Römer H, Marquart V, Hardt M
Lehrstuhl für Allgemeine Zoologie, Ruhr-Universität Bochum, Federal Republic of Germany.
J Comp Neurol. 1988 Sep 8;275(2):201-15. doi: 10.1002/cne.902750204.
The anterior intermediate sensory neuropile (aISN) is a prominent neuropile in the ventral nerve cord of locusts and bushcrickets. Previous studies have shown that it receives its main sensory input from auditory receptors. In this paper we examine the structural and physiological relationship between tympanal receptor terminations and the dendrites of sound-sensitive interneurones in the homologous neuropile of locusts and bushcrickets. Each individual receptor fibre of the bushcricket terminates in a somewhat different target area of the neuropile. The ordering is with respect to the characteristic frequency of the fibres (tonotopic) in the anterior-posterior and dorsoventral axis. In the locust, representatives of the four tympanal receptor groups branch in different areas of the aISN. Most of the dorsal neuropilar region, and the anterior ventral region, do not receive input from tympanal receptors. The dendrites of identified sound-sensitive interneurones were examined in the context of this afferent projection. Local interneurones as well as intersegmental interneurones in bushcrickets have dendritic branches in the whole aISN or part of it and thus overlap with at least some receptors. By recording intracellularly from their main neurites, short-latency synaptic potentials were found in response to receptor spikes indicating monosynaptic input. The tuning of these neurones could be predicted by their dendritic morphology. In contrast, in the locust only local and bisegmental neurones are monosynaptically connected with tympanal receptors, but not the studied intersegmental neurones. This is consistent with the finding that most or all branches of intersegmental neurones lie in the dorsal area of neuropile where no receptors terminate. Anatomical and physiological evidence is presented for identified local neurones providing the excitatory and inhibitory synaptic input for such intersegmental neurones. The difference in the basic wiring diagram in the homologous neuropile of the two orthopteran groups is discussed with respect to the possible different roles that sound plays in their behaviour.
前中间感觉神经纤维网（aISN）是蝗虫和螽斯腹神经索中一个显著的神经纤维网。先前的研究表明，它主要接收来自听觉感受器的感觉输入。在本文中，我们研究了蝗虫和螽斯同源神经纤维网中鼓膜感受器末梢与声音敏感中间神经元树突之间的结构和生理关系。螽斯的每一根单独的感受器纤维都终止于神经纤维网中略有不同的目标区域。这种排列是按照纤维的特征频率（音频定位）在前-后轴和背-腹轴上进行的。在蝗虫中，四个鼓膜感受器组的代表在aISN的不同区域分支。大部分背侧神经纤维网区域和前腹侧区域没有接收来自鼓膜感受器的输入。在这种传入投射的背景下，对已识别的声音敏感中间神经元的树突进行了研究。螽斯中的局部中间神经元以及节间中间神经元在整个aISN或其一部分中有树突分支，因此与至少一些感受器重叠。通过从它们的主要神经突进行细胞内记录，发现了对感受器尖峰有反应的短潜伏期突触电位，表明存在单突触输入。这些神经元的调谐可以通过它们的树突形态来预测。相比之下，在蝗虫中，只有局部和双节神经元与鼓膜感受器有单突触连接，而所研究的节间神经元则没有。这与节间神经元的大多数或所有分支位于神经纤维网的背侧区域这一发现一致，在该区域没有感受器终止。本文提供了解剖学和生理学证据，证明已识别的局部神经元为这类节间神经元提供兴奋性和抑制性突触输入。针对声音在这两个直翅目类群行为中可能扮演的不同角色，讨论了这两个直翅目类群同源神经纤维网基本布线图的差异。
