A team led by neuroscientist Dr. Perrine Ruby, a research fellow at the Lyon Neuroscience Research Center in France, studied the brain activity of those with high dream recall to those that normally do not remember their dreams in order to understand the differences between them.
In a study published in the journal Neuropsychopharmacology, the researchers discovered that the temporo-parietal junction, an information-processing hub in the brain, is more active in high dream recallers. Increased activity in this brain region, it is thought, might facilitate attention orienting toward external stimuli and promote intrasleep wakefulness, thereby facilitating the encoding of dreams in memory.
The reason for dreaming is still a mystery for the researchers who study the difference between “high dream recallers,” who recall dreams regularly, and “low dream recallers,” who recall dreams rarely.
Prior research has lead researchers to believe that “high dream recallers” have twice as many times 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 memorization of dreams during brief periods of wakefulness.
In this new study, the research team sought to identify which areas of the brain differentiate high and low dream recallers.
Investigators 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.
“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,” said Ruby.
“Indeed, the sleeping brain is not capable of memorizing new information; it needs to awaken to be able to do that.”
The South African neuropsychologist Dr. Mark Solms had observed in earlier studies that lesions in these two brain areas led to a cessation of dream recall.
The French team was able to show brain activity differences between high and low dream recallers during sleep and also during wakefulness.
“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,” concluded the research team.