“Freud Returns” by Mark Solms, and “Freud Returns? Like a Bad Dream” by J. Allan Hobson, in Scientific American (May 2004), 415 Madison Ave., New York, N.Y. 10017–1111.

Once so influential, Sigmund Freud and his metaphorical ideas about the unconscious and repression were history by the 1980s in the eyes of most neuroscientists. But their biological and chemical approaches to the human mind have failed to provide a “big picture,” and now “Freud is back,” reports Solms, a neuropsychologist who is director of the New York Psychoanalytic Institute’s Pfeffer Center for Neuro-Psychoanalysis.

Setting aside past antagonisms, neuroscientists and psychoanalysts are now working together in most of the world’s major cities. Neuro­scientists are proving some of Freud’s theories true and gaining glimpses of “the mechanisms behind the mental processes he described,” according to Solms.

In line with Freud’s central idea of the unconscious, research confirms that “a good deal of our mental activity is unconsciously motivated.” Some patients can’t consciously remember particular events that occurred after certain memory-encoding structures of their brains were damaged, yet their behavior is clearly influenced by those events. “Neuroscientists have also identified unconscious memory systems that mediate emotional learning.” In 1996, Joseph E. LeDoux, a neuroscientist at New York University, demonstrated that under the conscious cortex exists “a neuronal pathway” that lets current events trigger unconscious memories of emotionally potent past events, causing seemingly irrational conscious responses, such as “Men with beards make me uneasy.” Freud’s claim that humans actively repress unwelcome information also has been gaining support from case studies.

Of course, some things Freud said are not panning out. “Modern neuroscientists do not accept Freud’s classification of human instinctual life as a simple dichotomy between sexuality and aggression,” Solms notes. “Instead, through studies of lesions and the effects of drugs and artificial stimulation on the brain, they have identified at least four basic mammalian instinctual circuits, some of which overlap.” The “seeking” circuit, which motivates the pursuit of pleasure and is regulated by the neurotransmitter dopamine, “bears a remarkable resemblance to the Freudian ‘libido.’” It might also be “the primary generator of dreams”—a possibility currently under investigation.

However, Hobson, a professor of psychiatry at Harvard Medical School, says that Freud’s defenders are doing a little dreaming themselves. Scientific investigations show that “major aspects of Freud’s thinking” were probably wrong. “Psychoanalysis is in big trouble and no amount of neurobiological tinkering can fix it.”