Some people seem to remember their dreams every night, whereas others rarely remember any dreams. What accounts for these differences?
A recent study by a group of French neuroscientists provides a potential explanation. The researchers recruited subjects who remembered their dreams either often or rarely, and compared the brain activity of these two groups during sleep and during wakefulness.
Two brain areas were more active in high dream recallers during rapid eye movement (REM) sleep, when our most vivid and memorable dreams occur: the temporoparietal junction (where the temporal and parietal lobes meet, as the name suggests) and the medial prefrontal cortex in the frontal lobes.
So what does it mean that there was greater activity in these areas? The study authors offered some possible interpretations. One possibility is that these brain differences reflect something meaningful about the dreams themselves. In particular, they might indicate that people who often remember their dreams tend to have more exciting dreams.
Another explanation the authors propose is that individuals who remember their dreams more often are more likely to awaken during the night, allowing them to encode their dreams into memory (since memory generally is “turned off” during sleep).
Of course, these two explanations aren’t mutually exclusive. It could be that more interesting dreams are more likely to awaken a person, making their dreams doubly likely to be recalled the next day.
Incidentally, these two explanations are consistent with why REM dreams are more likely to be remembered than are dreams during non-REM deep sleep. Although we can dream in any sleep stage, our REM dreams tend to be the most gripping, and we’re also more likely to awaken briefly after a REM stage than after a stage of deep sleep, making it more likely that we’ll remember the dream.
So for people who wish they had more exciting dreams, perhaps better sleep is a nice consolation prize!
Reference: J.-B. Eichenlaub et al. (in press). Resting brain activity varies with dream recall frequency between subjects. Neuropsychopharmacology.