TY - JOUR TI - Diverse and complex muscle spindle afferent firing properties emerge from multiscale muscle mechanics AU - Blum, Kyle P AU - Campbell, Kenneth S AU - Horslen, Brian C AU - Nardelli, Paul AU - Housley, Stephen N AU - Cope, Timothy C AU - Ting, Lena H A2 - Fuglevand, Andrew A2 - Huguenard, John R A2 - Prochazka, Arthur A2 - Loeb, Gerald VL - 9 PY - 2020 DA - 2020/12/28 SP - e55177 C1 - eLife 2020;9:e55177 DO - 10.7554/eLife.55177 UR - https://doi.org/10.7554/eLife.55177 AB - Despite decades of research, we lack a mechanistic framework capable of predicting how movement-related signals are transformed into the diversity of muscle spindle afferent firing patterns observed experimentally, particularly in naturalistic behaviors. Here, a biophysical model demonstrates that well-known firing characteristics of mammalian muscle spindle Ia afferents – including movement history dependence, and nonlinear scaling with muscle stretch velocity – emerge from first principles of muscle contractile mechanics. Further, mechanical interactions of the muscle spindle with muscle-tendon dynamics reveal how motor commands to the muscle (alpha drive) versus muscle spindle (gamma drive) can cause highly variable and complex activity during active muscle contraction and muscle stretch that defy simple explanation. Depending on the neuromechanical conditions, the muscle spindle model output appears to ‘encode’ aspects of muscle force, yank, length, stiffness, velocity, and/or acceleration, providing an extendable, multiscale, biophysical framework for understanding and predicting proprioceptive sensory signals in health and disease. KW - proprioception KW - biophysical model KW - sensory coding JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -