Impairment of Postural Control in Rabbits With Extensive Spinal Lesions

Abstract

. Our previous studies on rabbits demonstrated that the ventral spinal pathways are of primary importance for postural control in the hindquarters. After ventral hemisection, postural control did not recover, whereas after dorsal or lateral hemisection it did. The aim of this study was to examine postural capacity of rabbits after more extensive lesion (3/4 section of the spinal cord at T 12 level), that is, with only one ventral quadrant spared (VQ animals). They were tested before (control) and after lesion on the platform periodically tilted in the frontal plane. In control animals, tilts of the platform regularly elicited coordinated electromyographic (EMG) responses in the hindlimbs, which resulted in generation of postural corrections and in maintenance of balance. In VQ rabbits, the EMG responses appeared only in a part of tilt cycles, and they could be either correctly or incorrectly phased in relation to tilts. Because of a reduced value and incorrect phasing of EMG responses on both sides, this muscle activity did not cause postural corrective movements in the majority of rabbits, and the body swayed together with the platform. In these rabbits, the ability to perform postural corrections did not recover during the whole period of observation (Յ30 days). Low probability of correct EMG responses to tilts in most rabbits as well as an appearance of incorrect responses to tilts suggest that the spinal reflex chains, necessary for postural control, have not been specifically selected by a reduced supraspinal drive transmitted via a single ventral quadrant. I N T R O D U C T I O NMaintenance of the basic body posture, upright in humans and dorsal-side-up in quadrupeds, and keeping balance is a fundamental motor function. This nonvolitional form of motor activity in many species is based on inborn neural mechanisms (Deliagina et al. 2006;Massion 1998). An efficient control of the basic posture is equally important for standing and during walking (Horak and Macpherson 1996;Macpherson et al. 1997;Orlovsky et al. 1999) as well as for providing support of voluntary limb movements (Massion and Dufosse 1988).Damage to the spinal communication system (descending and ascending spinal pathways), caused by, e.g., a spinal cord injury (SCI), can result in an impairment of the postural control. This affects equilibrium both during standing and during locomotion and can impair voluntary movements that need postural support (Horak and Macpherson 1996). Apparently, postural deficits depend on the location and extent of SCI. A complete lesion of the spinal cord in the thoracic region separates the spinal postural mechanisms of the hindquarters from the rest of the CNS. This has dramatic consequences. Studies on chronic spinal cats have shown that they exhibit very poor responses to disturbances of posture and are not able to maintain the dorsal-side-up orientation of the caudal part of their body (Barbeau et al. 2002;Macpherson and Fung 1999;Rossignol et al. 1999Rossignol et al. , 2002. However, a reduced postural control (...

Platform With Camera System for Measurement of Compensatory Movements of Small Animals

“…This combines a three-axis gyroscope, three-axis accelerometer, 16 bit ADC and a digital movement processor for an accurate monitoring of fast and slow movements in gyroscope ranges of ±250°/s as well as in accelerometer ranges of ±4 g. Ranges of angular movements of the three motors are limited to avoid coincidence between the platform and the base construction. The limit of the range of the motor movement is set to 46.8°, which is a higher value than in similar experiments [7,8]. A light tin holder with rails for the cameras of the subsystem and another one to hold the animal are fitted onto the platform.…”

“…To test and verify the designed system and method, the rotation of the animal around only one axis, similarly to several other studies of animal body segment movement [7,8], was chosen. The animal body can be rotated in transversal anatomical plane, i.e., by change in the roll angle of the platform [5][6][7][8].…”

“…The animal body can be rotated in transversal anatomical plane, i.e., by change in the roll angle of the platform [5][6][7][8]. Some studies, however, also describe the movement on sagittal plane; i.e., change in the pitch angle of the platform [7][8][9]. We primarily focused on the head movement in the sagittal plane and controlled the change of orientation in the pitch angle of the platform, where the most significant compensatory movements of the head can be expected.…”

“…Tilts are, therefore, usually symmetric in relation to the initial horizontal position of the platform. Maximum values of tilt angles can reach up to 40°i n healthy subjects, in the case of roll and pitch angles [7,8]. During an evaluation of pitch angles, even +90°/−90°angle was used, however, the movement of subjects was carried out manually and the movement record step was 20°, instead of electronically powered platform [4].…”

“…For some experiments with hares, the tilt platforms were additionally equipped with force sensors under the animals, while goniometers were used to measure their movement. The animals are mounted onto platforms with the holders placed on body segments [7], or, if the animals are trained, using only a rough platform surface; this safeguard prevents them from falling, [8]. Some more complex platforms and MoCap systems were used in the studies of nervous system of a domestic cat for an evaluation of its movement in [9,10].…”