Homberg U, Würden S
Institut für Zoologie, Universität Regensburg, Germany.
J Comp Neurol. 1997 Sep 29;386(3):329-46.
Several lines of evidence suggest that the accessory medulla of orthopteroid insects is implicated in the control of circadian rhythms. To investigate the role of this brain area in more detail, anatomical and physiological properties of accessory-medulla neurons of the locust were studied by intracellular recordings combined with Lucifer dye injections. The responses of these neurons to visual stimuli were compared with visual responses of adjacent tangential neurons of the medulla. Principal neurons of the accessory medulla showed weak tonic excitations to stationary light stimuli, but they were not sensitive to movement stimuli or to different e-vector orientations of polarized light. These neurons connected the accessory medulla to the lamina, the anterior medulla, and to several areas in the midbrain including the superior protocerebrum and the posterior optic tubercle. A second class of neurons had tangential arborizations in the medulla, a few sidebranches in the accessory medulla, and projections to the lamina or to the contralateral optic lobe. Several of these neurons were sensitive to polarized light. Finally, a third class of neurons had tangential arborizations in the medulla and axonal projections to the lobula and to the lateral protocerebrum. These neurons showed phasic responses to light and nondirectional selective responses to motion stimuli. The results show that neurons of the accessory medulla receive photic input and support an involvement of this neuropil in circadian timekeeping functions. The possible role of the accessory medulla in polarization vision is discussed.
多条证据表明，直翅目昆虫的副髓质与昼夜节律的控制有关。为了更详细地研究这个脑区的作用，通过细胞内记录结合荧光素染料注射，研究了蝗虫副髓质神经元的解剖学和生理学特性。将这些神经元对视觉刺激的反应与髓质相邻切向神经元的视觉反应进行了比较。副髓质的主要神经元对静止光刺激表现出微弱的强直兴奋，但它们对运动刺激或偏振光的不同电场矢量方向不敏感。这些神经元将副髓质与板层、前髓质以及中脑的几个区域相连，包括上原脑和后视结节。第二类神经元在髓质中有切向分支，在副髓质中有一些侧支，并投射到板层或对侧视叶。其中一些神经元对偏振光敏感。最后，第三类神经元在髓质中有切向分支，轴突投射到小叶和外侧原脑。这些神经元对光表现出相位反应，对运动刺激表现出非定向选择性反应。结果表明，副髓质的神经元接受光输入，并支持这个神经纤维网参与昼夜计时功能。本文还讨论了副髓质在偏振视觉中的可能作用。
