**5. Neuropasticity and VR**

*Proprioception*

etc.) and not provide visual information regarding its movement [4, 14, 45–47]. Additional opportunities are provided by the use of the "brain-computer" interface based on the motor imagery paradigm and the P300, the use of which allows visualizing the movement of a limb with motor impairments when activity appears according to electroencephalography or functional near-infrared spectroscopy data recorded globally, with all scalp surface of the head, or only in specified areas, which are a projection onto the scalp surface of the head of the motor or premotor areas of the cerebral cortex. For example, the target signal can be used for classification within the brain-computer interface in the contralateral motor or premotor cortex, which may slow down the rate of onset of the "rehabilitation plateau" and

In the detected functional improvements obtained as a result of motor rehabilitation, sensorimotor activation was observed not only in the contralateral hemisphere, but also in the ipsilateral hemisphere, which indicated the activation of latent connections that were not active before the start of the rehabilitation measures [48–50]. The ongoing rehabilitation in VR and the progress obtained with it in the restoration of motor function are primarily associated not with the compensation of movements, which is the result of maladaptation, but with the restoration of motor function due to the activation of neuroplasticity processes in the motor and

Even though VR provides many unique advantages over traditional or new rehabilitation approaches, there are limitations to its widespread practical use as a

First, there is currently no sufficient evidence base for clinical studies that would demonstrate the unambiguous effectiveness of using VR in sensorimotor rehabilitation in various clinical groups in comparison with various traditional methods of motor rehabilitation. In addition, there is still quite a bit of information regarding the possibility of replacing physical exercises only with classes in virtual reality, namely, how interchangeable, and acceptable it is for short-term and long-term results of motor rehabilitation. That is why it is still impossible to say unambiguously how high the advantages of sensorimotor rehabilitation in VR are relative to those in the real physical world. Thus, all these questions justify the need to continue research in the field of studying the possibility of expanding the use of VR, as well as studying the short-term and long-term effectiveness of using VR in sensorimotor or cognitive rehabilitation, by accumulating a clinical base and obtaining the possibility of conducting a meta-analysis of research data to achieve the maximum high level of evidence. And although nowadays there are several studies in which attempts have been made to solve these problems, rehabilitation using VR technology continues to be considered only as an adjuvant method of

The second important reason for the difficulty in the routine use of rehabilitation in VR is the relative high cost of equipment for using these systems as a method of rehabilitation within the framework of the telemedicine concept. A few years ago, the equipment needed to simulate VR, making it difficult to use for more than 40 minutes due to the heavy weight of the VR helmet, has become much more convenient today, because there has been an abrupt growth in the number of manufacturers of these technical devices offering more and more comfortable products

increase the rehabilitation potential in patients with CNS pathology.

**4. The current difficulties of using multisensor VR**

sensorimotor and cognitive rehabilitation [5, 52].

premotor cortex of the brain [51].

routine rehabilitation method.

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for use.

According to data obtained on biological models that allow studying the processes of neuroplasticity, the lack of stimulation of the motor cortex during the "critical period", which usually corresponds to an acute state after damage of any genesis, leads to the loss of corticospinal synaptic connections [53], while stimulation motor cortical networks in the same "critical period" may contribute to the partial restoration of some of these lost connections [54]. Long-term lack of stimulation of the motor cortex in the acute period after injury ultimately leads to the consolidation of existing changes that will prevent further restoration of function.

The key component of the theory of neuroplasticity activation is the dynamic nature of changes in neural connections during motor rehabilitation using VR technology, which can be adapted to the individual needs of the person being rehabilitated, providing a personalized approach to sensorimotor and cognitive rehabilitation.

Some studies demonstrate rich intrahemispheric cortical–cortical connections that link the occipital, parietal and frontal cortex [32, 33, 55]. Moreover, individual studies demonstrate that a significant number of motor neurons in the premotor and motor cortical areas are modulated by visual information [35, 37–39], suggesting that visual information can be a powerful signal for functional reorganization of sensorimotor connections.

The main parameters through which the processes of neuroplasticity can be activated, and which can be influenced when the immersive environment is formed, are visualized movement, biofeedback, motivation and learning through observation.

Rehabilitation measures in VR can also contribute to the process of functional reorganization in the CNS due to the activation of neuroplasticity processes.

The possibility of obtaining a significant rehabilitation result is achievable only with a long training process, because the formation of new skills, which is due to the activation of the processes of synaptogenesis or Hebb learning, as well as other mechanisms of neuroplasticity, does not give an immediate stable result, since stabilization requires subsequent reinforcement in order to stimulate the transition of interneuronal interaction from functional to morphologically fixed changes [56, 57].

Thus, in an immersive environment, it is quite easy to set the proper volume of tasks to be performed and combine them with secondary cognitive tasks, making the performance of a motor task interesting due to diversity, increasing the motivation of the person being rehabilitated for a long rehabilitation process [58].

Studies on biological models have demonstrated that the intensity and duration of physical exercise is one of the determining factors that have a significant impact on neuroplastic changes during rehabilitation [59]. For example, changes at the synaptic level in a biological experiment occurred after the animal was exposed to thousands of repetitions of a given task over a short period of time, i.e. 12,000 repetitions over 2–3 days [60, 61].

Also, it was noted that patients with CNS disease receiving rehabilitation on this occasion require more and more intensity of physical exercises in order to achieve positive results in restoring physical function, in comparison with the process of developing new motor skills in healthy people [62]. The duration of rehabilitation sessions to achieve positive effects in the restoration of function, for example, the upper limb, after a stroke also depends on the stage of stroke: from 1–2 hours in the acute stage [63] and up to 10–20 repetitions per training in the chronic stage of stroke [64]. At the same time, it is implied that during the entire time of the training, it is required to maintain a high level of motivation to achieve a positive result and maintain it throughout the entire course of rehabilitation.

The flexibility of most VR applications suggests that learning in a meaningful, enriched environment can be started earlier in recovery from an emerging CNS disease, such as a traumatic brain injury, compared to conventional exercise. An early start increases the rehabilitation potential by influencing neuroplastic processes and ensuring the activation of latent connections and cortical structures, which is also necessary to prevent the onset and progression of functional maladaptive processes. The same statement is relevant for patients with acute cerebrovascular accident, where verticalization in the first days after a stroke is limited due to pronounced concomitant pathology, which is usually the cause of the stroke, or the severity of the patient's movement disorders.

The possibility of automating the rehabilitation process in VR makes training more accessible for patients, and in the future can be used in telemedicine [65].

The hypothesis underlying the substantiation of the effectiveness of motor rehabilitation says that the success of motor learning occurs only at the moment of the maximum approximation of the rehabilitation exercise to real motor skills, which the rehabilitated person will use in the future in the real physical world, as well as when using neuro-feedback [57, 66].

In addition to using a simulated VR environment to restore basic movements or simple functions necessary to perform everyday household tasks, VR can become a training platform for developing patients' skills in using various means of individual rehabilitation, for example, for teaching the use of a motorized wheelchair or driving a car, etc. [67].
