Xu J, Wall J T
Department of Neurobiology and Anatomy, Medical College of Ohio, Toledo 43699, USA.
Somatosens Mot Res. 1996;13(3-4):187-97. doi: 10.3109/08990229609052575.
Dynamic properties of primate somatosensory maps are dependent on normal central adjacencies of cutaneous representations. The cuneate nucleus is an important brainstem processing center of cutaneous information. Surprisingly, there are no descriptions of functional representations of the skin in the primate cuneate nucleus; as a result, the relationships of functional representations at the brainstem level and other levels of the somatosensory neuraxis remain obscure. The present neurophysiological study indicates that the main cuneate nucleus of marmoset monkeys (Callithrix jacchus) contains organized representations of cutaneous inputs from the hand, forelimb, and adjacent body between the lateral face and proximal hindlimb. Inputs from the glabrous hand are represented continuously across transverse planes in the cuneate, whereas inputs from the hairy hand are represented discontinuously. Inputs from distal to proximal, and radial to ulnar, parts of the hand are mapped in an organized manner. At rostrocaudal levels where the cuneate nucleus is near its largest transverse area, the map of the hand is about 2600 times smaller than the hand skin area it represents. Cuneate representations of the forelimb and trunk are represented both medial and lateral to the hand representation, and interface with representations in the adjacent gracile and trigeminal nuclei. These findings provide a starting point for understanding functional representations of the skin in the cuneate nucleus of primates. Furthermore, they provide a basis for understanding relationships of cutaneous representations at different levels of the neuraxis. In this regard, comparisons of the present results to previously defined representations in the somatosensory (area 3b) cortex indicate that cuneate hand representations are several times smaller than cortical representations, and that there are similarities and differences in adjacencies of cuneate and cortical representations.
灵长类动物体感图谱的动态特性取决于皮肤代表区在中枢的正常邻接关系。楔束核是皮肤信息的一个重要脑干处理中心。令人惊讶的是，目前尚无关于灵长类动物楔束核中皮肤功能代表区的描述；因此，脑干水平与体感神经轴其他水平的功能代表区之间的关系仍不明确。目前的神经生理学研究表明，狨猴（绢毛猴）的主要楔束核包含来自手部、前肢以及侧面与近端后肢之间相邻身体部位的皮肤输入的有组织代表区。来自无毛手部的输入在楔束核的横切面上连续分布，而来自有毛手部的输入则不连续分布。手部从远端到近端、从桡侧到尺侧的输入以有组织的方式进行映射。在楔束核横截面积接近最大的前后水平，手部图谱比它所代表的手部皮肤面积小约2600倍。前肢和躯干在楔束核中的代表区位于手部代表区的内侧和外侧，并与相邻的薄束核和三叉神经核的代表区相衔接。这些发现为理解灵长类动物楔束核中皮肤的功能代表区提供了一个起点。此外，它们为理解神经轴不同水平的皮肤代表区之间的关系提供了基础。在这方面，将目前的结果与先前在体感（3b区）皮层中定义的代表区进行比较表明，楔束核中手部的代表区比皮层代表区小几倍，并且楔束核和皮层代表区在邻接关系上既有相似之处也有不同之处。
