Virtual reality exposure therapy for active duty soldiers

Virtual reality exposure (VRE) therapy is a promising treatment for a variety of anxiety disorders and has recently been extended to the treatment of posttraumatic stress disorder (PTSD). In this article, the authors briefly review the rationale for VRE and its key processes. They illustrate the treatment with an active-duty Army soldier diagnosed with combat-related PTSD. Six sessions of VRE were provided using an immersive simulation of a military convoy in Iraq. Self-reported PTSD symptoms and psychological distress were reduced at posttreatment relative to pretreatment reports, as assessed by the PTSD Checklist-Military Version and the Behavior and Symptom Identification Scale-24. The case outcomes parallel those reported in the research with other disorders and suggest the applicability of VRE in treating active duty soldiers with combat-related PTSD.     

The use of virtual reality in assessment and treatment of anxiety and related disorders

In recent years the development of new virtual environments has been qualitatively high and fast at the same time, but the dissemination of virtual reality (VR) in clinical practice is still scarce. The aim of this review is to give an insight into the state of the art of the use of VR as an assessment tool and treatment intervention in anxiety and related disorders as posttraumatic stress disorder and obsessive–compulsive disorders. Besides an overview into the efficacy of VR, a summary will be given on assumed working mechanisms in virtual reality exposure therapy and how this aligns with current theoretical models. Further, it will be discussed how VR is accepted by patients and research into the reluctance of therapist to use this technology during treatment with focus on the therapeutic alliance and how it may be influenced by the use of VR. Finally, we discuss clinical and future issues as, for example, dissemination into clinical practice and what VR has to offer therapists in future. This not only in adult population but as well in younger patients, as young adolescents VR has a great potential as it connects easily with its playful elements to this population and might be a low threshold step to offer treatment or preventive interventions.     

虚拟现实技术在医学中的应用

虚拟现实是一门新兴的学科 ,它在医学上已经得到了广泛的应用。本文从虚拟人、虚拟人同真实人体数据的融合以及虚拟的远程医疗系统三个方面介绍了虚拟现实在医学上的应用 ,并从对计算能力的要求、软硬件等方面介绍了医学虚拟现实背后的图形学支持。最后 ,对现有的分布式 VR系统做了一个简要的介绍。     

虚拟现实暴露疗法在蜘蛛恐怖症中的应用:机制、效果及展望

蜘蛛恐惧症是特定性恐惧症中的动物类型恐惧症,属于焦虑症范畴,目前尚不能通过药物治愈.虚拟现实暴露疗法(virtual reality exposure therapy,VRET)是治疗焦虑症的一种新的干预方法.由于其疗效好、经济、安全、可控等优势,广泛应用于精神障碍疾病的研究.研究发现,VRET可通过调节虚拟暴露刺激、...     

Detection of speed changes during pursuit eye movements

The human visual system is strikingly insensitive to speed changes attributed to the need to infer visual acceleration, observed during stationary fixation, indirectly by comparing velocities integrated over time. The objective of this study was to test if smooth pursuit eye movements improve the detection of speed changes. This was expected for two reasons: first, pursuit reduces the retinal image slip velocity, leading to smaller Weber fractions for velocity changes; secondly, pursuit provides acceleration-dependent retinal position cues unavailable during stationary fixation such as displacements of the target image away from the fovea due to unexpected changes in target velocity. In a first set of experiments thresholds for just noticeable speed changes were measured in ten healthy human subjects confronted with a horizontally moving target, changing its velocity unpredictably during its ramp-like movement. During stationary fixation, the Weber fraction averaged 0.13 for a starting velocity of the target being 15°/s. Smooth pursuit of the same target significantly reduced the Weber fraction down to 0.08. In a second set of experiments, the discrimination of speed changes was tested in patients (n=10) with pursuit disturbances characterized by increased retinal image slip and unidirectional retinal image displacements. These patients showed a strong perceptual bias to report speed increments and an insensitivity to speed decrements. We argue that this asymmetry is a necessary consequence of a mechanism exploiting retinal position errors for the detection of speed change, confronted with directionally biased errors due to the pursuit impairment. In summary, the detection of speed changes is facilitated by pursuit eye movements but is highly susceptible to pursuit insufficiencies.     

Influence of virtual reality on postural stability during movements of quiet stance

Introduction: Balance problems during virtual reality (VR) have been mentioned in the literature but seldom investigated despite the increased use of VR systems as a training or rehabilitation tool. We examined the influence of VR on body sway under different stance conditions. Methods: Seventeen young subjects performed four tasks (standing with feet close together or tandem stance on firm and foam surfaces for 60 s) under three visual conditions: eyes open without VR, eyes closed, or while viewing a virtual reality scene which moved with body movements. Angular velocity transducers mounted on the shoulder provided measures of body sway in the roll and pitch plane. Results: VR caused increased pitch and roll angles and angular velocities compared to EO. The effects of VR were, for the most part, indistinguishable from eyes closed conditions. Use of a foam surface increased sway compared to a firm surface under eyes closed and VR conditions. Conclusion: During the movements of quiet stance, VR causes an increase in postural sway in amplitude similar to that caused by closing the eyes. This increased sway was present irrespective of stance surface, but was greatest on foam.     

Discharge of frontal eye field neurons during saccadic and following eye movements in unanesthetized monkeys

Summary The cortical mechanism of eye-movement control was investigated by recording single cell activity from the frontal eye field (FEF) in unanesthetized monkeys seated in a primate chair with head restrained. Two types of cells (I and II) were found. Type I neurons fired during voluntary saccades occurring in a given direction and during the fast phase of nystagmus. Cells of this type were silent during slow pursuit movement. Type II cells showed steady discharge when the eyes were oriented in a specific direction. These cells discharged also during smooth pursuit movements and the slow phase of nystagmus, provided that the eyes were moving across positions which would have been associated with neuronal activity had the eyes come to rest there. All of Type II and a few of Type I neurons were identified by antidromic response to stimulation of the cerebral peduncle. These results indicate that cortical neurons have patterns of discharge distinctly related either to saccadic or to pursuit movements, in line with the view that these two different types of eye movement are generated by distinct neuronal mechanisms.     

Localization and motion perception during smooth pursuit eye movements

We investigated the relationship between compensation for the effects of smooth pursuit eye movements in localization and motion perception. Participants had to indicate the perceived motion direction, the starting point and the end point of a vertically moving stimulus dot presented during horizontal smooth pursuit. The presentation duration of the stimulus was varied. From the indicated starting and end points, the motion direction was predicted and compared with the actual indicated directions. Both the directions predicted from localization and the indicated directions deviated from the physical directions, but the errors in the predicted directions were larger than those in the indicated directions. The results of a control experiment, in which the same tasks were performed during fixation, suggest that this difference reflects different transformations from a retinocentric to a head-centric frame of reference. This difference appears to be mainly due to an asymmetry in the effect of retinal image motion direction on localization during smooth pursuit.     

虚拟现实视觉体验对脑功能网络的影响

随着虚拟现实(VR)技术的广泛应用和相关设备的迅速普及,长时间使用VR技术引起的脑疲劳问题受到广泛关注。本研究结合主观疲劳量表与脑电信号脑功能网络特征参数,研究VR技术引起的脑疲劳问题。随机选取16名健康受试者,同步采集观看相同题材的传统平面(TP)视频及VR视频时的脑电信号,观看视频前后填写主观疲劳量表,利用互相关方法对所采集到的脑电信号进行关联特性分析,构建两种视觉体验前后的脑功能网络,并从复杂网络的角度,对比分析平均度、平均聚类系数、平均路径长度、平均全局效率和"小世界"属性等脑网络特征参数。结果发现,观看视频后的量表分值均大于观看前,并且从主观感受上,受试者观看VR视频比观看TP视频更容易产生疲劳感;观看VR和TP视频后,脑网络互相关系数、平均度值、平均聚类系数和平均全局效率值均比观看视频前显著降低,平均路径长度值显著升高,"小世界"属性显著减小;并且相比观看TP视频,观看VR视频后脑网络特征参数变化量更大,且差异具有统计学意义(P <0.05)。通过本研究结果,或可为分析和评价VR视觉体验引发的脑疲劳提供理论依据和试验参考。     

Multi-degree of freedom joystick for virtual reality simulation

Abstract

A modular control interface and simulated virtual reality environment were designed and created in order to determine how the kinematic architecture of a control interface affects minimally invasive surgery training. A user is able to selectively determine the kinematic configuration of an input device (number, type and location of degrees of freedom) for a specific surgical simulation through the use of modular joints and constraint components. Furthermore, passive locking was designed and implemented through the use of inflated latex tubing around rotational joints in order to allow a user to step away from a simulation without unwanted tool motion. It is believed that these features will facilitate improved simulation of a variety of surgical procedures and, thus, improve surgical skills training.     

Possible mechanisms of disorders in saccadic eye movements in parkinsonian patients

Electrooculogram recording was used to examine the centrifugal horizontal saccades through an angle of 40° in patients with Parkinson's disease and healthy subjects. The patients demonstrated prolongation of latency and duration, as well as appearance of multiple saccades. The mean values of latency in the right and left saccades were significantly longer in patients than in normal subjects. Although the saccade duration in patients did not differ significantly from that in normal subjects, this parameter tended to increase in value and dispersion. The courses of the vision-controlled saccade disturbances in parkinsonian patients are discussed and hypothesis is forwarded on the disorder mechanisms with particular attention to GABAergic system. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 125, No. 3, pp. 254–259, March, 1998     

Anatomy education for medical students in a virtual reality workspace: A pilot study

The COVID-19 pandemic has posed a challenge for many medical schools, as they have had to adjust their curricula into an online format. This was particularly problematic for anatomy courses as in person dissections have historically been preferred for providing students with a three-dimensional learning environment. In this study, we aim to share our experience with conducting anatomy lectures for medical student using a virtual reality (VR) workspace. Additionally, we discuss the advantages of using VR and expand on how it may be used to improve students' understanding of anatomy in comparison to various other online lecture formats. To do this, we utilized a post-lecture survey to gain feedback from the medical students that participated in a VR anatomy workspace. We found that many of our participants expressed that having access to their course material from anywhere and anytime via a virtual space, and being able to manipulate anatomical structures by moving and modifying them provided the student with a strong advantage. Although there are still limitations, we hope that our experience will assist other anatomy teachers with improving their lecture methods, especially during the pandemic.     

Co-ordination of breathing with rhythmic head and eye movements and with passive turnings of the body

In the present study, we investigated co-ordination of breathing with active horizontal head and eye movements and with passive body turnings. The main purpose was to compare co-ordination with active voluntary and with passive movements. Co-ordination was defined according to the relative phases (RPs) between breathing and additional rhythms. It was present when at least five consecutive RPs scattered less than 25% of breath duration or at least three consecutive RPs scattered less than 10%. Additionally, we studied the influence of factors such as size of active muscle groups, mechanical interactions or involuntary motor activities. In consecutive experimental conditions, 17 healthy volunteers performed voluntary rhythmic head (with eyes open and closed) and eye movements and were moved passively (also with eyes open and closed). Co-ordination occurred in all experimental conditions. The highest percentage of co-ordinated breaths was found during active head movements with closed eyes but the difference with other conditions was not significant. However, periods of stable entrainment were observed only in this condition. The results demonstrate that co-ordination is possible even in the absence of voluntary rhythmic movements. Size of active muscle groups or mechanical interactions do not necessarily affect the degree of co-ordination. On the other hand, involuntary motor activities such as reflex eye movements associated with vestibular stimulation may have a considerable influence on co-ordination between other motor processes. These results strongly support the theory of co-ordination as an unconscious nervous interaction that is not based on mechanical or intentional factors.     

Effects of dual task demands on the accuracy of smooth pursuit eye movements

The effect of attention allocation on smooth pursuit eye movements (SPEM) was investigated. Eye movements were electrooculographically recorded in 27 healthy subjects who tracked a visual target that moved horizontally with constant or unpredictably varying velocity. In some trials, subjects performed additional auditory discrimination tasks varying in difficulty. Pursuit error decreased when attention was divided between both tasks. The pattern of results is incompatible with the assumption made in previous research that attention enhancement improves SPEM accuracy. Rather, ocular smooth pursuit appears to be executed in the automatic mode, although intentional and selective processes must contribute. Moreover, controlled attention directed to the tracking task interfered with smooth pursuit. A reinterpretation of earlier studies in which visual monitoring tasks were used to improve eye tracking is needed.     

Analog signal processing of eye movements for on-line digital computer analysis.

An analog signal processing circuit is described which allows accurate measurement of the amplitude, velocity, and interval of both fast and slow components of eye movements. This system, in conjunction with an on-line minicomputer, can measure amplitudes up to 32° and velocity to 640° per sec. The analog signal processing methods and technique for achieving a reliable output signal are discussed. Data obtained from human and animal subjects are portrayed.     

Modulation of phosphene perception during saccadic eye movements: a transcranial magnetic stimulation study of the human visual cortex

Saccadic suppression allows for perceptual stability during rapid movements of the eyes. One of the neural mechanisms may involve saccade-related modulation of neural activity in the visual cortex. Using the perception of phosphenes induced by transcranial magnetic stimulation (TMS) applied over the visual cortex (VC) as an index of cortical excitability, we sought to determine if VC excitability was modulated at varying times relative to saccade onset. We used two measures of excitability: (1) stimulator intensity required to induce phosphenes in 50% of trials, also called the phosphene threshold (PT), and (2) the subjective intensity of the phosphene. We found that there was no change in PT for different saccade-TMS onset asynchronies while there was an increase in perceived phosphene-intensity near the time of saccade onset (F(7,42)=4.34, P=0.001). Contrary to what would be expected from a saccadic suppression model, our results suggest that excitability of the visual cortex is slightly enhanced at the time of saccade onset.     

Validity of Listing's law during fixations, saccades, smooth pursuit eye movements, and blinks

In its original formulation, Listing's law referred only to eye positions during steady fixation. In recent years, however, several studies have suggested that Listing's law can be extended to the movements of the eyes, including during saccades and smooth pursuit. A major problem in deciding whether or not Listing's law is obeyed during eye movements is the influence of any spontaneous fluctuations in torsional eye position. To try to settle this question, the three-dimensional position of the eyes (around the three axes: horizontal, vertical, and torsional) was recorded with dual search coils in five normal subjects during fixations, 20° saccades, blinks, and 20° pursuit movements with a 20°/s stimulus velocity. Eye movements across a wide range of horizontal positions were measured at different elevations of gaze during 11 min. Variability (as reflected in the standard deviation of torsional eye position) was used as a measure of the validity of Listing's law. After linear detrending single trials, each lasting 21.5 s, to remove the effects of drift over minutes, the reduction in the standard deviation of torsional position in tertiary eye positions was 54% assuming a planar and 58% assuming a second-order curved Listing's surface. We attributed this long-term fluctuation of the torsional signal to slippage of the coil on the eye. The remaining variability was mainly due to short-term fluctuation of eye torsion over seconds. The impact of hysteresis, associated with consecutive centrifugal-centripetal horizontal movements, on the variability of torsional eye position appeared negligible. Peak increases in the standard deviation from the fixation baseline after fitting individual Listing's planes for each trial were 348% during blinks, 141% during saccades, and 72% during pursuit movements (median value of five subjects). In conclusion, Listing's law during blinks, saccades, and pursuit is less valid than during fixations, which raises doubts about the existence of an internal Listing's law operator for eye movements. Possibly, central eye velocity commands do not comply with Listing's law.