Some people with synesthesia always see the letters in the alphabet as a certain color. The color of each letter is always the same.

The number “6” is a bright shade of pink. Listening to a cello smells like chocolate. And eating a slice of pizza creates a tickling sensation on the back of your neck.

If you have experiences like this, you may be one of the special people with an unusual sensory condition called synesthesia (pronounced sin-uhs-THEE-zha).

People with synesthesia experience a “blending” of their senses when they see, smell, taste, touch or hear. Such people have specially wired brains, so that when something stimulates one of the five senses, another sense also responds. This blending can cause people to see sound, smell colors or taste shapes.

Dozens of different sensory combinations exist. In the most common form of synesthesia, numbers, letters or even days of the week appear in their own distinct color.

If you’ve encountered these types of events, you’re not alone. Scientists say as many as one in every 200 people may be a synesthetes, as people with this condition are called. The phenomenon is known to run in families, and may occur more often among women than men. Many famous people have had synesthesia, including Russian writer Vladimir Nabokov and physicist Richard Feynman.

One thing is certain; most synesthetes treasure their unusual ability to take in the world with an additional sense. After all, who wouldn’t want to experience the world in full, glorious color or sound?

“It’s absolutely a positive experience,” says Patricia Lynn Duffy, a synesthete who has talked to hundreds of others with the condition while writing a book on the subject. “If you proposed to take away someone’s synesthetic ability, I think they would say, ‘No, I like it this way.’’’

When people with certain types of synesthesia look at the image on the left, they can easily detect the six figures facing the opposite way, as shown in the image on the right. To these people, the “S” figures appear in a different color than the “2″ figu

What Color is my “i”?

Most synesthetes learn about their amazing gift by accident. They are surprised to learn that everyone does not experience the world as they do.

Though it may sound strange to many people, Duffy says the experiences are not scary. The people who have synesthesia have always experienced life that way.

“For as long as I could remember, each letter of the alphabet had a different and distinct color. This is just part of the way alphabet letters look to me,” says Duffy. “Until I was 16, I took it for granted that everyone shared those perceptions with me.”

Synesthetes do not actively think about their perceptions — they just happen. Some synesthetes report that they see such colors internally, in “the mind’s eye.” Others, such as Duffy, see their visions projected in front of them, like watching an image on a movie screen.

Scientists know that in synesthesia, those colors are real, not just figments of an active imagination. How? Studies show that the colors synesthetes see are highly specific and consistent over time. If the letter “b” is lime green, it will always be lime green.

Studies done in the mid-1990s showed that synesthesia also can be measured by brain-scanning techniques. For synesthetes who perceive colors when hearing words, a certain part of the brain involved with vision is active in response to sound. That type of activity didn’t occur in non-synesthetes.

Making Connections

So how can the sound of a musical instrument lead to color?

Scientists are still trying to discover exactly how information from the senses merge together in the brain. But this much is known:

Messages gathered from the eyes, ears, mouth, nose and nerves involved in the sense of touch travel to the brain for processing. Much of this sensory processing occurs in an area of the brain called the cortex, the outermost part of the brain that organizes and enables us to respond to the incoming messages.

Information from each of senses is first processed in its own special region. It’s then sent on to “higher” regions in the cortex for further processing. At certain points in the brain, these various senses converge.

One theory is that synesthesia may be caused by “cross-wiring” between areas of the brain that process different sensations, such as color, sound or taste. This theory draws on the fact that children are born with many nerve connections between nearby parts of the brain.

“During our first few years of life, our brain makes more connections than it needs, and then eventually prunes some of those away,” says Edward Hubbard, a post-doctoral researcher at the French National Institute for Health and Medical Research who studies what causes synesthesia.

One thing that may happen in synesthesia, Hubbard says, is that some of these connections don’t get pruned away. If so, then people may see specific colors with particular letters because they have extra connections between the brain areas involved in word and color perception.

Last summer, a group of scientists in the Netherlands found direct evidence of these types of extra connections.

The researchers used a method called DTI to scan the brains of 18 people with synesthesia. They also looked at the brains of 18 non-synesthetes.

Using a kind of magnetic resonance imaging called DTI (an example is shown above) to look at the brains of synesthetes and non-synesthetes, scientists showed that synesthetes who see colored letters have higher levels of white matter in three different br

DTI (which stands for diffusion tensor imaging) measures how water flows in the brain. Within certain brain tissues, or nerve fibers, water flows more freely in one direction than the other. This is especially true in a type of nerve fiber, or axon, that carries messages from brain cell to brain cell. Commonly called “white matter,” these axons connect different parts of the brain to each other.

By measuring the water flow through these tissues, the scientists could measure how many of these axons there were in each brain region. Brain regions that are highly connected will have more white-matter axons.

In synesthetes who saw colored letters, the scientists found higher levels of white matter in three different brain regions. One was in the letter and word region of the brain, known as V4. The other highly connected areas were found in brain regions involved in consciousness — the awareness that you’re thinking, feeling, seeing, hearing or any number of other things your brain enables you to do.

“We have lots of things impinging upon our senses, and some of them become conscious and some of them don’t,” says Hubbard. “Activity in this area might make a person more consciously aware of a synesthetic experience.”

These findings don’t rule out other possible causes of synesthesia, says Hubbard. Still, he is now working to see if this type of “cross-wiring” occurs in other forms of synesthesia. Other scientists are looking to see whether other parts of the brain are also involved in synesthesia.

Hubbard is also developing better ways to identify the various processing regions of the brain. “Everybody’s brain differs a little bit in its exact organization,” he says.

Duffy notes that these variations in nerve connections occur not only in synesthetes, but in all people.

“Everybody develops a neural pattern that’s kind of unique, just like a fingerprint,” she says. “That’s why no two people are seeing the world in exactly the same way.”

Going Deeper:

This image shows a neuron as it responds to an electrical signal. The blue traces the path of the signal as it moves through synapses to the neuron.

Think back to the first time you rode a bike or the last time you had ice cream for dessert. Now, imagine a perfect summer day. What’s going on in your noggin’ that allows you to remember, dream and think?

Lots. And some of the world’s brainiest scientists are conducting experiments/doing research to figure out how it all works.

The human brain is amazing. It lets you remember the way to your friend’s house, and how to pedal your bike to get there. It can conjure up memories of the fish you saw while snorkeling and remind you to feed your goldfish at home. It even controls stuff you don’t have to think about, such as your heart rate, breathing and blinking.

In recent years, brain-imaging techniques such as functional magnetic resonance imaging (fMRI) have allowed scientists to watch the brain in action. Studies using fMRI show how different parts of the brain do different things, says neuroscientist Sam Wang, who studies the brain at Princeton University.

For example, one part of the brain, called the amygdala (ah-MIGG-duh-luh), handles emotional information, and another part of the brain, the prefrontal cortex, makes plans for the future. Yet another brain system, the cerebellum (SEHR-eh-BELL-um), helps control your movements and balance, while the hypothalamus (HI-poh-THAH-luh-muss) works to control your body’s temperature.

The brain contains other systems, too. Your hippocampus (HIP-poh-CAM-pus), for example, has the job of transferring information between short-term and long-term memory.

By working together, these systems let you think, remember, see, hear, smell, taste and touch. The goal of this teamwork is to get you through life.

Though the human brain is sometimes compared to a computer, it’s not one. It’s actually much more complex, Wang says.

Computers, for example, are designed to record everything perfectly. Rather than recording everything, the brain sorts through all the information taken in through the senses and decides what to hold on to. Because the brain does all this pre-sorting, things such as the pattern in your rug or sound of songbirds outside your window don’t constantly distract you.

This illustration shows how the billions of neurons in your brain are linked by a web of connections. Neurons interact through electrical connections similar to those in a computer.

ktsimage/iStockphoto

The human brain can also do things that are in many ways faster and better than what any computer can do. For instance, you brain enables you recognize your friends — just from the way they walk — even from a distance. Computers can’t do that. Nor can a computer tell the difference between a cat and a dog, even though most toddlers can.

Though your brain is not a computer, they do share something in common: Both brains and computers use electrical signals to transmit information.

All fired up

Your brain doesn’t get its electrical energy from a socket in the wall, the way a computer does. Instead, it creates and sends electrical signals through specialized cells called neurons.

A neuron’s axons and dendrites help it to transmit electrical signals. Dendrites bring information to the body of the neuron, and axons take information away from the cell body.

U.S. National Cancer Institute

Neurons look different from other cells. That’s because neurons have long extensions called dendrites and axons. These work like electrical wires to transmit messages from your brain throughout your whole nervous system. Dendrites bring information to the body of the neuron, and axons take information away from the cell body.

Information is passed along throughout the nervous system from neuron to neuron. The region where the information is transferred from one neuron to another is called the synapse. The synapse is actually a small gap located between two neurons. When information is transferred from one neuron to another, chemicals called neurotransmitters are released from the end of one neuron and travel across the synapse to reach the other neuron. There, these chemicals attach to special structures called receptors, which are located on the receiving neuron. This attachment creates a small electrical response within the receiving neuron.

These electrical signals race up and down the dendrites and axons at super speeds — up to several hundred feet per second. That’s fast enough to help you flee from a wild animal, or pull your hand away from a sizzling hot frying pan.

The human brain contains billions of neurons, and each individual neuron may receive information from thousands of other neurons. To keep the mental machinery running smoothly, the neurons specialize in doing certain tasks.

Sensory neurons, for example, carry messages from your eyes, ears and other sensory organs to your brain. They alert your brain when your nose picks up a whiff of cinnamon rolls coming from the kitchen. Motor neurons carry signals from your brain to your muscles and organs, enabling you to walk, talk, breathe and scramble to the kitchen to grab a hot roll.

Other types of neurons in the brain help in building social relationships. Mirror neurons, for example, are specialized cells that help you show empathy and understanding to others. They fire not only when you take action, but also when you watch others take action.

“Mirror neurons are active when I pick up a cup, and are also active when I watch someone else pick up a cup,” Wang says. “If you’ve ever winced when you watched a TV surgeon slice into a patient, you have your mirror neurons to thank.”

Some neurons have very specific tasks. Things and people that you see on a regular basis — your mother, your dog and even your favorite celebrities — all have a group of dedicated neurons that fire specifically in response to them.

By working together, all the various types of neurons help build our thoughts and actions, Wang says. “Thoughts are basically neurons like these acting together, being put together in patterns.”

Hold that thought

So, with all the various neurons racing through the different brain regions, how can a person think straight? Figuring out how the mind gives rise to thoughts, actions and emotions isn’t easy, and scientists are still working to put all the pieces together. Imaging studies such as those using fMRI have provided some clues.

For example, fMRI studies show that the prefrontal cortex acts as a kind of traffic cop, directing signals to and from different brain regions. Information that comes into the brain through eyes travels to the prefrontal cortex before it is distributed to other brain regions for additional processing. The same holds true for information coming from the other senses.

Other fMRI studies show that when people are sitting around just thinking about something, multiple brain regions are activated. When volunteers in a study were asked to imagine that they are looking at something, the parts of their brain that handle visual information lit up. “The same brain regions that are active during direct visual experience are also active by imagining a scene,” Wang says.

Scientists have also found that your memory plays a role in imagining new scenarios. In recent years, researchers have discovered that the brain regions used to store and retrieve memories are activated when envisioning the future. So all those facts and autobiographical data stored in your brain actually help you construct and predict possible future events.

When it comes to learning new information, one thing is certain: Practice makes perfect. When messages travel from neuron to neuron, over and over, the brain creates a connection between the neurons to form a memory. Once this happens, processing and recalling information becomes easier.

This holds true whether you are trying to learn a new language or learn a new dance move, Wang says. “Memory formation requires multiple steps,” he says. “Once an initial idea or motion is laid down, it must be reinforced both by repetitions and recall.”

Allowing time for rest breaks also aids learning. That’s why spacing out your study time works better than trying to cram information all at once. Wang says one possible reason for this is that breaks provide time for information consolidation.

Now that’s something to keep in mind.

Going Deeper:

Most kids already have a ton of energy, but kids who drink a lot of cola often end up even more wired than usual. The soda’s high sugar content is partly to blame, but cola also usually includes an energy-sparking chemical called caffeine.

Drinking caffeinated soda can give kids a burst of hyperactive energy.

iStockphoto.com

Like cola, coffee is full of caffeine. That’s why many adults drink it first thing in the morning to help them wake up. The chemical is also naturally found in tea, chocolate, and hot cocoa. Because people crave the caffeine kick—and may even become addicted to it—food manufacturers add the chemical to many other sodas as well as to energy drinks and snacks.

Parents and teachers usually try to keep kids away from caffeine. But is this chemical actually bad for your health? The answer is complicated.

Good caffeine, bad caffeine

First the plus side. Some studies have shown that caffeine might help people respond to things more quickly and even run longer. Scientists have also recently found evidence that caffeinated coffee and tea can help protect the heart, brain, and other organs from disease.

On the other hand, too much caffeine can make people anxious and unable to sleep. A 2003 survey of more than 200 students in grades seven through nine found that kids who drank a 16-ounce bottle of cola slept less, woke up more often, and felt more tired the next day than kids who drank less caffeine. This is worrisome because sleeping well is an important part of staying healthy (See “Getting Enough Sleep”).

Caffeine can also raise your blood pressure, increase your heart rate, and make you feel more stressed, which may eventually lead to heart disease and other health problems.

“If you feel a lot of pressure at school, caffeine is going to make you feel even more anxious,” says Jim Lane, a psychologist at Duke University Medical Center in Durham, N.C.

Roasted coffee beans, like these, are ground and brewed into steaming cups of coffee. The fragrant beverage is the main source of caffeine for most adults.

Wikipedia

Love it or hate it, caffeine is hard to avoid. Coffee shops crowd city streets and malls. Vending machines offer caffeinated sodas in schools. And even though caffeine-free versions of coffee, tea, and cola are widely available, more than 80 percent of adults consume caffeine regularly in North America, according to a 2004 study, mostly in the form of coffee. And kids today are drinking more and more soda, caffeinated or not.

Some 30 percent of 8-to-13-year-olds surveyed by researchers at the University of Minnesota said that they drink soft drinks every day, according to a study published last year. And more probably would if they could: 95 percent of kids in the survey said they “like” or “strongly like” the taste of soda.

You’re feeling sleepy . . . NOT!

Caffeine works by blocking the effects of a sleep-inducing substance produced by your body called adenosine. The substance accumulates inside you throughout the day.

As adenosine levels rise, you become calm and drowsy. Later, as you sleep, adenosine levels drop. When you wake up, the cycle starts again. By not allowing adenosine to build up, caffeine keeps you feeling fired up—as if you’re ready to face a tiger attack.

Human brains aren’t the only ones that feel the effects of caffeine. These images show how an extreme amount caffeine affects the brain of a tiny creature. In this case, the top picture shows how a spider spins its web before caffeine and after (bottom).

NASA; Wikipedia

Caffeine raises the amount of sugar in your bloodstream, even if there is no sugar in your caffeinated drink. That’s what gives you extra energy. The chemical also increases your blood pressure, which may make you feel as if your chest is pounding. But if you consume too much caffeine, you will probably feel nervous and sick.

Caffeine claims for brains

People say they like caffeine because it makes them feel alert. In experiments, people who are given caffeine say they feel more awake than do people who have been given a caffeinefree pill or beverage instead, says psychologist Peter Rogers of the University of Bristol in England.

The caffeine in cola beverages like this one affects your brain and nervous system in ways that have nothing to do with sugar or other ingredients.

National Cancer Institute/Wikipedia

In other studies, caffeine appears to shorten reaction times: People press a button more quickly after seeing a symbol appear on a computer screen after they’ve had some caffeine.

On the basis of such findings, it’s tempting to conclude that caffeine helps people respond more quickly and pay better attention. However, says Rogers, there is another, more likely, conclusion.

Studies show that the people who do better on tests after taking caffeine tend to be regular caffeine users already. In other words, they are probably addicted to the chemical.

Taking caffeine away from habitual users causes them to have symptoms of withdrawal, such as headaches and sleepiness. It also slows their reaction times. So, when these people are given their daily dose of caffeine, they feel better and perform better on reaction-time tests than they do without it.

Coffee and other caffeinated beverages can be addictive, even for children.

iStockphoto.com

People who aren’t addicted, on the other hand, may feel jittery and more awake after taking caffeine, but the chemical doesn’t improve their performance on reaction-time tests. And regular caffeine users who get caffeine before the tests aren’t any more alert or quicker to react than people who don’t normally use the chemical and haven’t taken any.

Giving athletes a jolt

Caffeine has become popular with exercisers looking for an extra boost of energy. Research shows, however, that caffeine helps only athletes who are already in top condition and only when they are pushing themselves as hard as possible, says Terry Graham, a caffeine researcher at the University of Guelph in Canada.

In one study, Graham challenged nine runners to run on a treadmill at a very fast pace. On average, these athletes were able to run for about 32 minutes without caffeine. With caffeine in their systems, they ran 7 to 10 minutes longer.

Athletes often take caffeine for an extra boost of energy. But the chemical doesn’t necessarily make them faster or stronger.

iStockphoto.com

Though caffeine may help the performance of world-class athletes, it may harm the health of people who are overweight. Graham’s other research has shown that caffeine interferes with the body’s ability to process sugars, which may lead to a disease called type 2 diabetes.

Kids, who tend to be smaller than adults, feel the various effects of caffeine more strongly than adults do. And just like adults, kids and teens can become addicted to the chemical.

A can of caffeinated soda every now and then is probably OK, nutritionists say, but sip carefully!

The following list shows how many milligrams (mg) of caffeine are contained in some popular products. All beverages refer to an 8-ounce (1-cup) serving, unless otherwise noted.

Regular brewed coffee: 135 mg
Red Bull (8.5 oz): 80 mg
Black tea: 40-70 mg
Java Water: 62 mg
Starbucks Coffee Ice cream (1 cup): 40-60 mg
Espresso (1 oz): 30-50 mg
Green tea: 25-40 mg
Mountain Dew and Diet Mountain Dew: 37 mg
Diet Coke: 34 mg
Hershey’s Special Dark Chocolate Bar (1 bar – 1.5 oz): 31 mg
Pepsi: 28 mg
Diet Pepsi: 27 mg
Coca-Cola Classic: 26 mg
Snapple Iced Tea: 24 mg
Jolt gum (1 piece): 20 mg
Hershey’s Milk Chocolate Bar (1 bar – 1.5 oz): 10 mg
Hot cocoa: 5 mg
Chocolate milk: 5 mg
Decaffeinated coffee: 5 mg
Decaffeinated black tea: 4 mg

Going Deeper:

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