Barbay Scott, Peden Eric K, Falchook Gerald, Nudo Randolph J
Department of Molecular and Integrative Physiology and Center on Aging, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
J Neurophysiol. 2002 Sep;88(3):1339-51. doi: 10.1152/jn.00019.2002.
Previous studies have demonstrated that peripheral denervation of the skin is reflected in the CNS as a reorganization of somatotopic representations. In cases in which peripheral nerve regeneration occurs there is a gradual reactivation of cortex by novel receptive fields that is reversed as regenerated nerves reestablish connections with the original skin surface. Functional recovery appears to depend on the pattern in which somatotopic organization in the cortex is reestablished. The relationship between functional recovery and cortical topography is not precise, however, since the descriptions of postinjury representations in the cortex have been largely descriptive and not quantitative. The purpose of this study was to derive an index to quantify deviations from normal somatotopic organization in the somatosensory cortex. Multiunit recordings of cutaneous representations in the somatosensory cortex (S1) of the rat were defined using Semmes-Weinstein monofilaments to stimulate the skin over the distal hindlimb of the rat 2 and 4 months after a sciatic nerve crush. To derive a sensitive index of topography, the sciatic nerve crush was selected as the injury model since nerve regeneration following crush injuries has been reported to reinstate preinjury cortical topography. Group comparisons were made with an intact control group. The results show that there were subtle, but significant differences in topography between rats with a regenerated sciatic nerve and normal rats. In addition, average thresholds for evoking cortical responses were higher than normal (but within normal range) 2 and 4 months after the crush. These results demonstrate that the index of topography derived for this study can reveal deviations that may not be distinguishable from normal topography when based on qualitative descriptions.
先前的研究表明，皮肤的外周去神经支配在中枢神经系统中表现为躯体感觉表征的重新组织。在发生外周神经再生的情况下，新的感受野会逐渐重新激活皮层，而当再生神经与原始皮肤表面重新建立连接时，这种激活会逆转。功能恢复似乎取决于皮层中躯体感觉组织重新建立的模式。然而，功能恢复与皮层地形学之间的关系并不精确，因为对皮层损伤后表征的描述大多是描述性的，而非定量的。本研究的目的是得出一个指标，以量化躯体感觉皮层中与正常躯体感觉组织的偏差。在坐骨神经挤压伤后2个月和4个月，使用Semmes-Weinstein单丝刺激大鼠后肢远端的皮肤，对大鼠躯体感觉皮层（S1）中的皮肤表征进行多单位记录。由于据报道挤压伤后的神经再生可恢复损伤前的皮层地形学，因此选择坐骨神经挤压伤作为损伤模型，以得出一个敏感的地形学指标。将其与完整对照组进行组间比较。结果表明，坐骨神经再生的大鼠与正常大鼠在地形学上存在细微但显著的差异。此外，挤压伤后2个月和4个月，诱发皮层反应的平均阈值高于正常水平（但在正常范围内）。这些结果表明，本研究得出的地形学指标可以揭示基于定性描述可能无法与正常地形学区分的偏差。
