Sensory signal processing in the central complex of the cockroach Rhyparobia maderae

像许多脊椎动物一样，昆虫在空间定向过程中使用太阳的位置作为指导信号。此外，许多物种还可以利用蓝天的偏振模式进行导航。神经生物学研究表明，昆虫大脑中心的中央复合体在这些任务中发挥着关键作用。我的实验室对沙漠蝗虫的研究表明，方向的指南针状表示是中央复合体的柱状组织的基础，因为相邻柱状物的神经元在偏振光平面的首选方向和亮光点的首选水平方向方面存在系统性差异。因此，动物相对于天空信号的方向在中央复合体中以指南针的方式表示。这个系统的单个神经元具有类似于大鼠和其他哺乳动物大脑中的头部细胞的特性。为了更完整地了解中枢复合体的功能作用，我们计划研究夜间昆虫--蟑螂Rhyparobia maderae对感觉刺激的反应。蟑螂的细胞外记录显示，中央复合体的神经元编码动物相对于视觉背景的方向，神经活动可以预测随后运动的方向。此外，许多单位对蟑螂在黑暗中用来定向的触角的机械刺激做出反应。然而，由于细胞外记录技术，到目前为止，还没有记录到的神经元在形态上得到鉴定。我们实验室的初步工作表明，蟑螂中枢复合体的神经元组织与研究充分的蝗虫的神经元组织有很大不同。因此，我们计划在目前的提案中，在单个识别的神经元水平上分析蟑螂中枢复合体的组织和感觉处理。染料注射和免疫细胞化学染色将分析起作用的神经元系统，以及蟑螂中心复合体的层状和柱状组织。细胞内的记录与随后注入记录的神经元的染料相结合，将测试神经元是否对偏振光平面敏感和/或编码太阳刺激的方向。我们将分析这些信号是否像蝗虫一样，在中央复合体中以指南针的方式表现出来。最后，细胞内的记录将显示中央复合体的神经元是否编码天线的位置和运动，从而使用第二种感觉通道来编码空间。该项目将大大提高我们对中央复合体在昆虫大脑中的功能作用的理解，并将为后续的研究工作提供重要的推动力，这些研究也适用于蝗虫和果蝇等研究较好的物种。

Insects like many vertebrates use the position of the sun as a guiding cue during spatial orientation. In addition, many species can also navigate using the polarization pattern of the blue sky. Neurobiological studies showed that the central complex in the center of the insect brain plays a key role in these tasks. Studies from my laboratory on the desert locust showed that a compass-like representation of directions underlies the columnar organization of the central complex, because neurons of neighboring columns differ in a systematic way with respect to their preferred orientation of the plane of polarized light and their preferred horizontal direction of a bright light spot. The orientation of the animal relative to sky signals is thus represented in a compass-like manner in the central complex. Individual neurons of this system have properties similar to those of head-direction cells in the brain of rats and other mammals. To obtain a more complete understanding of the functional role of the central complex, we plan to study the responses to sensory stimuli in a nocturnal insect, the cockroach Rhyparobia maderae. Extracellular recordings from the cockroach showed that neurons of the central complex encode the orientation of the animal relative to visual background and that neural activity can predict the direction of subsequent locomotion. Moreover, many units responded to mechanical stimulation of the antennae, which are used by cockroaches for orientation in the dark. Because of the extracellular recording technique, however, none of the recorded neurons has so far been identified morphologically. Preliminary work for our laboratory showed that the neuronal organization of the cockroach central complex differs substantially from that of the well-studied locust. We, therefore, plan in the current proposal to analyze the organization and sensory processing in the cockroach central complex at the level of single identified neurons. Dye injections and immunocytochemical stainings will analyze the contributing neuronal systems as well as the layering and columnar organization of the cockroach central complex. Intracellular recordings combined with subsequent dye injection into the recorded neuron will test whether neurons are sensitive to the plane of polarized light and/or encode the direction of a sun stimulus. We will analyze whether, as in the locust, these signals are represented in a compass-like manner in the central complex. Finally, intracellular recordings will show whether neurons of the central complex encode the position and movements of the antennae, and thereby employ a second sensory modality for the encoding of space. The project will substantially enhance our understanding of the functional role of the central complex in the insect brain and will provide important impulses for subsequent work also in well studied species like locust and fruit fly.