We propose to continue our studies on the motor capacity of chronic spinalized cats. Under various experimental conditions, three types of movements will be assessed: automatic-rhythmical motions, weight-bearing locomotion and evoked reflexes. We have observed that all chronic spinalized cats exhibit airstepping (ASTP), rhythmical flexion and extension of the hindlegs patterned after regular locomotion, and paw shaking responses (PSR), rapid cycles of flexion and extension of one limb elicited by cutaneous stimuli applied to the paw. By specific measures of EMG from primary flexors and extensors of the hip, knee and ankle joints, we propose to elucidate the cycle characteristics and intralimb coordination of both movements. In additions, we will test our hypothesis that both ASTP and PSR are centrally generated patterns, and as such, parameters of intralimb coordination will not be determined by phasic feedback from the moving limb. To test this hypothesis, we will examine ASTP and PSR under conditions of hindlimb deafferentation and ankle-knee immobilization in cats cordotomized as kittens (6 wks. of age) or as young adults (8 mos. of age). If ASTP and PSR patterns are generated by interneuronal networks within the lumbosacral cord, intralimb coordination should not be disrupted under the two experimental conditions. We have domonstrated that following cord transection at T-12, young kittens have the capacity to develop weight-supporting locomotion with the hindlimbs, whether or not they receive daily training on the treadmill. Although weight-bearing can be achieved, performance on the treadmill varies greatly as determined by EMG and kinematic measures. To better understand the neural mechanisms that may underscore differences in treadmill performance, the following measures will be used to compare chronic spinalized kittens that are highly-rated on the treadmill with those that are poorly-rated: reflex development, ASTP cycle characteristics and treadmill kinematics.
Showing the most recent 10 out of 30 publications
