A Model of Predictive Postural Control Against Floor Tilting in Rats

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.

Roles of the cerebellar vermis in predictive postural controls against external disturbances

“…As previously discussed 15 , the basic mechanics of postural fluctuations due to floor-tilting disturbances are common between bipedal rats and humans. Therefore, the kinematic and neural strategies adopted by the rats in this study can be extrapolated from human studies.…”

“…However, as most of these studies used behavioral tasks that could be performed under head-fixed conditions, such as blinking, saccades, and licking, the detailed mechanisms of predictive postural control remain unclear. Under these circumstances, an experimental system for floor tilting, which has been widely utilized to evaluate postural stability 14 , has recently been developed for rats 15 . Biomechanical fluctuations in upright-standing rats due to the disturbance generally agreed with those in humans, and comparisons between the experimental data and a simulation suggested that the rats acquired predictive muscle outputs at the hind limb joints based on the time difference between the conditioning stimulus and disturbance.…”

A novel behavioral paradigm using mice to study predictive postural control

“…It has been shown that body segments of rats during quiet bipedal standing are comparable but flexed compared to those of humans which are nearly aligned (Funato et al, 2017). In the study that explored bipedal rats' postural responses to the backward rotation of the floor, the researchers showed that the postural responses were generally common between humans and rats but found the bending of the trunk in rats as a response to the floor rotation, which is not commonly observed in humans (Konosu et al, 2021). They suggested that this might be due to the mass and length of the trunk accounting for a greater proportion of the rat's whole body compared to humans, as well as the aforementioned alignment differences.…”

“…We developed a postural perturbation task in freely moving mice, modeled after those used in human studies (Horak et al, 1989;Kolb et al, 2002;Welch and Ting, 2014) and a recent rat study (Konosu et al, 2021), in which a dynamic platform is used to give reproducible perturbations.…”

“…In the present work, we established a novel mouse paradigm to measure predictive postural control that is modeled after those used in human studies (Horak et al, 1989;Kolb et al, 2002;Welch and Ting, 2014) and recent rat studies (Konosu et al, 2024(Konosu et al, , 2021. In the following sections, we describe the postural task that we developed and how we quantified the postural responses based on kinematics and reward acquisition.…”