How does the Drosophila brain compute and see visual motion?

动物具有检测视觉运动的神经机制，使它们能够推断视觉场景中移动物体的速度和方向。凭借其感知优势，检测运动的能力塑造了视觉系统的组织和功能。然而，视觉系统处理和路线运动信息的方式已被证明是一个难以破译的问题。该建议旨在阐明果蝇大脑中负责编码视觉运动的神经网络的功能组织。我们最近开发了一种极其通用的果蝇制剂，使我们能够真实的可视化转基因苍蝇大脑中的运动敏感神经元（LPTC）专门网络如何将场景中的运动图像转化为神经活动模式（钙和电压信号）。这些果蝇有对紫外线敏感的基因工程眼睛和表达绿色敏感荧光蛋白（光学报告分子）的大脑，这些蛋白对LPTC中神经活动的变化（这里是钙变化）做出反应。由于眼睛和光学报告者的光谱敏感性不重叠，当这样的苍蝇看着移动的物体时，我们可以看到LPTC中的神经活动，而不会注意到我们同时扫描它的大脑。为了充分利用这种新的制备方法，需要产生一种独特的混合实验装置，该装置可以可视化钙信号并同时测量尖锐微电极的电压响应。对于实时成像，将苍蝇放置在该装置中，在该装置中，向它们呈现移动的UV光图案，同时从LPTC监测钙和电压信号。使用这个系统，再加上进一步的基因修饰的眼睛和大脑的苍蝇，我们希望调查视觉运动信号是如何路由和处理的苍蝇的视觉系统。在这里，我们计划找到两个重要的开放问题的答案。不同类型的感光器在将视觉信息传递到大脑，从而推断场景中物体移动的速度和方向方面有何贡献？来自大脑的注意信号在视觉运动加工中的作用是什么？这些问题将通过监测转基因果蝇中LPTC的钙和电压信号的变化来研究，其中可以使用温度敏感的遗传开关打开和关闭来自眼睛或大脑的选择性神经通路。此外，相同的苍蝇的视觉行为将在我们的实验室运行的飞行模拟器系统的特点。通过这种方式，我们将能够将视觉运动信息的路由和处理中的遗传靶向变化与动物行为和认知现象相关联。在一个平行的方法，从这些实验的结果将进行分析和数学建模，以找到答案的开放性问题，如何在场景中移动的视觉对象被编码成移动的神经图像，由网络的活动模式表示的互联神经元在大脑中。

Animals have neural mechanisms for detecting visual motion, enabling them to infer the speed and direction of objects that move in visual scenes. With its perceptual advantages the ability to detect motion has shaped the organisation and function of visual systems. However, the way in which the visual systems process and route motion information has proven to be a difficult problem to decipher. This proposal aims to elucidate the functional organisation of neural networks responsible for encoding visual motion in the brain of the fruit fly, Drosophila. We have recently developed an extremely versatile Drosophila preparation that enables us to visualise in real time how a specialised web of motion sensitive neurones (LPTCs) in the brains of transgenic flies translate moving images in the scene into neural activity patterns (calcium and voltage signals). These flies have genetically engineered eyes that are sensitive to ultraviolet (UV) light and brains that express green-sensitive fluorescence proteins (optical reporters) that react to changes in the neural activity (here calcium changes) in LPTCs. Since the spectral sensitivities of the eye and optical reporters do not overlap, we can visualise neural activity in the LPTCs when such a fly looks at moving objects, being oblivious of us simultaneously scanning its brain. In order to fully utilise this novel preparation requires the generation of a unique hybrid experimental apparatus that can visualise calcium signals and measure voltage responses with sharp microelectrodes simultaneously. For live imaging the flies will be placed in this apparatus in which they are presented with moving UV-light patterns while calcium and voltage signals are monitored from the LPTCs. Using this system, together with further genetic modifications in the eyes and the brain of the flies, we wish to investigate how visual motion signals are routed and processed by the fly's visual system. Here we plan to find answers to two important open questions. What is the contribution of different photoreceptor types in routing visual information to the brain so that the speed and direction of objects moving in the scene can be inferred? and what is the contribution of attentional signals from the brain in the visual motion processing? These questions will be studied by monitoring changes in calcium and voltage signals of LPTCs in transgenic flies in which selective neural pathways from the eyes or from the brain can be turned on and off, using temperature-sensitive genetic switches. Furthermore, the visual behaviour of the same flies will be characterised in a flight simulator system running in our laboratory. In this way we shall be able to correlate the genetically targeted changes in the routing and processing of visual motion information to the animal behaviour and cognitive phenomena. In a parallel approach, the results from these experiments will be analysed and modelled mathematically to find answers to the open question of how moving visual objects in the scene are encoded into moving neural images, as represented by activity patterns of networks of interconnected neurones in the brain.