Some people seem to remember their dreams every night, while others rarely remember them at all. What accounts for the differences? A recent study by a group of French neuroscientists may provide an explanation.
The researchers recruited two groups of participants—those who remembered their dreams often and those who rarely remembered any dreams. Using a scanning technique called PET, they looked at the participants' brain activity while they were awake and during sleep.
In the high dream recallers, two brain areas were more active during rapid eye movement (REM) sleep, when our most vivid and memorable dreams occur—the temporoparietal junction (where the temporal and parietal lobes meet) and the medial prefrontal cortex in the frontal lobes.
So what does it mean that there was greater activity in these areas?
The authors offered some possible interpretations: Perhaps these brain differences reflect something about the dreams themselves. In particular, they might show that people who remember their dreams more often tend to have more exciting dreams. Another explanation the authors propose is that people who remember their dreams more often are more likely to wake up during the night, allowing them to encode their dreams into memory (since memory generally is “turned off” during sleep).
Of course, these explanations aren’t mutually exclusive. It could be that more interesting dreams are also more likely to awaken a person, making their dreams all the more likely to be recalled the next day.
These explanations are consistent with evidence that REM dreams are more likely to be remembered than are dreams during non-REM deep sleep. While we usually equate dreaming with REM sleep, we can actually dream in any sleep stage. But our REM dreams tend to be more vivid, bizarre, and gripping, while dreams during other sleep stages tend to be more mundane (like dreaming that you're sitting in the office filling out a form). We're more likely to remember REM dreams not only because they're weirder and more exciting but also because we’re more likely to wake up briefly after a REM stage than after a stage of deep sleep.
As for people who wish they had more exciting or memorable dreams, consider the consolation prize: Perhaps they're sleeping better.
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