Distorting Mental Maps Using Virtual Reality
Post by Anastasia Sares
What's the science?
If you’ve ever played Settlers of Catan, you are familiar with a hexagonal grid. Players place settlements at the intersection of hexagon-shaped terrains, and roads along the edges of the hexagons to connect them. Did you know that this is exactly how our brain represents the spaces we navigate through? In rats, we can measure this by putting electrodes in the entorhinal cortex to record neuronal activity as the animal moves around. Neurons in this region of the brain will fire at evenly spaced positions as the rat moves through the environment, creating a sort of grid. Previous research has shown that these grid cells also exist in humans, and they function the same way when we explore real and virtual environments. Many previous experiments on grid cells have taken place in environments with circular or square boundaries, but research in rodents suggests that in environments with different geometries, such as a trapezoid, the grid pattern can be distorted. This week in Nature Human Behavior, Bellmund and colleagues wanted to see how a distorted environment, like a trapezoid, would affect people’s navigation and spatial memory.
How did they do it?
The authors measured positional memory (i.e. the memory of where things are located in space) using a virtual reality (VR) game. Participants wearing VR goggles walked around on a motion platform that translated their steps into virtual movement. The participants had to find objects and learn their positions in the environment. Later, they were asked to put the objects back where they had been before. Participants did the task in both square and trapezoid-shaped environments. Later, they were presented with pairs of objects and asked how far apart they were.
What did they find?
During the VR game, participants in the trapezoidal environment replaced objects further away from their original location—in other words, they had more spatial errors. The increase in error was especially evident for the narrow part of the trapezoid, where studies in rodents have shown the most distortion of grid cells. In the distance rating part of the experiment, participants judged distances in the two parts of the trapezoid as different when they were, in fact, identical, showing that the distortions in the spatial map persisted outside of the VR simulation. The authors were able to use the participants’ distance ratings to reconstruct the remembered spatial maps of each person and see how accurate they were (using multidimensional scaling followed by a Procrustes analysis). These reconstructed locations lined up with the spatial error scores from the VR.
What's the impact?
This study connects distorted grid cell maps observed in rodents with spatial memory in humans, showing the same mechanisms at work. It reinforces the fact that the overall shape of our environment affects us; which could be informative for architects and designers, among other applications (Imagine what spatial maps look like in the Denver Art Museum!).
Bellmund et al. Deforming the metric of cognitive maps distorts memory. Nature Human Behavior (2019). Access the original scientific publication here.