When Brains Dream

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From The Wall Street Journal:

Sometime last August, five months into the pandemic lockdown, I had my first mask dream—I was in a crowded place and was the only person wearing a mask; it filled me with panic and I woke suddenly, scared out of my wits. Well into middle age, I still have nightmares that I’m back in college during finals week, and that there’s an entire course I forgot to attend.

Dreaming is a universal human experience; although there are some themes that run through them, dreams are also unique to the dreamer and can provoke calm, wonderment and fear. Animals have them, too, although we’re less certain about the content. About once a month, my wife and I find Madeleine, our 8-pound cairn terrier, doing battle with some unseen adversary as she whimpers and runs in her sleep; we wake her gently and comfort her because the whole thing seems so distressing to her. It sure seems as though she’s dreaming.

Antonio Zadra and Robert Stickgold, two of the world’s leading researchers in the science of sleep and dreams, have written a remarkable account of what we know and don’t know about this mysterious thing that happens during the night. The promise of “When Brains Dream” is to address four questions: “What are dreams? Where do they come from? What do they mean? And what are they for?” In a masterly narrative, the authors answer these and many more questions with solid scientific research and a flair for captivating storytelling.

Speaking of evolution across species, they note that “for it to have been maintained across half a billion years of evolution, sleep must serve functions critical to our survival.” One of those functions is cellular housekeeping. Sleep deprivation leads, for example, to impairments of insulin signaling; after being allowed only four hours of sleep for five nights, “otherwise healthy college students begin to look prediabetic.” Sleep also clears unwanted waste products from the brain, including ß-amyloid, which is a prime suspect in Alzheimer’s disease.

Attempts to understand and interpret dreams must be older than history—dreams and their meaning play parts in religious traditions from Tibetan Buddhism to the Old Testament, classical philosophy to Freud and Jung. To many, dreams are prophecies, implanted in our brains by God or angels; to others, they exist to encode our memories of the previous day, to others they are simply random neural firings. To still others, they are the products of fourth dimensional beings (such as the ones Clifford Pickover so eloquently describes in his book “Surfing Through Hyperspace”).

The weight of the evidence supports a more elaborate, nuanced and wondrous version of the memory-encoding hypothesis. Messrs. Zadra and Stickgold have designed a conceptual model they call Nextup (“Network Exploration to Understand Possibilities”), using it to describe the progression of dreams throughout the four sleep stages and their different functions. They debunk the common myth that we only dream during REM sleep and show that, in fact, we are typically dreaming throughout the night and in nonREM sleep states. They tie all of this into the brain’s “default mode network,” in which our minds are wandering and, often, problem-solving. When we’re awake, our brains are so busy attending to the environment that we tend to favor linear connections and thinking; when we allow ourselves to daydream, we solve problems that have distant, novel or nonlinear solutions.

. . . .

By the time we reach REM sleep, later in the night, our brains have entered a superelaborate and vivid version of that default mode network, where dreaming “extracts new knowledge from existing memories through the discovery and strengthening of previously unexplored weak associations. Typically, the brain starts with some new memory, encoded that day . . . and searches for other, weakly associated memories. . . . The brain then combines the memories into a dream narrative that explores associations the brain would never normally consider.”

During dreaming, then, “the brain is searching . . . digging for hidden treasures in places” it would be unaware of when we’re awake. This, in part, explains why some dreams seem to have such a bizarre, otherworldly quality. Could it be that the content or effectiveness of REM sleep among intelligent people differs from that of others? We don’t yet know. The future may see brain-training games that allow our default mode and our REM sleep to create remote associations more often.

Link to the rest at The Wall Street Journal (PG apologizes for the paywall, but hasn’t figured out a way around it.)