It was a typical Monday morning as I left Cité Universitaire, the complex where our dorms are located, and headed to the Accent building where our classes take place. I leave everyone morning at 9am to give myself an hour to travel and have extra time to stop by my favorite Parisian coffee shop, Starbucks (only place that gives American sized portions). As I was walking to the metro station, I ran into my friend, Swetha, and we began talking about our presentation later that day. Once we got to the metro station, the RER B had just arrived, so we quickly scanned our passes and hopped onto the last car of the train, which was overcrowded with passengers. This was typical in the mornings for a train to be packed like sardines in a can. We continued to talk as the train left the station.
A few minutes later we arrived at the next metro stop and the doors opened. Swetha and I were standing next to the door and could tell some passengers were trying to move to get off at this station, so we stepped outside of the train car to make it easier for people to leave. One-by-one passengers were exiting the car and I was getting excited because this meant we would have more personal space to stand and possibly even get a seat! But then we realized all of the people in our car were getting off, which seemed unusual. Confused by this, Swetha and I looked towards the front of the RER B and noticed that it wasn’t only our car, but all of the passengers from the entire train were exiting.
Swetha looked at me with a puzzled look and we decided to follow the mass of the people even though this was not the station we wanted to get off at. Did we miss an announcement (not that I would understand because I don’t speak French) that the RER B was closing? We quickly thought of an alternative route to get to class. We would ride line 6 for a few stops and then transfer to line 8 to get to our final destination, the Bastille station. We followed the signs towards line 6, but somehow this led us outside of the metro station! Confused by how this happened, we decided to follow the sign that had an arrow pointing to the left hoping this would lead us to the front of the metro station.
After walking for a couple minutes we realized the sign misled us (not the first time this has happened to me while in Paris). We were headed away from the metro station. We stopped and looked around to see if we had any clue of where we were, but nothing seemed familiar. At this point, our sense of direction was completely lost. But then I spotted the restaurant we had eaten dinner at the night before, which served delicious crepes, and I knew exactly how to get back to the entrance of the metro station. We used our memory of the path we took from the restaurant and successfully made it back to the metro station. We quickly headed towards line 6 hoping we would be able to make it to class on time and as we were walking a RER B train pulled up. Now we were really confused but quickly decided to hop on and go back to using our normal route to class. We came to the conclusion it was only our original train that was closing for the day because it let us off at an unfamiliar spot, hence why we were led outside of the station. After this eventful journey, we were finally back on track to class and we even made it in enough time for me to buy a much-needed coffee.
My experience of getting lost made me wonder about human’s sense of direction. Previous courses I have taken have taught me about the various ways animals can navigate, but most of these don’t apply to humans. Some animals use magnetoreception for navigation, in which they are sensitive to the earth’s magnetic fields. Other animals use orientation of the sun or orientation of the night sky by looking at the position of the sun or patterns of stars to navigate. One last way animals navigate is by learning specific landmarks in an environment. This is how I was able to navigate to the metro station, by using the restaurant as a landmark.
In order for an organism to be able to navigate in the world, it must know where it is and what direction it is facing. Previous studies have found a group of cells in the brain that respond to the location information of an organism and when the organism turns, the activation of the cells also rotates to the equivalent amount of movement the organism made (Knierim et al. 1995). These cells make up a neural compass. In order for the neural compass to be useful, the organism must have a heading, or a defined direction, relative to fixed features of the environment. This is similar to how a magnetic compass’s heading is defined relative to the north-south axis of the earth. An example of a heading for the neural compass would be the use of a landmark to anchor the organism’s sense of direction.
A study was previously performed by a group of researchers, and they looked for the brain region that is involved in using a local landmark as a heading for the neural compass and hypothesized that it is essential for use of a landmark to be able to retrieve memories about the environment (Marchette et al. 2014). To test these ideas, the researchers collected fMRI data (looking at areas of the brain activated during a task) while participants imagined themselves in a newly learned virtual environment and performed a judgment of relative direction (JRD) task (which I will explain in a moment).
The researchers created a virtual environment that consisted of a square park containing four rectangular buildings, or museums. The museums were identical in shape and size, but were distinguishable by the building design of textures and architectural features, such as columns. Surrounding the park were environmental features, such as a mountain range or forest, which made each side different. The inside of the museums were identical in the number of rooms and room size, but were decorated differently. Each museum contained 8 distinct nameable objects, and each of the objects could only be viewed from one specific direction in a room. Participants were given a training period to learn the layout of the virtual environment in which they explored the park freely for 15 minutes and then performed a guided learning tour in which the name of an object appeared on the screen and the participant had to navigate to find the location of the object. Participants navigated using arrow keys.
After participants were trained on the environment, they had to perform the JRD task. During this task, the names of a reference object and a target object were presented visually and simultaneously in gray letters on two different lines at the center of a black screen (for example, “Facing the Bicycle”, “Lamp”). Subjects were instructed to imagine themselves standing in front of and directly facing the reference object while they made a judgment about whether the target object from the training environment would be located to their left or right. This required them to imagine themselves in a specific location while facing a specific direction, which means that they must mentally reorient themselves (re-establish their sense of direction). Researches collected fMRI scans of participants while they performed this task.
After looking at the fMRI scans, the researchers found the retrosplenial complex (RSC), a region in the brain, was activated during the JRD task. They determined the RSC represents imagined facing direction and imagined location during memory retrieval of a place. The researchers discovered this happens by using a reference frame that is anchored to local environmental features and they found this task is generalized across the different museums/local environments with similar geometric structures. These findings suggest that the RSC is centrally involved in a critical component of navigation through environments by establishing one’s position and orientation relative to fixed elements of the external world.
A strength of this study was the performance of an additional task to verify that their findings about the RSC were due to activation of the brain from scenes and not due to the objects in the museum. They tested this by showing participants images of objects, scrambled objects, and scenes while performing a fMRI scan and found that the RSC responded significantly greater to the scenes than to the presentation of the objects or scrambled objects. While the study described results about using a reference frame (an object inside the museum), to make judgments about the location of another object in a museum, I would have liked to see the use of bigger, immobile structures as a reference frame. In the real world, and not the virtual environment, the reference objects could be moved and this would cause the location of a heading to orient a person’s sense of direction to be obstructed. If they had used the mountain range or a building as the reference for navigation, this would have related more to how humans use a landmark as a heading.
Although this study was performed in a virtual environment, it gave me insight about how humans navigate based on specific references. Next time I get lost in Paris, I will know which area of my brain is being used as I try to find a landmark to establish my position and orientation in order to be able to recall how to get to a metro station.
Knierim JJ, Kudrimoti HS, McNaughton BL (1995) Place cells, head direction cells, and the learning of landmark stability. J. Neuroscience 15:1648–1659
Marchette SA, Vass LK, Epstein JR, Epstein RA (2014) Anchoring the neural compass: coding of local spatial reference frames in human medial parietal lobe. Nature Neuroscience 17:1598-1606
Pictures 1-4 were taken by myself
Pictures 5-6 are from creative commons
Pictures 7-8 are images from Marchette et al. research paper
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