Motor imagery training improves precision of an upper limb movement in patients with hemiparesis

BACKGROUND: In healthy participants, beneficial effects of motor imagery training on movement execution have been shown for precision, strength, and speed. In the clinical context, it is still debated whether motor imagery provides an effective rehabilitation technique in patients with motor deficits.OBJECTIVE: To compare the effectiveness of two different types of movement training: motor imagery vs. motor execution.METHODS: Twenty-five patients with hemiparesis were assigned to one of two training groups: the imagery or the execution-training group. Both groups completed a baseline test before they received six training sessions, each of which was followed by a test session. Using a novel and precisely quantifiable test, we assessed how accurately patients performed an upper limb movement. RESULTS: Both training groups improved performance over the six test sessions but the improvement was significantly larger in the imagery group. That is, the imagery group was able to perform more precise movements than the execution group after the sixth training session while there was no difference at the beginning of the training.CONCLUSIONS: The results provide evidence for the benefit of motor imagery training in patients with hemiparesis and thus suggest the integration of cognitive training in conventional physiotherapy practice

How to Get There When You Are There Already? Defining Presence in Virtual Reality and the Importance of Perceived Realism

The aim of the current opinion paper is to challenge the current definition of presence in the context of virtual reality (VR). Opticians do not only measure visual acuity but also the visual field, stereoscopic vision, and color vision. In the same vein, presence researchers are encouraged to not only measure the experience of “being there” in the sense of attentional allocation to the virtual environment (VE), but also the perceived realism of the VE. Perceived realism is the result of an evaluation of the virtual world regarding (1) the subjective degree of reality of the depicted environment and (2) its overall plausibility and credibility. Thus, the sense of presence in a VE is conceived as a composite of being there and perceived realism. When in VR, a user will inevitably compare the look of virtual objects to real-world objects and judge the level of congruence (Sutcliffe and Gault, 2004). The user evaluates the plausibility and naturalness of the depicted world as well as the ease of interaction within the VE by answering questions such as: is there a shadow cast? Are the proportions of objects correct? Does the environment correspond to my own movements? Does my virtual body match the proportions of my real body? Just like the visual features, a story and its characters are also evaluated in terms of consistency and plausibility (Park et al., 2010; Gorini et al., 2011): are the consequences of actions plausible? Is the story coherent in itself? Does the causal sequence of events make sense? The answers to these questions define the degree of perceived realism. Perceived realism leads to the experience that a user not only feels surrounded by the VE, but rather has a compelling sense of reality and in extreme cases even forgets that he or she is wearing a head-mounted display (HMD). Previous papers on presence are based on the assumption that realism enhances presence (e.g., Heeter, 1992; Welch et al., 1996; Lombard and Ditton, 1997; Bystrom et al., 1999) suggested a conceptualization of presence as the degree to which a medium seems realistic. Interestingly, perceived realism is nevertheless not part of the most widely used presence definitions. It is either a possible trigger of presence or is blended in with the term being there. The conceptualization of presence as the experience of being there in a mediated environment dominates current presence definitions. Being there is strongly associated with attentional allocation and the sensation of being surrounded and absorbed by a mediated world. However, we claim that presence in VR requires much more than just being there. With the widespread use of immersive VR technology, it has become an easy task to absorb users in a VE. Thus, judgments about the realism of the VE become increasingly important. Being there and perceived realism are both important but yet different aspects of presence. They need to be combined in order to (1) adequately describe and define the experience of presence and (2) to obtain an appropriate and more complete assessment of presence in VR. Thus, theories and measures of presence need to be extended and establish perceived realism as an important domain besides being there. Presence in VR as a Two-Dimen

God is up and devil is down: mortality salience increases implicit spatial-religious associations

Most Christians in Western cultures associate God with upper space and devil with lower space. Measuring this spatial association captures the implicit metaphorical representations of religious concepts. Previous studies have shown that implicit measurements of the belief in God increase when people are confronted with their own mortality. Here we investigated the effect of mortality salience on implicit metaphorical representations of religiosity. Using a repeated measurement design, we found that implicit associations between God-up and devil-down increase when people think about their own death, but not when they think about a tooth treatment (control condition). The effect was moderated by self-esteem; only people with low and medium self-esteem were influenced by mortality salience. Our results show that mortality salience automatically activates religious contents and their cognitive representations that embody these abstract contents

Eye movements during mental imagery: A closer look at the spatial reference frame

People tend to look back at spatial locations of visually encoded information when they recall this information through visual imagery. Multiple studies confirmed this so-called looking-at-nothing (LAN) effect, but the nature of the spatial reference frame underlying this effect remains unclear. Specifically, the location of an object can be associated either with the absolute location of the object in the visual environment (i.e., its fixed coordinates) or with its relative location in relation to other spatial cues (e.g., other objects or some kind of spatial reference frame within the environment). In this study, we aimed to gain new insights into the underlying mechanisms of the LAN effect by investigating which spatial indexes (absolute vs. relative) play a role for eye movements to absent objects during visual imagination of previously seen objects. Participants (N = 34) were asked to memorize different objects that were subsequently presented in one of four possible quadrants in a central 2x2 grid during the encoding phase. In the following recall phase, they were asked to visualize each object in their mind’s eye for 7 s, and then answer to a verbally presented question about the object. Crucially, the position of the 2x2 empty grid during recall either remained centered ("static trials") or was shifted sidewards ("dynamic trials"), so that one of the four quadrants corresponded to the object's absolute position on the screen and a second quadrant to the object's relative position within the grid during encoding. The distribution of eye fixations in the four quadrants during recall was analyzed for static and dynamic trials. In static trials, the results confirmed that participants looked longer at the quadrant in which the object was previously presented. In dynamic trials, we mainly observed LAN behavior to the object's relative location for most of the recall time. However, for a short period during recall, we also observed LAN behavior to the object's absolute location. We conclude that the LAN effect can be divided into two different effects due to the recruitment of both a relative and an absolute spatial reference frame, while the former seems to dominate the latter

Imagery-related eye movements in 3D space depend on individual differences in visual object imagery.

During recall of visual information people tend to move their eyes even though there is nothing to see. Previous studies indicated that such eye movements are related to the spatial location of previously seen items on 2D screens, but they also showed that eye movement behavior varies significantly across individuals. The reason for these differences remains unclear. In the present study we used immersive virtual reality to investigate how individual tendencies to process and represent visual information contribute to eye fixation patterns in visual imagery of previously inspected objects in three-dimensional (3D) space. We show that participants also look back to relevant locations when they are free to move in 3D space. Furthermore, we found that looking back to relevant locations depends on individual differences in visual object imagery abilities. We suggest that object visualizers rely less on spatial information because they tend to process and represent the visual information in terms of color and shape rather than in terms of spatial layout. This finding indicates that eye movements during imagery are subject to individual strategies, and the immersive setting in 3D space made individual differences more likely to unfold

Understanding the psychological impact of the COVID-19 pandemic and containment measures: an empirical model of stress

Epidemics such as COVID-19 and corresponding containment measures are assumed to cause psychological stress. In a survey during the lockdown in Switzerland (n = 1565), we found substantially increased levels of stress in the population. In particular, individuals who did not agree with the containment measures, as well as those who saw nothing positive in the crisis, experienced high levels of stress. In contrast, individuals who are part of a risk group or who are working in healthcare or in essential shops experienced similar stress lev-els as the general public. The psychological mechanisms that determine stress, caused by the COVID-19 pandemic and containment measures, are not yet clear. Thus, we conducted a path analysis to gain a deeper understanding of the psychological mechanisms that lead to stress. Experiencing fear of the disease is a key driver for being worried. Our model fur-ther shows that worries about the individual, social, and economic consequences of the cri-sis, strongly boost stress. The infection rate in the canton (i.e., state) of residence also contributes to stress. Positive thinking and perceived social, organizational, and govern-mental support mitigate worries and stress. Our findings indicate that containment mea-sures increase worries and stress, especially for those who feel that these measures either are not sufficient or go too far. Thus, highlighting positive aspects of the crisis and convinc-ing people of the effectiveness and necessity of mitigation measures can, not only promote compliance, but also reduce stress. Our model suggests that people who feel protected by the authorities have fewer worries, which can, in turn, limit the negative impact of the crisis on mental health

A Hierarchical Bayesian Model for Measuring Motion Adaptation

Previous research has shown that motion imagery draws on the same neural circuits that are involved in perception of motion, thus leading to a motion aftereffect (Winawer et al., 2010). Imagined stimuli can induce a similar shift in participants’ psychometric functions as neural adaptation due to a perceived stimulus. However, these studies have been criticized on the grounds that they fail to exclude the possibility that the subjects might have guessed the experimental hypothesis, and behaved accordingly (Morgan et al., 2012). In particular, the authors claim that participants can adopt arbitrary response criteria, which results in similar changes of the central tendency μ of psychometric curves as those shown by Winawer et al. (2010)

Toward a Dynamic Probabilistic Model for Vestibular Cognition

We suggest that research in vestibular cognition will benefit from the theoretical framework of probabilistic models. This will aid in developing an understanding of how interactions between high-level cognition and low-level sensory processing might occur. Many such interactions have been shown experimentally; however, to date, no attempt has been made to systematically explore vestibular cognition by using computational modeling. It is widely assumed that mental imagery and perception share at least in part neural circuitry, and it has been proposed that mental simulation is closely connected to the brain’s ability to make predictions. We claim that this connection has been disregarded in the vestibular domain, and we suggest ways in which future research may take this into consideration

Learning by teaching in immersive virtual reality – Absorption tendency increases learning outcomes

We investigated the learning outcome of teaching an agent via immersive virtual reality (IVR) in two experiments. In Experiment 1, we compared IVR to a less immersive desktop setting and a control condition (writing a summary). Learning outcomes of participants who had explained the topic to an agent via IVR were better. However, this was only the case for participants who scored high on absorption tendency. In Experiment 2, we investigated whether including social cues in the task instructions enhances learning in participants explaining a topic to an agent. Instruction manipulation affected learning as a function of absorption tendency: Low-absorption participants benefitted most from being instructed to imagine they were helping a student peer pass an upcoming test, while high-absorption participants benefitted more when they were to explain the text to a virtual agent. The findings highlight the crucial role of personality traits in learning by teaching in IVR

The Illusion of Being Located in Dynamic Virtual Environments. Can Eye Movement Parameters Predict Spatial Presence?

Attention allocation towards the mediated environment is assumed to be a necessary precondition to feel localized in a virtual world. In presence research, however, the potential of eye movement research has not been fully exploited so far. In this study, participants (N=44) rode on a virtual roller coaster simulation. We compare participants scoring high versus low on presence. During the ride, the eye movements and subjective ex post presence judgments were assessed. We found high sensations of presence to be associated with fewer fixations and a tendency towards longer fixation durations. In contrast to the immersive tendency trait, eye movement parameters can predict presence