Manual device interaction requires precise coordination which may be difficult for users with motor impairments. Muscle interfaces provide alternative interaction methods that may enhance performance, but have not yet been evaluated for simple (eg. mouse tracking) and complex (eg. driving) continuous tasks. Control theory enables us to probe continuous task performance by separating user input into intent and error correction to quantify how motor impairments impact device interaction. We compared the effectiveness of a manual versus a muscle interface for eleven users without and three users with motor impairments performing continuous tasks. Both user groups preferred and performed better with the muscle versus the manual interface for the complex continuous task. These results suggest muscle interfaces and algorithms that can detect and augment user intent may be especially useful for future design of interfaces for continuous tasks.

Determining hand grasping forces and kinetic direction and magnitude are important for the development of dexterous neural prosthetics. While many earlier decoding methods have successfully predicted upper-limb kinematic output from cortical signals in the sensorimotor parietal and premotor regions, the full extent of the regions that characterize kinetic behavior is unknown. In this study, we found that neural dynamics based on electrocorticography (ECoG) recorded from the human brain surface can successfully encode structured and unstructured grasping and arm kinetic output. We found a time-averaged linear relationship between gamma band spectral ECoG power and sustained grasping force output with visual feedback. In the kinetic grasping task, we obtained classification accuracy of 47% (25% = chance) using quadratic discriminant analysis. Additionally, we also found a similar linear relationship between spectral power and cued isometric force generation, without concurrent visual feedback, in arm force application; this feature could also classify arm force output categories with an accuracy of 41% (33% = chance). In addition, we applied quadratic discriminant analysis with top 12 principal components to attain approximately 26% accuracy (chance is 16%) in determining arm kinetic force direction. We found that the gamma band spectral power from both experiments in posterior parietal cortex, as well as projections of high gamma variability along the top principal components, can be successfully used to predict sustained kinetic outputs and to explain both structured and unstructured force output variability. Our findings contribute to a deeper understanding of neural dynamics for fine kinetic behavior.

Although a critical step in the technology design process, ideation is often not accessible for people with disabilities. We present findings from a design workshop facilitated to brainstorm accessible ideation methods. Groups, mostly engineers, ideated on a design challenge and documented access barriers encountered by participants with disabilities. They then ideated and prototyped potential solutions for decreasing access barriers. We offer suggestions for more accessible communication and ideation on a design team and insights from using a workshop as a site for rethinking ideation.

This paper is about the aspects of ability, selfhood, and normalcy embodied in people's relationships with prostheses. Drawing on interviews with 14 individuals with upper-limb loss and diverse experiences with prostheses, we find people not only choose to use and not use prosthesis throughout their lives but also form close and complex relationships with them. The design of "assistive" technology often focuses on enhancing function; however, we found that prostheses played important roles in people's development of identity and sense of normalcy. Even when a prosthesis failed functionally, such as was the case with 3D-printed prostheses created by an on-line open-source maker community (e-NABLE), we found people still praised the design and initiative because of the positive impacts on popular culture, identity, and community building. This work surfaces crucial questions about the role of design interventions in identity production, the promise of maker communities for accelerating innovation, and a broader definition of "assistive" technology.