Slumber science
Your October 24 issue featuring sleep research was very interesting and helpful. However, it did not cover any research being done — there may be none — relating to the human brain and modern changes to the nighttime environment. For most of human history, not much activity could take place at night. The diurnal cycle of light and darkness and the yearly seasons north and south of the equator must have had great influences on our development, response, brain activity and sleep. Man and the other biota with brains all developed when these cycles of inactivity dominated their lives.
It has only been relatively recently that the human environment has had light for the entire 24-hour day. Being able to be awake for long durations allows human activities such as 24 hours of essentially instantaneous worldwide communications, global business activities and many pleasures of life. It seems to me that all of these are now probably contributing to the medical problems discussed. There is no time to sleep!
However, these are unique to man. Are other living things having similar problems with sleep? This would seem to be a fruitful area for comparative sleep research.
Warren L. Dowler, Brookings, Ore.

Your recent discussion of the need for sleep (“The why of sleep,” SN: 10/24/09, p. 16) cited Robert Stickgold as saying that the benefits for memory are, to date, the only explanation as to why consciousness has to be shut down during sleep. I propose that a key psychological benefit is the extinction of the emotional potency of the relatively intense and less worked-through moments from the preceding day.
Matthew Wilson talked about sleep replaying the day’s events. Recycling these strongly emotional moments would reduce their intensity, enabling them to move into longer-term memory with a reduced potential for restimulating images that would activate upsetting emotional arousal: They move toward becoming “my history.” In contrast, sleep deprivation leads to a lower threshold for emotional arousal (irritability) that increasingly interferes with the next day’s functioning. The tangential and symbolic or “distorted” qualities of dream content would be necessary to sustain sleep: Direct re­capitulations of whole events would likely keep awakening the sleeper. My hypothesis is that to do all this, the system must shut down consciousness.
Alex Caldwell, Los Angeles, Calif.

Dreaming during sleep was evidence something was going on in the brain long before EEGs were invented. Now that we know brain activity during sleep is comparable to, but different from, the awake state, we understand why body mobility must be shut down during sleep. It would not enhance survival if man followed the dictates of an active brain that had no attendant sensory inputs. It’s better to be immobile inside your cave than sleepwalking out of it.
Bernard Leitner, Palo Alto, Calif.

Your special issue on sleep is very interesting. I wonder whether a re-orientation of our viewpoint might be productive — that is, to consider the sleep state as the normal condition of living things, and consciousness as a periodic interruption to enable feeding and reproduction.
Walter Weller, Wakefield, La.

I am outraged by the casual description of a sleep experiment performed on laboratory rats: “A lab rat perishes when marooned for weeks on a disk that tips it into water when the rat dozes off.” What sentient creature would not perish after weeks of torture? If something was learned about sleep deprivation from this “experiment,” it was not worth the moral cost.
Anthony Weaver, New York, N.Y.

Virus appreciation
Your article “Enter the virosphere” (SN: 10/10/09, p. 22) was excellent. I had to read it three times to understand it, but it looks like viruses are the “order-keepers” of life, the “check and balance” of existence. They can change at will, are almost indestructible and can transfer genes from creature to creature.
If they could think, they could destroy a species that got out of whack. And if they could communicate, they would be devastating: Give somebody a flu shot, then the virus in their body figures out the change to protect itself, it could tell all the viruses in other bodies, and the flu shot no longer works.
John Carlton Hagerhorst, Frederick, Md.

One-way ticket to Mars
The “Scientific Observation” from Lawrence Krauss (SN: 10/10/09, p. 4) illustrates the decline of moral reasoning. Comparing an astronaut’s one-way trip to Mars to the voyages of Pilgrims and settlers to the New World centuries ago is quite specious. Certainly the Pilgrims and settlers generally did not intend to return to Europe, but they certainly did not intend simply to go to the New World and die. The Pilgrims sought to spread Christianity to the peoples of the New World and the settlers expected to leave descendants there. Astronauts have no reasonable expectation of doing either on Mars for quite some time.
John F. Fay, Mary Esther, Fla.

Lawrence Krauss (if quoted correctly) does not make a distinction between explorers and immigrants, and seems to make a false distinction between the safety measures required for a one-way trip to Mars versus a round-trip back to Earth. The planet to which the Pilgrims traveled had all the same properties as the planet on which they lived, and on which their ancestors had evolved. Before setting sail, the Pilgrims knew that the American environment was capable of sustaining human life because explorers had safely traveled there and returned.

Jeffry D. Mueller , Eldersburg, Md.