Tools enabling closed-loop experiments are crucial to delineate causal relationships between the activity of genetically labeled neurons and specific behaviors. We developed the Raspberry Pi Virtual Reality (PiVR) system to conduct closed-loop optogenetic stimulation of neural functions in unrestrained animals. PiVR is an experimental platform that operates at high temporal resolution (70 Hz) with low latencies (<30 milliseconds), while being affordable (<US$500) and easy to build (<6 hours). Through extensive documentation, this tool was designed to be accessible to a wide public, from high school students to professional researchers studying systems neuroscience. We illustrate the functionality of PiVR by focusing on sensory navigation in response to gradients of chemicals (chemotaxis) and light (phototaxis). We show how Drosophila adult flies perform negative chemotaxis by modulating their locomotor speed to avoid locations associated with optogenetically evoked bitter taste. In Drosophila larvae, we use innate positive chemotaxis to compare behavior elicited by real- and virtual-odor gradients. Finally, we examine how positive phototaxis emerges in zebrafish larvae from the modulation of turning maneuvers to orient in virtual white-light gradients. Besides its application to study chemotaxis and phototaxis, PiVR is a versatile tool designed to bolster efforts to map and to functionally characterize neural circuits.

支持闭环实验的工具对于描绘基因标记神经元的活动与特定行为之间的因果关系至关重要。我们开发了Raspberry Pi虚拟现实（PiVR）系统，用于对不受约束的动物的神经功能进行闭环光遗传学刺激。 PiVR 是一个实验平台，以高时间分辨率 (70 Hz) 和低延迟运行 (<30 id=46> 果蝇成年果蝇通过调节其运动速度来执行负趋化性，以避免与光遗传学诱发苦味相关的位置。在果蝇幼虫中，我们使用先天的正向趋化性来比较真实和虚拟气味梯度引起的行为，除了其在研究趋化性方面的应用之外，我们还研究了斑马鱼幼虫如何通过调节转向动作来出现正趋光性。 PiVR 是一种多功能工具，旨在支持神经回路的映射和功能表征。