Mizunami M, Iwasaki M, Okada R, Nishikawa M
Laboratory of Neuro-Cybernetics, Research Institute for Electronic Science, Hokkaido University, Sapporo, Japan.
J Comp Neurol. 1998 Sep 21;399(2):153-61. doi: 10.1002/(sici)1096-9861(19980921)399:2<153::aid-cne1>3.0.co;2-#.
The mushroom body (MB), a conspicuous neuropil structure in the insect brain, is implicated in associative memory and in some aspects of motor control. Intrinsic neurons of the MB (Kenyon cells) extend dendrites into the calyx, and their axons run through the pedunculus and then bifurcate to form the alpha and the beta lobes. At the pedunculus and the lobes, Kenyon cells make synaptic connections with dendrites of extrinsic (output) neurons. Previously, we reported that the alpha lobe of the cockroach MB consists of repetitive modular subunits (Mizunami et al. [1997] Neurosci. Lett. 229:153-156). Each subunit is composed of a dark layer and a light layer, and the layers are refereed to as slabs. Each slab is composed of axons of a specific subset of Kenyon cells. In the present study, we examined serial sections of reduced silver preparations and found that each dark and light slab continues throughout the length of the pedunculus and the alpha and beta lobes. We also found that Golgi-impregnated Kenyon cells often exhibit a characteristic grouping, forming a thin sheet interlaced by dozens or hundreds of axons. The sheet is much thinner than the slab, and each sheet remains within a particular slab throughout the length of the pedunculus and the lobes. Thus, the sheet is a component forming the slab. In the pedunculus and the beta lobe, a class of Golgi-impregnated extrinsic neurons exhibit segmented dendritelike arbors that interact with every other slab, i.e., either with only dark or light slabs. Because each neuron of this class interacts with each particular set of dark or light slabs, we conclude that the slabs are units for transmitting output signals from the MB.
蘑菇体（MB）是昆虫大脑中一个显著的神经纤维结构，与联想记忆以及运动控制的某些方面有关。蘑菇体的内在神经元（肯扬细胞）将树突延伸至花萼，其轴突穿过柄节，然后分叉形成α叶和β叶。在柄节和叶处，肯扬细胞与外在（输出）神经元的树突形成突触连接。此前，我们报道过蟑螂蘑菇体的α叶由重复的模块化亚单位组成（水波南等[1997]《神经科学快报》229:153 - 156）。每个亚单位由一个暗层和一个亮层组成，这些层被称为板层。每个板层由特定子集的肯扬细胞的轴突组成。在本研究中，我们检查了还原银制剂的连续切片，发现每个暗板层和亮板层在柄节、α叶和β叶的整个长度上都是连续的。我们还发现，经高尔基染色的肯扬细胞常常呈现出一种特征性的分组，形成一个由数十或数百条轴突交织而成的薄片。该薄片比板层薄得多，并且在柄节和叶的整个长度上，每个薄片都保留在特定的板层内。因此，该薄片是构成板层的一个成分。在柄节和β叶中，一类经高尔基染色的外在神经元呈现出分段的树突状分支，这些分支与其他每个板层相互作用，即要么只与暗板层相互作用，要么只与亮板层相互作用。因为这类神经元中的每个神经元都与特定的暗板层或亮板层组相互作用，所以我们得出结论，板层是用于传递来自蘑菇体输出信号的单位。
