Schröter Ulrike, Menzel Randolf
Institut für Neurobiologie, Freie Universität Berlin, D-14195 Berlin, Germany.
J Comp Neurol. 2003 Oct 13;465(2):168-78. doi: 10.1002/cne.10843.
The mushroom bodies of the honeybee are important neuropils for learning and memory. Therefore, knowledge about their input and output connections is essential to understanding how these neuropils function. A newly described input tract to the mushroom body is presented here, which is called the subesophageal-calycal tract (SCT) and connects the subesophageal ganglion with the calyces of the mushroom bodies. The neuronal somata of the SCT neurons lie in one cluster between the lobula of the optic lobe and a neuropil area that is formed from the fusion of the tritocerebrum and the subesophageal ganglion. Within the subesophageal ganglion, the dendritic fibers of SCT neurons overlap with terminals of sensory neurons from the proboscis. Therefore, we conclude that the SCT neurons might process gustatory and mechanosensory information from the proboscis. Individual SCT neurons receive unilateral input within the subesophageal ganglion and may connect to either the ipsilateral or the contralateral mushroom body. On their way to the mushroom bodies, the SCT neuron axons meet the roots of the antennocerebralis tracts (ACTs) and from this point follow the same path as the median ACT neurons for a short distance. Within the calyces, the SCT neurons innervate two separate areas, a small area within the dorsal collar just below the lip and a part of the basal ring. Double-labeling experiments show that the projections of the SCT neurons do not overlap with the projections of the olfactory projection neurons and visual projection neurons from the dorsal medulla. The possible function of the SCT neurons and the relation of the SCT to known input tracts of the mushroom bodies in other insects are discussed.
蜜蜂的蘑菇体是学习和记忆的重要神经纤维丛。因此，了解它们的输入和输出连接对于理解这些神经纤维丛的功能至关重要。本文介绍了一种新描述的通向蘑菇体的输入束，称为咽下-萼部束（SCT），它将咽下神经节与蘑菇体的萼部相连。SCT神经元的胞体位于视叶小叶和由后脑和咽下神经节融合形成的神经纤维网区域之间的一个簇中。在咽下神经节内，SCT神经元的树突纤维与来自喙的感觉神经元的终末重叠。因此，我们得出结论，SCT神经元可能处理来自喙的味觉和机械感觉信息。单个SCT神经元在咽下神经节内接受单侧输入，并可能连接到同侧或对侧的蘑菇体。在通向蘑菇体的途中，SCT神经元轴突与触角脑束（ACT）的根部相遇，从这一点起，它们在短距离内与中间ACT神经元走相同的路径。在萼部内，SCT神经元支配两个独立的区域，一个位于唇下方背环内的小区域和基部环的一部分。双标记实验表明，SCT神经元的投射与来自背髓的嗅觉投射神经元和视觉投射神经元的投射不重叠。本文还讨论了SCT神经元的可能功能以及SCT与其他昆虫中已知的蘑菇体输入束的关系。
