Scientists have peered in the brains of people who meditate, and have found some happy surprises.

Meditation yields a surprising number of health benefits, including stress reduction, improved attention, better memory, and even increased creativity and feelings of compassion. But how can something as simple as focusing on a single object produce such dramatic results? Here's what the growing body of scientific evidence is telling us about meditation and how it can change the way our brains function.

Before we get started it's worth doing a quick review of what is actually meant by meditation. The practice can take on many different forms, but the one technique that appears most beneficial, and which also happens to be among the most traditional, is called mindfulness meditation, or focused attention.

By mindfulness, practitioners are asked to focus their thoughts on one thought and one thought alone. An overarching goal is to be firmly affixed to the present moment. This typically means concentrating on the breath - observing each inhalation and exhalation - and without consideration to other thoughts. When a "stray" thought arises, the practitioner must be quick to recognize it, and then turn back to the focus of their attention. And it doesn't just have to be the breath; any single thought, like a mantra, will do.

Now, if you've ever tried it, you know how unbelievably difficult this is - particularly in this day in age when our attention spans are taxed to the limit. Our minds are notorious at wandering and moving from thought-to-thought; it's hard sometimes to string just a few seconds of focused attention together.

And indeed, notions that meditation is simply about relaxation or cleansing the mind of allthoughts are common misconceptions. Meditation is hard work and it takes a lot of practice to get better. The more you do it, the easier it becomes to stay focused. Progress can be measured by how long a single thought can be focused upon without straying.

Remarkably, for something so exceedingly simple, it can produce an astounding number of health benefits. Eager to learn more, a growing number of scientists are looking into the cognitive effects of meditation, including studies on Buddhist monks. And they're learning that meditation is a very powerful tool indeed.

As a quick aside, most of the studies cited here consider the benefits of focused attention. That's not to suggest that other practices, like open attention, can't yield positive results as well.

Changes to the Brain

Buddhists have meditated for literally thousands of years. They're familiar with its positive effects, including the way it works to instill the inner strength and insight required for the overarching spiritual practice; meditation, or "sitting," is to Buddhist monks what prayer is to Christians. But instead of trying to hack into the mind of God, Buddhists are trying to hack into their own mind to harness it under control.

But it has only been in recent times that neuroscientists have been able to peer directly into the brain to see what's going on. The advent of fMRIs and other brain scanning techniques have largely paved the way.

For example, neuroscientists observing MRI scans have learned that meditation strengthens the brain by reinforcing the connections between brain cells. A 2012 study showed that people who meditate exhibit higher levels of gyrification - the "folding" of the cerebral cortex as a result of growth, which in turn may allow the brain to process information faster. Though the research did not prove this directly, scientists suspect that gyrification is responsible for making the brain better at processing information, making decisions, forming memories, and improving attention.

Indeed, as much of the research is showing, meditation causes the brain to undergo physical changes, many of which are beneficial. Other studies, for example, have shown that meditation is linked to cortical thickness, which can result in decreased sensitivity to pain.

Or take the 2009 study with the descriptive title, "Long-term meditation is associated with increased gray matter density in the brain stem." Neuroscientists used MRIs to compare the brains of meditators with non-meditators. The structural differences observed led the scientists to speculate that certain benefits, like improved cognitive, emotional, and immune responses, can be tied to this growth and its positive effects on breathing and heart rate (cardiorespiratory control).

The integrity of gray matter, which is a major player in the central nervous system, certainly appears to benefit. Meditation has been linked to larger hippocampal and frontal volumes of gray matter, resulting in more positive emotions, the retention of emotional stability, and more mindful behavior (heightened focus during day-to-day living). Meditation has also been shown to have neuroprotective attributes; it can diminish age-related effects on gray matter and reduce cognitive decline.

A study from earlier this year showed that meditators have a different expression of brain metabolites than healthy non-meditators, specifically those metabolites linked to anxiety and depression.

But it's not just the physical and chemical components of the brain that's affected by meditation. Neuroscientists have documented the way it impacts on brain activity itself. For example, meditation has been associated with decreased activity in default mode network activity and connectivity - those undesirable brain functions responsible for lapses of attention and disorders such as anxiety, ADHD - and even the buildup of beta amyloid plaques in Alzheimer's disease.

And finally, meditation has been linked to dramatic changes in electrical brain activity, namely increased Theta and Alpha EEG activity, which is associated with wakeful and relaxed attention.

Health Benefits

While most of the studies listed above addressed the neuro-cognitive aspects of meditation, other studies have correlated meditation with many of the health benefits already described.

Perhaps the most significant benefit of meditation is its ability to improve attention. In 2010, researchers looked at participants who practiced focused attention meditation for about five hours each day over the course of three months (which is a lot!). After conducting concentration tests, the participants were shown to have an easier time sustaining voluntary attention. Which makes sense; if you can concentrate for extended periods of time during meditation, it should carry over to daily life. Focused attention is very much like a muscle, one that needs to be strengthened through exercise.

As an aside, five hours of meditation per day is a bit excessive. Other studies show that 20 minutes a day is all that's required to get beneficial results, like stress reduction.

Indeed, other research has shown that even a little bit of meditation can help. Studies indicate that, after 10 intensive days of meditation (pdf), people can experience significant improvements in mindfulness and contemplative thoughts, the alleviation of depressive symptoms, and boosts to working memory and sustained attention.

A not-so-surprising study from last year showed that meditation can significantly reduce stress after just eight weeks of training (pdf; more here). Participants who meditated, as compared to those who did not, performed better on stressful multitasking tests. This may have something to do with reduced levels of cortisol, which is a stress hormone. And interestingly, meditatingbefore a stressful situation may help reduce feelings of stress during the event.

For you creative types, open-monitoring (OM) meditation can promote idea generation. OM meditation is basically the polar opposite of focused attention meditation, requiring practitioners to non-reactively monitor the content of experience from moment to moment.

And lastly, meditation has also been shown to increase levels of empathy, but it has to come from a specific practice known as loving-kindness-compassion meditation. It's a kind of focused attention meditation, but the practitioner is asked to concentrate on feelings of love, compassion, and understanding. By comparing fMRI scans of novices to those of expert Buddhist monks (each with more than 10,000 hours of practice), researchers watched as emotional stimuli (sounds of people in distress) caused those areas of the brain linked to empathy light up; the monks exhibited greater degrees of empathetic response than the novices. In turn, the scientists speculate that compassion meditation can make a person more empathetic.

So what are you waiting for? Start sitting, and transform your brain!

Additional reporting by Joseph Bennington-Castro.