Scientists Are Finally Figuring Out Why We Dream—and the Brain Processes Responsible

Research on sleep recently won the Nobel Prize for Medicine. Pedro Simões/Flickr

The brain's dream factory has been identified, with scientists finding a so-called "hot zone" that can be used to predict if a person is dreaming and what they are dreaming about. The findings, published Monday in the journal Nature Neuroscience, challenge our understanding of conscious experiences during sleep, and could shed light on more fundamental questions, like why we dream at all.

Dreams—why we have them, what they are for—are not well understood. Many scientists believe they are related to information processing, potentially helping filter what we have been exposed to during waking hours and helping memories to form. Another idea is that they are randomly fired neurons that our brain tries to make sense of as we rest.

Sleep comes in four stages, with rapid eye movement, or REM, being the one scientists currently associate with dreaming. In this stage, the brain is highly active, almost to the point where brain scans appear to show a state of wakefulness. But a team of scientists led by Giulio Tononi of the University of Wisconsin–Madison, have now shown dreams can also take place in non-REM phases of sleep, challenging our current understanding of the neural mechanisms involved.

The team took electroencephalography recordings for 32 people who were asleep. After being woken up by the scientists at different times throughout the night, the participants were asked to report whether they had been dreaming and what they had been dreaming about. From this, the researchers looked for patterns of brain activity that corresponded with the provided answers.

Findings showed dreaming took place during both REM and non-REM sleep in an area at the back of the brain dubbed the posterior cortical hot zone. Heightened activity was linked with dreaming, while low-frequency activity was associated with an absence of dreams.

Next, the team looked at how neural activity changed in the hot zone during dreaming, and linked it with specific dreams. The team could eventually predict if the dream contained faces, speech and/or movement.

While far more research will be needed before we fully understand dreaming, researchers say they appear to have found one of the core regions of the brain involved.

"Electroencephalography permits us to study the cortex, which is the seat of higher brain functions. What we found is that the posterior 'hot zone' is the part of the cortex related to the dreaming experience and to some perceptual contents, such as seeing a face, speech perception and movement perception," Lampros Perogamvros, one of the first authors on the study, told Newsweek in an email interview.

He explained that under the cortex, there are various structures—including the hippocampus and amygdala, which are related to emotions and memory—that have not yet been studied in relation to dreaming. "Without studying the subcortex, too, we cannot be sure that the posterior hot zone is the only region related to dreaming, though it seems to be the one where consciousness rises in sleep," he said.