How we make our way through crowds

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A brain’s own GPS helps us navigate by detecting the movements of fellow humans around us.

Grid cells not only help us navigate our own paths in a complex environment, but also help us analyze the movements of other people, as scientists from the University of Vienna have now shown for the first time. Their new study in Nature Communications also suggests an explanation for a mechanism that could lead to disorientation in dementia patients.

Whether you are making your way through a crowded pedestrian zone or striving toward the goal in a team soccer match, in both situations it is important to think not only about your own movements but also those of others. These navigation and orientation processes are carried out by brain cells that register our current position, where we are coming from, where we are going and in which direction we are looking. Through their joint activity, they create a "map" of our surroundings. A special type of these cells are the so-called grid cells in the entorhinal cortex, a small brain region in the middle temporal lobe. They function like the brain’s own GPS, because they not only represent our position in space, but can also put it in relation to other points in space.

Whether these grid cells are also involved in mapping the movements of other individuals on this map was the question addressed by scientists led by Isabella Wagner and Claus Lamm from the Faculty of Psychology at the University of Vienna. For this purpose, the scientists had subjects navigate themselves in a virtual environment and observe the movements of another person, while their brain activity was measured using functional magnetic resonance imaging (fMRI).

They found that the brain activity recorded while observing others was comparable to the already known activity of grid cells. In addition, the team was able to show that this activity was involved in a network of other brain regions that are also associated with navigation processes. Interestingly, however, it turned out that the better a subject was at following the path of others, the less active this network was. "We interpret this as greater efficiency of the grid cells, which make it less necessary to draw on these brain areas," Wagner explains.

The results of the study thus indicate that grid cells belong to a larger network of brain regions that, among other things, coordinates navigation processes. However, this network is particularly affected by aging processes and especially by dementia. Wagner explains, "The function of grid cells decreases with age and in dementia. As a result, individuals can no longer find their way around and their orientation is impaired." The group’s further research is now dedicated to the question of whether grid cells are also involved in recognizing people - an aspect that is often impaired in advanced dementia.

Publication in Nature Communications :

Entorhinal grid-like codes and time-locked network dynamics track others navigating through space

Isabella C. Wagner, Luise P. Graichen, Boryana Todorova, Andre Lüttig, David B. Omer, Matthias Stangl, Claus Lamm

DOI 10.1038/s41467’023 -35819-3