Jerome Burne
Dreams are fascinating: they are personal, intimate and totally inaccessible to anyone else. And yet they are bizarre, mysterious and seemingly nothing to do with the dreamer. We still don’t understand why we dream, but new findings, presented to the recent Conference on the Scientific Study of Consciousness at Tucson, Arizona, have been upsetting theories.
Textbooks will tell you that sleep can be divided into REM (rapid eye movement) and non-REM, or slow-wave, sleep. We move in and out of these two types of sleep. REM is associated with dreaming, but not much happens in non-REM. This view may have to be revised, however, now that it has been discovered that slow-wave sleep is active in a way we never dreamed of.
“We have developed a new way of recording from the brain,” says Professor Bruce McNaughton of Arizona State university. “We can now measure the activity of 100 neurones at a time as a rat runs around a maze.” This has allowed McNaughton to enter sci-fi territory. By looking at the patterns made by the firing of just those 100 neurones, he can tell exactly where the rat is in a maze. One pattern emerges when the animal goes past a yellow wall; another when it turns a corner.
But besides opening windows on the waking brain, this new technique may be able to provide the first glimpse of the content of dreams from the outside.
Dreaming, according to the more respected theories, is part of the process of shunting daytime memories into long-term storage. Lessons that students learn during the day are remembered much less accurately if you stop them dreaming.
So would the rats’ daytime neurone patterns show up in dreams? McNaughton first recorded those 100 neurones while the rats were in REM sleep, but found no trace of the patterns. “That was kinda surprising, but when we started recording during the rest of the night, we had an even bigger surprise.” The patterns turned up during the slow-wave sleep, the periods when everyone thought not much happened.
That wasn’t all. “These patterns were being run 20 to 30 times faster than they had in the day.”
But other techniques are being used to explore dream secrets. The first scans of what goes on in sleeping human brains, made by Professor Alan Hobson of Harvard Medical School, go some way to explaining why we have the sort of dreams we do. “We found that one of the most active areas is the amygdala, which is involved in the emotions,” he says. “That’s why dreams are more often fearful and anxious. Also very busy is an area in the parietal lobe, which is involved in vision and movement. That’s why dreams have a hallucinatory quality.”
The most surprising finding was that an area in the frontal lobes involved in planning and self-reflection was turned off. “We expected the other two areas from animal studies,” Hobson says, “but this was a surprise. It makes sense of the feeling of not being in control in dreams, and it also helps to explain why dreams are so hard to remember, because this area is linked to memory.”
There is also a difference in the levels of various brain chemicals between sleeping and waking. One of the signs of sleep is that the level of the neurotransmitter serotonin drops almost to zero.
“The trouble is that drugs like Prozac keep serotonin levels artificially high and this can have damaging results,” says Hobson. He describes an alarming and increasingly common condition, known as REM sleep disorder, found in certain patients on Prozac.
“Their sleep pattern is totally disturbed,” he says. “They show REM sleep all through the night and they start acting out their dreams. Normally when we are in REM sleep our major muscles are paralysed, but in these patients the block comes off and they may have fights with the wardrobe or attack their partner.”
Dr Stephen la Berge of Stanford University has been exploring the curious phenomenon of lucid dreams. “With a bit of training it is possible to go to sleep, intending to become aware that you are dreaming and actually control and change the dream while remaining asleep,” he explains.
This allows a dreamer, hooked up to electrodes measuring eye movements, to signal to the experimenter that he is conscious.
La Berge says: “The sort of question you can use it to answer is: do people dream in real time? You agree before the person goes to sleep that he will signal with his eyes when he starts counting to 10 and again when he stops. Then you can check if the subjective dreaming for 10 seconds actually takes 10 seconds. And we’ve found that it does.”
It is hard to square Hobson’s new claims that the executive part of the brain is turned off during REM sleep with La Berge’s claims that you can be conscious and keep dreaming. Sleep is still pretty mysterious.