Understanding and Measuring the Cognitive Load of Amputees for Rehabilitation and Prosthesis Development

OBJECTIVE: To derive a definition of cognitive load that is applicable for amputation as well as analyze suitable research models for measuring cognitive load during prosthesis use. Defining cognitive load for amputation will improve rehabilitation methods and enable better prosthesis design. DATA SOURCES: Elsevier, Springer, PLoS, IEEE Xplore, and PubMed. STUDY SELECTION: Studies on upper limb myoelectric prostheses and neuroprostheses were prioritized. For understanding measurement, lower limb amputations and studies with individuals without lower limb amputations were included. DATA EXTRACTION: Queries including “cognitive load,” “neural fatigue,” “brain plasticity,” “neuroprosthetics,” “upper limb prosthetics,” and “amputation” were used with peer-reviewed journals or articles. Articles published within the last 6 years were prioritized. Articles on foundational principles were included regardless of date. A total of 69 articles were found: 12 on amputation, 15 on cognitive load, 8 on phantom limb, 22 on sensory feedback, and 12 on measurement methods. DATA SYNTHESIS: The emotional, physiological, and neurologic aspects of amputation, prosthesis use, and rehabilitation aspects of cognitive load were analyzed in conjunction with measurement methods, including resolution, invasiveness, and sensitivity to user movement and environmental noise. CONCLUSIONS: Use of “cognitive load” remains consistent with its original definition. For amputation, 2 additional elements are needed: “emotional fatigue,” defined as an amputee's emotional response, including mental concentration and emotions, and “neural fatigue,” defined as the physiological and neurologic effects of amputation on brain plasticity. Cognitive load is estimated via neuroimaging techniques, including electroencephalography, functional magnetic resonance imaging, and functional near-infrared spectroscopy (fNIRS). Because fNIRS measures cognitive load directly, has good temporal and spatial resolution, and is not as restricted by user movement, fNIRS is recommended for most cognitive load studies.