Hand dominance in the performance and perceptions of virtual reach control

PURPOSE

Efforts to optimize human-computer interactions are becoming increasingly prevalent, especially with virtual reality (VR) rehabilitation paradigms that utilize engaging interfaces. We hypothesized that motor and perceptional behaviors within a virtual environment are modulated uniquely through different modes of control of a hand avatar depending on limb dominance. This study investigated the effects of limb dominance on performance and concurrent changes in perceptions, such as time-based measures for intentional binding, during virtual reach-to-grasp.

METHODS

Participants (n = 16, healthy) controlled a virtual hand through their own hand motions with control adaptations in speed, noise, and automation.

RESULTS

A significant (p < 0.01) positive relationship between performance (reaching pathlength) and binding (time-interval estimation of beep-sound after grasp contact) was observed for the dominant hand. Unique changes in performance (p < 0.0001) and binding (p < 0.0001) were observed depending on handedness and which control mode was applied.

CONCLUSIONS

Developers of VR paradigms should consider limb dominance to optimize settings that facilitate better performance and perceptional engagement. Adapting VR rehabilitation for handedness may particularly benefit unilateral impairments, like hemiparesis or single-limb amputation.

What am I doing? It depends: agency and action identification

Actions can be identified at a range of levels, from higher level, outcome-related descriptions to lower level, movement-related descriptions. But how do these levels of identification influence the experience of control (agency) over a task? We addressed the relation between the level of action identification and agency using a hierarchical task modeled from typing. Participants memorized letter sequences and reported them by moving a cursor to targets that contained letters. To manipulate lower level (aiming) difficulty, the targets were either large or small. To manipulate higher level (memory) difficulty, the letter sequences were either constant or random within a block. We found effects of higher and lower level difficulty on agency and action identification. Moreover, we found interactive effects of higher and lower level difficulty on performance. We discuss these findings in terms of contributions to the study of agency, and some differences from the results of previous studies of action identification.

How using brain-machine interfaces influences the human sense of agency

Brain-machine interfaces (BMI) allows individuals to control an external device by controlling their own brain activity, without requiring bodily or muscle movements. Performing voluntary movements is associated with the experience of agency ("sense of agency") over those movements and their outcomes. When people voluntarily control a BMI, they should likewise experience a sense of agency. However, using a BMI to act presents several differences compared to normal movements. In particular, BMIs lack sensorimotor feedback, afford lower controllability and are associated with increased cognitive fatigue. Here, we explored how these different factors influence the sense of agency across two studies in which participants learned to control a robotic hand through motor imagery decoded online through electroencephalography. We observed that the lack of sensorimotor information when using a BMI did not appear to influence the sense of agency. We further observed that experiencing lower control over the BMI reduced the sense of agency. Finally, we observed that the better participants controlled the BMI, the greater was the appropriation of the robotic hand, as measured by body-ownership and agency scores. Results are discussed based on existing theories on the sense of agency in light of the importance of BMI technology for patients using prosthetic limbs.

Control used and control felt: Two sides of the agency coin

Agency has been defined as the sense of ownership and control of our actions, and the metacognition of agency has now been examined in a number of studies. Here we examined the relations between task demands, the feeling of being in control, and the feeling of using control. As task demands increase, we might feel as if we use a lot of control while feeling little control over the task. It therefore seems possible that the amount of control one feels they have used and how much in control one feels are separable components of the metacognition of control. In two experiments, we manipulated task demands and assessed these two aspects of metacognition. The source of task demand differed for the two experiments. In Experiment 1, we manipulated task demands by varying the sizes of targets in an aiming task. As predicted, we found that reports of control used increased, while reports of control felt decreased, for more difficult aiming conditions. In Experiment 2, we found a similar relation using a different source of demand: response conflict. We connect these reports of control to previous investigations of task demand and agency, as well as prominent conceptions of cognitive control.

Attention and the sense of agency: A review and some thoughts on the matter

Much is now known about the sense of agency and how it is produced. What is lacking, though, is an understanding of how it relates to other cognitive domains and operations. Here, the relationship between the sense of agency and attention is explored. A review of the literature suggests that attention is involved in the sense of agency in (at least) two key ways. First, agency processing is dependent on attentional resources. Second, attentional enhancement is necessary for extraneous information to have an influence over the sense of agency. These are discussed and some suggestions for future research are offered.

Uncovering effects of self-control and stimulus-driven action selection on the sense of agency

The sense of agency refers to feelings of causing one's own action and resulting effect. Previous research indicates that voluntary action selection is an important factor in shaping the sense of agency. Whereas the volitional nature of the sense of agency is well documented, the present study examined whether agency is modulated when action selection shifts from self-control to a more automatic stimulus-driven process. Seventy-two participants performed an auditory Simon task including congruent and incongruent trials to generate automatic stimulus-driven vs. more self-control driven action, respectively. Responses in the Simon task produced a tone and agency was assessed with the intentional binding task - an implicit measure of agency. Results showed a Simon effect and temporal binding effect. However, temporal binding was independent of congruency. These findings suggest that temporal binding, a window to the sense of agency, emerges for both automatic stimulus-driven actions and self-controlled actions.

My action lasts longer: Potential link between subjective time and agency during voluntary action

Time perception distorts across different phases of bodily movement. During motor execution, sensory feedback matching an internal sensorimotor prediction is perceived to last longer. The sensorimotor prediction also underlies sense of agency. We investigated association between subjective time and agency during voluntary action. Participants performed hand action while watching a video feedback of their hand with various delays to manipulate agency. The perceived duration and agency over the video feedback were judged. Minimal delay of the video feedback resulted in longer perceived duration than the actual duration and stronger agency, while substantial feedback delay resulted in shorter perceived duration and weaker agency. These fluctuations of perceived duration and agency were nullified by the feedback of other's hand instead of their own, but not by inverted feedback from a third-person perspective. Subjective time during action might be associated with agency stemming from sensorimotor prediction, and self-other distinction based on bodily appearance.

The Bodymind Model: A platform for studying the mechanisms of change induced by art therapy

This paper introduces the Bodymind model of Art Therapy and delineates the processes through which it has salutary effects on individuals coping with a variety of health related challenges. The goal of this model is to articulate how activation, reorganization, growth and reintegration of the self can emerge from bodymind processes activated by art therapy. It provides a framework for the conduct of research that will test the key theoretical mechanisms through which art therapy benefits clients. We expect this model to be a spring board for discussion, debate and development of the profession of art therapy. Furthermore, we hope readers can use this model to conduct sound mechanistic studies. This paper can inform social scientists and medical professionals on the manner in which art making can contribute to health.

Agency over a phantom limb and electromyographic activity on the stump depend on visuomotor synchrony: a case study

Most patients, post-amputation, report the experience of a phantom limb. Some even sense voluntary movements when viewing a mirror image of the intact limb superimposed onto the phantom limb. While delayed visual feedback of an action is known to reduce a sense of agency, the effect of delayed visual feedback on phantom motor sensation (i.e., sense of controlling a phantom limb) has not been examined. Using a video-projection system, we examined the effect of delayed visual feedback on phantom motor sensation in an upper-limb amputee (male; left upper-limb amputation). He was instructed to view mirrored video images of his intact hand clasping and unclasping during a phantom limb movement. He then rated the intensity of the phantom motor sensation. Three types of hand movement images were presented as follows: synchronous, asynchronous with a 250-ms delay, and asynchronous with a 500-ms delay. Results showed that phantom motor sensation decreased when the image was delayed by 250 and 500 ms. However, when we instructed the patient to adjust the phase of phantom limb movement to that of the image with a 500-ms delay, phantom motor sensation increased. There was also a positive correlation between intensity of phantom motor sensation and electromyographic (EMG) activity on deltoids at the patient’s stump. These results suggest that phantom motor sensation and EMG activity on the stump depend on visuomotor synchrony and top-down effects.