How Jaws Grabbed You

Being 'swept away' by a book involves different brain areas

MONDAY, May 21, 2001 (HealthDayNews) -- Read a good mystery, and you're hooked. The main character is pursued by street thugs, but it's your pulse that's racing and your heart that's pounding.

Researchers think they understand why: Whether you're imagining yourself or another person in a situation, you're using the part of your brain usually devoted to planning action. When you imagine action, your brain is planning to make a move, says a new study.

And if you're imagining yourself in the situation, you go a step further. You engage the part of the brain that communicates with your muscles when you act in real life. When deeply engaged in your imagination, you stop just short of physically moving. In contrast, when you imagine another person acting, you stop before you reach this stage, drawing a line between yourself and another, say the researchers.

"We have discovered the brain areas that are involved when we think about our own actions and intentions and those of others. Therefore, our study represents a first stage in understanding several dysfunctions of the mind that are due to brain disorders, for example, in psychiatric patients who can confuse the self and the other," " says Jean Decety, one of the study's authors and director of research at INSERM Unite 280 in Lyon, France.

The study involved 10 young men who knew Decety personally. The men were asked to imagine specific situations, like brushing their teeth or stapling papers. They then were asked to imagine Decety performing the same actions. While the men imagined the different scenes, researchers measured blood flow in the brain, using positron emission tomography (PET) scanning techniques.

Both imagining themselves and others performing an action produced activity in the premotor cortex in the frontal lobe, which is behind the forehead, Decety says.

"Anytime you make an action, your premotor cortex is activated to plan the action; that is, to send signals to the relevant muscles," Decety says. Thus, as you imagine yourself and others taking actions, you are planning to take such actions, he says.

But imagining just yourself stapling a paper, you enter a deeper layer of imagination. Blood flows more rapidly to the somatosensory cortex, at the back of the brain, Decety says. This brain area normally is engaged when you're really moving, receiving information from the skin, muscles and joints. Your imagination, then, stops just short of actually acting, Decety says.

"To find activation in this very region only during first-person simulation is an argument to say that this simulation process involves nearly all processing stages of a real action. The first-person simulation goes to deep level of movement processing," Decety says. In addition, he says the left parietal cortex in the back of the brain also is engaged, just as if you were initiating action.

These areas do not show increased blood flow when you're imagining someone else executing an action, Decety says. Instead, heightened activity stimulates the right parietal cortex which usually is involved in distinguishing your sense of self through body awareness.

Andy Straka, author of a new detective series starring private investigator and falconer Frank Pavlicek, says he certainly isn't thinking of how his readers' brains are engaged when he writes his novels. Rather, he says he writes about his characters by imagining himself in their shoes, probably bringing his brain to that deeper level of imagination Decety describes.

"I intensely imagine myself in that situation," Straka says.

And he says he's conscious that readers are most interested in a character when they imagine themselves as the character.

"When someone's really involved in a novel, oftentimes it's because they really, intensely identify with a character or main character. They're in that person's shoes," Straka says.

Decety says his research could be most helpful to those studying schizophrenics who describe a distorted sense of themselves and those around them. He cites another study in which schizophrenic patients using a joystick had PET scans showing increased activity in brain areas that correspond to imagining another person acting.

What To Do

For more about PET scans, try the Howard Hughes Medical Institute. And for a detailed map of the brain, try the Head Injury Hotline. Also, you can read more about Straka and his novels here.

For more stories on schizophrenia, including several detailing early signs of the condition, try HealthDay.

SOURCES: Interviews with Jean Decety, Ph.D., director of research at INSERM Unite 280 in Lyon, France; Andy Straka, author of A Witness Above; May 2001 Nature Neuroscience
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