Abstract
Impairment of inferior olivary neurons (IONs) affects whole-body movements and results in abnormal gait and posture. Because IONs are activated by unpredicted motion rather than regular body movements, the postural dysfunction caused by ION lesions is expected to involve factors other than simple loss of feedback control. In this study, we measured the postural movements of rats with pharmacological ION lesions (IO rats) trained to stand on their hindlimbs. The coordination of body segments as well as the distribution and frequency characteristics of center of mass (COM) motion were analyzed. We determined that the lesion altered the peak properties of the power spectrum density of the COM, whereas changes in coordination and COM distribution were minor. To investigate how the observed properties reflected changes in the control system, we constructed a mathematical model of the standing rats and quantitatively identified the control system. We found an increase in linear proportional control and a decrease in differential and nonlinear control in IO rats compared with intact rats. The dystonia-like changes in body stiffness explain the nature of the linear proportional and differential control, and a disorder in the internal model is one possible cause of the decrease in nonlinear control.
Highlights
IOexp (n = 8) and IO (IOtest: n = 8; and IOexp: n = 1) rats
We adopted the following approach: (1) intact and IO rats were maintained in the bipedal upright posture and their motions were measured; (2) the coordination among joints was analyzed from the measured motions; (3) the distribution and power spectra of the center of mass (COM) position were derived to explore the changes in behavior required to maintain the COM; and (4) the control system was identified from the COM behavior and the changes in the control system caused by a lesion in the olivo-cerebellar system were quantitatively evaluated
The present study analyzed the posture of bipedally standing rats and investigated changes in postural control systems associated with a lesion in the olivo-cerebellar system
Summary
Neurons in the rMAO, rDAO, and rPO were counted for IOexp, and n/a represents data not available. By investigating the standing motion of IO rats and identifying the control system from their motion, we can address the stabilized and destabilized mechanisms of posture control. We adopted the following approach: (1) intact and IO rats (created using 3-acetylpyridine and nicotinamide injection) were maintained in the bipedal upright posture and their motions were measured; (2) the coordination among joints was analyzed from the measured motions; (3) the distribution and power spectra of the COM position were derived to explore the changes in behavior required to maintain the COM; and (4) the control system was identified from the COM behavior and the changes in the control system caused by a lesion in the olivo-cerebellar system were quantitatively evaluated
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