Johnson J I, Ostapoff E M, Warach S
Neuroscience. 1982 Apr;7(4):915-36. doi: 10.1016/0306-4522(82)90052-5.
In raccoons the somatic sensory neocortex is greatly expanded, with separate gyral crowns devoted to and intervening sulci separating, sensory representations of separate body parts, most strikingly those of the volar surfaces of individual forepaw digits. Most of the cortex in this region is buried in widely ramifying sulcal walls, wherein sensory projections have not been studied. We have determined mechanosensory projections to the fourth digit representation region including all neighboring sulcal walls, using tungsten microelectrodes for 3-dimensional micromapping. We found no significant alteration in the location and pattern of projections when the following different anesthetics were used: dial-urethane, chloralose, or methoxyflurane with nitrous oxide. The precisely organized somatotopic representation of the distal volar surface of the fourth digit, on the causal aspect of its gyral crown, continues down the anterior bank of the triradiate sulcus. This meets, at the fundus, projections from the proximal volar surface of the digit which occupy the posterior sulcus wall; they in turn meet projections from the volar palm at the gyral crown. In the anterior part of the crown containing the representation of the distal volar digit, across the crown. In the anterior part of the crown containing the representation of the distal volar digit, across the crown of the gyral bridge intervening between the medial and lateral segments of the central sulcus, throughout the posterior walls of the central sulci, and in the walls of the interbrachial sulcus, we found a distinctive border-zone of projections from heterogeneous receptive fields. Within a roughly somatotopic basic pattern of organization we found intermingled projections from single and multiple claws and dorsal hairy surfaces of digits and proximal hand, along with additional projections from volar surfaces. These projections can be construed as forming something of a distorted mirror-image of the representation of the volar hand. Beyond this was a second zone of distinctive projections from afferents of the forelimb muscles, in the anterior walls of the central sulci. These projections are interrupted where the sulci are interrupted. The zone of muscle afferent projections corresponds to those seen between sensory and motor regions in other species; its strict association with sulcal folding here and in other species suggests a general relationship of these projections to central sulci. The zone of heterogeneous projections resembles similar zones seen at other levels of this system in raccoons, in the cortex of other species, and it may relate to some of the multiple representation reported in other species. It also may be related to the formation of sulci in this region and may be a specialized zone for cortico-cortical connections.
在浣熊中，躯体感觉新皮质显著扩展，有独立的脑回顶部专门用于不同身体部位的感觉表征，中间的脑沟将其分隔开，最显著的是单个前爪指腹面的感觉表征。该区域的大部分皮质埋藏在广泛分支的脑沟壁中，其中感觉投射尚未得到研究。我们使用钨微电极进行三维微图谱绘制，确定了向包括所有相邻脑沟壁在内的第四指表征区域的机械感觉投射。当使用以下不同麻醉剂时：二乙氨甲酸乙酯、氯醛糖或甲氧氟烷与氧化亚氮，我们发现投射的位置和模式没有显著变化。第四指腹面远端在其脑回顶部的精确组织的躯体定位表征，沿着三叉沟的前缘延续。在沟底，它与来自指近端腹面的投射相遇，这些投射占据后沟壁；它们又在脑回顶部与来自手掌腹面的投射相遇。在包含指腹面远端表征的脑回顶部前部，穿过中央沟内侧和外侧段之间的脑回桥顶部，在中央沟的整个后壁以及臂间沟壁中，我们发现来自异质感受野的投射形成了一个独特的边界区。在大致的躯体定位基本组织模式内，我们发现来自单个和多个爪子以及指和近端手部背侧毛面的投射相互交织，还有来自腹面的额外投射。这些投射可以被理解为形成了手掌腹面表征的某种扭曲镜像。在此之外，在中央沟的前壁有来自前肢肌肉传入纤维的第二个独特投射区。这些投射在脑沟中断的地方也中断。肌肉传入投射区与其他物种感觉和运动区域之间所见的区域相对应；它在这里和其他物种中与脑沟折叠的严格关联表明这些投射与中央沟存在普遍关系。异质投射区类似于在浣熊这个系统的其他水平以及其他物种皮质中所见的类似区域，它可能与其他物种中报道的多重表征有关。它也可能与该区域脑沟的形成有关，并且可能是皮质 - 皮质连接的一个特殊区域。
