While undergoing MRI brain scans at the University of Pennsylvania, two dozen volunteers were asked to picture themselves in a variety of pleasant and not-so-pleasant scenarios.

Winning the lottery. Sitting on the beach on a sunny day. Watching their houses burn down.

Though imaginary, these ruminations yielded a very real response on the brain scans. When neuroscientists analyzed the details, they could identify specific regions that “lit up” when the volunteers used their imaginations. In effect, it was an electronic rendering of what helps makes us human: our ability to hope, plan, and dream.

The goal of the research was pure science. But the findings, published in the Journal of Neuroscience, also might have implications for mental health treatment and, someday, in the diagnosis of Alzheimer’s, the authors say.

The spark of imagination has captivated philosophers and artists for ages — what Shakespeare described as the mind giving form to “airy nothing.” But it has received relatively little attention from neuroscientists, despite the availability of MRI machines and other increasingly sophisticated tools to probe the workings of the brain, said Joseph Kable, a Penn psychology professor and senior author of the new study.

“We’ve made a lot of progress understanding what happens when we’re in the here and now,” he said. “We have focused less on what people spend a lot of time doing: thinking about things that aren’t in front of our faces.”

Still, there were clues. In previous research, when people were asked to close their eyes and simply let their minds wander, MRI scans revealed activity in a patchwork of regions that has been dubbed the “default mode network.” Far from being a waste of time, these mental ramblings were thought to play a role in planning and problem-solving.

Subsequent studies suggested that this network was really two distinct sets of brain regions that become activated independently of one another. One of them includes parts of the cortex. The other includes the hippocampus — a central, tube-shaped region that plays a key role in memory — and an area near the top rear of the brain called the precuneus.

Working with graduate students Arthur Lee and Trishala Parthasarathi, Kable set out to discover what each “subnetwork” was doing.

They came up with a list of 32 imaginary scenarios with varying degrees of vividness and pleasantness, breaking them into four groups: vivid-positive, vivid-negative, nonvivid-positive, and nonvivid-negative.

Volunteers were asked to rate the vividness and positivity of each scenario while undergoing a functional MRI, which identifies brain activity in various regions through indirect measurements of blood flow.

The subnetwork with the hippocampus became more active in response to vivid scenarios, and seems to be “constructive” — that is, the source of imagination, Kable said. The other subnetwork responded more to the emotional, positive-vs.-negative aspect of each imagined event.

The “vividness” network likely is central to a person’s ability to achieve goals, said Jessica Andrews-Hanna, a University of Arizona assistant professor of psychology. She was not involved with the Penn research, but said the findings echoed her own.

Andrews-Hanna has identified brain regions involved in picturing the granular details of an event, both in the past and future, and they largely overlap with the areas that Kable’s group associated with vividness. Strong activity in those regions, she said, is a sign of someone who knows how to get things done.

“When we set a goal that we want to achieve, we’re going to be much more likely to reach that goal if we can imagine the goal with a lot of imagery and a lot of detail in our minds, and picture ourselves reaching that goal, and imagine all of the obstacles and steps that are needed to ultimately reach that goal,” she said.

The emotion-centered, “evaluative” subnetwork, on the other hand, might be useful to measure in someone who has become mired in negative, repetitive thinking, she said. Unusual activity patterns in some of the same brain regions have previously been associated with depression.

With additional study, such MRIs might someday be useful in conjunction with mental health therapy, she said. And other research suggests that patterns in these “default” brain regions might be used to help diagnose Alzheimer’s.

In the meantime, now that he is able to measure these components of imagination, Kable wants to tackle all sorts of pure-science questions.

Among them: Does the vividness with which a person imagines an event depend on how soon it is expected to occur? That could help to explain a well known psychological phenomenon: that people tend to devalue a future reward relative to one that is close at hand.

“They’ll give up more money in the future in order to get less money today,” Kable said.

And might the MRIs reveal differences in imagination between the young and old? Between those in creative professions and those who are not?

Then there’s the age-old question of what sets humans apart from other animals.

Lots of animals engage in forms of planning and decision-making, but those behaviors often are the result of conditioning and reinforcement, not necessarily picturing possible outcomes, Kable said.

Then again, some of the brain regions that his team studied can be found in other primates. The differences between species might be a matter of degree or complexity.

In a way, the topic of Kable’s research is one of the qualities that led him to pursue it. What better way to describe the scientific method than as the art of asking questions, imagining possible answers, and devising ways to get closer to the truth?

Kable first heard about the use of MRI machines to study brain activity when studying chemistry as an undergraduate at Emory University, in the early 1990s, and it’s fair to say it captured his imagination. An adviser steered him away from pursuing the then-new technique, suggesting it was not yet ready for prime time.

But the promise of unlocking the brain’s secrets stuck with him, and he went on to earn a Ph.D. in neuroscience at Penn, later earning an appointment to the faculty. And, as he once imagined, MRI machines are now among the tools of his trade.