Freud's dream theory gets boost from imaging work
Meaning in dreams may be less disguised than commonly believed.
By Siri Carpenter
Freud's theory that dreams are the "royal road" to understanding the unconscious mind has come under fire over the past 30 years as scientists have probed the neural bases of dreaming. But new findings from brain imaging studies are beginning to show that there may be some truth behind Freud's hypotheses.
The results have narrowed the gulf between basic researchers' beliefs that dreams are merely the byproduct of random neuron firings and psychoanalysts' stance that dreams reveal people's deepest instincts and impulses.
In his 1900 book, "The Interpretation of Dreams," Freud wrote that the purpose of dreams is to express primitive, sexual and aggressive wishes. Such wishes, Freud thought, are rooted in early childhood experiences but are too anxiety-provoking to break the surface of consciousness. Indeed, he theorized, even while dreaming these forbidden impulses are symbolically disguised in bizarre dream imagery, and it is the job of the psychoanalyst to uncover dreams' latent meaning.
Freud's dream theory began to unravel in the 1960s, when scientists discovered that REM sleep, the phase in which dreaming most often occurs, is controlled not by the brain's emotion or motivation centers but by the pons, the part of the brainstem involved in automatic jobs such as respiration, thermo-regulation and cardiac activity.
"The conclusion was obvious," says neuropsychologist Mark L. Solms, PhD, of St. Bartholomew's and Royal London School of Medicine, London. "Freud was wrong. Dreams are regulated by a lowly, elementary physiological mechanism [that has] absolutely nothing to do with wishes and memories and feelings and desires and your grandmother."
That was where things stood until recently.
New support for an old idea
The advent of imaging techniques that reveal the brain at work have given researchers a fresh look at what's happening when people dream. Positron emission tomography (PET) and functional MRI techniques have revolutionized dream research, says neurologist Allen R. Braun, MD, of the National Institute on Deafness and Other Communication Disorders (NIDCD).
Using PET, Braun and his colleagues found that the limbic and paralimbic regions of the brain--areas that control emotion and motivation--were highly active during REM sleep. In addition, areas of the prefrontal cortex, which sustain working memory, attention, logic and self-monitoring, were inactive, the researchers reported in Science (Vol. 279, p. 91-95).
Suppression of the prefrontal cortex during REM sleep may help explain several of the cardinal features of dreaming, such as bizarre imagery, loss of critical insight and logic, diminished self-reflection, inability to shift attention, morphing of time, place and identity and forgetting of dreams, says Braun.
His team also found that the primary visual cortex--the point of entry for visual information from the external world--was deactivated during REM, but regions of the brain that conduct higher-level visual processing remained activated, perhaps explaining why people continue to "see" while dreaming, even while the brain is cut off from the outside world.
"The data are consistent with a number of elements of classical Freudian theory," Braun says. Deactivation of the prefrontal cortex may be consistent with Freud's ideas of encoding of wishes into dream imagery, emotional disinhibition and instinctual needs, he says.
In research that complements the brain imaging findings, Solms studied patients who had damage either in the pons region of the brainstem or in areas of the forebrain involved in motivation. Although the REM sleep of people with damage in the pons was disrupted, dreaming was not. In contrast, people with damage to motivation centers in the forebrain reported a loss of dreaming even though their REM sleep was not disturbed.
"I think that both my and Braun's findings suggest that dreaming is a higher mental function, generated by forebrain mechanisms," Solms says. "Dreams are evidently produced by motivational, emotional, memory and perceptual systems of the forebrain. It is, in short, the 'wishing system,' to allude back to Freud. Nothing that we know about in the brain comes closer to being the neurophysiological equivalent of what Freud described as the libidinal wish or libidinal drive."
'Genuine breakthrough'
Leaders in the field who once entirely dismissed Freud's theories say that Braun's and Solms's findings are very significant.
"I think it's a genuine breakthrough," says psychiatrist John A. Hobson, MD, of Harvard Medical School. "Either one of these methods would constitute a new look. But the fact that they've come simultaneously and complement one another makes you sit up and take notice."
But Hobson doesn't agree that the new research demonstrates that dreams serve as wish-fulfillment, as Freud proposed.
"The term 'wishing system' seems inappropriate here," he says. "Clearly, many parts of the brain are involved in motivated behavior. You're really stretching the point to assume that all of these unpleasant dreams are wish-fulfilling because they involve motivation." And there's scant neuroscientific evidence for Freud's argument that dreams carry hidden agendas--that their superficial content symbolically disguises their real meaning.
"I think there are points of departure [from Freudian theory]," Braun says. "Rather than metaphor or symbol, dreams may constitute more direct, albeit distorted, access to unconscious processes. And meaning in dreams may be less disguised and more apparent than commonly believed."Y
Siri Carpenter is a writer in New Haven, Conn.
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