In this blog post, we will look at why there are differences in the ability to find one’s way, which is different for each person, and how it is related to the structure of the brain.
The phone keeps ringing, but the building that the person is looking for is nowhere to be seen. The map says it is a seven-minute walk, but it has already been 30 minutes. This is a story of people who have difficulty finding a specific place and easily get lost. I, too, have a hard time finding my way when I go to a new place. I have a poor sense of direction and spatial perception. These “bad directions” often cause people to get lost or not find a building in their daily lives. Why do people differ in their ability to find and remember directions? This can be explained by the hippocampus located in the inner temporal lobe of the cerebrum and the neurons of the parietal cortex around it.
First of all, in order to safely reach a specific place, you must follow the directions. So how does the brain work when a person is looking for a way? A related experiment was conducted by John O’Keefe, a professor at the University of London in the 1970s. He studied the hippocampus located in the cerebral cortex. During the experiment, electrodes were inserted into the hippocampus of the test mice to record the electrical signals of the nerve cells. This signal is based on the principle that a nerve cell responds only when the sensory information is stimulated and converted into an electrical signal above a threshold value. Through this experiment, O’Keefe found that ‘place cells’, which send signals only when the mice reach a specific place, exist in the CA1 region of the hippocampus. They also confirmed that these place cells exchange information with neurons in other regions. Place cells remember specific places or shapes and help people find their way. O’Keefe said that these place cells create a “map in the head” using visual information as a cue. Once this map is stored in the cerebral cortex as long-term memory through learning and repetition, people can find their way without relying on cues.
However, even if you have been to the same place many times, you may still not be able to find a specific place. An experiment on this is the research of May-Britt Moser. While conducting experiments on experimental rats’ hippocampus and its surroundings, May-Britt Moser discovered new electrical signals in the olfactory cortex. Unlike place cells, these signals showed a characteristic of responding even in the dark. The signals appeared at regular intervals, and when the locations were connected, they formed a honeycomb-shaped hexagonal pattern. These nerve cells came to be called “grid cells.” It was found that these grid cells allow rats to know the location of specific coordinates in the entire space they perceive, and to calculate the distance between the coordinates.
In a follow-up study, May-Britt Moser found that the positional information of the entorhinal cortex is sometimes transmitted directly to CA1, but can also be transmitted to CA1 via CA3. They conducted an experiment to determine which pathway signals related to spatial response or place memory are transmitted. First, they let the rats find their way without blocking the signal pathway from CA3 to CA1 and observed the effects from the olfactory cortex. As a result, the place cells in the CA1 region of the rats accurately and reliably received information, and the rats performed the spatial recognition experiment smoothly. In contrast, when the same experiment was conducted after blocking the CA3 signal, it took the rats longer to find the path they had previously experienced, even though they had experienced it before. This shows that blocking the signals transmitted in the CA3 impairs the rats’ ability to recall spatial information. These results suggest that there are at least two functionally separate memory circuits in the hippocampus. In other words, even if there is no signal from CA3, CA1, which is directly connected to the posterior insular cortex, is sufficient for recognizing a place, but the connection between CA3 and CA1 is necessary for recalling memories. This suggests that even if you have been to a place many times, you may have difficulty finding it if the signal between CA3 and CA1 is blocked.
With the development of brain imaging technology, it has been confirmed that place cells and grid cells found in laboratory mice also exist in humans. The causes of poor navigation have been partially revealed through brain research, but no fundamental treatment has yet been proposed. This is because brain science still requires a lot of research and there are many problems to be solved. For now, the solutions provided to people who have trouble navigating are simple and superficial. However, as virtual reality research progresses, we hope that a permanent solution will be found to improve the ability to navigate.
