Pearson P P, Li C X, Waters R S
Department of Anatomy and Neurobiology, University of Tennessee, Memphis, College of Medicine, 855 Monroe Avenue, Memphis, TN 38163, USA.
Exp Brain Res. 1999 Oct;128(3):315-31. doi: 10.1007/s002210050852.
The physiological representation of the shoulder and surrounding body was examined in layer IV of somatosensory cortex (SI) in rats that had underground removal of the forelimb, either as newborns on postnatal day three (PND-3) or as adults (at least 8 weeks of age). Electrophysiological recordings were used to map the shoulder and body representations (physiological map), and the mitochondria marker, cytochrome oxidase (CO), was used to visualize recording sites in barrel and barrel-like structures (morphological map) in layer IV of deafferents and intact controls. The SI shoulder representation lies in a nebulously stained region that lies posterior to the forearm, wrist, and forepaw representations; the latter region is associated with the well-defined forepaw barrel subfield (FBS). The major findings are: (1) the shoulder is represented as a single zone located at the posterior extent of the SI body map in intact rats; (2) limb deafferentation in adult or neonatal rats that were physiologically mapped 6-16 weeks post-amputation resulted in two or more islets of "new" representation of the shoulder in the FBS in addition to the representation of the "original" shoulder in the posterior part of the body map; (3) deafferentations made in neonatal rats, physiologically mapped as adults, had a significantly greater (Mann-Whitney U) amount of "new" cortical representation within the FBS than did rats deafferented as adults; (4) fewer unresponsive sites in the FBS were found for neonate deafferents than for adult deafferents; (5) evoked response latencies following electrical stimulation of the shoulder were shortest for cortical sites within the "original" shoulder representation in intact controls, and latencies recorded at the "original" shoulder representation in deafferents were also shorter than latencies recorded in "new" shoulder representations in both groups of deafferents; and (6) morphological maps of the FBS were altered in neonate deafferents to the extent that the barrel structure was poorly formed, as exemplified by the absence of the four mediolateral running bands; however, the overall ovoid shape of the FBS was still apparent, but not as sharply defined as for intact controls or adult deafferents. Possible mechanisms for reorganization following large-scale deafferentation are discussed.
在出生后第三天（PND - 3）作为新生大鼠或成年大鼠（至少8周龄）进行前肢皮下切除的大鼠体感皮层（SI）IV层中，研究了肩部及周围身体的生理表征。采用电生理记录来绘制肩部和身体表征图（生理图谱），并使用线粒体标记物细胞色素氧化酶（CO）来可视化去传入组和完整对照组IV层桶状及桶状样结构中的记录位点（形态图谱）。SI肩部表征位于前臂、腕部和前爪表征后方的一个染色模糊的区域；后一区域与明确的前爪桶状亚区（FBS）相关。主要发现如下：（1）在完整大鼠中，肩部表现为位于SI身体图谱后部的单个区域；（2）在截肢后6 - 16周进行生理图谱绘制的成年或新生大鼠肢体去传入，除了身体图谱后部的“原始”肩部表征外，还在FBS中导致两个或更多“新”的肩部表征岛；（3）新生大鼠去传入后作为成年大鼠进行生理图谱绘制，其FBS内“新”皮层表征的量（曼 - 惠特尼U检验）显著多于成年大鼠去传入后的情况；（4）在FBS中，新生大鼠去传入后发现的无反应位点比成年大鼠去传入后的少；（5）在完整对照组中，电刺激肩部后，“原始”肩部表征内的皮层位点诱发反应潜伏期最短，去传入组中“原始”肩部表征处记录的潜伏期也比两组去传入组中“新”肩部表征处记录的潜伏期短；（6）新生大鼠去传入后FBS的形态图谱发生改变，桶状结构形成不良，例如缺少四条中外侧走行带；然而，FBS的整体卵形形状仍然明显，但不如完整对照组或成年大鼠去传入后的那样清晰界定。讨论了大规模去传入后重组的可能机制。
