Could Scientists Peek Into Your Dreams?
In small study, computer programs and brain MRIs identified visual images during sleep
The researchers chose to awaken the subjects in light sleep rather than in deeper "rapid eye movement" (REM) sleep solely to make the research easier to do. Kamitani said that because it takes at least an hour to reach first REM stage, it would be difficult to get sleep and dream data from multiple participants. "REM dreams may contain richer contents, so we are interested in decoding REM dreams in the future," he said.
Although this study doesn't help identify why people dream, it could potentially be useful in advancing understanding, Kamitani said. "I believe our method may provide a tool for investigating what is the function of dreaming."
As to why it is so hard to remember a dream minutes after waking up, Kamitani said he thinks it is because particular neurotransmitters or brain regions involved in memory are not active during sleep. But he hopes his research will help explain.
"During sleep and dreaming, part of the brain -- the higher visual cortex -- is working as if seeing images," he said. "Since the contents of a verbal report were predicted only from brain activity immediately before awakening -- zero to 15 seconds before -- [it may be that we] only remember contents related to brain activity [we experience] immediately before we wake up."
While one expert said the results are intriguing, he was cautious. "The results are interesting, but in view of previous disappointments relating brain activity to complex visual experience, one would like to see this replicated," said Dr. Irwin Feinberg, a professor emeritus at the University of California, Davis.
Feinberg emphasized that the research was not designed to determine a cause-and-effect relationship. "It's a correlation of brain activity and visual experience, largely statistical and purely by association," he said. "It does not shed light on the function of sleep or the function of dreaming within sleep."
But Feinberg said the researchers' focus on non-REM sleep is interesting and valuable. "Non-REM sleep constitutes 75 percent of our sleep; REM is only 25 percent. Nature knows what it needs, so the fact that non-REM occupies such a large percentage and occurs first suggest that it is of far greater importance than is REM."