Fig. 1. Amputation architecture and efferent-afferent signaling mechanism.

Schematic of the agonist-antagonist myoneural interface (AMI), a neural prosthetic interface that involves surgically coapting an agonist-antagonist muscle pair to preserve physiological agonist-antagonist muscle dynamics and muscle-tendon proprioceptive afferent signaling, in an individual with lower limb amputation. In the AMI surgical framework, a single AMI, or muscle pair, is created for each biological joint that is to be amputated for which an improved phantom awareness and prosthetic controllability is ultimately sought. This study investigated the link between the AMI amputation and central neuroplasticity in the areas of motor execution and sensory perception through an examination of efferent motor commands (shown in green; tested by EMG during motor control tasks), fascicle dynamics (measured by ultrasound), proprioceptive afferents (measured by functional magnetic resonance imaging), and phantom sensation (shown in blue; measured by psychometric survey). Encircled in black is the depiction of afferent and efferent pathways from the peripheral nervous system synapsing with the central nervous system.