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No. 134: MAR-APR 2001

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Sleep-work And Dream-work

To dream an animal must sleep, and sleep is a dangerous state in the natural world. The animal is motionless, its senses are diminished; it is very vulnerable. Neither is there any provable biochemical value to sleep. (See BHF31 in Humans II) Yet, a large fraction of an animal's life is spent in this apparently useless and hazardous condition. Why, then, did sleep ever evolve?

But with sleep, come dreams, and maybe an answer is to be seen in them.

Cats establish long-term memories during sleep. First, it is relevant that an animal's brain (a cat's brain here) seems to be active even when an animal is sleeping deeply but not dreaming.

It seems that during an extremely quiet phase of sleep, when researchers thought that nothing much was happening in the [cat's] brain, groups of cells involved in the formation of new memories signal one another. The signals, discovered only a few years ago, allow cells in many parts of the brain to form lasting links. Then, when a few cells are stimulated during waking hours, the links are activated and an entire memory is recalled.

Deep, dreamless sleep has long been thought to be of little value to an animal. Apparently this is not the case. Deep sleep seems to be valuable in memory activation. Score one for sleep.

(Blakeslee, Sandra; "Researchers Link Deep Sleep to Memory Recall," Austin American-Statesman, December 2000. Cr. D. Phelps.)

Rats rerun mazes in their dreams.

Rats apparently can't escape the rat race, even when they're sound asleep.

Research at the Massachusetts Institute of Technology say they have entered the dreams of rats and found them busily working their way through the same lab mazes they negotiate during the day.

The MIT maze-running rats were hooked up to equipment that recorded the neuron-firing patterns in the rats' hippocampus where memories are processed. The patterns were the same when the rats were dreaming and when running the maze during waking hours. From the patterns, it was even possible to tell exactly where a rat dreamed it was in the mazes.

Whether the rats worked out better maze solutions in their dreams and thereby made their dreaming worthwhile could not be determined from the article. Simple memory-review does not seem to have much survival value.

(Anonymous; "Lab Rats Found to Dream of Mazes, Researchers Say," Baltimore Sun, January 25, 2001.)

Humans conceptualize and create while dreaming. A few anecdotes suggest that human dreaming may be innovative. The following three oft-told tales are truthfully no more convincing to a scientist than many UFO anecdotes.

(Mazzarello, Paolo; "What Dreams May Come?" Nature, 408:523, 2000.)

Comments. These mammalian anecdotes involving sleep and dreams are amusing, but most dreams are frivolous, bizarre, and of very little practical value, Mendeleyev notwithstanding. The utility of sleeping and dreaming do not seem at all commensurate with the accompanying vulnerability and the loss of waking hours.

However, speculation is fun. There are at least two rather far-fetched explanations for characteristics (sleeping and dreaming here) that do not appear to have very much survival value.

Are sleeping and dreaming humans slouching toward Teilhard de Chardin's Omega Point or possibly A.C. Clarke's Childhood's End?

From Science Frontiers #134, MAR-APR 2001. � 2001 William R. Corliss

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