  The lumbosacral organ (LSO) is a lumbosacral spinal canal morphology that is
universally and uniquely found in birds. Recent studies suggested an
intraspinal mechanosensor function that relies on the compliant motion of soft
tissue in the spinal cord fluid. It has not yet been possible to observe LSO
soft tissue motion in vivo due to limitations of imaging technologies. As an
alternative approach, we developed an artificial biophysical model of the LSO,
and characterize the dynamic responses of this model when entrained by external
motion. The parametric model incorporates morphological and material properties
of the LSO. We varied the model's parameters to study the influence of
individual features on the system response. We characterized the system in a
locomotion simulator, producing vertical oscillations similar to the trunk
motions. We show how morphological and material properties effectively shape
the system's oscillation characteristics. We conclude that external
oscillations could entrain the soft tissue of the intraspinal lumbosacral organ
during locomotion, consistent with recently proposed sensing mechanisms.
