Primitive based biomechanical simulations predict feedback gating

Sensorimotor integration during spinal reflexes is discontinuous and context based unlike previously proposed continuous feedback models. Cutaneous and proprioceptive modalities play a key role in planning and execution of the hindlimb wipe reflex in adult spinal bullfrogs (Rana catesbeiana). However the temporal dynamics of this integration is still unclear. Studies have suggested that intrinsic musculoskeletal properties can correct for path deviations caused by pulsed force perturbations, without the need for active corrections. In this study, we test the efficacy of these intrinsic properties throughout the physiological workspace of the frog by employing a computational biomechanical simulation paradigm built in Opensim. Our results suggest that although viscoelastic effects lead to better convergence in trajectories, they are not as effective throughout the workspace. However targeting performance is significantly improved by contextually gating the proprioceptive feedback. These results are in agreement with observed activity in the frogs and suggest that reflex gating may be an important component of spinal sensorimotor reflex control.