Brain-Computer Interface and Motor Imagery Training: The Role of Visual Feedback and Embodiment

Controlling a brain-computer interface (BCI) is a difficult task that requires extensive training. Particularly in the case of motor imagery BCIs, users may need several training sessions before they learn how to generate desired brain activity and reach an acceptable performance. A typical training protocol for such BCIs includes execution of a motor imagery task by the user, followed by presentation of an extending bar or a moving object on a computer screen. In this chapter, we discuss the importance of a visual feedback that resembles human actions, the effect of human factors such as confidence and motivation, and the role of embodiment in the learning process of a motor imagery task. Our results from a series of experiments in which users BCI-operated a humanlike android robot confirm that realistic visual feedback can induce a sense of embodiment, which promotes a significant learning of the motor imagery task in a short amount of time. We review the impact of humanlike visual feedback in optimized modulation of brain activity by the BCI users

What the study of spinal cord injured patients can tell us about the significance of the body in cognition

Although in the last three decades philosophers, psychologists and neuroscientists have produced numerous studies on human cognition, the debate concerning its nature is still heated and current views on the subject are somewhat antithetical. On the one hand, there are those who adhere to a view implying ‘disembodiment’ which suggests that cognition is based entirely on symbolic processes. On the other hand, a family of theories referred to as the Embodied Cognition Theories (ECT) postulate that creating and maintaining cognition is linked with varying degrees of inherence to somatosensory and motor representations. Spinal cord injury induces a massive body-brain disconnection with the loss of sensory and motor bodily functions below the lesion level but without directly affecting the brain. Thus, SCI may represent an optimal model for testing the role of the body in cognition. In this review, we describe post-lesional cognitive modifications in relation to body, space and action representations and various instances of ECT. We discuss the interaction between body-grounded and symbolic processes in adulthood with relevant modifications after body-brain disconnection

Body schema plasticity after stroke: Subjective and neurophysiological correlates of the rubber hand illusion

[EN] Stroke can lead to motor impairments that can affect the body structure and restraint mobility. We hypothesize that brain lesions and their motor sequelae can distort the body schema, a sensorimotor map of body parts and elements in the peripersonal space through which human beings embody the reachable space and ready the body for forthcoming movements. Two main constructs have been identified in the embodiment mechanism: body-ownership, the sense that the body that one inhabits is his/her own, and agency, the sense that one can move and control his/her body. To test this, the present study simultaneously investigated different embodiment subcomponents (body-ownership, localization, and agency) and different neurophysiological measures (galvanic skin response, skin temperature, and surface electromyographic activity), and the interaction between them, in clinically-controlled hemiparetic individuals with stroke and in healthy subjects after the rubber hand illusion. Individuals with stroke reported significantly stronger body-ownership and agency and reduced increase of galvanic skin response, skin temperature, and muscular activity in the stimulated hand. We suggest that differences in embodiment could have been motivated by increased plasticity of the body schema and pathological predominance of the visual input over proprioception. We also suggest that differences in neurophysiological responses could have been promoted by a suppression of the reflex activity of the sympathetic nervous system and by the involvement of the premotor cortex in the reconfiguration of the body schema. These results could evidence a body schema plasticity promoted by the brain lesion and a main role of the premotor cortex in this mechanism.This work was supported by Ministerio de Economia y Competitividad of Spain (Project NeuroVR, TIN2013-44741-R, Project REACT, TIN2014-61975-EXP, and Grant BES-2014-068218), and by Universitat Politecnica de Valencia (Grant PAID-10-14).Llorens Rodríguez, R.; Borrego, A.; Palomo, P.; Cebolla, A.; Noé-Sebastián, E.; Bermúdez I Badia, S.; Baños Rivera, RM. (2017). Body schema plasticity after stroke: Subjective and neurophysiological correlates of the rubber hand illusion. Neuropsychologia. 96:61-69. https://doi.org/10.1016/j.neuropsychologia.2017.01.00761699

The embodied user : corporeal awareness & media technology

Human beings are proficient users of tools and technology. At times, our interactions with a technological artifact appear so effortless, that the distinction between the artifact and the body starts to fade. When operating anthropomorphically designed teleoperation systems, for example, some people develop the vivid experience that they are physically there at the remote site (i.e., telepresence). Others might even come to sense the slave robot’s arms and hands as their own. The process in which the central nervous system categorizes an object as a part of the body, and in which a discrimination is made between what is contained within and outside the bodily boundaries, is called self-attribution. The aim of this thesis is twofold: (a) To determine the personal factors (e.g., the characteristics of an individual’s psychological makeup) and situational factors (e.g., the appearance of objects) that constrain or facilitate self-attribution, and (b) to determine the degree to which these factors affect people’s experiences with media technology. In Chapter 2, we describe the theoretical framework of our research which is centered on a conception of the user of technology as an embodied agent. In this chapter we distinguish two important, but often confused aspects of embodiment: the body schema, and the body image. The body schema is defined as a dynamic distributed network of procedures aimed at guiding behavior. In contrast, we defined the body image as a part of the process of consciousness and, thus, as consisting of those higher-order discriminations (or qualia) that pertain to the body, and one’s self-perception thereof. To investigate the individual and situational factors that constrain or facilitate selfattribution (i.e., incorporation into the body image), we employ the experimental paradigm of the rubber-hand illusion (Botvinick & Cohen, 1998). In this illusion, which is induced by stroking a person’s concealed hand together with a visible fake one, some people start to sense the fake hand as an actual part of their body. In Chapter 3, we investigate the rubberhand illusion under two mediated conditions: (1) a virtual reality condition, where both the fake hand and its stimulation were projected on the table in front of the participant, and (2) a mixed reality condition, where the fake hand was projected, but its stimulation was unmediated. Our experiment reveals that people can develop the rubber-hand illusion under mediated conditions, but the resulting illusion may, depending on the technology used, be less vivid than in the traditional unmediated setup. In Chapter 4, we investigate the extent to which visual discrepancies between the foreign object and a human hand affect people in developing a vivid rubber-hand illusion. We found that people experience a more vivid illusion when the foreign object resembles the human hand in terms of both shape and texture. Taken together, the experiments in Chapters 3 and 4 support the view that the rubber-hand illusion is not merely governed by a bottom-up process (i.e., based on visuotactile integration), but is affected, top-down, by a cognitive representation of what the human body is like (e.g., Tsakiris and Haggard, 2005). In the rubber-hand illusion, people commonly misperceive the location of their concealed hand toward the direction of the fake hand (Tsakiris & Haggard, 2005). As such, this so-called proprioceptive drift is often used as an alternative to self-reports in assessing the vividness of the illusion (e.g., Tsakiris & Haggard, 2005). In Chapter 5, we investigate the extent to which the observed shift in felt position of the concealed hand can be attributed to experiencing the illusion. For this purpose, we test how various features of the experimental setup of the rubber-hand illusion, which in themselves are not sufficient to elicit the illusion, affect proprioceptive drift. We corroborate existing research which demonstrates that looking at a fake hand or a tabletop for five minutes, in absence of visuotactile stimulation, is sufficient to induce a change in the felt position of an unseen hand (e.g., Gross et al., 1974). Moreover, our experiments indicate that the use of proprioceptive drift as a measure for the strength of the rubber-hand illusion yields different conclusions than an assessment by means of self-reports. Based on these results, we question the validity of proprioceptive drift as an alternative measure of the vividness of the rubber-hand illusion. In Chapter 6, we propose and test a model of the vividness of the rubber-hand illusion. In two experiments, we successfully modeled people’s self-reported experiences related to the illusion (e.g., "the fake hand felt as my own") based on three estimates: (a) a person’s susceptibility for the rubber-hand illusion, (b) the processing demand that is required for a particular experience, and (c) the suppression/constraints imposed by the situation. We demonstrate that the impressions related to the rubber-hand illusion, and by inference the processes behind them, are comparable for different persons. This is a non-trivial finding as such invariance is required for an objective scaling of individual susceptibility and situational impediment on the basis of self-reported experiences. Regarding the validity of our vividness model, we confirm that asynchrony (e.g., Botvinick & Cohen, 1998) and information-poor stimulation (e.g., Armel & Ramachandran, 2003) constrain the development of a vivid rubber-hand illusion. Moreover, we demonstrate that the correlation between a person’s susceptibility for the rubber-hand illusion and the extent of his of her proprioceptive drift is fairly moderate, thereby confirming our conclusions from Chapter 5 regarding the limited validity of proprioceptive drift as a measure of the vividness of the rubber-hand illusion. In Chapter 7, we investigate the extent to which the large individual differences in people’s susceptibility for the illusion can be explained by body image instability, and the ability to engage in motor imagery of the hand (i.e., in mental own hand transformations). In addition, we investigate whether the vividness of the illusion is dependent on the anatomical implausibility of the fake hand’s orientation. With respect to body image instability, we corroborate a small, but significant, correlation between susceptibility and body image aberration scores: As expected, people with a more unstable body image are also more susceptible to the rubber-hand illusion (cf. Burrack & Brugger, 2005). With respect to the position and orientation of the fake hand on the table, we demonstrate that people experience a less vivid rubber-hand illusion when the fake hand is orientated in an anatomically impossible, as compared to an anatomically possible manner. This finding suggests that the attribution of foreign objects to the self is constrained by the morphological capabilities of the human body. With respect to motor imagery, our results indicate a small, but significant, correlation between susceptibility and response times to a speeded left and right hands identification task. In other words, people who are more attuned to engage in mental own hand transformations are also better equipped to develop vivid rubber-hand illusions. In Chapter 8, we examine the role of self-attribution in the experience of telepresence. For this purpose, we introduce the technological domain of mediated social touch (i.e., interpersonal touching over a distance). We anticipated that, compared to a morphologically incongruent input medium, a morphologically congruent medium would be more easily attributed to the self. As a result, we expected our participants to develop a stronger sense of telepresence when they could see their interaction partner performing the touches on a sensor-equipped mannequin as opposed to a touch screen. Our participants, as expected, reported higher levels of telepresence, and demonstrated more physiological arousal with the mannequin input medium. At the same time, our experiment revealed that these effects might not have resulted from self-attribution, and thus that other psychological mechanisms of identification might play a role in telepresence experiences. In Chapter 9, the epilogue, we discuss the main contributions and limitations of this thesis, while taking a broader perspective on the field of research on media technologies and corporeal awareness

Enhanced lower-limb motor imagery by kinesthetic illusion

Brain-computer interface (BCI) based on lower-limb motor imagery (LMI) enables hemiplegic patients to stand and walk independently. However, LMI ability is usually poor for BCI-illiterate (e.g., some stroke patients), limiting BCI performance. This study proposed a novel LMI-BCI paradigm with kinesthetic illusion(KI) induced by vibratory stimulation on Achilles tendon to enhance LMI ability. Sixteen healthy subjects were recruited to carry out two research contents: (1) To verify the feasibility of induced KI by vibrating Achilles tendon and analyze the EEG features produced by KI, research 1 compared the subjective feeling and brain activity of participants during rest task with and without vibratory stimulation (V-rest, rest). (2) Research 2 compared the LMI-BCI performance with and without KI (KI-LMI, no-LMI) to explore whether KI enhances LMI ability. The analysis methods of both experiments included classification accuracy (V-rest vs. rest, no-LMI vs. rest, KI-LMI vs. rest, KI-LMI vs. V-rest), time-domain features, oral questionnaire, statistic analysis and brain functional connectivity analysis. Research 1 verified that induced KI by vibrating Achilles tendon might be feasible, and provided a theoretical basis for applying KI to LMI-BCI paradigm, evidenced by oral questionnaire (Q1) and the independent effect of vibratory stimulation during rest task. The results of research 2 that KI enhanced mesial cortex activation and induced more intensive EEG features, evidenced by ERD power, topographical distribution, oral questionnaire (Q2 and Q3), and brain functional connectivity map. Additionally, the KI increased the offline accuracy of no-LMI/rest task by 6.88 to 82.19% (p < 0.001). The simulated online accuracy was also improved for most subjects (average accuracy for all subjects: 77.23% > 75.31%, and average F1_score for all subjects: 76.4% > 74.3%). The LMI-BCI paradigm of this study provides a novel approach to enhance LMI ability and accelerates the practical applications of the LMI-BCI system

Rubber Hands Feel Touch, but Not in Blind Individuals

Psychology and neuroscience have a long-standing tradition of studying blind individuals to investigate how visual experience shapes perception of the external world. Here, we study how blind people experience their own body by exposing them to a multisensory body illusion: the somatic rubber hand illusion. In this illusion, healthy blindfolded participants experience that they are touching their own right hand with their left index finger, when in fact they are touching a rubber hand with their left index finger while the experimenter touches their right hand in a synchronized manner (Ehrsson et al. 2005). We compared the strength of this illusion in a group of blind individuals (n = 10), all of whom had experienced severe visual impairment or complete blindness from birth, and a group of age-matched blindfolded sighted participants (n = 12). The illusion was quantified subjectively using questionnaires and behaviorally by asking participants to point to the felt location of the right hand. The results showed that the sighted participants experienced a strong illusion, whereas the blind participants experienced no illusion at all, a difference that was evident in both tests employed. A further experiment testing the participants' basic ability to localize the right hand in space without vision (proprioception) revealed no difference between the two groups. Taken together, these results suggest that blind individuals with impaired visual development have a more veridical percept of self-touch and a less flexible and dynamic representation of their own body in space compared to sighted individuals. We speculate that the multisensory brain systems that re-map somatosensory signals onto external reference frames are less developed in blind individuals and therefore do not allow efficient fusion of tactile and proprioceptive signals from the two upper limbs into a single illusory experience of self-touch as in sighted individuals

Virtual Body Ownership Illusions for Mental Health: A Narrative Review.

Over the last 20 years, virtual reality (VR) has been widely used to promote mental health in populations presenting different clinical conditions. Mental health does not refer only to the absence of psychiatric disorders but to the absence of a wide range of clinical conditions that influence people\u2019s general and social well-being such as chronic pain, neurological disorders that lead to motor o perceptual impairments, psychological disorders that alter behaviour and social cognition, or physical conditions like eating disorders or present in amputees. It is known that an accurate perception of oneself and of the surrounding environment are both key elements to enjoy mental health and well-being, and that both can be distorted in patients suffering from the clinical conditions mentioned above. In the past few years, multiple studies have shown the effectiveness of VR to modulate such perceptual distortions of oneself and of the surrounding environment through virtual body ownership illusions. This narrative review aims to review clinical studies that have explored the manipulation of embodied virtual bodies in VR for improving mental health, and to discuss the current state of the art and the challenges for future research in the context of clinical care

Widening the body to rubber hands and tools: what's the difference?

The brain represents the body in different ways (e.g., perceptual, motor) for different purposes (recognising oneself, acting in space). Several concepts and even more numerous labels (e.g., body image, body schema) have historically been proposed to define these representations in operational terms. Recent evidence of embodiment of external objects has added complexity to an already quite intricate picture. In particular, because of their perceptual and motor effects, both rubber hands and tools can be conceived as embodied, that is, represented in the brain as if they were parts of one's own body. But are there any limits to what we can embody? What constraints lay upon embodiment? And are they similar both for motor embodiment (i.e. integration within the body schema) and for perceptual embodiment (i.e. integration within the body image)? Here, we consider the implications emerging from the different, and up-to-now relatively separate research domains of tool use and rubber hand illusion for understanding the rules of embodiment. In particular, we compare what the embodiment of tools and prostheses may or may not have in common. We conclude that in both cases, although for different reasons and with different constraints, embodiment is only partial

Hybrid Brain-Computer Interface Systems: Approaches, Features, and Trends

Brain-computer interface (BCI) is an emerging field, and an increasing number of BCI research projects are being carried globally to interface computer with human using EEG for useful operations in both healthy and locked persons. Although several methods have been used to enhance the BCI performance in terms of signal processing, noise reduction, accuracy, information transfer rate, and user acceptability, the effective BCI system is still in the verge of development. So far, various modifications on single BCI systems as well as hybrid are done and the hybrid BCIs have shown increased but insufficient performance. Therefore, more efficient hybrid BCI models are still under the investigation by different research groups. In this review chapter, single BCI systems are briefly discussed and more detail discussions on hybrid BCIs, their modifications, operations, and performances with comparisons in terms of signal processing approaches, applications, limitations, and future scopes are presented