Does Augmenting Virtual Reality-Based Cognitive Training with Longitudinal, Anodal Transcranial Direct Current Stimulation Improve Visual Search Performance? A Neurobehavioral Evaluation

Shah D., K Rao A., Bhavsar A., Roy Chowdhury S., Chandra S., Dutt V.

Rao A.K., Chandra S., Dutt V.

Dynamic decision-making involves a series of interconnected interdependent confluence of decisions to be made. Experiential training is preferred over traditional methods to train individuals in dynamic decision-making. Imparting experiential training in physical settings can be very expensive and unreliable. In virtual reality (VR), synthetic environments play a significant role in providing flexible and cost-effective training environments to enhance dynamic decision-making. However, it is still unclear how VR can be used to impart dynamic decision-making training to increase cognitive performance in complex situations. Besides, different repetitive training methods like desirable difficulty framework and heterogeneity of practice have been evaluated on generic cognitive and motor tasks. However, an evaluation of how these repetitive training methods facilitate dynamic decision-making in an individual in a virtual complex environment setting is lacking in the literature. The objective of this study is to evaluate the effect of different repetitive training methods in immersive VR on dynamic decision-making in a complex search-and-shoot environment. In a lab-based experiment, 66 healthy subjects are divided equally and randomly into three between-subject training conditions: heterogenous, difficult, and sham. On Day 1, all the participants, regardless of the condition, executed an environment of a baseline difficulty level. From Days 2 to 7, the participants alternatively executed the novice difficulty and expert difficulty versions of the environment in the heterogenous condition. In difficult conditions, the participants executed the expert difficulty version of the environment from Days 2 to 7. In the sham condition, the participants executed an unrelated VR environment from Days 2 to 7. On Day 8, the participants executed the baseline difficulty version of the environment again in all the conditions. Various performance and workload-based measures were acquired. Results revealed that the participants in the heterogenous and difficult conditions performed significantly better on Day 8 compared with Day 1. The results inferred that a combination of immersive VR environment with repetitive heterogenous training maximized performance and decreased cognitive workload at transfer. We expect to use these conclusions to create effective training environments in VR for imparting training to military personnel in dynamic decision-making scenarios.

Gan T., Huang Y., Hao X., Hu L., Zheng Y., Yang Z.

Monotonous and repetitive tasks cause vigilance, or sustained attention decrement, which possibly leads to irreparable accident consequences in the aerospace and nuclear industry. Buffering the decrement of vigilance in visual search tasks is essential for cognitive enhancement and ergonomic research. This study aimed to evaluate the efficacy of anodal transcranial direct current stimulation (tDCS) applied to the left frontal eye field (FEF) to improve the performance of the sustained visual search. Twenty-seven healthy participants received anodal and sham tDCS of 2 mA for 28.8 min and completed a visual search task lasting for approximately 40 min without any break. For the online effect, results showed that the d′ hit rate and accuracy under anodal tDCS were significantly higher than those under sham conditions during 0–19.2 min time intervals. For the after-effect, compared with sham, anodal tDCS caused significantly higher d′ in the 10 min after completing the tDCS. Our findings suggest that anodal tDCS over the left FEF could effectively mitigate the decline of visual vigilance performance by buffering cognitive resource depletion.

Newman M., Gatersleben B., Wyles K.J., Ratcliffe E.

Virtual reality (VR) can be extremely useful in simulating nature when physical presence is not possible. Additionally, it allows for environments to be customised (e.g., weather, or topography) and facilitates the design of controlled experimental settings. However, VR can involve the use of expensive equipment and complex software to create highly realistic immersive experiences. But is it necessary for experiences to rival the latest Hollywood blockbuster? This paper explores whether such investment can be valuable in research on nature experiences. Two studies were conducted to examine how realism of environmental presentations impact affective responses and participant perceptions. Study One ( n = 16) explored perceptions of the same lake presented to participants in the real world, in VR and as a video. Study Two ( n = 120) compared participant's affective responses to one of four possible virtual environments differing in level of realism ( high or low ) and type ( natural or built ). Study One showed that experiences of VR presentations fell between real and video presentations. Study Two found that more realistic VR environments evoked more positive affective and serenity responses, as well as a greater sense of presence. In both studies, participants stressed the importance of naturalistic interaction, sensory immersion, and graphical realism in the experiences, which may help explain these effects. The level of realism that can be attained with VR does impact affective responses and perceptions. Investment in VR for future research can be highly beneficial. • Virtual reality (VR) enables highly realistic immersive experiences. • Two VR studies examined how level of realism impacted affective responses. • VR can elicit similar positive affective responses to a real natural scene. • High realism VR environments provided a greater sense of presence and restoration. • Realism is important, particularly for environmental restoration research.

Rao A.K., Chandra S., Dutt V.

Two-dimensional (2D) desktop and three-dimensional (3D) Virtual-Reality (VR) play a significant role in providing military personnel with training environments to hone their decision-making skills. The nature of the environment (2D versus 3D) and the order of task difficulty (novice to expert or expert to novice) may influence human performance in these environments. However, an empirical evaluation of these environments and their interaction with the order of task difficulty has been less explored. The primary objective of this research was to address this gap and explore the influence of different environments (2D desktop or 3D VR) and order of task difficulty (novice to expert or expert to novice) on human performance. In a lab-based experiment, a total of 60 healthy subjects executed scenarios with novice or expert difficulty levels across both 2D desktop environments (N = 30) and 3D VR environments (N = 30). Within each environment, 15 participants executed the novice scenario first and expert scenario second, and 15 participants executed the expert scenario first and novice scenario second. Results revealed that the participants performed better in the 3D VR environment compared to the 2D desktop environment. Participants performed better due to both expert training (performance in novice second better compared to novice first) and novice training (performance in expert second better compared to expert first). The combination of a 3D VR environment with expert training first and novice training second maximized performance. We expect to use these conclusions for creating effective training environments using VR technology.

Yao X., Cui L., Wang J., Feng W., Bao Y., Xie Q.

Non-invasive brain stimulation techniques have been shown in several studies to improve the motor recovery of the affected upper-limbs in stroke patients. This study aims to investigate whether or not cathodal transcranial direct current stimulation (c-tDCS), combined with virtual reality (VR), is superior to VR alone in reducing motor impairment and improving upper limb function and quality of life in stroke patients. Forty patients who suffered ischemic stroke between 2 weeks to 12 months were recruited for this single-blind randomized control trial. The patients were randomly assigned either to an experimental group who receiving c-tDCS and VR, or a control group receiving sham stimulation and VR. The cathodal electrode was positioned over the primary motor cortex (M1) of the unaffected hemisphere. The treatment session consisted of 20 min of daily therapy, for 10 sessions over a 2-week period. The outcome measures were the Fugl-Meyer Upper Extremity (FM-UE), the Action Research Arm Test (ARAT) and the Barthel Index (BI). The two groups were comparable in demographic characteristic and motor impairment. After 2 weeks of intervention, both groups demonstrated significant improvement in FM-UE, ARAT and BI scores (P<0.05).The experiment group demonstrated more improvement in FM-UE than the control group (10.1 vs. 6.4, p = 0.003) and, ARAT (7.0 vs 3.6, p = 0.026) and BI (12.8 vs 8.5, p = 0.043). The findings from our study support that c-tDCS, along with VR, can facilitate a stronger beneficial effect on upper limb motor impairment, function and quality of life than VR alone in patients with ischemic stroke. The study was registered in the Chinese Clinical Trial Registry ( ChiCTR1800019386 ) in November 8, 2018-Retrospectively registered.

Srivastava P., Rimzhim A., Vijay P., Singh S., Chandra S.

Use of virtual reality (VR) technology is proliferating for designing and upgrading entertainment devices, and creating virtual environments that could be used for research and training. VR is becoming a strong research tool by providing a tighter control on the experimental environment and by allowing almost limitless possibilities of creating ecologically valid stimuli. However, the enhanced fidelity between the real and virtual worlds that VR provides does not always benefit human performance. For a better understanding, and increasing VR’s usability, we need to identify the relevant constituent components of immersive technologies, and differentiate their roles, for example, how visual and interaction fidelity differentially improves human performance. We conducted an experiment to examine how two common VR display modes, head mounted display (HMD) and desktop (DT), would affect spatial learning when we restrict ambulatory locomotion in HMD. This manipulation allowed examining the role of varying visual fidelity with low interaction fidelity. We used a between-group design with 40 naïve participants. They explored a virtual environment and later drew its sketch-map. Our results showed participants spent more time and perceived less motion-sickness and task effort using desktop than HMD VR. With reduced interaction fidelity, the high visual fidelity of HMD as compared to desktop resulted in similar or poorer performance on different spatial learning tasks after accounting for motion-sickness and workload effort. Participants were better in recalling spatial components related to junction and cyclic order of the navigated virtual space in desktop versus HMD VR, and performed equally well on components related to street segments and object associations. We explain these results in terms of deficient idiothetic information in nonambulatory HMD and lesser sensory conflicts in desktop mode. Overall, our results highlight the differential effect of visual versus interaction fidelity on human performance based on using immersive technologies, how such an effect depends on the nature of cognitive and functional behavior users employ, and the higher usability of traditional desktop VR. These results are relevant for developing customized and sustainable virtual reality human-computer interactions.

Rao A.K., Pramod B.S., Chandra S., Dutt V.

In the real-world, manned and unmanned vehicles may be used for a number of applications. Visual technologies like indirect visual display (IVD) and virtual reality (VR) have been used to train operators in both manned and unmanned environments. The main objective of this research was to evaluate the effectiveness of manned and unmanned interfaces in IVD and VR display designs. Using an underwater search-and-shoot scenario, we developed two variations in display designs (IVD and VR) and two variations in type of interface-based training (manned and unmanned). A total of 60 subjects participated in the experiment, where 30 subjects were randomly assigned to simulations in IVD and the rest in VR. In both the simulations, 15 randomly selected participants executed the manned interface first and the remaining 15 executed the unmanned interface first. Results revealed that the subjects performed better in VR compared to IVD, and also performed better when they executed the unmanned interface first. We highlight the implications of our results for training personnel in scenarios involving manned and unmanned operations in IVD and VR interfaces.

Sung K., Gordon B.

Whether transcranial direct current stimulation (tDCS) affects mental functions, and how any such effects arise from its neural effects, continue to be debated. We investigated whether tDCS applied over the visual cortex (Oz) with a vertex (Cz) reference might affect response times (RTs) in a visual search task. We also examined whether any significant tDCS effects would interact with task factors (target presence, discrimination difficulty, and stimulus brightness) that are known to selectively influence one or the other of the two information processing stages posited by current models of visual search. Based on additive factor logic, we expected that the pattern of interactions involving a significant tDCS effect could help us colocalize the tDCS effect to one (or both) of the processing stages. In Experiment 1 (n = 12), anodal tDCS improved RTs significantly; cathodal tDCS produced a nonsignificant trend toward improvement. However, there were no interactions between the anodal tDCS effect and target presence or discrimination difficulty. In Experiment 2 (n = 18), we manipulated stimulus brightness along with target presence and discrimination difficulty. Anodal and cathodal tDCS both produced significant improvements in RTs. Again, the tDCS effects did not interact with any of the task factors. In Experiment 3 (n = 16), electrodes were placed at Cz and on the upper arm, to test for a possible effect of incidental stimulation of the motor regions under Cz. No effect of tDCS on RTs was found. These findings strengthen the case for tDCS having real effects on cerebral information processing. However, these effects did not clearly arise from either of the two processing stages of the visual search process. We suggest that this is because tDCS has a DIFFUSE, pervasive action across the task-relevant neuroanatomical region(s), not a discrete effect in terms of information processing stages.

Lee S.J., Chun M.H.

To investigate the effects of combination cathodal transcranial direct current stimulation (tDCS) and virtual reality (VR) therapy for upper extremity (UE) training in patients with subacute stroke.Pilot randomized controlled trial. Patients were randomly assigned to 1 of 3 groups: group A received cathodal tDCS, group B received VR, and group C received combination therapy (cathodal tDCS was simultaneously applied during VR therapy).University hospital.Patients (N=59) with impaired unilateral UE motor function after stroke.Fifteen sessions of treatment over a 3-week period.The Modified Ashworth Scale, manual muscle test (MMT), Manual Function Test (MFT), Fugl-Meyer Scale (FMS), and Box and Block Test were used to assess UE function. To evaluate activities of daily living, the Korean-Modified Barthel Index (K-MBI) was used. All outcomes were measured before and immediately after treatment.After treatment, all groups demonstrated significant improvements in MMT, MFT, FMS, and K-MBI scores. The change in MFT and FMS scores was different between the 3 groups. Post hoc analysis revealed that the improvement of MFT and FMS scores in group C was significantly higher than those of the other 2 groups.In the present pilot study, the combination of brain stimulation using tDCS and peripheral arm training using VR could facilitate a stronger beneficial effect on UE impairment than using each intervention alone. This combination therapy might be a helpful method to enhance recovery of the paretic UE in patients with stroke.

Duncan J., Humphreys G.W.

A new theory of search and visual attention is presented. Results support neither a distinction between serial and parallel search nor between search for features and conjunctions. For all search materials, instead, difficulty increases with increased similarity of targets to nontargets and decreasedsimilarity between nontargets, producing a continuum of search efficiency. A parallel stage of perceptual grouping and description is followed by competitive interaction between inputs, guiding selective access to awareness and action. An input gains weight to the extent that it matches an internal description of that information needed in current behavior (hence the effect of targetnontarget similarity). Perceptual grouping encourages input weights to change together (allowing "spreading suppression" of similar nontargets). The theory accounts for harmful effects of nontargets resembling any possible target, the importance of local nontarget grouping, and many other findings.