## 4 Discussion  
We have compared the evaluation of human spatial navigation obtained with previously validated tests to a new system composed of a multi-test circular arena and a novel protocol simulating a complex maze. Our arena is freely inspired by previously reported circular mazes [28; 29; 30] including a new system with a laser beam to point a spot in any position on the floor, inside wall-screens to present spatial cues, and a video camera to track the path and distances, able to recreate many different spatial navigation tests for humans, and versatile enough to implement new protocols. The new system was created with the goal of including free body movement, in a complex maze, in real space, but all enclosed in a reduced space, while allowing evaluation of both egocentric and allocentric navigation, neural activity recording, and difficulty level customization, in all cases if/when required. The dynamic of this new test was created trying to recapitulate the continuous orientation and reorientation one has to perform while navigating spaces where some spatial cues (necessary to find a path) are only available as long as the participant is doing short displacements, such as for example into a department store, where one has to reorientate after going around many repetitive aisle displays (with a similar average size than our system) while advancing from the starting position to a distant target end [33]. The system presents several advantageous features. First, it allows the evaluation of freely moving subjects. This is very relevant for spatial navigation, as the proprioceptive component of movement has long been underrated, especially in the on-screen orientation tests implemented with computers. Recently, head-mounted VR systems or omnidirectional treadmills (reviewed by [1]) have improved the analysis of spatial navigation including vestibular, proprioceptive, and somatosensory cues, although the limitation of the move ment still remains a challenge. One solution would be to evaluate the subjects in a large complex maze, but laboratories cannot usually afford it due to the size necessary to implement such an arena. In our system, we have tried to solve this problem by implementing a design including hardware, software, and a dedicated protocol, all allowing to evaluate spatial navigation in freely moving subjects that have to orientate through a complex maze with dead ends and occasional non-linear movements. A usual test to perform our maze takes a mean of 20 min, and the participant walks a mean of 70-80 m during the test, although the circular arena is only 3 m in diameter. This is because the system is designed to recreate a set of different spatial cues on the screens on the inside walls of the arena. This is done in such a way that when the subjects orientate themselves according to the map and the cues, and exit the arena, they have to enter again the arena at a specific different entrance point, and meanwhile the inside scenario has automatically changed through a computer to recreate the new location the participant has chosen to go. This way, the participant can be tested in a complex maze as the experiment requires (see map in Figure 1b) but still in a controlled, reduced space. This design is useful to customize the difficulty of the test, because the experimenter can easily change the number of locations the participant will have to go to reach the target, the difficulty of the path to transit to those locations, the number of dead-ends and non-linear movements, and the on-screen spatial cues. This is useful to design specific experiments devoted to analyzing spatial navigation with children, adults, elders, neurodegenerative patients, or any other conditions. It allows to measure horizontal properties of several spatial navigation tests such as pattern separation or completion, by modifying the spatial cues. The experimenter could even change some of the system features on the test, depending on the path the participant is following, which can be tracked live in situ.