Neurons in the hippocampus and olfactory cortex of the brain, especially place cells and grid cells, play an important role in spatial perception and memory formation. Experiments have shown that these neural structures are involved in remembering and navigating specific places, but no one has yet found a way to fundamentally solve this problem.
The phone keeps ringing, but the building he’s looking for is nowhere in sight. The map says it’s 7 minutes away, but it’s already been 30 minutes. These are stories of people who have trouble finding a specific place and get lost easily. I also have a hard time finding my way when I go to a new place. I have a poor sense of direction and spatial awareness. These “wayfarers” often get lost in their daily routine or fail to find buildings. Why do people differ in their ability to find and remember directions? This can be explained by the hippocampus and its surrounding olfactory cortex nerve cells, located inside the temporal lobe of the brain.
First of all, we need to follow directions to get to a certain place safely. So, how does the brain work when we navigate? One of the most interesting experiments was conducted by John O’Keefe, a professor at University College London in the 1970s. He studied the hippocampus, which is located in the cerebral cortex. In his experiments, he placed electrodes in the hippocampus of laboratory rats to record the electrical signals of nerve cells. These signals are based on the principle that nerve cells only respond if they are above a threshold when sensory information is stimulated and converted into electrical signals. From these experiments, O’Keefe found that “place cells” exist in the CA1 region of the hippocampus that fire only when the rat reaches a specific place. He also found that these place cells exchange information with neurons in other regions. Place cells remember specific places or shapes and help people find their way around. O’Keefe says that these place cells use visual cues to create a “mental map” of the world. When this map is stored as long-term memory in the cerebral cortex through learning and repetition, we can find our way around without relying on cues.
However, there are times when we can’t find a specific place even though we’ve traveled it many times. One such experiment was conducted by May-Britt Moser. While conducting experiments with electrodes in and around the hippocampus of laboratory rats, she discovered a new electrical signal in the olfactory cortex. Unlike place cells, these signals responded in the dark. The signals appeared at regular intervals, and when their locations were connected, they formed a honeycomb-like hexagonal pattern. These neurons became known as ‘grid cells’. It turns out that these grid cells allow rats to know the location of specific coordinates in the overall space they perceive, and even calculate the distance between them.
In subsequent studies, May-Brett Moser found that positional information from the olfactory cortex can be transmitted directly to CA1, but it can also be transmitted via CA3 to CA1. They conducted experiments to determine which pathway signals related to spatial responses and place memory were traveling. First, they asked rats to navigate without blocking the CA3-to-CA1 signaling pathway and observed the effects on the olfactory cortex. The results showed that place cells in the rats’ CA1 region received information accurately and reliably, and the rats performed well in spatial recognition tests. However, when the same experiment was conducted after blocking CA3 signaling, the rats took longer to find the path, even though it was one they had previously experienced. This shows that blocking signaling from the CA3 impairs the rats’ ability to recall space. These results suggest that there are at least two functionally separate memory circuits in the hippocampus: CA1, which is directly connected to the olfactory cortex, is sufficient for recognizing places even in the absence of signals from CA3, but connections between CA3 and CA1 are necessary for recalling memories. This suggests that even if you’ve been to a place many times, if the signal between CA3 and CA1 is blocked, you can still recognize it, but you may have trouble finding it.
Advances in brain imaging technology have confirmed that place cells and grid cells found in laboratory rats exist in humans as well. While brain research has shed some light on the causes of disorientation, there is no cure for it yet. This is because brain science still needs a lot of research and there are still many questions to be answered. For now, the solutions offered to people with disorientation are simple and superficial. However, as virtual reality research progresses, it is hoped that one day there will be a permanent solution to improve navigational skills.
