Why do some people remember dreams while others don't?

A new study helps explain the difference between "high dream recallers," who can regularly remember their dreams, and "low dream recallers," who rarely recall dreams.

The research team, led by Perrine Ruby, Inserm researcher at the Lyon Neuroscience Research Center, wanted to look at different areas of the brain that created the distinction between these two groups. They used Positron Emission Tomography (PET) to measure the spontaneous brain activity of 41 volunteers while they were awake and asleep. Twenty-one participants were determined to be "high dream recallers" because they remembered 5.2 dreams a week on average, and 20 people were classified as "low dream recallers" because they reported remembering only two dreams per month on average.

Both during wakefulness and sleep, the high dream recallers showed stronger spontaneous brain activity in the medial prefrontal cortex (mPFC) and in the temporo-parietal junction (TPJ), which is related to paying attention to external stimuli. The results establish that "high dream recallers" wake up twice as much during sleep compared to "low dream recallers," and their brains react more to auditory stimuli while asleep and awake. Increased brain reactivity can cause someone to wake up more during the night; therefore, they can better remember their dreams during this time because, according to Ruby, the brain needs to be awake to memorize new information.

South African neuropsychologist Mark Solms, who was not involved in the study, observed in past studies that lesions in the two aforementioned areas of the brain could stop dream recall.

The researchers, whose work is published in the journal Cerebral Cortex, note it's possible that part of the difference may lie in the number of dreams actually produced.

"Our results suggest that high and low dream recallers differ in dream memorization, but do not exclude that they also differ in dream production. Indeed, it is possible that high dream recallers produce a larger amount of dreaming than low dream recallers," they concluded in a press release.