In the context of stroke rehabilitation, new training approaches mediated by virtual reality and videogames are usually discussed and evaluated together in reviews and meta-analyses. This represents a serious confounding factor that is leading to misleading, inconclusive outcomes in the interest of validating these new solutions.
Extending existing definitions of virtual reality, in this paper I put forward the concept of virtual reality experience (VRE), generated by virtual reality systems (VRS; i.e. a group of variable technologies employed to create a VRE). Then, I review the main components composing a VRE, and how they may purposely affect the mind and body of participants in the context of neurorehabilitation. In turn, VRS are not anymore exclusive from VREs but are currently used in videogames and other human-computer interaction applications in different domains. Often, these other applications receive the name of virtual reality applications as they use VRS. However, they do not necessarily create a VRE. I put emphasis on exposing fundamental similarities and differences between VREs and videogames for neurorehabilitation. I also recommend describing and evaluating the specific features encompassing the intervention rather than evaluating virtual reality or videogames as a whole.
This disambiguation between VREs, VRS and videogames should help reduce confusion in the field. This is important for databases searches when looking for specific studies or building metareviews that aim at evaluating the efficacy of technology-mediated interventions.
In the context of stroke rehabilitation, new training approaches mediated by virtual reality and videogames are usually discussed and evaluated together in reviews and meta-analyses for upper limb [1, 2], and balance and gait . Certainly, the expected superiority of virtual reality over conventional therapy post stroke has been questioned when using off-the-shelf (e.g., Nintendo Wii) or ad-hoc videogames. This conclusion, however, is based on the wrong assumption that videogames deliver same experiences than virtual reality applications. In my opinion, this represents a serious confounding factor that may lead to misleading, inconclusive outcomes in the interest of validating these new solutions. Indeed, in Laver’s Cochrane article, a positive effect for virtual reality versus conventional therapy for improving upper limb function post stroke is found only when dedicated virtual reality based interventions, i.e. specifically designed for rehabilitation settings, are used. The effect vanishes when standard off-the-shelf videogames are considered. Indeed, the use of Nintendo Wii (but referring to it as virtual reality) often leads to a non-inferiority clinical outcome, being as effective as conventional therapy  or alternative playful interventions such as playing cards . In another study with mobile-based and dedicated games (again referred to as virtual reality), partial functional and motor improvements were observed as compared to standard occupational therapy .
This heterogeneity in the reported virtual reality and videogames studies for neurorehabilitation calls for use of appropriate labelling for the approaches and variables assessed. A correct identification of the specific factors (and their weight) contributing to any eventual change post treatment are required for interpreting those changes and building further evidence on the specific solution. Therefore, in this paper I propose to reframe the traditional interpretation of the term virtual reality. I advocate disentangling two conceptual components that may help the field standardize its use: virtual reality experience (VRE) and virtual reality systems (VRS). I put emphasis on exposing fundamental similarities and differences between VREs and videogames, often mistakenly used as synonyms or exchangeable terms despite the different underlying interventional techniques and brain mechanisms they can enable. I then use neurorehabilitation as exemplary application field to discuss the implications of differentiating between them.[…]