**3. Prospects for VR in motor rehabilitation**

Understanding the importance of ensuring the formation of proprioceptive sensations, when solving a range of physical rehabilitation tasks, is also based on a

**135**

stroke [17].

*Proprioception in Immersive Virtual Reality DOI: http://dx.doi.org/10.5772/intechopen.96316*

of various origins.

with VR [14].

further exercises [16].

more intense activation of neuroplasticity processes when performing motor tasks with multisensory and, first of all, proprioceptive reinforcement, demonstrated in a number of experiments both on biological models and in patients with different pathology. The formation of biofeedback stimulates the processes of neurogenesis and neuroplasticity, due to the formation of new interneuronal connections, initially of a functional nature, but subsequently fixed at the structural level due to the activation of latent connections between individual functional structures of the CNS. That is why VR is an ideal immersive environment that makes it possible to maximally activate the processes of neuroplasticity for more effective recovery of not only motor, but also cognitive impairments in patients with damage to the CNS

Learning how to perform new skills within the framework of solving motor tasks modeled in VR is of decisive importance for inducing neuroplasticity processes, and as a result, contributes to a more effective restoration of impaired functions due to various injuries of the CNS or the musculoskeletal system. The immersive environment created in VR is a particularly effective tool for carrying out tasks of interacting with objects in three-dimensional space. The restoration of this level of motor function is especially important in increasing the independence of patients with motor defects of varying severity, which is one of the ultimate goals of motor rehabilitation or habilitation. Additional technical capabilities in the form of using various sensors, telemetry during training in VR allow a detailed analysis of the motor activity of the rehabilitated person, which can serve as initial data for the formation of a recommendation system to increase the effectiveness of the rehabilitation process, or to adapt exercises during the rehabilitation process, for example, by gradually complicating them. Implementation, not allowing the

For example, today there is many studies that formed the basis of several publications demonstrating the effectiveness of restoration of upper limb functions in patients after acute cerebrovascular accident when using exercises

However, these studies were based only on clinical data carried out in patients in the late rehabilitation period after suffering acute cerebrovascular accident. At the same time, the high safety and effectiveness of such exercises in VR suggests that the use of virtual reality will also be effective in patients in the acute period, after acute cerebrovascular accident. Such results regarding the use of implicit multimodal VR with visual and proprioceptive confirmation of walking have been demonstrated in a study on the restoration of lower limb function in patients in the

One of the reasons underlying the effectiveness of using VR as a method for restoring motor function is the ability to model new motor tasks that make the rehabilitation process more interesting, increasing the motivation of patients for

VR can be used for multimodal sensory impact on the rehabilitated person. The addition of multimodal sensory reinforcements after performing the required interactions with virtual objects made it possible to use VR in a wide variety of areas, and it also significantly increases the potential for using this immersive environment in motor rehabilitation. Solving the problems of motor rehabilitation, using personalized, motor training, has a more significant impact on the processes of neuroplasticity than implicit or extra-contextual interaction with objects of the VR environment. For example, according to fMRI data, this method demonstrates a higher degree of activation of the motor cortex when performing specific motor tasks and when solving the problem of restoring motor disorders in patients after a

rehabilitated person to lose interest and motivation to practice.

acute period of stroke **Figures 1** and **2** [15].

#### *Proprioception in Immersive Virtual Reality DOI: http://dx.doi.org/10.5772/intechopen.96316*

*Proprioception*

conditions and tasks, thus achieving a personalized approach to solving rehabilitation problems [10]. In addition to restoring motor skills, VR can be considered as a tool in the treatment of cognitive impairments of various origins, in the treatment of post-traumatic stress disorder, as well as various pain syndromes. One of the promising options for the use of VR is its use in the study of the ontogeny of the nervous system, which will be extremely necessary for understanding the formation of a pathological process, since any pathology in the context of ontogeny can be considered as regressive development, i.e. return to earlier stages of the existence and functioning of the CNS as a whole or its individual components [11]. In this regard, it is extremely important to provide neuro-feedback, preferably multisensory, primarily through the visual and proprioceptive sensory channels, because the formation of motor skills without these sensory systems is not possible. In several studies on the adaptation of the motor system after the demonstrated visual inconsistency of movements in VR to movements in the real physical world, it was found that the activity of the visual-motor connection in children is higher than in adolescents and adults, since such adaptation to motor activity in real in the physical world, after such a demonstration in children, it was much slower [12, 13]. Over time, as they grow older, this connection weakens, but obviously, only because of functional restructuring, and not anatomical, therefore, in a saturated immersive environment, you can get the results of visual-motor interaction, which are not always achievable in the physical world. Thus, a separate study of the motor system, as well as its functioning in health and disease, without connection with sensory systems, is inappropriate and incorrect from a physiological point of view.

VR technology can be used to provide a meaningful and effective impact on various human sensory systems; it also provides significant opportunities for modeling their functioning to compensate for lost sensory and motor functions. Now, the most technically simple VR systems are with implicit interaction with VR objects. These VR environments allow the person to be rehabilitated to act as a passive observer of the displayed content, while interaction occurs through the visual and auditory channel. Some expansion of the application of this technology occurs due to the use of various manipulators or joysticks, while the interaction with VR objects acquires the features of explicit interaction, however, the manipulation of VR objects with the use of these VR devices by objects is surrogate in nature, not

The main problem in this interaction is the absence of physical sensations provided

by the proprioceptive system, namely, the feeling of weight, density of an object, position in space. The importance of these sensations in the process of rehabilitation or habilitation lies in the fact that most of the movements performed by a person are the result of the functioning of the proprioceptive system, which ensures all their diversity and successful performance, regardless of external and internal factors. Thus, locomotor activity, devoid of fine tuning, provided by biofeedback based on the proprioceptive system, becomes less effective, and in some situations it is simply impossible, for example, walking at night or interacting with an object in threedimensional space in the absence of visual control in patients with afferent paresis in the hand. An exception is interaction with objects in three-dimensional space, which is provided by cortical motor centers and the corresponding centers of praxis, in the implementation of which the visual analyzer has an equal or more significant role.

Understanding the importance of ensuring the formation of proprioceptive sensations, when solving a range of physical rehabilitation tasks, is also based on a

giving the fullness of physical sensations.

**3. Prospects for VR in motor rehabilitation**

**134**

more intense activation of neuroplasticity processes when performing motor tasks with multisensory and, first of all, proprioceptive reinforcement, demonstrated in a number of experiments both on biological models and in patients with different pathology. The formation of biofeedback stimulates the processes of neurogenesis and neuroplasticity, due to the formation of new interneuronal connections, initially of a functional nature, but subsequently fixed at the structural level due to the activation of latent connections between individual functional structures of the CNS. That is why VR is an ideal immersive environment that makes it possible to maximally activate the processes of neuroplasticity for more effective recovery of not only motor, but also cognitive impairments in patients with damage to the CNS of various origins.

Learning how to perform new skills within the framework of solving motor tasks modeled in VR is of decisive importance for inducing neuroplasticity processes, and as a result, contributes to a more effective restoration of impaired functions due to various injuries of the CNS or the musculoskeletal system. The immersive environment created in VR is a particularly effective tool for carrying out tasks of interacting with objects in three-dimensional space. The restoration of this level of motor function is especially important in increasing the independence of patients with motor defects of varying severity, which is one of the ultimate goals of motor rehabilitation or habilitation. Additional technical capabilities in the form of using various sensors, telemetry during training in VR allow a detailed analysis of the motor activity of the rehabilitated person, which can serve as initial data for the formation of a recommendation system to increase the effectiveness of the rehabilitation process, or to adapt exercises during the rehabilitation process, for example, by gradually complicating them. Implementation, not allowing the rehabilitated person to lose interest and motivation to practice.

For example, today there is many studies that formed the basis of several publications demonstrating the effectiveness of restoration of upper limb functions in patients after acute cerebrovascular accident when using exercises with VR [14].

However, these studies were based only on clinical data carried out in patients in the late rehabilitation period after suffering acute cerebrovascular accident. At the same time, the high safety and effectiveness of such exercises in VR suggests that the use of virtual reality will also be effective in patients in the acute period, after acute cerebrovascular accident. Such results regarding the use of implicit multimodal VR with visual and proprioceptive confirmation of walking have been demonstrated in a study on the restoration of lower limb function in patients in the acute period of stroke **Figures 1** and **2** [15].

One of the reasons underlying the effectiveness of using VR as a method for restoring motor function is the ability to model new motor tasks that make the rehabilitation process more interesting, increasing the motivation of patients for further exercises [16].

VR can be used for multimodal sensory impact on the rehabilitated person. The addition of multimodal sensory reinforcements after performing the required interactions with virtual objects made it possible to use VR in a wide variety of areas, and it also significantly increases the potential for using this immersive environment in motor rehabilitation. Solving the problems of motor rehabilitation, using personalized, motor training, has a more significant impact on the processes of neuroplasticity than implicit or extra-contextual interaction with objects of the VR environment. For example, according to fMRI data, this method demonstrates a higher degree of activation of the motor cortex when performing specific motor tasks and when solving the problem of restoring motor disorders in patients after a stroke [17].

**Figure 1.** *ReviVR rehabilitation walk simulator.*

**Figure 2.** *First-person view in ReviVR rehabilitation walk simulator.*

The data of objective methods for assessing changes in the activity of the cerebral cortex demonstrate the relationship between the specificity of the performed motor task and the degree of activation of neuroplastic changes.

Visual-motor and proprioceptive feedback, implemented in VR, provides realistic, up-to-date information during the rehabilitation exercise. It is realism and maximum proximity to physical sensations that are the most important factors that activate neuroplastic processes in the central nervous system (CNS).

Visual information, which is the most powerful sensory signal that is activated in the immersive environment, is a modeling factor for the reorganization of sensorimotor connections. For example, errors demonstrated during visual accompaniment of motor tasks performed in VR affect the motor and premotor cortex during motor learning, changing the activity of these zones [18–22].

**137**

*Proprioception in Immersive Virtual Reality DOI: http://dx.doi.org/10.5772/intechopen.96316*

activity of the visual cortex of the brain [35–39].

being rehabilitated [40].

rehabilitation exercises.

complexity [42–44].

brain [23].

Active and rewarding exercises (by demonstrating the progress of the performed exercise or another method) within the framework of the performed rehabilitation tasks can significantly enhance biofeedback, leading to a significant decrease in the number of errors in the restored movements, i.e. making them more energy efficient and accurate. According to fMRI data, at this moment there is a significant activation of the motor and premotor regions of the frontal cortex of the

The very observation and subsequent ideomotor presentation of this movement leads to a significant facilitation of the formation of motor evoked potential and increases intercortical interactions in the motor and premotor regions [24–27]. It should be noted that the implementation of all this activation of the motor areas through exposure, for example, on the visual analyzer, becomes possible due to the proven numerous intrahemispheric corticocortical connections [28, 29]. These connections combine the visual cortex with the motor, premotor, parietal, and frontal lobes into a single functional system [30–34]. At the same time, there is a large number of experimental studies that demonstrate that a significant number of neurons in the motor, premotor and parietal regions can be modulated by the

Moreover, in contrast to proprioception, the activation of which in the physical world is necessarily associated with active or passive movements of the limbs, visual neurofeedback in VR can be provided independently of the fact of movement, for example, by simply demonstrating it. Also, it is interesting that the demonstration of this movement can be significantly changed and, most importantly, it can be completed to its full volume, regardless of the initial motor activity of the person

Thus, visual biofeedback allows modulation of the motor system, without the need for active or passive movements. The visual system has a high degree of reliability and specificity in the implementation of this biofeedback, because visual afferentation predominates over other sensory modalities, such as proprioceptive or

An additional, but important rationale for the advisability of using the visual cortex as a sensory input for modulating motor function is that during an acute cerebrovascular accident, it is not damaged simultaneously with the motor or premotor cortex, due to their location in different blood supply basins of the brain, but namely carotid and vertebrobasilar. For acute cerebrovascular accident, in the first episode, the defeat of two pools is not a common manifestation of the disease. The defeat of the cortical representation of the visual analyzer in the form of hemianopsia and contralateral hemiplegia is observed only in the villous artery syndrome, but the preservation of the opposite visual fields allows using the VR environment for

Thus, VR allows the user to receive multimodal sensory information, which can cause a real sense of presence and provide cognitive, sensory and emotional immersion in the formed rehabilitation task, which has varying degrees of

The use of VR makes it possible to implement various modifications of the displayed object or its movement, highlighting it against the general background, for example, by changing the color, brightness or its shape. This opportunity allows the patient to focus on the target elements of the rehabilitation exercise, enhancing his motivation. With the help of VR, it is possible to achieve modeling of the conditions that in traditional therapy are carried out by limiting the movement of a hand that does not have motor impairments due to stroke, through its fixation to the trunk. To implement this type of therapy in VR, one can ignore the activity of a healthy limb (recorded by telemetry or contact sensors: electromyography, accelerometers,

auditory, and is used by a person more effectively in everyday activities [41].

#### *Proprioception in Immersive Virtual Reality DOI: http://dx.doi.org/10.5772/intechopen.96316*

*Proprioception*

**Figure 1.**

*ReviVR rehabilitation walk simulator.*

**136**

**Figure 2.**

The data of objective methods for assessing changes in the activity of the cerebral cortex demonstrate the relationship between the specificity of the performed

Visual information, which is the most powerful sensory signal that is activated in the immersive environment, is a modeling factor for the reorganization of sensorimotor connections. For example, errors demonstrated during visual accompaniment of motor tasks performed in VR affect the motor and premotor cortex during

Visual-motor and proprioceptive feedback, implemented in VR, provides realistic, up-to-date information during the rehabilitation exercise. It is realism and maximum proximity to physical sensations that are the most important factors that

motor task and the degree of activation of neuroplastic changes.

*First-person view in ReviVR rehabilitation walk simulator.*

activate neuroplastic processes in the central nervous system (CNS).

motor learning, changing the activity of these zones [18–22].

Active and rewarding exercises (by demonstrating the progress of the performed exercise or another method) within the framework of the performed rehabilitation tasks can significantly enhance biofeedback, leading to a significant decrease in the number of errors in the restored movements, i.e. making them more energy efficient and accurate. According to fMRI data, at this moment there is a significant activation of the motor and premotor regions of the frontal cortex of the brain [23].

The very observation and subsequent ideomotor presentation of this movement leads to a significant facilitation of the formation of motor evoked potential and increases intercortical interactions in the motor and premotor regions [24–27].

It should be noted that the implementation of all this activation of the motor areas through exposure, for example, on the visual analyzer, becomes possible due to the proven numerous intrahemispheric corticocortical connections [28, 29]. These connections combine the visual cortex with the motor, premotor, parietal, and frontal lobes into a single functional system [30–34]. At the same time, there is a large number of experimental studies that demonstrate that a significant number of neurons in the motor, premotor and parietal regions can be modulated by the activity of the visual cortex of the brain [35–39].

Moreover, in contrast to proprioception, the activation of which in the physical world is necessarily associated with active or passive movements of the limbs, visual neurofeedback in VR can be provided independently of the fact of movement, for example, by simply demonstrating it. Also, it is interesting that the demonstration of this movement can be significantly changed and, most importantly, it can be completed to its full volume, regardless of the initial motor activity of the person being rehabilitated [40].

Thus, visual biofeedback allows modulation of the motor system, without the need for active or passive movements. The visual system has a high degree of reliability and specificity in the implementation of this biofeedback, because visual afferentation predominates over other sensory modalities, such as proprioceptive or auditory, and is used by a person more effectively in everyday activities [41].

An additional, but important rationale for the advisability of using the visual cortex as a sensory input for modulating motor function is that during an acute cerebrovascular accident, it is not damaged simultaneously with the motor or premotor cortex, due to their location in different blood supply basins of the brain, but namely carotid and vertebrobasilar. For acute cerebrovascular accident, in the first episode, the defeat of two pools is not a common manifestation of the disease. The defeat of the cortical representation of the visual analyzer in the form of hemianopsia and contralateral hemiplegia is observed only in the villous artery syndrome, but the preservation of the opposite visual fields allows using the VR environment for rehabilitation exercises.

Thus, VR allows the user to receive multimodal sensory information, which can cause a real sense of presence and provide cognitive, sensory and emotional immersion in the formed rehabilitation task, which has varying degrees of complexity [42–44].

The use of VR makes it possible to implement various modifications of the displayed object or its movement, highlighting it against the general background, for example, by changing the color, brightness or its shape. This opportunity allows the patient to focus on the target elements of the rehabilitation exercise, enhancing his motivation. With the help of VR, it is possible to achieve modeling of the conditions that in traditional therapy are carried out by limiting the movement of a hand that does not have motor impairments due to stroke, through its fixation to the trunk. To implement this type of therapy in VR, one can ignore the activity of a healthy limb (recorded by telemetry or contact sensors: electromyography, accelerometers,

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 increase the rehabilitation potential in patients with CNS pathology.

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 premotor cortex of the brain [51].
