Biology subjects

Dideriksen, J. L.

Publications and source records attributed to Dideriksen, J. L..

2 recordsLinked to original sources

bioRxiv2023

Measuring and monitoring skill learning in closed-loop myoelectric hand prostheses using speed-accuracy tradeoffs

ObjectiveClosed-loop myoelectric prostheses, which combine supplementary sensory feedback and electromyography (EMG) based control, hold the potential to narrow the divide between natural and bionic hands. The use of these devices, however, requires dedicated training. Therefore, it is crucial to develop methods that quantify how users acquire skilled control over their prostheses to effectively monitor skill progression and inform the development of interfaces that optimize this process. ApproachBuilding on theories of skill learning in human motor control, we measured speed-accuracy tradeoff functions (SAFs) to comprehensively characterize learning-induced changes in skill - as opposed to merely tracking changes in task success across training - facilitated by a closed-loop interface that combined proportional control and EMG feedback. Sixteen able-bodied and one amputee participated in a 3-day experiment where they were instructed to perform the box-and-blocks task using a timed force-matching paradigm at four specified speeds to reach two target force levels, such that the SAF could be determined. Main resultsWe found that the participants accuracy increased in a similar way across all speeds we tested. Consequently, the shape of the SAF remained similar across days, at both force levels. Further, we observed that EMG feedback enabled participants to improve their motor execution in terms of reduced trial-by-trial variability, a hallmark of skilled behavior. We then fit a power law model of the SAF, and demonstrated how the model parameters could be used to identify and monitor changes in skill. SignificanceWe comprehensively characterized how an EMG feedback interface enabled skill acquisition, both at the level of task performance and movement execution. More generally, we believe that the proposed methods are effective for measuring and monitoring user skill progression in closed-loop prosthesis control.

bioengineering↗

bioRxiv2022

Estimating Speed-Accuracy Trade-offs to Evaluate and Understand Closed-Loop Prosthesis Interfaces

ObjectiveClosed-loop prosthesis interfaces, combining electromyography (EMG)-based control with non-invasive supplementary feedback, represent a promising direction to develop the next generation of user prosthesis interfaces. However, we still lack an understanding of how users make use of these interfaces, and how to evaluate competing interfaces. In this study we use the framework of speed accuracy trade-off functions (SAF) to understand, evaluate and compare the performance afforded by two closed-loop user-prosthesis interfaces. ApproachTen able-bodied participants and one amputee performed a force matching task in a functional box-and-blocks setup at 3 different speeds. All participants were subject to both interfaces in a crossover fashion with a one-week washout period. Importantly, both interfaces used (identical) direct proportional control but differed in the feedback provided to the participant - EMG feedback vs force feedback. We thereby estimated the SAFs afforded by the two interfaces, and additionally sought to understand how participants planned and executed the task in the various conditions. Main resultsWe found that execution speed significantly influenced the performance, and that EMG feedback afforded better performance overall. Notably, we found that there was a difference in SAF between the two interfaces, with EMG feedback enabling participants to attain higher accuracies faster than Force feedback. Further, both interfaces enabled participants to develop flexible control policies, while EMG feedback also afforded participants to generate smoother more repeatable EMG commands. SignificanceOverall, the results indicate that closed-loop prosthesis interfaces afford subjects to exhibit a wide range of performance, which is affected both by the interface and the execution speed. Thereby, we argue that it is important to consider the speed accuracy trade-offs to rigorously evaluate and compare (closed-loop) user-prosthesis interfaces.

bioengineering↗