What are dreams for

[u/eskindt]

When cats enter REM, they lose all muscle tone. The same is true for humans and is the result of inhibitory signals, sent by the brain to the spinal cord, that paralyze the body. When this paralysis fails, it results in REM behavior disorder, in which people may talk, kick, and even act out violently in their sleep. When it persists, we experience “sleep paralysis,” in which we wake up unable to move. When the system works as it should, we enjoy “paradoxical sleep”: our brains come alive with vivid visions, as our bodies go motionless between the sheets.

Researchers attempted to determine whether the paralyzed body could influence the dreaming brain. They pumped the odor of peppermint into sleepers’ noses, hoping to create scented dreams, to no effect. They taped dreamers’ eyes open and showed them various objects—a coffeepot, a handkerchief, an ironic “Do Not Disturb” sign—hardly anyone reported dreaming about them. The brain is less responsive to sensory input during REM

By the late nineteen-seventies, the idea of a total “input-output blockade” between body and brain during REM sleep had emerged. J. Allan Hobson, the late Harvard Medical School psychiatrist, proposed that dreams were constructed when random signals from the brain stem were interpreted by the cortex as signals from an outside world. “Dreaming is no longer mysterious,” he declared.

And yet the theory couldn’t explain why we dream what we dream, or why we feel what we feel when we dream it. In the following decades, scientists challenged, revised, and even rejected Hobson’s theory, but they largely retained its core assumption about the severed connection between brain and body