To disclose the neuronal basis of brain functions such as memory, cognition, and behavior, it is necessary to monitor the neuronal activity from behaving animals. Until now, there has been a great development in the method to measure neuronal activity in the brain, such as intracellular/patch-clamp recordings, live cell imaging using voltage-sensitive dyes and/or calcium probes. However, since these techniques require vibration-free condition or a huge imaging system, it is hard to apply to a freely moving rodents. To overcome this problem, a virtually free-movable environment for the head-restrained rodent have been provided by the virtual reality (VR) technology, i.e. the combination of an immersive visual display, an omnidirectional treadmill and a virtual environment simulator. Since the virtual environment is generated by a computer software, this system has advantages in freedom of design of experimental condition. In addition, it allows automation of training of animals and improves reproducibility of the animal's experience. In this talk, we will survey fundamentals and recent developments of the virtual reality technologies for neuroscience in rodents.