognitive rehabilitation concerns the concept of "transfer" of learning from a VR learning environment to the actual "real world" environment. As referred to earlier in this report, it is intuitively appealing to assume that one of the strongest assets of a VR approach to cognitive rehabilitation is it's capacity to simulate "real world" environments. Hence, transfer or generalization of learning to the actual real world functional environment is expected to be optimal. This cannot always be assumed to be the case, as a study by Kozak, Hancock, Arthur, and Chrysler (1993) found no evidence of transfer from a VR "pick and place sequence task" to a real world task. However, the authors' indictment that "...individuals learn performance characteristics specific only to the VR context." seems a bit overstated in light of the long history of positive results reported in the simulator literatures from the aviation industry, NASA, and the military. In a recent report on the theoretical issues concerning transfer of learning from simulators, Johnston (1995) cites a Transfer Effectiveness Ratio in the aviation simulation research of .48. This ratio indicates that for every hour spent in aviation simulator training, one-half hour is saved in actual aircraft training. In addition, research is beginning to emerge in the VR literature which provides evidence of positive learning transfer from virtual training environments (Regian, Shebilske, & Monk, 1993; Paton, 1995; Standon & Cromby, 1995). One of these studies, conducted at Motorola University (Paton, 1995) is of particular practical interest in that the results indicated positive transfer from a VR "factory" training program to the actual factory line. Some evidence of positive learning transfer from a non-immersive virtual training setting has also been presented (Standon & Cromby, 1995) for a group of developmentally disabled students. In this preliminary report, students with significant cognitive impairments were trained on a PC-based, non-HMD, virtual system to navigate through and select specific items in a virtual supermarket. In addition to suggesting positive transfer results, this study is noteworthy in that it suggests an efficacious approach to increasing the independence of persons with cognitive difficulties for whom a fully immersive HMD strategy may not be practical. The above cited investigations represent essential "first-steps" in determining whether VR training can foster transfer of learning to activities of daily living. For persons whose learning abilities may already be challenged due to neurological trauma, this line of research is especially important. The "generalization problem" has plagued the overall field of cognitive rehabilitation since it's inception. This makes it essential that intuitive expectations of positive VR learning transfer be, in fact, supported with quality research. This will be vital in order for the VR approach to be taken seriously in this field.
Pragmatic Research Approaches
These early studies investigating the pragmatic issues of VR related side-effects and the transfer of training are essential to building a foundation for the "reasoned" application of VR techniques in the area of cognitive rehabilitation. However, at this early phase of VR technology, a number of obstacles exist which have impeded the development of active research specifically testing persons with acquired brain injuries. These obstacles include the relative lack of familiarity with the technology and problems with financial commitment for an untested and fairly expensive new treatment modality. While these concerns can be seen as short-term difficulties (VR awareness is increasing while system costs are decreasing), there is a need for creative research approaches which can currently address initial feasibility questions in this area. One such approach is presently available which could serve to commence active research programs in this field. This strategy requires the cognitive rehabilitation researcher to seek out already existing VR systems developed for other purposes, creatively adapt an experimental design around the capabilities of the system, and, of course, enlist the cooperation of the system's owner for its temporary rental or gratis use. If an agreement could be reached which would limit the inconvenience to the system owner, the researcher's development and funding requirements could be substantially reduced. For illustration sake, three systems where this approach would be feasible regarding the research questions of incidence of side effects and transfer of learning with brain injured subjects will be described. (Author's Note--these examples are simply meant to illustrate feasibility issues and are in no way designed for, or should be construed as, a solicitation of the actual system owners) Systems where these research questions could currently be addressed include: Motorola's "Virtual Factory" (Paton, 1995), the Miami Valley Regional Transit Authority's "Train to Travel" project sponsored by the University of Dayton (Mowafy, Pollack, Stang, & Wallace, 1995), and Frederick Brook's "Walkthrough" program of UNC's Sitterson Hall.
Each of these VR settings would provide a different type of sensorimotor experience and set of response challenges which would appear to have some face validity for investigating the side effect and transfer of learning research questions. At each of these locations, research participants could be solicited from the local populations' of individuals with brain injuries. Participants could experience a standardized period of training within these VR settings which would be customized for the purpose of the specific research questions being asked. For example, utilizing the Motorola "Virtual Factory" system might involve participants in learning the procedural tasks of starting up and operating a subset of the factory line's equipment during three temporally spaced 20 minute VR training periods. Participants could then have their performance tested on the actual criterion tasks with the appropriate subset of real equipment. This would provide for some measure of learning transfer, while allowing for side effect assessment to occur, over time, during each training session. Similarly, the "Walkthrough" program at UNC would provide a VR setting where participants could be exposed to training sessions which would focus on teaching goal-directed navigation skills within the VR building with the learning transfer then being tested at a later time in the actual building. The University of Dayton sponsored "Train to Travel" program, while still under development, could provide similar research opportunities in the near future. This immersive VR system was primarily designed to teach persons with developmental disabilities how to use key routes on the Miami Valley Regional Transit System. As with the previously outlined programs, this system could provide an experimental setting where research participants with cognitive difficulties could be trained in VR, assessed for side effects, and tested for learning transfer within the actual real world environment. Additionally, performance data for these systems may already exist from other populations which might provide useful data for comparison purposes and serve as an aid in hypothesis generation. While this research approach is not without it's pragmatic difficulties, on an intuitive level it appears to be a cost effective option during these "early years" in the development of VR applications in the field of cognitive assessment and rehabilitation for persons with acquired brain injuries.
As seen by the various examples presented for the rehabilitation of cognitive processes, it may be possible to design VR environments which both remediate functional deficits and systematically retrain thinking abilities. Rehabilitation tasks with these parameters are extremely difficult to efficiently administer, score, raise difficulty level, and provide immediate feedback for, within a standard therapist/patient training session. The VR approach would have the benefits of consistent, repetitive, and hierarchical presentation of tasks, and could provide immediate feedback to the person regarding performance. VR systems would provide the potential to tabulate performance over time to reflect long-term progress, as well as allowing a person to practice exercises alone, or at home with some link to a central system. Also, the potential merging of the compensatory and restorative approaches that could occur using VR techniques could provide exciting new possibilities for treatment in this field. These factors taken together, suggest that a VR system for cognitive rehabilitation could improve treatment cost effectiveness and could serve to enhance treatment outcomes.
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