Why can some people not dream

What distinguishes "dream rememberers"

"Tonight I dreamed that ..." Almost every morning, some people can report in detail which dream stories they lived through during the night. For many others, however, sleep usually seems uneventful - they can rarely remember a dream. French researchers have now investigated the question of how the brain function of these two types differs. They were able to show that certain brain regions that play an important role in attentiveness to external stimuli are particularly active in typical “dream memories”. This could lead to more frequent waking states during the course of sleep, in which the dreams are stored in the memory.

Whether we remember or not, everyone dreams during certain phases of sleep. But why do these two types of “good and bad dream rememberers” exist? The researchers around Perrine Ruby from the Neuroscientific Research Center in Lyon have been investigating this question for some time. At the beginning of last year they were able to show that good dream reminders wake up twice as often as bad ones during sleep. In addition, they react more intensely to auditory stimuli both during sleep and when they are awake. Presumably these factors lead to the increased short waking phases. In these barely noticeable sleep interruptions, the memories of the dreamed are then stamped into the memory, the researchers explain. In their current study, Ruby and her colleagues wanted to explore in detail the brain functions that distinguish good and bad dream memories.

To answer this question, they examined the brain activity of 41 study participants while they were awake and asleep. The researchers use so-called positron emission tomography (PET), an imaging process that can show biochemical and physiological functions in the form of cross-sectional images. The test subjects were assigned to the two dreamer categories through interviews: 21 good memories - they can remember an episode at night on an average of 5.2 days - and 20 bad memories, who only have a dream twice a month.

The peculiarity of the dreamer brains

The comparisons of the brain scans showed: In good dream rememberers, two areas of the brain were comparatively strongly active, both when awake and asleep: the medial prefrontal cortex and the temporoparietal junction. This result fits in well with the earlier study results of the researchers, because these areas of the brain are already known to play a role in the attention to external stimuli. If they are more active, they probably ensure that we react more strongly to external stimuli during sleep and that we wake up. According to the scientists, there are also reports that damage in these two brain regions means that people can no longer remember dreams well.

 

“Our results suggest that good and bad dream reminders differ in the frequency of imprinting phases during sleep,” the research team sums up. However, they emphasize that another factor could possibly come into play: Maybe the good rememberers actually dream more. However, further investigations will only be able to show whether this is the case.

Original work by the researchers:

© Wissenschaft.de - Martin Vieweg
17th February 2014