Abstract
Humans and animals learn the internal model of bodies and environments from their experience and stabilize posture against disturbances based on the predicted future states according to the internal model. We evaluated the mechanism of predictive control during standing, by using rats to construct a novel experimental system and comparing their behaviors with a mathematical model. In the experiments, rats (n = 6) that were standing upright using their hindlimbs were given a sensory input of light, after a certain period, the floor under them tilted backward. Initially, this disturbance induced a large postural response, including backward rotation of the center-of-mass angle and hindlimb segments. However, the rats gradually adjusted to the disturbance after experiencing 70 sequential trials, and a reduction in the amplitude of postural response was noted. We simulated the postural control of the rats under disturbance using an inverted pendulum model and model predictive control (MPC). MPC is a control method for predicting the future state using an internal model of the control target. It provides control inputs that optimize the predicted future states. Identification of the predictive and physiological parameters so that the simulation corresponds to the experiment, resulted in a value of predictive horizon (0.96 s) close to the interval time in the experiment (0.9–1.15 s). These results suggest that the rats predict posture dynamics under disturbance based on the timing of the sensory input and that the central nervous system provides plasticity mechanisms to acquire the internal model for MPC.
Highlights
Most daily activities and skillful motor performance require predictive postural control to stabilize the posture against internal and external disturbances
We numerically evaluated the neural mechanism of predictive postural controls against external disturbances through a combination of experiments in rats and simulation with model predictive control (MPC)
The center of mass (CoM) angle monotonically increased after the start of the tilt, but this fluctuation gradually decreased with repeated trials
Summary
Most daily activities and skillful motor performance require predictive postural control to stabilize the posture against internal and external disturbances. Predictive Postural Control in Rats while participants maintain a static standing posture, greatly contribute to understanding the stabilization mechanisms of the upright posture and finding automatic responses with a latency of approximately 100 ms (Nashner, 1976; Carpenter et al, 1999). Several studies have examined predictive postural controls for external disturbances while incorporating classical conditioning into floor-tilting systems. Even without the floor tilt, the sensory input alone evoked predictive movement to cancel the upcoming postural response and suppress the excessive stretch reflex as a result of this association (Campbell et al, 2009). It has been found that patients with cerebellar defects cannot establish these predictive controls (Kolb et al, 2004)
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