When moving through a dynamic environment, we need to consider other people’s movements in addition to our own position. A study now shows that the same brain cells are probably involved that enable our own navigation. According to this, so-called grid cells are active both when we move and orient ourselves and when we observe the movements of others. The results also provide an explanation as to why people with dementia suffer from disorientation.
In order to move safely in a complex, changing environment, our brain has to process a lot of information at the same time: Where are we in relation to other points in space? Where do we come from and where are we going and at what speed? And: How do our fellow human beings move? This information is important, for example, in order not to constantly collide with others in a crowded pedestrian zone, but also to solve cooperative tasks, for example to drive the ball towards the goal in teamwork in football.
Navigation in virtual reality
A team led by Isabella Wagner from the University of Vienna has now investigated which areas of our brain are responsible for this. It was already known that so-called grid cells in the entorhinal cortex, a small brain region in the middle temporal lobe, are responsible for detecting our position in space and relating it to other points in our environment. In cooperation with other brain regions, they create a kind of cognitive map of our environment.
In order to find out to what extent the grid cells are also involved in depicting the movements of other people on this map, Wagner and her colleagues first had 58 test subjects observe in virtual reality how a person walks through a defined area. The test subjects were then supposed to control their figure themselves and follow the previously observed path. During both tasks, the research team monitored the subjects’ brain activity using functional magnetic resonance imaging.
Similar activation for observation and own navigation
And indeed, both tasks showed a similar activation pattern. “Even when the participants merely observed the path of another person, we registered significant grid cell-like codes in their entorhinal cortex,” the researchers report. In addition, they found that a network of other brain regions previously associated with navigation and orientation, including the hippocampus and striatum, became active. “The activity of this network was temporally coupled to the activity of the grid cell-like codes,” the authors say.
To the surprise of the researchers, it turned out that during the observation, this network was particularly active in those people who performed the worst in the subsequent navigation task. “We interpret this as greater efficiency of the grid cells, which makes it less necessary to access these brain areas,” explains Wagner.
Mechanism for disorientation in dementia
“Although we cannot currently say whether these results are specifically related to social processing, the results suggest that the grid cells may be involved in socio-spatial navigation,” the authors said. “We surmise that grid cell-like codes and the network dynamics associated with them may serve to propagate information about the location of others throughout the brain, thereby laying the foundation for an internal compass that allows us to orient ourselves into crowded and ourselves.” to navigate the dynamically changing environments we encounter in everyday situations.”
The results could also contribute to a better understanding of why people with dementia often experience disorientation. “The function of grid cells decreases with age and with dementia,” says Wagner. “As a result, people can no longer find their way around and orientation is impaired.” In future studies, the team wants to find out to what extent the grid cells are also involved in recognizing people – an aspect that is often impaired in advanced dementia.
Source: Isabella Wagner (University of Vienna, Austria) et al., Nature Communications, doi: 10.1038/s41467-023-35819-3