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A Physiology of Dreams?


REM Sleep 

In 1953 neurobiology conquered dream research. The discovery of REM sleep - a certain phase of sleep named for the dreamer's rapid eye movements - marked the beginning of a new era in the study of dreams (and sleep). The emphasis on physiology gave rise to new ideas about dreams, the most radical of which consider dreams to be mere trash cans for our sleeping brains.

For Nobel laureate Francis Crick of the Salk Institute in San Diego, dreams are nothing but random attempts, without any deeper meaning, to clear from the brain unneeded or even harmful memory. Crick claims this is a necessary step to reset the brain for the next day, much as one erases old data from a floppy disc to reuse it or rewinds a VCR tape to record the latest Seinfeld.

Not quite brain garbage, yet still randomized products created by uncontrolled fireworks of nerve cells in our sleeping brain - that is how J. Allan Hobson, a Harvard psychiatrist and neurophysiologist, describes dreams. In his view, dreams come into being when these random signals reach the cortex, the brain's center of thinking and reasoning, which tries hard to make sense of the arbitrary inputs. Random firings, Hobson says, are due to a very different composition of signal-transmitting chemicals, called neurotransmitters, in the brain during REM sleep as compared to the waking brain. According to Hobson, a different brain chemistry also explains - through chaotic nerve impulses - our wild and bizarre dreamscapes during REM sleep.

However, the great majority of the dreams Domhoff analyzed contain familiar settings and known characters that take part in recognizable, and reasonable, activities. "Dreams are, in fact, generally well-organized and lack bizarre elements," agrees David Foulkes, a professor Emeritus of psychology at Emory University in Atlanta.

Nor can dreams simply be equated with REM sleep, which is what both Crick and Hobson focus on, Domhoff says. The equation between REM sleep and dreams was the prevailing credo among dream/sleep researchers in the late 1950s and early 1960s. For the first time, psychologists could trace a mental process - dreams - to a physiological activity - REM sleep. "It was a very exciting time and an exploding field. We were the hot guys on the block - even newspapers wanted to talk to us," Domhoff remembers. But the simple equation did not stand the test of time. The longer psychologists studied sleeping subjects, the more it became obvious that dreaming occurs in all other phases of sleep, Domhoff says.

Domhoff and Foulkes are particularly aggravated by neuroscientific attempts to explain the nature of dreams by reducing them to some physiological phenomena, such as the measurement of brain activities. Says Foulkes, "No PET scan, or any other fancy biotechnical doodad, is capable of observing or characterizing the nature of dreaming." They refer to such approaches as "biologic reductionism."

"I am always very wary about neurobiological findings. Dreams are not just eye movements," Domhoff says. "There might be a neurobiology of dreaming, but never a neurobiology of dreams. "

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