Everyone has experienced the gripping fear of being lost. Whether it is accidentally wandering too far from Mom in a department store or making a wrong turn down a dead-end street, getting lost is a normal part of life. We make mistakes, can’t find our way for a few moments, but we always end up making our way back to safety soon enough. For some people, though, that feeling of being lost is not a rare event, but a daily occurrence. For those suffering from Developmental Topographical Disorientation (DTD), not knowing where they are is as normal as breathing.
Meet Sharon Roseman, who has lived in Denver, Colorado for over twenty years. In that time span, most people would know their neighborhoods like the back of their hands, but for Ms. Roseman, just remembering where her kitchen is located in her house is a struggle. In a New York Times documentary, Ms. Roseman describes, “It’s almost as if somebody picks up the entire world, turns it, and sets it back down.” (Siddique, 2013).
But what exactly is DTD? To answer this question, we first need to determine exactly how people remember directions and locations. Navigation can be grouped into two categories: landmark orientation and path integration (Iaria, 2011). Landmark orientation takes geographic and manmade features and turns them into signs telling you when to turn or move straight ahead. For example, you might know that your friend’s street is the second left after the bakery. In this case, the bakery is a landmark which helps you decide where to go. Path integration relies more on memorization of how many turns a person needs to make or how far they need to move. This type of navigation is what allows you to get up in middle of the night and get a glass of water without banging into walls or tripping over furniture. Your brain automatically remembers how many turns to make to get out of your room or steps to take down the hall, so even in your sleepy state, you can find your way.
Luckily for you, your brain seamlessly combines both landmark orientation and path integration so you can move about without thinking too much. Unfortunately, for some people the brain simply can’t retain all this information. Neuroscientist Giuseppe Iaria of the University of Calgary, the man who discovered DTD, explains that patients with DTD can’t form “cognitive maps,” meaning they cannot mentally visualize their surroundings, and so never form memories of their locations (Siddique, 2013).
Scientists are still not sure what causes DTD; even the concept of human navigation is still not thoroughly understood. Previous models involved placing rats into mazes to see if they could remember how to navigate their way to reach food at the other end (Green and Cook, 1997). From these experiments, researchers were able to determine that for each specific area in the maze, a “place cell” in the hippocampus of the brain would be activated. Each “place cell” would help the rat determine where it was and what direction it would need to head in next.
Neuroscientists Dr. Nachum Ulanovsky and his student, Dr. Michael Yartsev, of the Weizmann Institute were not satisfied. They realized that rat models only dealt with movement in a two-dimensional space, yet, humans do much more than run in straight lines; they move in a three-dimensional space.
In order to update the model for spatial navigation, scientists are beginning to study the brains of our furry mammalian friends: bats. Bats move three dimensions: right or left, forward or back, and also up or down. Bats are best known for their ability to navigate using a series of sound waves, also known as echolocation.
Echolocation has its limitations, though; since these waves cannot travel farther than a few meters, bats need to rely on their spatial memories to properly move about. In a study conducted by Stanford researcher Jonathan R. Barchi, big brown bats, Eptesicus fuscus, were released into a dark room with hanging chains multiple times over the course of a week (Barchi, 2012). On the first day, Barchi noted that the bats seemed to rely heavily on echolocation to navigate. By the end of the week, the bats used echolocation far less and seemed to follow the same path through the room each time. Even when released from various points in the room, the bats still followed the same flight path. A month later, Barchi took the same bats and placed them in the room again. Despite having not been in the room for a period of time, the bats still remembered the obstacles and used the same, original flight path. These results suggest that bats are able to take a single scene of their environment and take a snapshot of it, creating a unique flight path that they continue to rely upon. Further research into how the bats do this, neurologically, can open the doors to finding a cure for DTD.
Patients with Developmental Topographic Disorientation wake up every day only to face a strange, seemingly new world. Tasks that many of us do without even thinking are constant battles. Now, new studies using bats shine a ray of hope for those with this condition. Perhaps by studying more about bats’ incredible spatial memories, we can harness their secrets to navigation and find a cure for Ms. Roseman and many like her.
- Developmental Topographic Disorientation (DTD) is a mental condition with no known cause or cure that stops people from forming mental maps of their surroundings.
- People with DTD are unable to remember how to move to and from places, even those as familiar as their own homes.
- Recent studies involving bats’ ability to form long-term spatial memories of specific environments offer a new way to learn more about the causes of DTD.
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