The aim of this study was to characterize impairment and subsequent recovery of postural control after spinal cord injuries. Experiments were carried out on rabbits with three types of lesion—a dorsal (D), lateral (L), or ventral (V) hemisection (HS) at T12 level. The animals were maintaining equilibrium on a platform periodically tilted in the frontal plane. We assessed the postural limb/trunk configuration from video recordings and postural reflexes in the hindquarters from kinematical and electromyographic (EMG) recordings. We found that for a few days after DHS or LHS, the animals were not able to maintain the dorsal-side-up position of their hindquarters. This ability was then gradually restored, and the dynamic postural reflexes reached the prelesion value within 2–3 wk. By contrast, a VHS almost completely abolished postural reflexes, and they did not recover for ≥7 wk. The DHS, LHS, and VHS caused immediate and slowly compensated changes in the postural limb/trunk configuration as well as gradually developing changes. After DHS, both hind limbs were placed in an abnormal rostral and medial position. After LHS, the limb on the undamaged side was turned inward and occurred at the abnormal medial position; LHS also caused a gradually developing twisting of the caudal trunk. VHS caused gradually developing extension of the ankle and knee joints. These findings show that ventral spinal pathways are of crucial importance for postural control. When a part of these pathways is spared, postural reflexes can be restored rapidly, but not the postural limb/trunk configuration. Spinal and supraspinal mechanisms responsible for postural deficits and their compensation are discussed.

, and specific postural training (SPT). The factors were used either alone (SPT group) or in combination (DOIϩSPT, EESϩSPT, and DOIϩEESϩSPT groups) or not used (control group). It was found that in none of these groups did normal postural corrective movements in response to lateral tilts of the supporting platform reappear within the month of treatment. In control group, reduced irregular electromyographic (EMG) responses, either correctly or incorrectly phased in relation to tilts, were observed. By contrast, in DOIϩSPT and EESϩSPT groups, a gradual threefold increase in the proportion of correctly phased EMG responses (compared with control) was observed. The increase was smaller in DOIϩEESϩSPT and SPT groups. Dissimilarly to these long-term effects, short-term effects of DOI and EES were weak or absent. In addition, gradual development of oscillatory EMG activity in the responses to tilts, characteristic for the control group, was retarded in DOIϩSPT, EESϩSPT, DOIϩEESϩSPT, and SPT groups. Thus regular application of the three tested factors and their combinations caused progressive, long-lasting plastic changes in the isolated spinal networks, resulting in the facilitation of spinal postural reflexes and in the retardation of the development of oscillatory EMG activity. The facilitated reflexes, however, were insufficient for normal postural functions. postural corrections; spinal cord injury; (Ϯ)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride; rabbit WHEN STANDING, QUADRUPEDAL ANIMALS maintain the dorsalside-up body orientation and equilibrium due to the activity of the postural system (Deliagina et al.

During free behaviors animals often experience lateral forces, such as collisions with obstacles or interactions with other animals. We studied postural reactions to lateral pulses of force (pushes) in the cat during standing and walking. During standing, a push applied to the hip region caused a lateral deviation of the caudal trunk, followed by a return to the initial position. The corrective hindlimb electromyographic (EMG) pattern included an initial wave of excitation in most extensors of the hindlimb contralateral to push and inhibition of those in the ipsilateral limb. In cats walking on a treadmill with only hindlimbs, application of force also caused lateral deviation of the caudal trunk, with subsequent return to the initial position. The type of corrective movement depended on the pulse timing relative to the step cycle. If the force was applied at the end of the stance phase of one of the limbs or during its swing phase, a lateral component appeared in the swing trajectory of this limb. The corrective step was directed either inward (when the corrective limb was ipsilateral to force application) or outward (when it was contralateral). The EMG pattern in the corrective limb was characterized by considerable modification of the hip abductor and adductor activity in the perturbed step. Thus the basic mechanisms for balance control in these two forms of behavior are different. They perform a redistribution of muscle activity between symmetrical limbs (in standing) and a reconfiguration of the base of support during a corrective lateral step (in walking).

To keep balance when standing or walking on a surface inclined in the roll plane, the cat modifies its body configuration so that the functional length of its right and left limbs becomes different. The aim of the present study was to assess the motor cortex participation in the generation of this left/right asymmetry. We recorded the activity of fore-and hindlimb-related pyramidal tract neurons (PTNs) during standing and walking on a treadmill. A difference in PTN activity at two tilted positions of the treadmill (± 15 deg) was considered a positional response to surface inclination. During standing, 47% of PTNs exhibited a positional response, increasing their activity with either the contra-tilt (20%) or the ipsi-tilt (27%). During walking, PTNs were modulated in the rhythm of stepping, and tilts of the supporting surface evoked positional responses in the form of changes to the magnitude of modulation in 58% of PTNs. The contra-tilt increased activity in 28% of PTNs, and ipsi-tilt increased activity in 30% of PTNs. We suggest that PTNs with positional responses contribute to the modifications of limb configuration that are necessary for adaptation to the inclined surface. By comparing the responses to tilts in individual PTNs during standing and walking, four groups of PTNs were revealed: responding in both tasks (30%); responding only during standing (16%); responding only during walking (30%); responding in none of the tasks (24%). This diversity suggests that common and separate cortical mechanisms are used for postural adaptation to tilts during standing and walking.