Norman Doidge, head of long-term psychoanalytic psychotherapy for the University of Toronto’s psychotherapy program, points out that Freud is the most cited intellectual of the 20th century — a distinction bound to lead to any number of erroneous claims made on his behalf. One misconception frequently attributed to Freud is that people — and our dreams — are motivated solely by sexual desire. Freud did claim sex is deeply significant, and he had a broad understanding of sexuality as something that begins long before puberty. But to say that, for Freud, it all boils down to sex, “is a gross oversimplification of a very complicated model,” says Doidge. “It wouldn’t make the first cut of the Idiot’s Guide to Freud.”

Mills agrees. He notes that Freud followed his classic 1900 treatise, The Interpretation of Dreams, with 40 more years of research and writing. “Early in his work,” says Mills, “Freud very much believed that dreams are the disguised, distorted fulfillment of unconscious wishes, some being primordial urges or impulses, such as sexuality.” But by the end of his career, he amended those views, postulating a role for aggression, unconscious guilt and anxiety.

And Freud’s credentials as a scientist? He was a “hard-core neuroscience researcher,” says Doidge. “He knew an incredible amount” about the way the brain works. Doidge offers a compelling example. When we are awake, our forebrains process visual information in three stages: the primary visual cortex registers things like lines, colour and movement, which are then visually dramatized in a secondary association area; a third area relates those images to an idea, or abstract thought. Freud hypothesized, says Doidge, that “the dreaming mind regresses.” In other words, when we dream, that process is reversed: an abstract idea generates an image. “If the idea is something like, ‘I’m special, I don’t have to go by the rules the way everyone else does,’ ” explains Doidge, “you might have a dream of being able to walk on water or fly through the air.”

It’s now pretty clear that Freud had that part right. What’s more, research carried out by Mark Solms has proved as much — leading that neuroscientist to radically challenge Hobson’s and McCarley’s brain-stem theory of dreaming. In the mid-1980s, Solms began interviewing patients with damage to certain areas of their forebrain. In waking life, a damaged primary visual cortex causes blindness; a damaged secondary association area causes complex perceptual disorders; while lesions in the third area have no direct effect on perception.

But in dreaming, Solms discovered, that pattern is reversed. Patients with damage to the third area experience a total loss of dreaming, while those with lesions in the secondary association area report complex dream image disorders (such as an absence of colour or people without recognizable faces). Lesions in the primary visual cortex have no effect on dreaming. In other words, says Solms, when we dream, our brains do process information in the opposite direction, just as Freud hypothesized.

Interviews with some of Solms’s other subjects, however, revealed something truly unexpected. Nine of the 365 people in his study had suffered damage to what’s called the ventromesial frontal quadrant of their brains, which includes the white fibres located just behind the eyes. All nine reported a total and permanent loss of dreaming. But their REM sleep continued, leaving Solms to postulate that REM sleep and dreaming are distinct phenomena — sometimes associated, sometimes not. As well, the fact that dreaming ceased in sleepers with frontal lobe damage despite normal functioning of the brain stem led Solms to conclude, contrary to Hobson and McCarley, that dreams must originate in the frontal lobe, the highest, quintessentially human, part of the forebrain.

Nine cases, however, could hardly be considered authoritative, and Solms began searching for a way to corroborate his theory. Then he recalled that fibres in the ventromesial frontal quadrant had been deliberately severed in thousands of people who underwent prefrontal leucotomies (the successor operation to the infamous frontal lobotomy) in the 1950s and 1960s to treat severe psychotic illnesses. A tour through reports from that period confirmed his suspicion: those patients had stopped dreaming, too. And while Solms’s theory grew out of his work with brain-lesioned patients in the 1980s, today’s PET scans, he says, confirm it: “The structures that scans show as activated during dreaming sleep are the same structures that, when damaged, as my research showed, lead to abnormal dreams or a total loss of dreaming.”

THE POSSIBILITY that dreams originate in the ventromesial quadrant is good news for Freud backers. Because that is part of the forebrain, Solms concludes, it follows that dreams do have something to do with our mental capacities, our feelings and thoughts. What’s more, that area of the forebrain connects the limbic system with the higher frontal areas, making it an essential part of our motivational system. It is, he says, “what makes us turn to the world to look for the thing that we need.” Think of a dog foraging for a bone, he adds, “wagging its tail, twitching its whiskers.” Such a basic need-driven function corresponds nicely with the Freudian claim that dreams represent our unconscious wishes or urges. Solms is careful to say his work doesn’t prove Freud was right. But, he adds, “it’s strikingly consistent with the sort of thing Freud was claiming on the basis of an entirely different type of approach.”

Peering into the brain, then, has reignited a century-old debate. And, once again, neurologists are redefining its terms, albeit by relying on more hard-core scientific methods than Freud’s. Solms credits Hobson and McCarley with discovering the mechanism for REM sleep, but believes their dream theory relies too heavily on those mechanisms. While REM sleep, he notes, is “the most likely and most sustained trigger for dreams during sleep,” it’s not the only trigger. “If you want to understand what a dream is,” Solms says, “you want to look at the mechanisms in the forebrain, not at what it is that sets them working, especially since the thing that sets them working is neither necessary nor sufficient.” Hobson’s claim that specific forebrain structures are activated in response to chemicals firing up from the pons, Solms adds, cannot account for other neuroscientific research that shows people with damage to the pons still report dreams.