Jones T A, Schallert T
Department of Psychology, University of Texas at Austin 78712.
J Neurosci. 1994 Apr;14(4):2140-52. doi: 10.1523/JNEUROSCI.14-04-02140.1994.
Unilateral damage to the forelimb representation area of the sensorimotor cortex in adult rats increases dendritic arborization of layer V pyramidal neurons of the contralateral homotopic cortex. Arbor size was maximum at approximately 18 d postlesion, following which there was a partial elimination, or pruning, of dendritic processes. These neural changes were closely associated with behavioral events. The overgrowth of dendrites was related in time to disuse of the contralateral (to the lesion) forelimb and over-reliance on the ipsilateral forelimb for postural and exploratory movements. The pruning of dendrites was related to a return to more symmetrical use of the forelimbs. To investigate the possibility that lesion-induced asymmetries in motor behavior contributed to dendritic arborization changes, movements of the forelimb ipsilateral to the lesion were restricted during the period of dendritic overgrowth through the use of one-holed vests. This interfered with the increase in dendritic arborization. In contrast, animals that were allowed to use both forelimbs, or only the forelimb ipsilateral to the lesion, showed the expected increases. When sham-operated rats were forced to use only one forelimb, no significant increases in arborization were found. Therefore, neither a lesion nor asymmetrical limb use alone could account for the dendritic overgrowth--it depended on a lesion-behavior interaction. Furthermore, greater sensorimotor impairments were found when the dendritic growth was blocked, suggesting that the neural growth and/or associated limb-use behavior were related to functional recovery from the cortical damage. Finally, in a second experiment, immobilization of the impaired limb during the pruning period did not prevent the elimination of processes. Thus, the pruning of neural processes was not related simply to the recovery of more symmetrical forelimb use. There may be a period early after brain damage during which marked neural structural changes can occur in the presence of adequate behavioral demand.
成年大鼠感觉运动皮层前肢代表区的单侧损伤会增加对侧同位皮层第V层锥体神经元的树突分支。损伤后约18天树突大小达到最大，随后树突过程会部分消除或修剪。这些神经变化与行为事件密切相关。树突过度生长在时间上与对侧（损伤侧）前肢的废用以及在姿势和探索运动中对同侧前肢的过度依赖有关。树突的修剪与前肢使用恢复到更对称状态有关。为了研究损伤诱导的运动行为不对称是否导致树突分支变化，在树突过度生长期间通过使用单孔背心限制损伤同侧前肢的运动。这干扰了树突分支的增加。相比之下，允许使用双侧前肢或仅使用损伤同侧前肢的动物表现出预期的增加。当假手术大鼠被迫仅使用一只前肢时，未发现分支有显著增加。因此，单独的损伤或不对称肢体使用都不能解释树突过度生长——它依赖于损伤与行为的相互作用。此外，当树突生长受阻时发现感觉运动障碍更严重，这表明神经生长和/或相关的肢体使用行为与皮层损伤后的功能恢复有关。最后，在第二个实验中，在修剪期固定受损肢体并不能阻止树突过程的消除。因此，神经过程的修剪不仅仅与前肢使用恢复到更对称状态有关。在脑损伤后的早期可能存在一个时期，在此期间在有足够行为需求的情况下会发生明显的神经结构变化。
