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

像许多脊椎动物一样，昆虫在空间定位时使用太阳的位置作为指导线索。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，昆虫大脑中心的中枢复合体在这些任务中起着关键作用。我的实验室对沙漠蝗虫的研究表明，像指南针一样的方向表示是中心复合体柱状组织的基础，因为相邻柱状组织的神经元在偏振光平面的首选方向和明亮光点的首选水平方向方面有系统的不同。因此，动物相对于天空信号的方向在中央复合体中以类似指南针的方式表示。该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指向头部的细胞的特性。为了更全面地了解中央复合体的功能作用，我们计划研究夜行昆虫——蜚蠊对感觉刺激的反应。来自蟑螂的细胞外记录显示，中央复合体的神经元对动物相对于视觉背景的方向进行编码，神经活动可以预测随后运动的方向。此外，许多单位对触角的机械刺激有反应，触角是蟑螂在黑暗中定位的工具。然而，由于细胞外记录技术，迄今为止还没有记录的神经元被形态学鉴定。我们实验室的初步工作表明，蟑螂中央复合体的神经元组织与经过充分研究的蝗虫的神经元组织有很大不同。因此，我们计划在当前的提案中分析蟑螂中央复合体的组织和感觉处理在单个已识别的神经元水平上。染料注射和免疫细胞化学染色将分析蟑螂中枢复合体的神经元系统以及分层和柱状组织。细胞内记录结合随后的染料注射到被记录的神经元将测试神经元是否对偏振光平面敏感和/或对太阳刺激的方向进行编码。我们将分析这些信号是否像蝗虫一样，在中心复合体中以类似指南针的方式表示。最后，细胞内记录将显示中枢复合体的神经元是否对触角的位置和运动进行编码，从而采用第二种感觉方式对空间进行编码。该项目将大大提高我们对昆虫大脑中心复合体功能作用的理解，并将为后续研究蝗虫和果蝇等物种的工作提供重要的推动力。

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.