My memories from that week are a jumble of misfiled pieces. But at the end of the second week, I had a dream that remains crisp and vivid in my mind.

I sat up in bed and saw my father across the room. His figure was full and healthy and framed by the yellow light that glowed in the stairwell outside my door. He was grinning, green eyes on me, and listening to sounds from the dining room below, the clinking of plates and the voices of my extended family laughing and sharing memories of him. He raised his dark eyebrows and laughed with them.

"Back to life" or "visitation" dreams, as they are known among dream specialists and psychologists, are vivid and memorable dreams of the dead. They are a particularly potent form of what Carl Jung called "big dreams," the emotionally vibrant ones we remember for the rest of our lives.

Big dreams are once again on the minds of psychologists as part of a larger trend toward studying dreams as meaningful representations of our concerns and emotions. "Big dreams are transformative," Roger Knudson, director of the Ph.D. program in clinical psychology at Miami University of Ohio, said in a telephone interview. The dreaming imagination does not just harvest images from remembered experience, he said. It has a "poetic creativity" that connects the dots and "deforms the given," turning scattered memories and emotions into vivid, experiential vignettes that can help us to reflect on our lives.

Grief itself is transformative. It is a process of disassembly. The bereaved must let go of the selves they were, as well as the loved ones they have lost. The dreams we have while grieving are an important part of that process.

"Our dreams have to do with how we internalize the people we love," said Pamela McCarthy, director of counseling services at Smith College. "You learn to look within for the loved one and the particular function that person played in your life, such as caretaking or guidance in the case of a parent. This becomes part of a function that you can provide for yourself."

Cultural narratives in regions like Vietnam and North and South America assign special importance to such dreams and consider them actual encounters with the spirits of lost loved ones. "This notion is so widely shared by traditions all across the globe that some scholars have gone so far as to argue that religion itself actually originated in dream experience," Kelly Bulkeley, past president of the Association for the Study of Dreams, wrote in his book "Transforming Dreams: Learning Spiritual Lessons From the Dreams You Never Forget" (2000).

Current dream study has its epic narrative in the life and dreams of the pseudonymous Ed, a widower who recorded 22 years of dreams about Mary, his deceased wife. Ed made his journal available to G. William Domhoff, a psychology professor at the University of California, Santa Cruz, a leading dream theorist.

Domhoff and Adam Schneider, his research assistant, categorized the 143 dreams and cross-referenced them with Ed's waking reflections on his wife, their marriage and her death from ovarian cancer on June 15, 1980. In a path-breaking study in 2004, Domhoff asserted that Ed's dreams could not be the nonsensical noise of a restless brain stem.

They represented the currents of loss, love and confusion in Ed's waking life.

Ed and Mary's love began on a seaside boardwalk in 1947. They wed a year later, when Ed was 25 and Mary 22. In his more comforting dreams, Mary appears young and radiant as she did that day, with dark hair and bewitching eyes.

In Ed's dreams, his companionship with Mary and her withdrawal during an arduous illness are recurrent themes. Sometimes, his mind weaves these threads together to poignant effect, as when Ed finds himself standing across the street from where Mary sits in a car, unable to cross over.

Other times, they form jumbled, comic events. Ed and Mary are lost in a city. They see Jerry Seinfeld and ask him for directions. Soon, Ed realizes that Mary has left with Seinfeld. He broods behind a building and begins to sink in quicksand.

Almost 20 years after Mary's death, Ed dreams he is walking down a hall in their old apartment. It leads to Mary's hospital room, where she lies, gaunt and still. Her head, according to Ed's journal, is "hanging over the top edge of the bed." Her hair is sparse, as it was after chemotherapy. "I sit on the bed," he writes, "and cradle her in my arms."

Such composite images and sudden scene changes, Domhoff conceded, may be the brain's effort to make sense of random neuron fire. But they are more likely to be symbolic of Ed's emotional struggle.

Dreams, Domhoff wrote, are the "embodiment of thoughts" from our waking lives.

Dreams that occur during rapid eye movement, or REM, cycles are the most memorable and emotionally powerful, said John Antrobus, a retired professor of psychology and sleep research at the City College of New York who founded the sleep laboratory there in 1965. The dreams have power because brain activity during REM is most similar to that of a waking state.

In REM, the amygdala, the lima-bean-size gland at the base of the skull responsible for emotions, and the hippocampus, the tissue curled up under the temples that enables memory, are active. The two organs, along with areas in the frontal and prefrontal lobes near the forehead that enable attention and coordination, work simultaneously in producing dreams. "You have an image of a lost loved one, and along come all kinds of emotions you've tied up with them," Antrobus said. "Their image comes up, and all parts of the brain associated with the loss get activated, as well in REM sleep, because they're part of our survival system."

In a study last year, Antrobus and City College graduate students linked the body's circadian cycle and the singular level of brain activity in REM to the high emotionality of REM dreams.

Core body temperature rises gradually from its nadir in the middle of the night during slow-wave sleep, the least active brain state. As morning nears, subcortical brain activity tied to the circadian cycle increases. When these cycles coincide in the last and longest REM phase, the study found, the mind produces its most dramatic dreams.

"The brain is waking up," Antrobus said in an interview. "It starts waking up long before you are fully awake."

Dreams during this active period are more likely to be highly memorable, vivid, and experiential, what Antrobus calls "superdreams."

"That's what people talk about," he said. "That's what they're usually remembering. That's what these 'big dreams' are."

He added that the four or five phases of REM in a normal night's sleep might include similar dream content. Just as the image of a lost loved one stimulates parts of the brain associated with loss, the content of dreams early in the sleep cycle could set the tone for that night's dream experiences. Our memories upon waking, therefore, may be our recollection of a night's cumulative dream content. Apart from an effort to understand the physiology behind the content of dreams, what do we do with big dreams? If we ignore them, said Knudson of Miami University of Ohio, "we discount our most valuable resource in understanding ourselves."