You are in: eMedicine Specialties > Neurology > Computer Applications in Neurology Virtual Reality: Overview of its Application to NeurologyArticle Last Updated: Oct 11, 2006AUTHOR AND EDITOR INFORMATIONSection 1 of 7
  Author: Morris Steffin, MD, Chief Science Officer, Virtual Reality Neurotech Lab Editors: Sydney Louis, MD, Emeritus Professor, Department of Neurology, Brown University School of Medicine; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Richard J Caselli, MD, Professor, Department of Neurology, Mayo Medical School, Rochester, MN; Chair, Department of Neurology, Mayo Clinic of Scottsdale; Matthew J Baker, MD, Consulting Staff, Collier Neurologic Specialists, Naples Community Hospital; Nicholas Y Lorenzo, MD, Chief Editor, eMedicine Neurology; Consulting Staff, Neurology Specialists and Consultants Author and Editor Disclosure Synonyms and related keywords: VR, medical applications of virtual reality, virtual surgery, neurologic applications of virtual reality, virtual reality motor assistance, pain management, epilepsy monitoring, virtual reality immersion, cybersickness, VR immersion INTRODUCTIONSection 2 of 7
  Virtual reality (VR) is a concept that uses multiple novel approaches to allow interaction with human sensorimotor and cognitive systems. It is a global approach toward the temporary fusion of experience and function with an artificial environment in which the links to reality fall to a large extent under the control of the VR designer. To achieve these ends, VR systems produce high levels of immersion, or the perception that the subject has entered into the "world" constructed by a set of computer-generated stimuli. Moreover, the computer (which in the strict etymologic sense refers to a thinking aid) takes on the additional role of an experience enhancer. The interactions of the VR milieu now are emerging in attempts to understand and intervene in a variety of neurologic disorders. BACKGROUNDSection 3 of 7
Techniques for producing experiential effects may result in a relatively nonimmersive environment. Such arrangements typically employ a video screen and headphones or loudspeakers for presentation of audiovisual stimuli and a mouse or joystick for patient response. While one may think that the subject involvement is at a low level in such a situation, consider the strong hold that the typical video game exerts on the participant. Direct bodily movements also can direct the computer to produce a strongly interactive environment. Increasing levels of immersion require more sophisticated input/output devices. These include wide-field stereoscopic head-mounted displays (HMDs) for audio and visual stimuli, with modification of video and audio stimuli in accordance with patient movement, to simulate scene changes with head and body movement. These higher levels of immersion may produce cybersickness in susceptible individuals. Symptoms can include nausea, vertigo, and anxiety and may in some instances resemble the symptoms of acrophobia. The symptoms of cybersickness are probably secondary to an artificially induced mismatch between vestibular and ocular inputs, which in many respects is the putative etiology of acrophobic symptoms. Interestingly, the capacity to produce these symptoms in the VR environment appears to parallel the effectiveness of cueing in the therapeutic approaches to acrophobia. Haptic (force-feedback) devices provide reaction to the subject's movements by producing forces simulating those generated in an actual subject environment. These devices may take the form of simulated endoscopic instruments, such as bronchoscopic devices that can be combined with imaging (CT) for 3-dimensional modeling and surgical instruments to provide texture and resistance feedback. Transducers may simulate pilot controls of an airplane or can be configured as gloves or even bodysuits that measure subject movement and respond to force, vibrational inputs, and regional temperature changes. Input from these transducers can control virtual musical instruments and increase the precision of motor control for persons with disabilities, while sensory augmentation can compensate for visual loss. Olfactory simulators can be integrated within the HMD for additional limbic stimulation and realism. Vibrational and acceleration stimulation can assist in simulating posterior column and vestibular inputs of an actual subject environment. MEDICAL APPLICATIONSSection 4 of 7
The realism of the environment shows considerable promise in medical applications in the following areas. Psychiatry In the treatment of acrophobia, taking a patient to the edge of a virtual high building in a nonthreatening environment presents several advantages. The brainstem cues involving vestibulo-ocular mismatch that produce physical symptoms when the individual with acrophobia is placed in the offending environment (eg, ledge high above the street) can be reproduced with sufficient fidelity in a known nonthreatening environment (ie, VR laboratory). This produces nausea and vertigo and evokes sympathetic responses. Conversely, the patient is aware that he or she is in fact in a safe environment. Thus a cognitive dissonance is evoked, ie, the sensorineural perception of height juxtaposed with knowledge of the actual safe environment. Neuroplastic mechanisms then can come into play to begin resetting the brainstem-visual interaction. The symptoms remain overpowering if the cognitive damping effect of knowledge of the actual safe environment is absent. In this situation, the patient is unable to endure the exposure to the height necessary for the neuroplastic response to develop. Moreover, the patient can be exposed to a gradually increasing level of stimulation by increasing the perceived height of the building or decreasing the distance to the ledge. The patient also can control the configuration of the environment by walking closer to the virtual edge or by looking up or down. In each case, the virtual environment is recalculated in essentially real time to produce the needed environmental consistency. Deconditioning in such environments has been quite effective. Similar approaches have been used for treatment of arachnophobia and fear of flying. In these approaches, the realism of the stimulus can be graded, eg, from a clearly artificial stick spider to a quite realistic, animated representation with spiderlike texture and movement patterns. Moreover, the movement patterns can be made responsive to the patient's movements, and haptic (tactile) input can be added. Virtual surgery Traditional surgical training requires immediate exposure of the physician to actual patients. The mechanical facets of surgical technique, including identification of anatomic landmarks, instrument manipulation, and reaction to changes in the surgical field, require live patients and interaction with an experienced surgeon-teacher. With VR training paradigms, the surgeon under training manipulates instruments that are attached to force transducers. A visual environment showing anatomic structures is experienced and changes within the field of view in accordance with the actions taken using the virtual instruments (and with changes in the field of view). Such an approach is useful in learning the basic surgical maneuvers. This environment allows for unlimited practice, limited only by the realism of the virtual surgical field, until the trainee-surgeon demonstrates sufficient manual and visuospatial adaptation to warrant treating actual patients. The same techniques allow the accuracy of the surgical technique to be increased to greater than human levels. For example, by using virtual instruments to activate microrobotic devices, approaches to microsurgery have been developed to suppress effects of natural human tremor and motor fatigue while preserving the realistic interaction between the surgeon and the field. Further expansion of this technique ultimately will allow performance of procedures currently too delicate for the human hand. Combination of these techniques with improved computer-integrated imaging (eg, MRI, CT scan) allows much more accurate approaches to biopsy and surgical procedures. VR techniques quietly are revolutionizing the teaching and perception of anatomic relationships. Dynamic imaging Processing of image data from both visual anatomic data sets and medical imaging systems has allowed virtual "fly-through" examinations of internal organs in actual patients. Moreover, computational systems have been developed to allow haptic interaction with these surfaces, vastly expanding the capabilities for tissue interaction in presurgical evaluations and fundamentally altering the process of noninvasive organ examination. NEUROLOGIC APPLICATIONSSection 5 of 7
VR applications for neurologic investigation and therapy are being developed quickly. If the evolution of medical VR applications is considered, then one can proceed from an essentially open-loop condition toward a closed-loop condition. That is, the computer in fact generates many of the features of the virtual environments previously described. The presentation is varied according to the response, but the patient remains in an artificially created milieu. As virtual surgery and dynamic imaging develop, the operating feedback loops between human and machine will be closing and therefore will become more functional and clinically applicable. This functional enhancement will be realized for systems involving both microsurgical and imaging responses to patient space, whether using actual or computed images (eg, CT scan, MRI). The computer must manipulate images derived from an actual physical environment rather than images developed by its internal program. VR can be applied for measurement and therapeutic approaches to neurologic diseases on the basis of more complete closure of the patient-VR loop. Rather than dealing with pre-acquired images (as with virtual surgery or imaging), the computer must interact on a real-time basis with salient features of the patient and his or her environment and immediately respond to these features to produce audiovisual, haptic, and tactile responses to correct maladaptive or impaired behavior. Virtual reality motor assistance Consider the visual-haptic assistance paradigm. Here the patient may reach for a target. The computer must sense that target in the patient's space as a discretely localized entity in order to formulate a trajectory to assist the patient in reaching the target. The haptic input to the patient must use the target as well as the patient's responses in formulating the corrective forces that guide the patient to complete the task. Only by producing a response in real time keyed to the features of the patient's environment and to the patient's own responses to that environment can the VR system produce an appropriate response. Approaches to retraining in movement disorders will rely on these design principles and will capitalize on the previously untapped potential of neuroplasticity. Pain management VR systems can aid in pain management by producing sufficient immersion to distract the patient from the pain by overriding the noxious stimuli with pleasant sensory input and by modulating pain gating systems. In this situation, the patient-computer loop also must be closed, but the orientation is directed toward control of autonomic responses rather than cognitive interactions. The computer must sense whether the presented stimuli are effective in reducing pain responses and should modify stimuli routines accordingly. Intelligent quantification of patient space - Epilepsy monitoring By extending the concept of real-time analysis of patient space, the VR computer also can add co-intelligence to clinician The approach described is open loop. However, by enabling the computer to track regions of interest according to significance of the body part and the movement patterns generated, a map of these patterns can be presented to the clinician. This reduces the need for manual intervention to track relevant movements and renders such data to the clinician in VR form. Analysis of information processing in neuropil Just as VR continues to augment the conception of anatomic relationships, so will future applications allow rendering of physiology in terms that will enhance understanding far beyond present techniques. As an example, VR presentation of information flow in neuropil can be expected to allow meaningful dialogue between regions of neuropil and the experimenter. Analysis of such activity must take into account the holographic nature of central nervous system (CNS) processing in order to transcend the point-to-point methods currently in use, which provide relatively little insight into the nature of processes such as speech recognition and production, visual pattern recognition, spatial perception, and integrated (praxic) motor responses. The result should be an increased understanding of CNS function on a systems level that is likely to lead to a new family of clinical diagnostic instruments and to rational, less empiric methods of neuropharmaceutic development. CONCLUSIONSection 6 of 7
Presently, VR represents a broad range of techniques that rapidly are evolving from the melding of diverse fields of computer graphics and haptics, coupled with the increasing availability of sufficiently powerful hardware platforms. VR applications to clinical neurology and psychiatry are in their infancy, but they will revolutionize many concepts in rehabilitation, neurophysiology, and neuropharmacology. REFERENCESSection 7 of 7
Virtual Reality: Overview of its Application to Neurology excerpt Article Last Updated: Oct 11, 2006 |
