Virtual Reality and Assistive Technologies: A Survey <s> II. VIRTUAL ENVIRONMENT AND TARGET GROUPS <s> Recent experimental evidence suggests that rapid advancement of virtual reality (VR) technologies has great potential for the development of novel strategies for sensorimotor training in neurorehabilitation. We discuss what the adaptive and engaging virtual environments can provide for massive and intensive sensorimotor stimulation needed to induce brain reorganization. Second, discrepancies between the veridical and virtual feedback can be introduced in VR to facilitate activation of targeted brain networks, which in turn can potentially speed up the recovery process. Here we review the existing experimental evidence regarding the beneficial effects of training in virtual environments on the recovery of function in the areas of gait, upper extremity function and balance, in various patient populations. We also discuss possible mechanisms underlying these effects. We feel that future research in the area of virtual rehabilitation should follow several important paths. Imaging studies to evaluate the effects of sensory manipulation on brain activation patterns and the effect of various training parameters on long term changes in brain function are needed to guide future clinical inquiry. Larger clinical studies are also needed to establish the efficacy of sensorimotor rehabilitation using VR approaches in various clinical populations and most importantly, to identify VR training parameters that are associated with optimal transfer into real-world functional improvements. <s> BIB001 </s> Virtual Reality and Assistive Technologies: A Survey <s> II. VIRTUAL ENVIRONMENT AND TARGET GROUPS <s> Abstract Hand and finger functions are of critical importance for independence in everyday activities, but their recovery is often limited following neurological injury, motivating the need for novel therapeutic and assistive tools. The objective of this chapter is to provide a comprehensive overview of robotic approaches for the rehabilitation of hand function and underline their potential to complement conventional rehabilitation. First, we present the design concepts of existing hand exoskeletons and end-effector devices and then review and discuss the clinical evidence underlining the feasibility of robot-assisted rehabilitation of hand function. We conclude by discussing promising research directions to further exploit the potential of robot-assisted rehabilitation of hand function in neurological patients. <s> BIB002
Any disability may be associated with one or more of the following impairments: (a) mobility impairment, (b) cognitive impairment, and (c) visual impairment. Below is a brief description of different kinds of impairments followed by the classification of a VE on the basis of how it addresses different impairments. Mobility impairments can happen due to several reasons. Patients who have undergone stroke or spinal cord injury, elderly people or Parkinsons patients suffer from motor control deficits that can lead to mobility impairments. Motor paralysis can also be due to traffic accidents, multiple sclerosis (MS), cerebral palsy, neurofibromatosis, traumatic brain injury (TBI), and post-polio syndrome BIB001 ). Depending on the severity of brain tissue damage, movements of the affected limbs can be restricted. In motor paralysis among post-stroke patients, the hand tends to be the most affected limb because of the fact that a large portion of the sensorimotor cortex is allocated to the human hand BIB002 . Patients grasping and reaching activities can be affected. Patients may even fail to move the paretic arm. When lower limbs are affected, patients may exhibit motor deficits in the form of postural imbalance and longer gait cycles with decreased cadences. Patients suffering from chronic knee injury may also exhibit abnormal gait patterns. Parkinsons patients frequently exhibit freezing gait and persistently struggle to regain normal gait. Patients with frozen shoulder (adhesive capsulitis) suffer from a stiff and painful shoulder with a very limited range of shoulder movement. Post-stroke patients suffering from hemiplegia are left with partial paralysis on one side of the body and movement can be severely restricted in the affected sides hand, arm or leg. People suf-fering from quadriplegia are paralyzed in both arms and both legs and are only capable of moving their faces. Next comes psychological or cognitive impairment which includes attention or memory deficit, phobia or irrational fear of or aversion to something, hallucinations, or more. Children suffering from neurological disorders like cerebral palsy, autism, elderly people or people undergoing post TBIphase or similar events suffer from functional deficiencies such as little or no response to surrounding events, longer reaction time, mental distraction, forgetfulness, depression, or lack of problem-solving ability. They can have difficulty even in performing the basic activities of daily living (Christiansen et al. 1998). Post-TBI and post-stroke patients may exhibit both cognitive and physical disorders. Symptoms include gaze instability, vertigo, attention deficits, and motion sensitivity as well as clumsy body movement  . The visually impaired are the next target group. According to WHO classification, this group includes the blind (people with complete or nearly complete loss of vision), legally blind (people with a level of visual impairment considered by law as disabled), or people having a decreased ability to see to a degree that causes problems not fixable by usual means, such as glasses. In most rehabilitation systems, visual feedback-based virtual environment is used. With the integration of haptic force feedback devices, users can touch, feel or grasp virtual objects. Commonly used exercise equipment such as treadmills or bicycles can also be integrated into a VE to provide the user with better performance metrics. Table 1 categorizes VR-based rehabilitation systems on the basis of subjects requirements and available feedback options (e.g., visual, haptic). All of the above-mentioned VR-based rehabilitation systems can be enhanced with auditory cues for verbal guidance and environment enrichment. Though in the classification hearing impairment has not been specifically mentioned, all categories of VE can be used for cognitive empowerment of the deaf.