One Sunday morning in March, 19 years ago, as Dr. James Austin waited for a train in London, he glanced away from the tracks toward the river Thames. The American neurologist, who was spending a sabbatical year in England, saw nothing out of the ordinary: the grimy Underground station, a few dingy buildings, some pale gray sky. He was thinking, a bit absent-mindedly, about the Zen Buddhist retreat he was headed toward. And then, Austin suddenly felt a sense of enlightenment unlike anything he had ever experienced. His sense of individual existence, of separateness from the physical world around him, evaporated like morning mist in a bright dawn. He saw things "as they really are," he recalls. The sense of "I, me, mine" disappeared.

"Time was not present," he says. "I had a sense of eternity. My old yearnings, loathings, fear of death and insinuations of selfhood vanished. I had been graced by a comprehension of the ultimate nature of things."

Call it a mystical experience, a spiritual moment, even a religious epiphany, if you like — but Austin will not. Rather than interpret his instant of grace as proof of a reality beyond the comprehension of our senses, much less as proof of a deity, Austin took it as "proof of the existence of the brain." He isn't being smart-alecky. As a neurologist, he accepts that all we see, hear, feel and think is meditated or created by the brain. Austin's moment in the Underground therefore inspired him to explore the neurological underpinnings of spiritual and mystical experience. In order to feel that time, fear and self-consciousness have dissolved, he reasoned, certain brain circuits must be interrupted. Which ones? Activity in the amygdala, which monitors threats and registers fear, must be damped. Parietal-lobe circuits, which orient you in space and mark the sharp distinction between self and world, must go quiet. Frontal- and temporal-lobe circuits, which mark time and generate self-awareness, must disengage. When it happens, wrote Austin in a recent paper, "what we think of as our 'higher' functions of selfhood appear briefly to 'drop out', 'dissolve', or be 'deleted from consciousness'." When he spun out his theories in 1998, in "Zen and the Brain", it was published not by some flaky New Age outfit but by MIT Press.

Since then, more and more scientists have flocked to "neurotheology", the study of the neurobiology of religion and spirituality. Last year the American Psychological Association published "Varieties of Anomalous Experiences", covering enigmas from near-death experiences to mystical ones. At Columbia University's new Center for the Study of Science and Religion, one program investigates how spiritual experiences reflect "peculiarly recurrent events in human brains". In December, the scholarly Journal of Consciousness Studies devoted its issue to religious moments ranging from "Christic visions" to "shamanic states of consciousness". This month the book "Religion in Mind," tackling subjects such as how religious practices act back on the brain to inspire optimism and even creativity, reaches stores.

What all the new research shares is a passion for uncovering the neurological underpinnings of spiritual and mystical experiences — for discovering, in short, what happens in our brains when we sense that we "have encountered a reality different from — and, in some crucial sense, higher than — the reality of everyday experience," as psychologist David Wulff of Wheaton College in Massachusetts puts it. In neurotheology, psychologists and neurologists try to pinpoint which regions turn on, and which turn off, during experiences that seem to exist outside time and space. Spiritual experiences are so consistent across cultures, across time and across faiths, says Wulff, that it "suggest［s］ a common core that is likely a reflection of structures and processes in the human brain."

In "Why God Won't Go Away", published in April, Dr. Andrew Newberg of the University of Pennsylvania and his late collaborator, Eugene d'Aquili, use brain-imaging technology to identify what seems to be the brain's spirituality circuit. Newberg had a colleague at Penn, Dr. Michael J. Baime, a practitioner of Tibetan Buddhist meditation; sit on the floor of a small darkened room. A string of twine lay beside him. Concentrating on a mental image, he focused, quieting his conscious mind (he told the scientists afterward) until something he identifies as his true inner-self emerged. When he reached the "peak" of spiritual intensity, he tugged on the twine. Newberg, huddled outside the room, quickly injected a radioactive tracer into an IV line that ran into Baime's left arm. After a few moments, he whisked Baime off to a SPECT (single photon emission computed tomography) machine. By detecting the tracer, it tracks blood flow in the brain. Blood flow correlates with neuronal activity.

The SPECT images are as close as scientists have come to snapping a photo of a transcendent experience. As expected, the prefrontal cortex, seat of attention, lit up: Baime, after all, was focusing deeply. But it was a quieting of activity that stood out. A bundle of neurons in the superior parietal lobe, toward the top and back of the brain, had gone dark. This region, nicknamed the "orientation association area", processes information about space and time, and the orientation of the body in space. It determines where the body ends and the rest of the world begins. Specifically, the left orientation area creates the sensation of a physically delimited body; the right orientation area creates the sense of the physical space in which the body exists.

The orientation area requires sensory input to do its calculus. "If you block sensory inputs to this region, as you do during the intense concentration of meditation, you prevent the brain from forming the distinction between self and not-self," says Newberg. With no information from the senses arriving, the left orientation area cannot find any boundary between the self and the world. The brain seems to have no choice but "to perceive the self as endless and intimately interwoven with everyone and everything," Newberg and d'Aquili write in "Why God Won't Go Away". The right orientation area, equally bereft of sensory data, defaults to a feeling of infinite space.

That a religious experience is reflected in brain activity is not too surprising, actually. Everything we experience — from the sound of thunder to the sight of a poodle — leaves a trace on the brain. Just because an experience has a neural correlate does not mean that the experience exists "only" in the brain, or that it is a figment of brain activity with no independent reality. Think of what happens when you dig into an apple pie. The brain's olfactory region registers the aroma of the cinnamon and fruit. The somatosensory cortex processes the feel of the flaky crust on the tongue and lips. The visual cortex registers the image of the pie. Remembrances of pies past (Grandma's kitchen, the corner bake shop ...) activate association cortices. A neuroscientist with too much time on his hands could undoubtedly produce a PET scan of "your brain on apple pie". But that does not negate the reality of the pie. Says Newberg: "There is no way to determine whether the neurological changes associated with spiritual experience mean that the brain is causing those experiences ... or is instead perceiving a spiritual reality". In other words, seeing what the brain does during a religious experience does not necessarily tell us anything about religion — specifically, whether or not God exists.

In fact, some of the same brain regions involved in the pie experience create religious experiences, too. When the image of a cross, or a Torah crowned in silver, triggers a sense of religious awe, it is because the brain's visual-association area, which interprets what the eyes see and connects images to emotions and memories, has learned to link those images to that feeling. Visions that arise during prayer or ritual are also generated in the association area: electrical stimulation of the temporal lobes (which nestle along the sides of the head and house the circuits responsible for language, conceptual thinking and associations) produces visions.

Temporal-lobe epilepsy — abnormal bursts of electrical activity in these regions — takes this to extremes. Although some studies have cast doubt on the connection between temporal-lobe epilepsy and religiosity, others find that the conditions seems to trigger vivid, Joan of Arc-type religious visions and voices. In his recent book "Lying Awake", novelist Mark Salzman conjures up the story of a cloistered nun who, after years of being unable to truly feel the presence of God, begins having visions. The cause is temporal-lobe epilepsy. Sister John of the Cross must wrestle with whether to have surgery, which would probably cure her — but would also end her visions. Dostoevsky, Saint Paul, Saint Teresa of Avila, Proust and others are thought to have had temporal-lobe epilepsy, leaving them obsessed with matters of the spirit.

The somewhat common experience of hearing the voice of God may also have to do with electrical activity in the temporal lobes. It seems to arise when you misattribute inner speech (the "little voice" in your head that you know you generate yourself) to something outside yourself. During such experiences, the brain's Broca's area (responsible for speech production) switches on. Most of us can tell this is our inner voice speaking. But when sensory information is restricted, as happens during meditation or prayer, people are "more likely to misattribute internally generated thoughts to an external source", suggests psychologist Richard Bentall of the University of Manchester in England in the book "Varieties of Anomalous Experience".

Are spiritual experiences within the reach of anyone? Neurologists, for all their powerful new imaging toys, are still clueless on this question. In numerous surveys since the 1960s, 30 or 40 percent of respondents say they have, at least once or twice, felt "very close to a powerful, spiritual force that seemed to lift you out of yourself." Gallup polls in the 1990s found that 53 percent of American adults said they had had "a moment of sudden religious awakening or insight". Psychologists believe that those people most open to mystical experience tend also to be open to new experiences generally. They are usually creative and innovative, with a breadth of interests and tolerance for ambiguity. Since "we all have the brain circuits that mediate spiritual experiences, probably most people have the capacity for having such experiences", says Wulff. "But it's possible to foreclose that possibility. If you are rational, controlled, not prone to fantasy, you will probably resist the experience."

Brain-imaging studies have helped explain how nonspiritual people can be moved by religious ceremonies and liturgy. Drumming, dancing, incantations — all rivet attention on a single, intense source of sensory stimulation, and at the same time evoke powerful emotional responses. This combination sends the brain's arousal system into hyperdrive, much as intense fear does, causing one of the brain structures responsible for maintaining equilibrium — the hippocampus — to put on the brakes. It inhibits the flow of signals between neurons, like a traffic cop preventing any more cars from entering the on-ramp to a tied-up highway. The result is that certain regions of the brain — including the one that goes quiet during meditation and prayer — are deprived of neuronal input.

Neurotheology may wind up having its biggest impact on our thinking about consciousness, arguably the biggest mystery of neuroscience. "In mystical experiences, the content of the mind fades, sensory awareness drops out, so you are left only with pure consciousness," says Robert K. Forman, a comparative-religion scholar at Hunter College in New York.

— Newsweek, May 14, 2001