New Clues To How We Remember Dreams

This morning, I woke up with a very strong memory of staging a political coup in my sleep. Why I happened to remember my dream so vividly when I woke up, it’s hard to say, since we don’t fully understand the underlying cognitive science of dreams.
 We don’t know exactly how or when our brains produce dreams as we sleep, and we don’t know why some people remember their dreams all the time while others rarely remember them at all.

But according to a new study on the neurophysiology of sleeping, brain function differs significantly between those of us who remember our dreams more vividly than those who only faintly recall a dream once or twice a month. People who are better at remembering their dreams wake up more often during the night, and respond more strongly to the sound of their own name–both when they’re asleep and when they’re awake.

In a study from the Lyon Neuroscience Research Center in Lyon, France, researchers hauled in 36 healthy young subjects to sleep in a lab for a night hooked up to EEG sensors, wearing ear phones that occasionally played different auditory stimuli at rare intervals, including a recording of a male voice saying that person’s first name as well as an unfamiliar first name.

Half of the subjects were low recallers, meaning they only remember a dream once or twice a month, and half were high recallers, meaning they remember their dreams almost every day. First names were chosen as a stimulus because they are complex sounds that people seem to exhibit a large response to.

"In response to first names, the high and low recallers produced different waves," Perrine Ruby, the study’s lead author, told "The high recallers seem to be much more reactive to the environment. Low recallers seem to be much more resistant," she says. This high reactivity could be related to why the high recallers woke up more often during their sleep, a process that probably explains why they remember more in the morning. "There is a strong hypothesis that awakening during sleep facilitates [encoding a] dream in memory," she explains.

Ruby expected to see differences in the EEG between the high and low dream recallers when they heard their names while they were sleeping, but she was surprised to find the high recallers also had a greater spike in their brain’s electrical activity than low recallers when they were awake to hear their name. "We thought maybe if high recallers were dreaming much more, dreaming could interfere with the processing of external sounds, but during wakefulness we had no reasons to expect differences," she says.