  This study demonstrates that the soft biological tissues of humans can be
used as a type of soft body in physical reservoir computing. Soft biological
tissues possess characteristics such as stress-strain nonlinearity and
viscoelasticity that satisfy the requirements for physical reservoir computing,
including nonlinearity and memory. The aim of this study was to utilize the
dynamics of human soft tissues as a physical reservoir for the emulation of
nonlinear dynamical systems. To demonstrate this concept, joint angle data
during motion in the flexion-extension direction of the wrist joint, and
ultrasound images of the muscles associated with that motion, were acquired
from human participants. The input to the system was the angle of the wrist
joint, while the deformation field within the muscle (obtained from ultrasound
images) represented the state of the reservoir. The results indicate that the
dynamics of soft tissue have a positive impact on the computational task of
emulating nonlinear dynamical systems. This research suggests that the soft
tissue of humans can be used as a potential computational resource.
