Can virtual reality offer enriched environments for rehabilitation?

Keywords::

• motor learning
• motor recovery
• plasticity
• rehabilitation
• technology

Recent research on the mechanisms of neuroplasticity has led to great advances in our understanding of the adaptive capacity of the nervous system [1]. This, in turn, has led to an increasing interest in how neurological therapeutic interventions can best be delivered to drive neuroplasticity in order to shape recovery after brain injury or disease. Animal and human research has identified some of the key principles of rehabilitation for optimizing recovery in many areas, including language, behavior, cognition and sensorimotor function. For sensorimotor recovery, in particular, a major emphasis has been placed on the processes of learning and experience-dependent plasticity [2]. Brain damage alters learning processes because of changes in neuronal and non-neuronal connectivity in reaction to cell death and reorganization. Yet, evidence suggests that the principles of learning, identified in the intact nervous system, may not necessarily be the same in individuals with brain damage. Brain damage often affects cognitive processes, such as attention and executive function, as well as working memory, which are important for motor learning [3]. For example, attention modifies neural responses in the visual, auditory and somatosensory systems (e.g., [4,5]). Another principle, fundamental to sensorimotor learning in the intact nervous system, is the type of task practice (e.g., repetitive blocked- or varied-task practice). Different practice paradigms influence immediate changes in motor skills and the ability to retain such changes for a period of time after the end of practice.

Are the same principles described for learning in the intact nervous system applicable after brain damage? In partial answer to this question, Cirstea et al. found that individuals with chronic stroke needed to repeat a much larger number of trials of a reaching movement before improvements in movement outcomes, such as movement speed and precision, were obtained [6]. The number of repetitions needed for improvements in reaching movement to occur varied with stroke severity, such that even individuals with mild poststroke hemiparesis needed to practice twice the number of trials before movement error was reduced. For those with more severe hemiparesis, the number of repetitions was increased several-fold and learning was often incomplete. Other researchers have found that not all types and schedules of feedback may result in beneficial motor outcomes for all stroke survivors. Lesion location appears to affect the individual’s ability to make use of specific types of feedback, such as intrinsic or extrinsic feedback [7,8]. Thus, it is becoming apparent that patients with different lesion types and severity vary in their responses to different types of intervention. The question of which patients with brain damage can benefit from which rehabilitation intervention(s) is also now being recognized as a critical one, as our understanding of learning and adapted learning processes progresses. For example, recent research has demonstrated that, when evaluating treatment effectiveness that relies on learning processes, we need to consider not only the mechanisms of synaptic and neuronal processes involved in learning, but also how genetic expression influences these processes in different individuals (see [9]).

Nevertheless, there is agreement that motor recovery after brain damage necessitates that the individual engages in repetitive, intensive and salient task practice. These are but three of the ten principles of experience-dependent neural plasticity arrived at by a consensus panel of experts in neurorehabilitation, summarized in a recent paper by Kleim and Jones [2]. Emphasis is placed on the targeted engagement of a specific brain function to avoid its functional degradation and to enhance its activity. For example, in animal models of stroke, loss of motor circuitry after ischemic lesions was minimized and reorganization in the undamaged cortex was facilitated following intensive practice of skilled reaching [10,11]. An important aspect of rehabilitative training is that the learner has opportunities to meaningfully interact with objects in the environment and to receive salient feedback about their performance to enhance the learning experience. The learner’s level of engagement or motivation is also an integral element for learning to occur through neuroplastic mechanisms [10]. Although conventional rehabilitation practice usually includes these key features of motor learning: repetitive and intensive practice, interactive environments, feedback and learner’s motivation, the advent of new technology, such as virtual reality, allows us the opportunity to manipulate the learning environment and provide a more intensive learning experience.

Virtual reality is a computer-based technology that provides a multisensory environment with which the user can interact [12]. Several types of virtual reality applications have been developed, ranging from fully immersive 3D cave systems to game-like applications played on computer screens or with robotic assistive devices for motor re-education. Virtual reality systems can use sophisticated equipment, including specialized graphic software and interfaces, such as head-mounted displays and peripheral haptic devices for provision of somatosensory feedback, or simple low-technology applications using webcams, computer screens and joysticks. Applications using virtual reality are also varied, including gait and balance retraining, executive functioning, multitasking, pain management and upper-limb rehabilitation in both adults and children (e.g., [13]).

An important caveat is that the technology itself is far more advanced and varied than the scientific evidence supporting its effectiveness. In addition, the technology is changing so rapidly that even when evidence does appear, it may apply to already obsolete equipment and applications. The rapid evolution of the field is highlighted by the recent establishment of a consortium of international societies devoted to the development of virtual reality technology and its applications under the umbrella of the International Society for Virtual Rehabilitation [101]. Virtual rehabilitation is still a young field and one that requires a sustained and close dialog between those in industry, academia and clinical practice.

We are still at the early stages of gathering evidence of the effectiveness of various virtual reality applications in rehabilitation areas pertaining to children and adults. The first reports published were mainly technical spreadsheets and descriptions of virtual environments and applications. Currently, the evidence for effectiveness of these applications is encouraging, but still not very strong in scientific terms. For children, studies have focused on how well virtual reality interventions may induce playfulness, how much it motivates children to do more exercise, how pleasurable or acceptable it is and how it impacts motor and visual–perceptual skills (for a recent review, see [14]). In adults, in a recent meta-analysis of the effectiveness of virtual reality applications for upper-limb rehabilitation in stroke patients by Saposnik and Levin, 12 randomized clinical trials, observational and pre- and post-intervention studies using virtual reality applications were retrieved, ranging from an immersive cave system to a commercially available interactive game platform [15]. All of these studies have reported some degree of positive outcomes in each of these areas, but research about the specific attributes of virtual reality leading to good rehabilitation outcomes is still lacking. At this point, it can be concluded that virtual reality interventions are safe and feasible for use with children and adults with neurological disorders [15]. Virtual reality technology has a great potential to enable us to design individualized and enriched practice environments that take advantage of the principles of motor learning and neural plasticity to optimize recovery after brain damage or injury. Still, more research is needed before definitive statements about the effectiveness and added value of virtual reality applications, over and above conventional treatment approaches, can be made and guidelines provided about the optimal treatment parameters needed to achieve various treatment goals.

Financial & competing interests disclosure

The author holds a Tier 1 Canada Research Chair in Motor Recovery and Rehabilitation. Research projects are funded by Canadian Institutes of Health Research, Heart and Stroke Foundation of Canada, Natural Sciences and Engineering Research Council of Canada and the Rehabilitation Research Network of Quebec. The author has no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.