Barth T M, Stanfield B B
Laboratory of Neurophysiology, National Institute of Mental Health, National Institutes of Health Animal Center, Poolesville, Maryland 20837.
J Neurosci. 1990 Oct;10(10):3449-59. doi: 10.1523/JNEUROSCI.10-10-03449.1990.
Following unilateral lesions of the somatic sensorimotor cortex (SMC) in neonatal, but not adult, rats, an aberrant ipsilateral corticospinal projection originates from the undamaged hemisphere (Hicks and D'Amato, 1970; Leong and Lund, 1973; Castro, 1975). We have evaluated the contribution of the hemisphere contralateral to a unilateral lesion of the SMC in the recovery of tactile forelimb-placing behavior. Neither adult-lesioned or neonatally lesioned animals show evidence for placing deficits with either forelimb when tested 30 or 42 d after the lesion. However, in adult-lesioned animals, a subsequent lesion of the undamaged SMC on postlesion day 42 produces placing deficits only with the forelimb contralateral to the second lesion, while such a second lesion in the neonatally lesioned rats results in placing deficits with both forelimbs. Anatomical observations in the animals used for behavioral analyses confirm previous reports of a substantial ipsilateral corticospinal projection in rats with unilateral SMC damage as neonates and demonstrate that many of these aberrant fibers recross the midline within the spinal cord to arborize extensively within the ipsilateral spinal gray. These findings indicate that, following unilateral SMC lesions in neonates, the contralateral hemisphere mediates some aspects of the recovery of forelimb placing. The aberrant ipsilateral corticospinal projection may provide the anatomical substrate through which the cortex effects this recovery.
新生大鼠而非成年大鼠在体感觉运动皮层（SMC）单侧受损后，未受损半球会产生异常的同侧皮质脊髓投射（希克斯和达马托，1970年；梁和伦德，1973年；卡斯特罗，1975年）。我们评估了SMC单侧损伤对侧半球在触觉前肢放置行为恢复中的作用。在损伤后30天或42天进行测试时，成年损伤组和新生损伤组动物的任一前肢均未表现出放置缺陷的迹象。然而，在成年损伤组动物中，损伤后第42天对未受损的SMC进行后续损伤，仅导致与第二个损伤对侧的前肢出现放置缺陷，而新生损伤大鼠中的这种第二次损伤则导致双侧前肢出现放置缺陷。用于行为分析的动物的解剖学观察结果证实了先前的报道，即新生时单侧SMC损伤的大鼠存在大量同侧皮质脊髓投射，并表明许多这些异常纤维在脊髓内穿过中线，在同侧脊髓灰质内广泛分支。这些发现表明，新生大鼠单侧SMC损伤后，对侧半球介导了前肢放置恢复的某些方面。异常的同侧皮质脊髓投射可能提供了皮层实现这种恢复的解剖学基础。
