Why That Thriller Is Actually Good for You
PHOTO: Scientists reveal how reading books can improve your brain.

It's amazing you can read these words.

It took millions of years for humans, and our recent ancestors, to develop the visual and motor and auditory skills that let us function in the complex world we inhabit today. But in less than 5,000 years, a brief span in human history, we learned how to read.

And that skill, or at least our understanding of it, is still evolving.

Scientists are using some of their most sophisticated tools to peer inside the human brain to see what happens when we engage in the process of reading, and they are finding a number of surprises:

-- Reading is a very complex task that requires several different regions of the brain to work together.

-- But surprisingly, we don't use the same neural circuits to read as we grow from infants to adults. So our brains are constantly changing throughout our lives.

-- It appears possible that reading can improve the "connectivity" between the various brain circuits that are essential to understanding the written word.

-- And there is recent evidence that simply reading a good novel can keep that enhanced "connectivity" working for days, and possibly longer, after we have finished the book.

Reading is not just one of the talents we were born with, like seeing and hearing. It is a "recent cultural invention," as one researcher put it. Just a few thousand years ago, some creative human probably carved the first symbol in the wall of a cave, launching his followers on a rich, new adventure -- reading.

But not much evolutionary time has passed between that caveman's attempts to leave a message for someone else and today.

So it seems likely that we are retraining old tools, like sight, for a new purpose, like reading. Only in the last couple of decades have scientists been able to start unraveling that story, and there is still much that is unknown.

One of their main tools is functional magnetic resonance imaging (fMRI,) a scanner that allows them to see what is going on in the brains of human subjects without having to cut their skulls open.

Blood rushes to the parts of the brain that are active, thus telling researchers which areas are responsible for different functions, like dreaming, and reading, and thinking about making love.

Neuroscientists at Emory University in Atlanta have determined that just reading a gripping novel makes changes in the way the brain connects with different circuits, and most importantly, those changes last for at least five days. They may not be permanent, but that at least suggests that the rewards from reading last longer than the act itself.

Emory's Gregory Berns and his colleagues put 21 students (12 females and nine males) through an fMRI for about 30 minutes a day for 19 days to collect their data. During the experiment the participants read the 2003 novel, "Pompeii," by Robert Harris, based on the destruction of that city by the eruption of Mount Vesuvius.

The students were scanned for five days before reading the book, and five days after they had finished. During the intermittent nine days they read one chapter each evening before the scanning the following morning.

The scanner revealed a sharp spike in two neural networks after the first chapter, and that continued throughout the rest of the experiment, including the five days after the reading was over.

"Even though the participants were not actually reading the novel while they were in the scanner, they retained this heightened connectivity," Berns said in releasing the study.

The effect lasted, but the experiment left more questions than answers.

"It remains an open question for further study as to how lasting these effects are," the study concludes.

The study underscores the difficulty of conducting brain research among healthy subjects when it's impossible to control every aspect of their lives.

They obviously read the book, because they passed a quiz each day before being rolled into the scanner, but what else did they do? Were they still thinking about the book while in the scanner, although they were supposed to be at a "resting state" in which they are mentally unengaged? And it is known now that the human brain is never really "at rest." It remains an active processor, even in our sleep.

The fact that the participants' neural circuits were active while they were reading is not surprising, because some circuits light up whenever we do anything. But the effect lasted beyond the book, and that has intrigued other scientists who must now duplicate, and expand, the findings for them to remain viable.

There is some support for the Emory scientists from unrelated research projects. Researchers at Carnegie Mellon University, for example, found that children who had trouble reading gained a major benefit during a six-month effort to raise their reading skills.

The children improved their ability to read, but they also increased the neural connectivity within a key network. That research showed that behavioral training -- reading, in this case -- can actually "enhance brain function," Thomas R. Insel, director of the National Institute of Mental Health, which supported the work, said in announcing the findings in 2009.

Interestingly, those improved circuits may not be the same circuits the children will use as they grow older.

Scientists at the Washington University School of Medicine in St. Louis found that even the seemingly simple act of reading involves 17 regions of the brain, but not all at the same time. They studied 30 persons ranging in age from seven to 35 and found that some regions actually grew less active with age, so even the physical activity in the human brain is not constant.

And that reinforces something our mothers tried to teach us: Start early. Read often. Give your brain a little help.

More ABC News