In a quiet laboratory, Andrew Newberg takes photographs of what believers call the presence of God.
The young neurologist invites Buddhists and Franciscan nuns to meditate and pray in a secluded room. Then, at the peak of their devotions, he injects a tracer that travels to the brain and can reveal its activity at the moment of transcendence.
A pattern has emerged from Newberg's experiments. There is a small region near the back of the brain that constantly calculates a person's spatial orientation, the sense of where one's body ends and the world begins. During intense prayer or meditation, and for reasons that remain utterly mysterious, this region becomes a quiet oasis of inactivity - a fact that could explain the borderless spiritual communion felt by the faithful for millenia.
''It creates a blurring of the self-other relationship,'' said Newberg, an assistant professor at the University of Pennsylvania whose work appears in the April 10 issue of Psychiatry Research: Neuroimaging. ''If they go far enough, they have a complete dissolving of the self, a sense of union, a sense of infinite spacelessness.''
Newberg and other scientists are finding that man's diverse array of devotional traditions has a powerful biological reality. During intense meditation and prayer, the brain and body both experience signature changes, as yet poorly understood, that could yield insights into the religious experience and, one day, even provide clues to living more healthy, more fulfilling lives.
Already, scientists say, the young field has provided evidence that these meditative states - which rely on shutting down the senses and repeating words, phrases, or movements - are a natural part of the brain; that humans are, in some sense, inherently spiritual beings.
''Prayer is the modern brain's means by which we can connect to more powerful ancestral states of consciousness,'' said Gregg Jacobs, an assistant professor of psychiatry at Harvard Medical School who has published several studies of the way brain waves change during meditation.
With meditative states, people seem to turn off what Gregg called ''the internal chatter'' of the higher, conscious brain.
During meditation, increases have been observed in the activity of the ''theta'' brain wave, a type that moves slowly and is known to inhibit other activity in the brain. Based on a preliminary analysis of recent data, Gregg said, he has observed inhibitory theta activity coming from the same region of the brain, called the parietal lobe, that unveils the becalmed oasis during prayer. Eventually, researchers hope that they can identify a common biological core in the world's many varieties of worship.
As scientists increasingly bring sophisticated technologies to the study of religion, though, many caution that these first glimpses of mysterious territory should not be over-interpreted.
''Whatever we can learn about these states is going to be a great advantage to us,'' said Lawrence E. Sullivan, the director of the Harvard University Center for the Study of World Religions. But there is the danger ''that our technologies and our conclusions won't be equal to the richness and complexity of religion.''
Even prayer itself is spectacular in its diversity, said Sullivan, citing the Taoist tradition of deep meditation in which the practitioners re-imagine their own birth, and the chanting, dancing ritual of a people who live near Venezuela's Orinoco River in which teenagers achieve an ecstatic trance-like state and then metaphorically die.
In the last century, researchers have been rediscovering the power of the brain to affect the body. By the 1970s, some scientists had begun to look seriously for therapeutic value in religion. Herbert Benson, president of the Mind/Body Medical Institute, affiliated with Harvard University, coined the term ''relaxation response'' to describe the healthful physiological changes in those who followed Eastern meditative practices.
Recently, scientists have begun to consider similarly intense Western prayer practices as well. And last year, the National Institutes of Health said it was sponsoring a clinical trial at Johns Hopkins University to study the effects of lengthy group prayer sessions among African-American women with breast cancer - the first such study ever.
One of the most striking findings came in 1997, when a team of researchers from the University of California at San Diego found what they called the ''God module'' in the brain. They studied patients who suffer from a form of epilepsy that affects the brain's temporal lobe. These patients experience deep religious feelings during the attacks and remain fascinated by mystical questions after the attacks.
The researchers, headed by Vilayanur Ramachandran, said the seizures were strengthening a portion of the brain that responds to religious words, implying that religious feeling is a part of the brain's architecture.
Pennsylvania's Newberg, who is the author of a book out this month called ''Why God Won't Go Away,'' said the mystery of religious experience was inherently difficult to solve in the lab, especially with a noisy brain scanner clanging away. His strategy has been to use a technique called SPECT, which relies on a tracer that fixes on the brain's pattern of activity when it is injected, but can be observed later, under a scanner.
Nobody yet knows why the brain has this ability to reach other kinds of conscious states merely by turning inward, quieting down, focusing on a shimmering image, or repeating a sacred phrase.
Some will interpret the research as evidence that God is a product of the brain, while others will say it is evidence that the brain is a product of some higher power's hand - that, as Benson put it, ''perhaps God gave us the mechanism to understand and experience God in a certain way.''
Gareth Cook can be reached by e-mail at cook@globe.com