Everyone does dream. Even people who claim they never dream or haven’t dreamed in years exhibit dream-like brain activity while asleep, according to research. However, as one Discover blog points out, “Maybe they are just behaving as if they are dreaming, but without any conscious content.” Which begs the question, what constitutes a dream? Do you “see” and “hear” things in order for it to be called a dream?
Researchers have now discovered how we store dreams – and why some people can never remember them the morning after.
The French research team have stated that they have identified two types of different dreamers – and only one can remember them after they take place. They discovered a region in the brain responsible for remembering dreams, allowing them to be encoded in our memory while we sleep.
Researchers used Positron Emission Tomography (PET) to measure the spontaneous brain activity of 41 volunteers during wakefulness and sleep. The volunteers were classified into 2 groups: 21 ‘high dream recallers’ who recalled dreams 5.2 mornings per week in average, and 20 ‘low dream recallers,’ who reported 2 dreams per month in average. High dream recallers, both while awake and while asleep, showed stronger spontaneous brain activity in the medial prefrontal cortex (mPFC) and in the temporo-parietal junction (TPJ), an area of the brain involved in attention orienting toward external stimuli. The team were puzzled by the fact some people recall a dream every morning, whereas others rarely recall one.
“It’s really not about remembering,” Robert Stickgold, an associate professor of medicine at Harvard Medical School and director of the Center for Sleep and Cognition at Beth Israel Deaconess Medical Center, Harvard Medical School. “It’s about waking at the right time.”
According to Stickgold, it’s easiest to remember your dream if you wake up during the end of a sleep cycle and do so “slowly and with little movement.” Most often, you awaken during the REM stage, the sleep cycle in which we dream. It makes sense: waking up calmly and slowly right after you have a dream may make it easier to remember said dream. Of course, alarm clocks, early rising pets, and outside stimuli don’t always make it easy to awake gently.
The team led by Perrine Ruby, an Inserm Research Fellow at the Lyon Neuroscience Research Center studied the brain activity of these two types of dreamers in order to understand the differences between them. The researchers soon discovered that they believe the temporo-parietal junction, an information-processing hub in the brain, is more active in high dream recallers. Increased activity in this brain region might facilitate the encoding of dreams in memory.
In another study published in the journal Neuropsychopharmacology, the team of researchers found ‘high dream recallers’ have twice as many time of wakefulness during sleep as ‘low dream recallers’ and their brains are more reactive to auditory stimuli during sleep and wakefulness. This increased brain reactivity may promote awakenings during the night, and may thus facilitate memorisation of dreams during brief periods of wakefulness.
‘This may explain why high dream recallers are more reactive to environmental stimuli, awaken more during sleep, and thus better encode dreams in memory than low dream recallers. Indeed the sleeping brain is not capable of memorising new information; it needs to awaken to be able to do that,’ said Perrine Ruby, the researcher who led the study.
The South African neuropsychologist Mark Solms had observed in earlier studies that lesions in these two brain areas led to a cessation of dream recall. The originality of the French team’s results is to show brain activity differences between high and low dream recallers during sleep and also during wakefulness.
The team found those who slept badly were more likely to remember their dreams ‘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’ concludes the research team.
In this new study, the research team sought to identify which areas of the brain differentiate high and low dream recallers. High dream recallers, both while awake and while asleep, showed stronger spontaneous brain activity in the medial prefrontal cortex (mPFC) and in the temporo-parietal junction (TPJ), an area of the brain involved in attention orienting toward external stimuli.