Vivid Dreams May 'Drain' the Brain's Energy, Scientists Discover

Researchers at Tohoku University in Japan have uncovered an unusual feature of brain activity during rapid eye movement (REM) sleep—the stage in which most dreams occur. The findings were published in the journal Communications Biology.

During REM sleep, the brain remains almost as active as it is during wakefulness. By monitoring the brains of mice during natural sleep, the researchers found that blood flow increases dramatically about 50 seconds before REM sleep begins, boosting the delivery of oxygen and nutrients to the brain.

At the same time, however, the scientists observed an unexpected phenomenon: levels of adenosine triphosphate (ATP)—the primary molecule that supplies energy to cells—declined in neurons.

According to the researchers, this suggests that during vivid dreaming, the brain may consume energy so rapidly that it cannot replenish its ATP stores quickly enough.

The team believes these increased energy demands are linked to processes involved in memory formation and consolidation, as well as the reorganization of connections between neurons that takes place during sleep.

The authors say the findings provide new insight into how the brain allocates its limited energy resources. Unlike computers, the brain operates with a finite energy supply and is able to flexibly direct energy to the areas where it is needed most.

The researchers hope their findings will improve understanding of the role of sleep in brain function and may help explain why people sometimes wake up feeling tired after experiencing particularly vivid dreams.

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