ABSTRACT
Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is now widely used to alleviate symptoms of Parkinson's disease (PD). The specific aim of this study was to identify posture control measures that may be used to improve selection of DBS parameters in the clinic and this was carried out by changing the DBS stimulation amplitude. A dynamic posture shift paradigm was used to assess posture control in 4 PD STN-DBS subjects. Each subject was tested at 4 stimulation amplitude settings. Movements of the center of pressure and the position of the pelvis were monitored and several quantitative indices were calculated. The presence of any statistically significant changes in several normalized indices due to reduced/no stimulation was tested using the one-sample t test. The peak velocity and the average movement velocity during the initial and mid phases of movement towards the target posture were substantially reduced. These results may be explained in terms of increased akinesia and bradykinesia due to altered stimulation conditions. Thus, the dynamic posture shift paradigm may be an effective tool to quantitatively characterize the effects of DBS on posture control and should be further investigated as a tool for selection of DBS parameters in the clinic.
ABSTRACT
Recent research has shown that after spinal cord injury, the nervous system reorganizes. Nevertheless, little is known of the effects of neural reorganization, or plasticity, on motor skills. In this work, we present a method that utilizes kinetic and kinematic analysis, for investigating balance control in a rodent model of incomplete spinal cord injury. In this setup, the animals sit unconstrained on their hindlimbs on a platform while they eat a Fruitloop. In this posture, the animal is supporting all the body weight on its hindquarters removing the need for the animal to support itself on its hindlimb or maintain appropriate forelimb-hindlimb coordination for functional gait. The platform is bolted to a force transducer to provide measurements of shear forces in orthogonal directions in the horizontal plane. Reflective markers on the hip and tail of the animal indicate sway of the animals body. Using this method the effect of extensive 12 week long treadmill locomotor training on balance control in rodents with incomplete thoracic spinal cord contusion injury (iSCI) was assessed. One iSCI rat did not undergo training, while a sham injured and 3 other iSCI rats underwent training. The shear forces and sway produced by the injured untrained rat were much larger than for the sham or the injured but trained rats. Stance width assessed from overground walking in a separate study was also larger in the injured untrained rat. These data suggest that balance control may be improved by a locomotor training paradigm. This simple method for assessing balance control could thus be utilized in longitudinal studies to evaluate the effectiveness of pharmacological and locomotor therapies for repair and recovery after spinal cord injury.
