Pansopha Poonsup, Ando Noriyasu, Kanzaki Ryohei
Graduate School of Information Science and Technology, University of Tokyo, Tokyo 113-8654, Japan.
Research Center for Advanced Science and Technology, University of Tokyo, Tokyo 153-8904, Japan.
J Exp Biol. 2014 May 15;217(Pt 10):1811-20. doi: 10.1242/jeb.090266.
Several insects require both olfactory and visual cues during odour-source localisation to successfully locate an odour source. In the male silkmoth, Bombyx mori, detection of the female sex pheromone triggers a programmed walking pattern, starting from a surge (straight-line walking) followed by zigzag walking. Although pheromone-triggered behaviour in silkmoths is well understood, the role of visual cues remains obscure. To address this question, we performed behavioural experiments on tethered-walking moths by recording their locomotion during stimulation with a pheromone and a visual motion pattern (optic flow). The experiments were conducted under open- and closed-loop visual stimuli. We found that the use of optic flow input was determined by the behavioural state of surge and zigzagging. Silkmoths exhibited an optomotor response, which is a behavioural visual response, by turning towards the same direction as optic flow stimuli only during surge, but not during zigzagging. In addition, modulation of the zigzag walking pattern was observed when the moths were presented with biased closed-loop visual stimuli (visual feedback with biased constant optic flow); however, the directional preference mechanism was different from that of the optomotor response. Based on these findings, we suggest that the optomotor response is utilised for course control during straight-line walking, whereas the absence of optomotor response during zigzagging is used to effectively perform the programmed walking pattern. Considering the neural basis of programmed behaviour, we speculate that at least two visual pathways are involved in the state-dependent use of optic flow during odour tracking behaviour in silkmoths.
几种昆虫在气味源定位过程中需要嗅觉和视觉线索才能成功找到气味源。在雄性家蚕中，对雌性性信息素的检测会触发一种程序化的行走模式，从激增（直线行走）开始，然后是曲折行走。虽然家蚕中信息素触发的行为已得到充分了解，但视觉线索的作用仍不清楚。为了解决这个问题，我们对系留行走的蛾子进行了行为实验，记录它们在受到信息素和视觉运动模式（光流）刺激时的运动。实验在开环和闭环视觉刺激下进行。我们发现光流输入的使用取决于激增和曲折的行为状态。家蚕仅在激增期间，而不是在曲折期间，通过转向与光流刺激相同的方向表现出视动反应，这是一种行为视觉反应。此外，当蛾子受到有偏差的闭环视觉刺激（具有有偏差的恒定光流的视觉反馈）时，观察到曲折行走模式的调制；然而，方向偏好机制与视动反应不同。基于这些发现，我们认为视动反应用于直线行走期间的路线控制，而曲折期间视动反应的缺失用于有效地执行程序化的行走模式。考虑到程序化行为的神经基础，我们推测至少有两条视觉通路参与家蚕气味追踪行为中光流的状态依赖性使用。
