Seelig Johannes D, Jayaraman Vivek
Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, Virginia 20147, USA.
Nature. 2015 May 14;521(7551):186-91. doi: 10.1038/nature14446.
Many animals navigate using a combination of visual landmarks and path integration. In mammalian brains, head direction cells integrate these two streams of information by representing an animal's heading relative to landmarks, yet maintaining their directional tuning in darkness based on self-motion cues. Here we use two-photon calcium imaging in head-fixed Drosophila melanogaster walking on a ball in a virtual reality arena to demonstrate that landmark-based orientation and angular path integration are combined in the population responses of neurons whose dendrites tile the ellipsoid body, a toroidal structure in the centre of the fly brain. The neural population encodes the fly's azimuth relative to its environment, tracking visual landmarks when available and relying on self-motion cues in darkness. When both visual and self-motion cues are absent, a representation of the animal's orientation is maintained in this network through persistent activity, a potential substrate for short-term memory. Several features of the population dynamics of these neurons and their circular anatomical arrangement are suggestive of ring attractors, network structures that have been proposed to support the function of navigational brain circuits.
许多动物利用视觉地标和路径整合的组合来导航。在哺乳动物大脑中，头部方向细胞通过表示动物相对于地标的方向来整合这两种信息流，同时基于自身运动线索在黑暗中保持其方向调谐。在这里，我们使用双光子钙成像技术，对在虚拟现实竞技场的球上行走的头部固定的黑腹果蝇进行研究，以证明基于地标的定向和角路径整合在神经元群体反应中相结合，这些神经元的树突覆盖椭球体，这是果蝇大脑中心的一个环形结构。神经群体编码果蝇相对于其环境的方位，在有视觉地标时跟踪它们，并在黑暗中依靠自身运动线索。当视觉和自身运动线索都不存在时，通过持续活动在这个网络中维持动物方向的表征，这是短期记忆的一个潜在基础。这些神经元群体动力学的几个特征及其圆形解剖排列暗示了环形吸引子，即被认为支持导航脑回路功能的网络结构。
