As scientists work to unravel the mysteries of the mind, people with unusual conditions are helping add to our understanding.

Illustration: Lincoln Agnew

Sharon remembers the first day it happened, in 1952. She was 5 years old and blindfolded while her friends ran around her, laughing, trying not to be caught in a game of blindman's bluff. But when she whipped off the scarf, panic set in. The house, the street, even the mountains were in the wrong place. She was totally disoriented.

She told her mother that everything around her looked different. Her mother pointed a finger at her. "Don't ever tell anybody about this," she said. "Because they'll say you're a witch and burn you."

Sharon, who lives in Denver, didn't know it at the time, but she had lost the ability to create a mental map of her environment. Her disorientation began to occur more frequently until it became a constant presence throughout her day. She became almost permanently lost.

Yet she didn't mention her problem to anyone. Instead, she hid it for 25 years, using her sense of humor and intelligence to complete her education, make friends and even get married without anyone ever knowing her secret. At home, she followed the cries of her children to find their bedroom at night. Her saving grace was a trick she had learned early on - spinning around seemed to temporarily correct her mental map. "My Wonder Woman impression," she calls it.

She eventually learned she had an unusual condition called developmental topographical disorientation disorder, or DTD. (She thinks her mother had it, too - the condition has a genetic link.)

Throughout history, unfortunate accidents, maverick surgeries, disease and genetic mutations have helped scientists learn how different parts of the brain work. Phineas Gage, who turned from jovial and kind to aggressive and rude after a metal rod shot through his head in 1848, showed us that our personalities are intimately tied up in the front regions of the brains. Savants like Alonzo Clemons - who sadly suffered a traumatic head injury as a toddler, leaving him with learning difficulties and a low IQ but an incredible ability to sculpt - have helped propel our understanding of creativity.

We are by no means close to understanding the mind in its entirety. None of what we call our "higher" functions - memories, decision-making, creativity, consciousness - are close to having a satisfying explanation.

What is clear is that the unusual brain provides a unique window into the mysteries of the so-called normal one. It reveals some of the extraordinary talents locked up inside us all, waiting to be unleashed. It shows us that our perceptions of the world aren't always the same. It even forces us to question whether our own brain is as normal as it would have us believe.

'There are tricks we
can learn to forge
more permanent
memories.'

For two years, I traveled around the world to meet people with extraordinary brains. They have all been tested, scanned and analyzed by multiple doctors and researchers. Through their stories I uncovered the mysterious manner in which the brain can shape our lives in unexpected - and, in some cases, brilliant or alarming - ways. They also taught me some of the secrets of my own mind.

Take Sharon. We only began to understand how we navigate in the 1960s, when neuroscientist John O'Keefe, at University College London, placed a set of electrodes into the hippocampi of rats, to record the spikes of electricity that occur in this brain region as the animals explored their environment. In doing so, he discovered "place cells" - cells that only fire when a rat is in a specific location. The combination of their activity forms a kind of electrical map inside the brain.

Illustration: Daniel Baxter

But place cells can't do this job alone. Later research showed that they communicate with many other cells, those that process which way our head is turned and where walls and boundaries are, together with an important brain region called the retrosplenial cortex, responsible for incorporating permanent landmarks into our mental map.

It wasn't until 2009, however, that it was discovered that this map could go terribly wrong. Giuseppe Iaria, then at the University of British Columbia, was investigating why some people are better navigators than others. In the process, he met a patient who, like Sharon, was permanently lost. He called the condition DTD and later published a paper in Neuropsychologia stating that the problem resulted from a lack of communication between all the regions of the brain involved in creating a mental map.

For anyone who has a bad sense of direction, Dr. Iaria says it's never too late to improve your navigational skills. "If you're in a new area, you should return to one point often, as this will help you build a better mental map," he says. Paying attention to specific landmarks and their orientation to one another can also assist your retrosplenial cortex in building these into your mental map and help you find your way home.

Not all brain disorders are as detrimental as DTD. Bob, a TV producer from Los Angeles, remembers every day of his life as if it happened yesterday. His perfect memory is a gift, he says: "I don't have to mourn people after they've passed away because my memory of them is so clear."

The condition was discovered by James McGaugh at the University of California, Irvine, in 2001, after he received a peculiar email from a woman named Jill. "Since I was 11 I have had this unbelievable ability to recall my past," she said. "When I see a date…I go back to that day and remember where I was, what I was doing, what day it fell on and on and on."

The exact nature of memory is hotly debated, but the general consensus is that memories are stored at synapses - gaps between brain cells called neurons. As one neuron sends signals to another, the connection between these two cells strengthens, gluing different aspects of a memory together.

Dr. McGaugh wondered whether Jill's unprecedented memory came down to the way she stored memories. But he soon discovered that Jill wasn't great at other memory tasks, like remembering strings of numbers. In 2006, he published a paper naming the condition Highly Superior Autobiographical Memory (HSAM).

A decade later, Dr. McGaugh had a group of around 50 people with HSAM. By scanning their brains while they carried out memory tasks, he discovered that they had an enlarged caudate nucleus and putamen - two areas implicated in obsessive compulsive disorder. Dr. McGaugh concluded that their extraordinary powers of memory are rooted not in their ability to form memories, but in an unconscious rehearsal of their past. They accidentally strengthen their memories by habitually recalling and reflecting upon them - "a unique form of OCD," he says.

While we may not be able to remember as much as Bob or Jill, there are tricks we can learn to forge more permanent memories. Studies by Eleanor Maguire at University College London and her colleagues helped demonstrate that the brain prefers to store memories as images in an orderly location. They did this by comparing the brain activity of world memory champions with a control group, while they memorized lists of items.

Results showed the only difference was that the champions preferentially used parts of the brain responsible for navigation and spatial awareness during the tasks. It turned out that they had better memories purely because they were placing items they needed to remember as images around a "mind palace." A mind palace is a location you know well, like your walk to work - and anyone can use it. Simply place items you want to remember along this route and you'll be able to recall them easily by mentally retracing your steps and picking them up.

Joel, a doctor at Massachusetts General Hospital in Boston, has a unique condition that has both benefits and drawbacks. It is called mirror-touch synesthesia, and it's the ability to feel other people's touch, pain and emotions as if they are happening to your own body. A scratch of the head, a frown, a punch on the arm - if Joel sees it, he feels it. In other words, he is hyper-empathetic.

'When Joel injects a
person, he feels the
sensation of a needle
entering his own skin.'

We all experience others' worlds to some extent. For that we can thank our mirror neurons - brain cells that act in the same way whether I make a movement or see someone else make that same movement. Most of us receive veto signals from other cells that damp our mirror neuron activity and allow us to distinguish between what's happening to us and what's happening to those around us. When Michael Banissy at Goldsmiths, University of London, scanned the brains of 16 mirror-touch synesthetes, he discovered that they lack these veto signals and have less brain tissue in an area that helps us distinguish the self from other.

When Joel injects a person, he feels the sensation of a needle entering his own skin; upon seeing an amputated arm, his own arm feels as though it has been ripped apart. He feels other people's emotions, too, which he says helps him to connect with patients. "If someone looks nervous, then my brain will feel those movements as if they are happening to my own face and say, 'You're nervous.' It helps me understand what they're really feeling."

This tallies with the work of neuroscientist Antonio Damasio of the University of Southern California, who states that feelings only occur after our brain senses physical changes in our body and attaches value to them. You can test this theory now. Pull the corners of your mouth up, squeeze your cheeks and crinkle your eyes - there, you're smiling. Stay like that. Do you feel better? Several studies have shown that the physical act of smiling makes you feel instantly happier.

While the mind can't be fooled into a permanent state of bliss, the idea that our feelings are a result of the things that happen to our body can help us in other ways. Our ability to sense the physical state of our body - a rumbling stomach, a sense of thirst - is called interoception, and it constantly guides our thoughts and behavior. ​When most people look at pictures designed to elicit an aversive reaction, such as of a cockroach, the brain's insula lights up with activity.

For some people, this system goes awry in a condition called depersonalization. Louise, a teacher from the U.K., was 8 years old when it first happened to her. "I woke up that morning and suddenly felt like I'd been dropped into my body," she says. "It's really hard to describe, but it was like I was just born. Everything around me felt new."

Like many people with depersonalization, Louise has great difficulty describing her state of mind. "When you're in this state, everything around you feels like it is screaming at you to get noticed. But at the same time your whole world seems like it's happening to someone else, someone you're not in control of. It's like walking through tar. It's exhausting," she says.

When most people look at pictures
designed to elicit aversive reactions,
(e.g. a cockroach,) the brain's insula
lights up with activity. Photo: IStock

The region that integrates all this interoceptive information is the insula, a fold in the center of the brain. The front of the insula "is the area of the brain that forms a default setting of 'This is me here and now,' " says Nick Medford, a consciousness expert at Brighton and Sussex Medical School. Dr. Medford spends much of his time placing people in brain scanners and showing them pictures of grotesque surgery, filthy bathrooms and cockroaches - images designed to elicit aversive reactions. When we look at these kinds of highly evocative stimuli, the insula lights up with activity. When Dr. Medford showed 14 people with depersonalization these images, however, he found a startling lack of activity.

You can check your own interoceptive abilities now, simply by counting your heartbeat without touching your chest. Studies have found that people who are better at this task are also more empathetic, better at dividing their attention and make better decisions. It suggests that our gut feelings, on which we often base decisions, may rely on an awareness of subconscious body signals.

There could be one way to improve interoception. Vivien Ainley and her colleagues at Royal Holloway, University of London, showed that people are more accurate at counting their heartbeats while staring at a picture of themselves. It's thought that this helps shift the brain's attention from the outside world to the internal world, via the insula. Whether this could eventually lead to persistent levels of increased interoception is under investigation. In a world full of brain-training apps and drugs that promise a shortcut to a brighter brain, I like the idea that we might be able to improve ourselves simply by looking in the mirror.

It goes without saying that we should relish the lives that our brains create - particularly those that aren't "normal." In fact, as we unravel the mysteries of the mind, it is becoming clearer that all our perceptions of the world may be unique. We all possess a remarkable feat of neural engineering. Let's celebrate its differences.

This essay is adapted from Ms. Thomson's new book "Unthinkable: An Extraordinary Journey Through the World's Strangest Brains," published by Ecco, an imprint of HarperCollins (which, like The Wall Street Journal, is owned by News Corp).

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