Why do we dream?
Sleep cycles through stages; in REM the brain replays, recombines, and consolidates the day, and the experience of that activity is the dream.
Most dreaming happens in REM
Sleep isn’t one thing. The brain cycles through quiet, restorative deep sleep and wildly active rapid-eye-movement (REM) sleep about every 90 minutes.
During REM, parts of the brain that handle vision and emotion light up while the parts that judge plausibility quiet down, which is why dreams feel vivid and strange.
Why bother dreaming at all?
the day floods the brain with raw inputsmemories sit unsortedbecause encoding happens fast, organising is slow
REM replays and recombines thempatterns get stitched togetherbecause the hippocampus and cortex talk in long, slow waves
we wake with consolidated learningand a half-remembered narrativebecause the experience of all that activity is the dream
What thinkers have said
“Dreams are the royal road to a knowledge of the unconscious activities of the mind.”
- Sigmund Freud The Interpretation of Dreams, 1900, a metaphor more than a measurement.
Modern neuroscience is more cautious: dreams may be partly meaningful, partly random, a side-effect of the brain doing housework while we’re offline.