Study of Full-body Virtual Embodiment Using noninvasive Brain Stimulation and Imaging

PurposeWe describe two case studies that use embodiment in virtual reality as a treatment for chronic low back pain. The purpose of this case series was to determine the feasibility of a novel virtual reality-based digital therapeutic for the treatment of chronic pain.Patients and MethodsTwo patients with chronic low back pain received seven sessions, two sessions per week, of a novel digital therapeutic that combines virtual embodiment with graded motor imagery to deliver functional rehabilitation exercises using an off-the-shelf virtual reality system. Pain intensity was measured using a visual analog scale before and after each session to get an indication whether individual sessions of virtual embodiment training decrease pain intensity. Pain catastrophizing scale was assessed before the first session and after the seventh session to determine the extent to which virtual embodiment training can improve psychological symptoms of chronic low back pain.ResultsIn both patients, pain intensity was improved after individual sessions of virtual embodiment training as measured by a paired t-test: (Patient A: t = 2.890, P < 0.05) and (Patient B: t = 5.346, P < 0.005). This indicates that individual sessions of virtual embodiment training decrease pain intensity. In both patients, improvements were observed in three subscales of the pain catastrophizing scale (rumination, magnification, and helplessness). This indicates that virtual embodiment training may have benefits for chronic pain symptoms such as pain intensity, pain-related mobility impairment, and disability.ConclusionThis case series provides evidence that embodiment in virtual reality improves symptoms of persistent chronic low back pain. We propose a mechanism by which virtual embodiment may improve chronic pain symptoms by recontextualizing sensory feedback from the body as patients engage in functional rehabilitation exercises while in virtual reality.

The Sense of Embodiment (SoE) refers to the subjective experience of perceiving a non-biological body part as one's own. Virtual Reality (VR) provides a powerful platform to manipulate SoE, making it a crucial factor in immersive human-computer interaction. This becomes particularly relevant in Electroencephalography (EEG)-based Brain-Computer Interfaces (BCIs), especially motor imagery (MI)-BCIs, which harness brain activity to enable users to control virtual avatars in a self-paced manner. In such systems, a strong SoE can significantly enhance user engagement, control accuracy, and the overall effectiveness of the interface. However, SoE assessment remains largely subjective, relying on questionnaires, as no definitive EEG biomarkers have been established. Additionally, methodological inconsistencies across studies introduce biases that hinder biomarker identification. This study aimed to identify EEG-based SoE biomarkers by analyzing frequency band changes in a combined dataset of 41 participants under standardized experimental conditions. Participants underwent virtual SoE induction and disruption using multisensory triggers, with a validated questionnaire confirming the illusion. Results revealed a significant increase in Beta and Gamma power over the occipital lobe, suggesting these as potential EEG biomarkers for SoE. The findings underscore the occipital lobe's role in multisensory integration and sensorimotor synchronization, supporting the theoretical framework of SoE. However, no single frequency band or brain region fully explains SoE. Instead, it emerges as a complex, dynamic process evolving across time, frequency, and spatial domains, necessitating a comprehensive approach that considers interactions across multiple neural networks.

Friendship with a robot: Children’s perception of similarity between a robot’s physical and virtual embodiment that supports diabetes self-management

IntroductionIn recent years, non-invasive brain stimulation (NIBS) interventions for attention-deficit/hyperactivity disorder (ADHD) have received increasing attention. However, which of the various NIBS methods is more effective in improving cognitive functions and core symptoms in patients with ADHD remains unclear.MethodsRandomized controlled trials (RCTs) on NIBS in patients with ADHD were searched. Standardized mean differences (SMDs) for cognitive functions and core symptoms changes were pooled in Bayesian network meta-analyses.ResultAfter reviewing 3,976 retrieved citations, a total of 37 RCTs (N = 1,615 participants) were included. This NMA provides evidence that none of the NIBS interventions significantly improved inhibitory control compared to sham controls. However, a statistically significant difference was observed between anodal transcranial direct current stimulation (tDCS) over the left DLPFC plus cathodal tDCS over the right supraorbital area 1.5 mA (SMD = −0.87, 95% CI: −1.80 to −0.07) and High-definition anodal transcranial direct current stimulation over the vertex 0.25 mA (SMD = −1.04, 95% CI: −2.09 to 0.00). In terms of working memory, anodal tDCS over the left DLPFC plus cathodal tDCS over the right DLPFC (SMD = 0.95, 95% CI: 0.05–1.84) and anodal tDCS over the right inferior frontal cortex (rIFC) plus cathodal tDCS over the right supraorbital area (SMD = 0.86, 95% CI: 0.28–1.45) were associated with significant improvements compared to sham stimulation. For cognitive flexibility, only anodal tDCS over the left DLPFC plus cathodal tDCS over the right supraorbital area (SMD = −0.76, 95% CI: −1.31 to −0.21) demonstrated a statistically significant benefit relative to sham. Regarding inattention, both transcranial pulse stimulation (SMD = −2.62, 95% CI: −6.35 to 1.12) and transcranial alternating current stimulation 10 Hz (SMD = −2.35, 95% CI: −5.00 to 0.30) showed favorable trends in comparison with sham; however, these differences did not reach statistical significance, though they approached the threshold. Finally, no NIBS intervention was found to significantly improve hypersensitivity or impulsivity when compared to sham stimulation.ConclusionThe dual-tDCS and a-tDCS may be considered among the preferred NIBS interventions for improving cognitive function in ADHD. Specifically, anodal tDCS over the left DLPFC plus cathodal tDCS over the right supraorbital area improved cognitive flexibility; while anodal tDCS over the left DLPFC plus cathodal tDCS over the right DLPFC enhanced working memory; both dual-tDCS and a-tDCS demonstrated superior efficacy relative to repetitive transcranial magnetic stimulation (rTMS) for inhibitory control; further research is needed to investigate TPS for improving attention and impulsivity.

P 35. Investigating a causal role of the supramarginal gyrus for pitch memory using transcranial direct current stimulation

68. The effect of a neuromodulation protocol on executive functions in healthy elderly: Psychometric and EEG evidences

Effect of Dual-Mode and Dual-Site Noninvasive Brain Stimulation on Freezing of Gait in Patients With Parkinson Disease

ObjectivePhantom limb pain (PLP) is notoriously difficult to treat, partly due to an incomplete understanding of PLP‐related disease mechanisms. Noninvasive brain stimulation (NIBS) is used to modulate plasticity in various neuropathological diseases, including chronic pain. Although NIBS can alleviate neuropathic pain (including PLP), both disease and treatment mechanisms remain tenuous. Insight into the mechanisms underlying both PLP and NIBS‐induced PLP relief is needed for future implementation of such treatment and generalization to related conditions.MethodsWe used a within‐participants, double‐blind, and sham‐controlled design to alleviate PLP via task‐concurrent NIBS over the primary sensorimotor missing hand cortex (S1/M1). To specifically influence missing hand signal processing, amputees performed phantom hand movements during anodal transcranial direct current stimulation. Brain activity was monitored using neuroimaging during and after NIBS. PLP ratings were obtained throughout the week after stimulation.ResultsA single session of intervention NIBS significantly relieved PLP, with effects lasting at least 1 week. PLP relief associated with reduced activity in the S1/M1 missing hand cortex after stimulation. Critically, PLP relief and reduced S1/M1 activity correlated with preceding activity changes during stimulation in the mid‐ and posterior insula and secondary somatosensory cortex (S2).InterpretationThe observed correlation between PLP relief and decreased S1/M1 activity confirms our previous findings linking PLP with increased S1/M1 activity. Our results further highlight the driving role of the mid‐ and posterior insula, as well as S2, in modulating PLP. Lastly, our novel PLP intervention using task‐concurrent NIBS opens new avenues for developing treatment for PLP and related pain conditions. ANN NEUROL 2019;85:59–73.

BackgroundParkinson’s disease (PD) induces progressive deficits in motor and cognitive functions as well as impaired dual-task performance requiring both motor and cognitive functions. This systematic review and meta-analysis evaluated the effects of non-invasive brain stimulation (NIBS) on dual-task performance in patients with PD.Methods11 studies met the following inclusion criteria: (a) patients with PD, (b) NIBS intervention, (c) comparison with the sham stimulation group, (d) motor and cognitive performance outcomes during dual tasks, and (e) randomized controlled trials with parallel or crossover designs. Individual effect size (i.e., comparison) was quantified by comparing motor and cognitive performances changes during dual tasks between active NIBS and sham stimulation conditions. Thus, higher values of the overall effect size indicate more improvements in either motor or cognitive performances after NIBS. Moreover, moderator variable analyses determined whether NIBS effects on dual-task performances differed depending on targeted brain regions. Finally, meta-regression analyses determined whether NIBS effects on dual-task performances were associated with demographic characteristics.ResultsThe random-effects model meta-analysis revealed that NIBS significantly improved motor (73 comparisons from 11 studies) and cognitive (12 comparisons from four studies) performances during dual tasks in patients with PD. Specifically, anodal transcranial direct current stimulation protocols on the dorsolateral prefrontal cortex were effective. Moreover, greater improvements in motor performance during dual tasks significantly correlated with decreased age and increased proportion of females, respectively.ConclusionThis meta-analysis suggests that excitatory stimulation on the dorsolateral prefrontal cortex may be effective for improving dual-task performance in patients with PD.

Virtual reality (VR) is considered a technological megatrend that is driving the digitization of all aspects of human life. Avatars, virtual bodies controlled by users, play an important role in VR. Many scholars consider the sense of embodiment as a key affordance of avatars. However, our understanding of how to optimize embodiment through avatar representation in VR remains underdeveloped. This study systematically reviewed a body of 43 studies from 41 research papers that investigated the manipulations of avatars in VR. The corpus was coded with head-mounted display (HMD) models, avatar creation tools, mirror use, task context, and avatar manipulations. Based on these experiment-based studies, we discuss how different types of avatar representations affect users’ embodiment. Based on the findings, we indicate practical implications of avatar design in VR applications.

What does it feel like to own, to control, and to be inside a body? The multidimensional nature of this experience together with the continuous presence of one's biological body, render both theoretical and experimental approaches problematic. Nevertheless, exploitation of immersive virtual reality has allowed a reframing of this question to whether it is possible to experience the same sensations towards a virtual body inside an immersive virtual environment as toward the biological body, and if so, to what extent. The current paper addresses these issues by referring to the Sense of Embodiment (SoE). Due to the conceptual confusion around this sense, we provide a working definition which states that SoE consists of three subcomponents: the sense of self-location, the sense of agency, and the sense of body ownership. Under this proposed structure, measures and experimental manipulations reported in the literature are reviewed and related challenges are outlined. Finally, future experimental studies are proposed to overcome those challenges, toward deepening the concept of SoE and enhancing it in virtual applications.

Transcranial direct current stimulation (TDCS) of primary motor cortex (M1) can transiently improve paretic hand function in chronic stroke. However, responses are variable so there is incentive to try to improve efficacy and or to predict response in individual patients. Both excitatory (Anodal) stimulation of ipsilesional M1 and inhibitory (Cathodal) stimulation of contralesional M1 can speed simple reaction time. Here we tested whether combining these two effects simultaneously, by using a bilateral M1–M1 electrode montage, would improve efficacy. We tested the physiological efficacy of Bilateral, Anodal or Cathodal TDCS in changing motor evoked potentials (MEPs) in the healthy brain and their behavioural efficacy in changing reaction times with the paretic hand in chronic stroke. In addition, we aimed to identify clinical or neurochemical predictors of patients' behavioural response to TDCS. There were three main findings: 1) unlike Anodal and Cathodal TDCS, Bilateral M1–M1 TDCS (1mA, 20min) had no significant effect on MEPs in the healthy brain or on reaction time with the paretic hand in chronic stroke patients; 2) GABA levels in ipsilesional M1 predicted patients' behavioural gains from Anodal TDCS; and 3) although patients were in the chronic phase, time since stroke (and its combination with Fugl–Meyer score) was a positive predictor of behavioural gain from Cathodal TDCS. These findings indicate the superiority of Anodal or Cathodal over Bilateral TDCS in changing motor cortico-spinal excitability in the healthy brain and in speeding reaction time in chronic stroke. The identified clinical and neurochemical markers of behavioural response should help to inform the optimization of TDCS delivery and to predict patient outcome variability in future TDCS intervention studies in chronic motor stroke.

In Virtual Reality, a number of studies have been conducted to assess the influence of avatar appearance, avatar control and user point of view on the Sense of Embodiment (SoE) towards a virtual avatar. However, such studies tend to explore each factor in isolation. This paper aims to better understand the inter-relations among these three factors by conducting a subjective matching experiment. In the presented experiment ( n=40), participants had to match a given "optimal" SoE avatar configuration (realistic avatar, full-body motion capture, first-person point of view), starting by a "minimal" SoE configuration (minimal avatar, no control, third-person point of view), by iteratively increasing the level of each factor. The choices of the participants provide insights about their preferences and perception over the three factors considered. Moreover, the subjective matching procedure was conducted in the context of four different interaction tasks with the goal of covering a wide range of actions an avatar can do in a VE. The paper also describes a baseline experiment ( n=20) which was used to define the number and order of the different levels for each factor, prior to the subjective matching experiment (e.g. different degrees of realism ranging from abstract to personalised avatars for the visual appearance). The results of the subjective matching experiment show that point of view and control levels were consistently increased by users before appearance levels when it comes to enhancing the SoE. Second, several configurations were identified with equivalent SoE as the one felt in the optimal configuration, but vary between the tasks. Taken together, our results provide valuable insights about which factors to prioritize in order to enhance the SoE towards an avatar in different tasks, and about configurations which lead to fulfilling SoE in VE.

The lack of effective treatments for managing pain and associated symptoms in fibromyalgia (FM) poses both a clinical challenge and an economic burden on the health sector. Typical FM therapies include an array of pharmacological and non-pharmacological interventions. Commonly used drugs have demonstrated only mild improvements in FM while benefitting only a minority of patients. In this scenario, repeated anodal transcranial direct current stimulation (tDCS) and mindfulness-based interventions have emerged as two promising non-pharmacological treatments for pain relief and improvement of FM-associated symptoms. However, the strength and durability of the therapeutic benefits of these methods vary across studies. The combination of non-pharmacological therapies has been proposed as a way to optimise and bolster the therapeutic effects of monomodal interventions. Although the combination of tDCS and mindfulness meditation (MM) has shown synergistic effects in both healthy individuals and patients with neuropsychiatric disorders and some chronic pain conditions, it has not yet been investigated in patients with FM. The rationale behind exploring this combination was to modulate the brain state via MM, with the goal of boosting the neuroplastic effects of currently recommended conventional tDCS protocols for chronic pain. In this dissertation, the current state of the literature on combining these two methods was reviewed. A sham-controlled randomised pilot clinical study was conducted to test the preliminary therapeutic efficacy and safety of a ten-day intervention concurrently applying anodal tDCS targeting the left primary motor cortex (M1) and MM, administered as a clinicbased treatment, in patients with FM. Prior to the combined therapy, participants received a fiveday training in MM. Patients in the active tDCS group reported a larger clinically meaningful improvement in quality of life following the combined intervention, compared to those receiving sham tDCS paired with MM or treatment-as-usual. No differences in pain reduction and improvements in sleep quality or psychological well-being were observed among the groups. Building on these findings and addressing the limitations of the pilot study, we investigated the therapeutic and mechanistic impact of a ten-day treatment combining anodal tDCS over the left 8 M1 and MM on pain relief, quality of life, and associated symptoms in individuals with FM trained in mindfulness. Participants in this trial completed a four-week brief mindfulness intervention tailored for FM (BMIF) prior to randomisation. The combined treatment was administered as an at-home intervention under remote supervision. To investigate the possible underlying mechanisms, we measured changes in cortical excitability using transcranial magnetic stimulation (TMS) of the left M1. Finally, we implemented a responder analysis approach to decipher the effects of the BMIF and the add-on combination of tDCS and MM with regard to emotion regulation (ER), which is one of the primary targets mediating improvement in symptom burden and management in FM. Although patients showed improvements in clinical symptoms, no superior therapeutic benefits were observed when pairing MM with anodal tDCS, compared to the combination of MM with sham tDCS. Both groups demonstrated substantial and acute pain relief and improvements in quality of life, sleep quality, affect, and psychological well-being following the combined intervention. The lack of group differences in TMS metrics failed to provide meaningful insights into the potential synergistic mechanisms of tDCS and MM. Interestingly, clinical responders to the combined intervention in the active tDCS group exhibited impaired ER compared to the sham group, even suggesting potential antagonistic effects of pairing M1-tDCS with MM for ER. Moreover, the reduction of the cortical excitability of the left M1, likely mediated by daily MM practice, might block the mechanistic consequences of anodal tDCS of the left M1. On the other hand, the nonspecific main effect of time in clinical outcomes, alongside a large significant increase in mindfulness over time, hints at a potential ‘mindfulness effect’, in line with previous studies showing that longer MM practice results in greater therapeutic benefits in FM. The introduction of the Medical Device Regulation in 2021 and the recent reclassification of some of the non-invasive brain stimulation (NIBS) devices (for example, tDCS and TMS) to the same risk level as invasive deep brain stimulation in the European Union have imposed a considerable hindrance to the research and further development of tDCS. A multinational participatory study including different stakeholders involved in the consumption, use, manufacturing, and regulation of NIBS was conducted to address the clinical, academic, legal, ethical, and social concerns surrounding NIBS. The different stakeholders’ perspectives were analysed and compiled to draft a set of recommendations for the use and regulation of NIBS, including tDCS in the European subcontinent. To improve the accessibility of tDCS to patients, 9 the optimisation of currently available NIBS treatments via broader administration and further development of home-based tDCS as well as personalisation of therapy have been suggested by the stakeholders. Stricter regulation of tDCS for non-medical reasons and research focused on higher effectiveness of tDCS, underlying mechanisms, and development of responders were also proposed, among others. Taken together, our work challenges the combination of M1-tDCS and MM as a strategy to optimise tDCS treatment for pain relief and symptom improvement in patients with FM. However, this dissertation highlights the pivotal role of clinical research regarding combined interventions, whereby two therapies beneficial on their own might not necessarily be more effective when combined. Future research should explore the additional effect of combining MM and tDCS compared to tDCS and MM alone and delve deeper into the workings of the combined intervention using more sophisticated neuroimaging tools, with the goal of developing novel and individualised methods to optimise the currently available NIBS technologies for the treatment of FM.

By engaging with network technologies on computers and digital devices, equipped with sensors such as cameras, we are part of the telematic society that can connect with people in real-time near as well as far apart. While digital technology enables us to connect and maintain relationships with other people, we still rely on virtual embodiment to represent our persona in the digital world. There is a range of visual representations that function as a virtual embodiment in the digital world, often a profile image, an avatar or a graphic device are used as a proxy. In this particular practice-based research project, I am exploring how the risks of sharing biometric data can be prevented, by prototyping an abstract virtual embodiment in an art installation. The computational design applied to procedures such as facial recognition driven by artificial intelligence (AI), and machine learning can result in intrusive experiences. If the act of being detected or identified by AI becomes intrusive, are there ways we can use abstract virtual embodiments to represent ourselves without being detected? This visual essay is positioning the practice-based research in an art context while documenting the conceptual process of an interactive prototype.