Secrets of Sleep A Discoveries Special Report

Secrets of Sleep A Discoveries Special Report

Dream World is Beckoning Neuroscience

Brain Scans beginning to explain origin, tone of nocturnal adventures

By Marcia Barinaga, Special Contributor, Dallas Morning News

This report has featured in the course notes of the National College of Hypnosis and Psychotherapy for many years. Dreams, once the exclusive turf of psychologists and psychiatrists, are now yielding some of their secrets under a different type of scrutiny – in the neuroscience laboratory.  New findings suggest, among other things, a biological basis for some of Freud’s theories and a model for how dreams may help solve many of those nasty problems that people decide to “sleep on”.

Allen Braun of the National Institute on Deafness and Other Communication Disorders and his colleague Thomas Balkin of the Walter Reed Army Institute of Research have used brain scans to study the activity in the brain’s visual areas during sleep.  In 1998 they found that the higher visual areas – those that process visual images – were hopping with activity.  But the primary visual cortex – the area that normally receives signals from the eyes – was silent.

That silence is not a surprise, since the eyes are closed.  But the activity in those higher areas means they are “self-stimulated”, says Dr Braun, doodling on their own with no input from the environment.

The brain-scan studies also provide a possible explanation for the general weirdness of dreams.  Not only is the brain creating images independent of the senses, but the brain area that would normally serve as a reality-checker – the prefrontal cortex – is off-line, silent during REM sleep.

The prefrontal cortex is a brain region that contributes to the “working memory” of events from one moment to the next.  And the absence of working memory during REM, Dr Braun says, could explain “the bizarre shifts in orientation during dreams, the morphing of identities, the fact that plots don’t occur in a linear sequence.”  It may also be why people typically don’t remember a dream unless they wake up while it is happening.

But are these bizarre nocturnal adventures just an entertaining byproduct of sleep, or do they have some function?  In 1977, Harvard sleep researchers J. Allan Hobson and Robert McCarley proposed that dreams begin with random neural activity that the brain fits a story to, as best it can.

Many researchers still accept some form of that general theory.  But it doesn’t rule out the psychological value of dream analysis.

“Dreams are physiological Rorschachs,” says Harvard sleep researcher Robert Stickgold, referring to the inkblots used in psychological tests.  “No one claims that those inkblots are anything but random patterns.”  Likewise, dreams may begin with random visual activity, but it is the brain’s interpretation of that activity that can provide insights.

In the March 1999 issue of the Journal of Cognitive Neuroscience, Drs. Stickgold and Hobson and colleagues reported on a study suggesting that dreams may do more than just reflect inner psychology; they may help the dreamer to view problems in new ways.

The study used a “semantic-priming” task, in which words or non-sense words are flashed on a screen, and the human subject has to tell as quickly as he can whether each one is a word or not.   Subjects are a bit faster in recognizing a word if a so-called priming word, related in some way to the test word, is flashed first.  If wrong were the test word, for example, right might be a strong prime, and thief might be a weak prime.

In the study, researchers woke people during REM sleep and had them do the semantic task before they were fully awake.  For subjects in that sleep-befuddled state, Dr. Stickgold says, “the strong primes don’t work anymore, and the weak primes work twice as well as during waking.”  That, he says, suggests the brain has “been shifted into a state where the rules of association are changed, activating weak associations.”

And that, he says, may enable the brain to look for novel associations that it would not consider during waking or test different possible outcomes or strategies.  After all, he says, “the most simple dreaming takes memories, or pieces of memories, puts them together in strange and unexpected ways and watches what happens.”

Dreaming, says Dr. Stickgold, “is almost like Freud’s couch: Lie down, relax, let your mind wander, don’t try to think about anything in particular, just see what floats up.”

Indeed, it is hard to discuss dreams without mentioning Sigmund Freud.  Sleep scientists have generally dismissed most of Freud’s ideas.  For example, Freud claimed that dreams used complex symbols to disguise their underlying meaning, a notion that holds little water in light of the neurological findings, says Dr. Braun.  “That processing would be accomplished by the frontal cortex,” he says, “and the frontal cortex is shut down.

But some neuroscientists think that certain of Freud’s theories were dismissed too quickly as the neurological underpinnings of sleep began to emerge.

Dr. Braun notes that the emotion-processing limbic system of the brain is very active during REM sleep, and that could explain “the vivid visual imagery during dreaming and its coupling with emotional content that may represent wishes” – a modernized spin on Freudian theory.

Mark Solms, a neuroscientist at St. Bartholomew’s and Royal London School of Medicine in the United Kingdom, goes a step further in giving Freud his due.  By studying patients with brain lesions resulting from stroke or injury, Dr. Solms has found two brain areas that are essential for dreams.  And he notes that those areas are closely linked to the kind of desires and drives that Freud claimed are at the root of dreams.

Dr. Solms found nine patients whose brain lesions eliminated their ability to dream, although they still had REM sleep.  The areas both were in the part of the brain called the forebrain.

He bolstered the size of his own study when he realized that one of the dream-related brain areas had been the target, in the 1960’s, of a surgical procedure called modified prefrontal leukotomy.  The procedure was performed on thousands of psychotic patients to control hallucinations and delusions, which, Dr Solms points out, “are a dreamlike type of thinking.

He looked back at the research reports and found that one of the side effects of the procedure was the elimination of dreams.

Both of the dream-related brain areas contain neurons that use the brain chemical dopamine, and Dr. Solms thinks these neurons may be key.  Dopamine can cause vivid dreams and hallucinations – an occasional side effect for patients who are receiving the drug L-dopa for Parkinson’s disease.

Those dopamine neurons are also known to be responsible for motivation.  Their activity “motivates us to look out to the world to satisfy our drives,” Dr. Solms says.  “Freud claimed dreams were driven by libidinal drive, appetite states, states of instinctual need.”

Dr Solms says it’s only a hypothesis, and he does not mean to claim that Freud is vindicated.  “But I do think we need to take more seriously the possibility that dreams are motivated mental states.”

Marcia Barinaga is a free-lance writer based in Oakland, Calif.

Reprinted with permission of the author and The Dallas Morning News

First published August 27th 2001 in The Dallas Morning News