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Infant lesion effect: I. Development of motor behavior following neonatal spinal cord damage in cats
Insights
Spinal cord damage in kittens impacts motor development, with later-developing functions showing some resilience. However, long-term effects reveal immature motor behaviors despite initial recovery after neonatal lesions.
Area of Science:
- Neuroscience
- Developmental Biology
- Animal Models
Background:
- Spinal cord lesions impact motor function.
- Understanding recovery and development after neonatal spinal cord injury is crucial.
- The timing of motor pattern onset may influence functional survival after injury.
Purpose of the Study:
- To investigate the effect of spinal cord damage on motor development in kittens.
- To determine if motor patterns with later onset show greater functional survival than those present at birth.
- To compare recovery after neonatal versus adult spinal cord lesions.
Main Methods:
- Examined postnatal development of postural reflexes and locomotion in normal and spinal-lesioned kittens (neonatal lesions).
- Assessed kittens during the first 4 months of life.
- Compared functional recovery and development after neonatal lesions to known outcomes after adult lesions.
Main Results:
- Neonatal spinal cord lesions caused deficits in motor development, though initial hindlimb function remained normal.
- Reflex recovery underlies locomotion recovery after both neonatal and adult lesions.
- Tactile placing unexpectedly recovered after neonatal lesions, unlike in adult lesions, suggesting spared function.
- Later-developing motor patterns did not show greater long-term survival; all functions remained immature.
Conclusions:
- Motor development onset is not dependent on ipsilateral descending input, but maturation is.
- Spinal cord lesions in neonates can lead to partial functional sparing, particularly for later-developing reflexes.
- Despite initial recovery, long-term motor behavior maturation is impaired after neonatal spinal cord lesions.
Abstract:
This study was undertaken to determine the effect of spinal cord damage on motor development, and to determine whether there is greater survival of motor function in those motor patterns with a later onset of function than in those which are present at birth. The postnatal development of postural reflexes and locomotion was examined during the first 4 months of life in normal kittens and in those which had received a spinal cord lesion (at high cervical or low thoracic levels) at birth. The results suggest that there are some similarities in normal development, recovery of function after adult lesions and recovery and/or development of function after neonatal lesions. After neonatal lesions, just as after lesions in adults, reflex recovery appears to underlie recovery of locomotion. After spinal lesions, the pattern and sequence of motor development was identical to that seen in normal animals. Hindlimb motor development was normal for some time after the spinal lesion, but deficits appeared later. These observations suggest that postural reflexes and locomotion are not dependent upon ipsilateral descending input for their onset, but only for their maturation. Unexpectedly, tactile placing developed after neonatal spinal cord lesions. This represents sparing of function, for tactile placing is abolished and does not recover after the same lesion sustained in adulthood. Tactile placing is the last of the series of postural reflexes to develop. It depends on the last of the spinal pathways to develop, the corticospinal tract. Two aspects of this study support the hypothesis that later developing motor patterns will have a greater chance for survival and subsequent development than those which are present at birth. First, the immediate effects of spinal cord lesions on postural reflexes are more severe on those reflexes that are more mature at birth. Second, the spinal cord lesions produce more severe impairment of the more mature forelimb motor function than of the less mature hindlimb motor function. The hypothesis is not supported, however, when the long-term effect of spinal cord lesions on the maturation of motor behavior is considered. All postural reflexes and locomotion fail to mature fully, i.e. they retain characteristics of the immature responses.