McCandlish C A, Li C X, Waters R S, Howard E M
Department of Anatomy and Neurobiology, University of Tennessee, Memphis, College of Medicine 38163, USA.
Exp Brain Res. 1996 Mar;108(3):417-26. doi: 10.1007/BF00227264.
The physiological representation of the forepaw in rat primary somatosensory cortex (SI) is topographically organized. This representation is associated with the unique arrangement of barrels in layer IV of the forepaw barrel subfield (FBS) in SI and provides an example of a relationship between cortical structure and function. It has been reported that removal of peripheral afferent input to the FBS prior to postnatal day 5 or 6 results in a disorganized FBS, while deafferentation at later times produces little or no alteration of the FBS. Therefore, restricted deafferentations of individual digits in adult rats should result in little, if any, disruption of the FBS, while at the same time eliminating afferent input to the FBS from a localized region of the periphery. This manipulation is likely to create a mismatch between structure and function and offer insight into what barrels actually represent in the adult deafferent. In the present study, we amputated digit three (D3) in eight adult rats, allowed a 1-month survival time, physiologically mapped the representation of D2, D4, and the stump, and compared this physiological map to the underlying barrels in the FBS. Our results showed that FBS barrels formerly associated with the representation of D3 were now associated with the representation of surrounding digits D2 and D4, as well as the remaining stump. By superimposing the morphological and physiological map upon one another, it was clear that the D2 and D4 representations expanded into the former D3 barrel territory and septae between the barrels. The reorganized physiological map was somatotopically organized, even though the general configuration of the morphological map remained unaltered, as visualized with cytochrome oxidase staining. These results suggest that in the deafferent, neurons within FBS barrels previously associated with the representation of punctate regions of skin become associated with neighboring regions of skin. A morphological substrate to account for this cortical reorganization is described.
大鼠初级体感皮层（SI）中前爪的生理表征呈拓扑组织化。这种表征与SI中前爪桶状亚区（FBS）第IV层中桶的独特排列相关，并提供了一个皮层结构与功能之间关系的例子。据报道，在出生后第5天或第6天之前去除FBS的外周传入输入会导致FBS紊乱，而在之后的时间进行去传入则对FBS几乎没有或没有产生改变。因此，成年大鼠中单个手指的局限性去传入应该对FBS几乎没有（如果有的话）破坏，同时消除从外周局部区域到FBS的传入输入。这种操作可能会造成结构与功能之间的不匹配，并有助于深入了解在成年去传入动物中桶状结构实际代表的是什么。在本研究中，我们对8只成年大鼠的第三指（D3）进行了截肢，给予1个月的存活时间，对D2、D4和残端的表征进行了生理图谱绘制，并将该生理图谱与FBS中潜在的桶状结构进行了比较。我们的结果表明，以前与D3表征相关的FBS桶状结构现在与周围手指D2和D4以及剩余残端的表征相关。通过将形态学和生理图谱相互叠加，可以清楚地看到D2和D4的表征扩展到了以前的D3桶状区域以及桶之间的间隔。尽管用细胞色素氧化酶染色显示形态图谱的总体构型保持不变，但重新组织的生理图谱仍呈躯体定位组织化。这些结果表明，在去传入动物中，FBS桶状结构内以前与皮肤点状区域表征相关的神经元与相邻的皮肤区域相关联。本文描述了一种解释这种皮层重组的形态学基础。
