Henry G H, Mark R F
Centre for Visual Sciences, Australian National University, Canberra.
Brain Behav Evol. 1992;39(6):358-70. doi: 10.1159/000114131.
Extra-cellular recordings from single cells in the dorsal lateral geniculate nucleus (dLGN) of the tammar wallaby, Macropus eugenii, were made to find out whether the stratification of the nucleus could be correlated with the receptive field properties of units. Retinofugal fibres terminate in the lateral geniculate nucleus of the wallaby in nine interleaved eye-specific layers. These may be grouped into a lateral alpha segment of six laminae and a medial beta segment of three, in which the cells are less densely packed. Ninety percent of the geniculate neurons recorded from in the alpha segment gave brisk responses to stimulation of their receptive fields. Cells with sluggish responses predominated in the beta segment, but there was also a sizable minority of cells with brisk responses that were indistinguishable from those recorded in the alpha segment. In contrast, other response properties were rarely differentiated in individual layers. Thus, in most layers, the numbers of cells with transient or sustained responses were not significantly different, and this was also true for cells with ON- or OFF- responses. For each of these response pairings, however, the numbers of one type (ON- and transient) predominated in every layer. The accumulation of this laminar distinction lead to significant differences in the alpha and beta segments and in the nucleus as a whole. We conclude that cells in the individual layers of the dLGN of the tammar wallaby show no evidence of having receptive field properties in common that might correlate with separate functional streams. There is a functional segregation of receptive field properties between the alpha and beta segments. The organization of these two segments resembles that of the A and the C layers of the dLGN in cats and, possibly, the magnocellular and koniocellular components of the dLGN in primates. These broad similarities in functional partition of the dLGN of different species suggests that this aspect of the organization of the nucleus is independent of lifestyle.
对帚尾袋貂（Macropus eugenii）背外侧膝状核（dLGN）中的单细胞进行细胞外记录，以确定该核的分层是否与神经元的感受野特性相关。视网膜传出纤维在袋貂的外侧膝状核中终止于九个相互交错的眼特异性层。这些层可分为一个由六个板层组成的外侧α段和一个由三个板层组成的内侧β段，β段中的细胞排列较稀疏。在α段记录到的膝状神经元中，90%对其感受野的刺激产生快速反应。β段中反应迟缓的细胞占主导，但也有相当一部分反应快速的细胞，与α段记录到的细胞无法区分。相比之下，其他反应特性在各层中很少有差异。因此，在大多数层中，具有瞬态或持续反应的细胞数量没有显著差异，对开-关反应的细胞也是如此。然而，对于这些反应配对中的每一种，在每一层中一种类型（开反应和瞬态反应）的细胞数量占主导。这种层间差异的累积导致α段和β段以及整个核中存在显著差异。我们得出结论，帚尾袋貂dLGN各层中的细胞没有证据表明具有可能与不同功能流相关的共同感受野特性。α段和β段之间存在感受野特性的功能分离。这两个段的组织结构类似于猫dLGN的A层和C层，可能也类似于灵长类动物dLGN的大细胞和小细胞成分。不同物种dLGN功能分区的这些广泛相似性表明，该核组织的这一方面与生活方式无关。
