In order to reach her office job, the 43-year-old Canadian woman gets on the same bus every morning and rides it to a distinctive downtown square. She then exits the bus and walks 30 yards to the tall building in front of her. At day’s end, she follows these simple directions in reverse to get home. Any change, and she will become hopelessly lost.
It’s been like this her whole life. Despite normal cognitive development, friends or relatives led her to school every day throughout childhood. In adulthood, she needs a guide to go to the grocery store, movies, or anywhere besides work.
In the journal Neuropsychologia, cognitive neuroscientist Giuseppe Iaria, Ph.D., and his colleagues at the University of British Columbia, published a case study of the woman’s affliction, dubbing it DTD, or “developmental topographical disorientation.” Certain forms of brain damage, including Alzheimer’s, can rob adults of their ability to form mental maps. But this woman was the first published case of a person seemingly born lost.
“We published our paper in August,” says Iaria, “and since then, we have been contacted by 500 people with this same disorder. It’s an extremely frustrating and anxiety-causing problem, and many of them are relieved to find that there’s actually a name for their condition, that they’re not stupid.”
Most of us take for granted the ability to form some type of mental map, even if the accuracy varies greatly. Some, like me, must constantly stop to ask for directions. Others seem blessed with preternatural homing abilities. “Australian Aborigines and the Puluwat Islanders of the South Pacific,” says Gonzales, “seem so inexplicably good at navigating that researchers once wondered if they had a magnetic sense.”
Though migratory birds have neurons that sense magnetic fields, no evidence exists that humans are equipped with such an internal compass. What we do have, however, is no less miraculous: an interplay of complex neurological systems that together allow us to navigate through the world.
For complex routes we habitually travel, for example, a brain region called the caudate nucleus encodes the directions. Neuroscientists have dubbed this “procedural memory,” and it lets us perform many well-practiced behaviors on autopilot. The advantage of route-by-rote navigation is that, once ingrained, it demands little conscious attention, freeing our brains to concentrate on other matters.
But there’s a decided disadvantage, too, with habitual routes. “Well-meaning people sometimes trap nuisance squirrels and move them to the woods, believing this is a humane solution to a pest problem,” says Gonzales. “It’s not. Once you take them out of their territory and they don’t know where they are, they rarely survive.”
Fortunately, people are less reliant than squirrels on procedural memory alone. “Our brains can learn not only where different landmarks are, but where each one is relative to the others,” explains Iaria. “Thus we can form a mental map of the environment in our heads and visualize alternative pathways leading to the same destination.”
Creating and manipulating these cognitive maps requires distinct high-powered skills, from visual memory to the ability to mentally rotate objects in space. Though various brain regions play a role, the most important is the hippocampus. It contains specialized “place” cells that fire rapidly whenever we pass a familiar landmark. In recent work, Iaria and company found that a person’s mental mapping ability depends largely on the structural integrity of the hippocampus. Victims of Alzheimer’s and DTD alike, it now appears, can’t find their way because of hippocampal impairment.
Of course, we’re all doomed to some deterioration. In one recent study comparing volunteers in their 20s with those in their mid-50s, researchers found that the older we get, the longer it takes us to form cognitive maps–and the more error-prone we become when using them.
But don’t lose hope. A simple technique can help virtually everyone consolidate new directional data into long-term memory: Get a good night’s sleep after exposure to new geography. Whether you’ve spent the day hiking through unfamiliar woods, or scrutinizing topographical maps to plan an alpine crossing, sleep will help fix new bearings into your cognitive map. Veteran hikers can also take satisfaction in another research finding: When it comes to navigational acumen, practice makes perfect. One study of longtime London taxi drivers found that years of exercising their mental mapping skills led to a physical increase in hippocampal volume. Adrift in the Frank, I can’t help but wonder which description fits me better: London hack in training or transplanted nuisance squirrel?