As neurologists learn more about the brain, there's been renewed interest in merging psychiatry with neurology - and that means renewed interest in many of Sigmund Freud's ideas. A recent Scientific American Mind (subscription required) article discusses how modern neuroscience supports many of the ideas Freud proposed and is creating a 'new intellectual framework for psychiatry.' Some of the ideas include:

1) Unconscious Motivation - Freud believed that many of our mental processes that determine our thoughts and feelings occur unconsciously. Today, cognitive neurologists study the behavior of patients who cannot consciously remember certain events that occurred after damage to particular areas of their brains. For instance in 1996, Dr. Joseph LeDoux showed that there is a neuronal pathway that lies under the conscious cortex which connects perceptual information with the primitive brain structures responsible for generating fear responses.

Because this pathway bypasses the hippocampus - which generates conscious memories - current events routinely trigger unconscious memories - current events routinely trigger unconscious remembrances of emotionally important past events causing conscious feelings that seem irrational such as 'Men with beards make me uneasy.'

Similarly, Freud introduced a concept called infantile amnesia - where we can't remember our earliest memories as infants. Neuroscience explains this by demonstrating that major brain structures that contribute to conscious thought are not functional during the first two years of life.

2) Repression Vindicated - Freud believed that we actively repress ideas we don't like. In a 1994 experiment at the University of California, San Diego, behavioral neurologist, Dr. Ramachandran, studied a patient with damage to the right parietal region of her brain. The patient had suffered a stroke eight days before that had paralyzed her left arm yet she denied that anything was wrong with her. After Dr. Ramachandran stimulated her right hemisphere, she suddenly recognized that her left arm was paralyzed. However, when the effects of the stimulation wore off, she reverted back to the belief that there was nothing wrong with her arm. Similarly, she remembered being interviewed by Dr. Ramachandran but forgot the part where she acknowledged her arm was paralyzed.

3) Pleasure Principle - Freud believed that the repressed part of our unconscious mind is governed by wishful thinking that disregards logic and reality. In modern neuroscience, there are cases involving patients with damage to the frontal limbic region of the brain, which controls aspects of self-awareness. For instance, Dr. Solms saw a patient with a tumor in his frontal lobe that caused amnesia. Though they met 50 minutes every day for 12 consecutive days, the patient failed to recall that he had ever met Dr. Solms or underwent an operation to remove the tumor. Instead, he fabricated reasons why he was there, why there was a scar on his head, and who Dr. Solms was. Each day, he invented a new story consistent with what he believed on that day. One day, he believed that Dr. Solms was a drinking buddy and kept looking around the room for his beer. Or, to quote the article, 'The man simply recast reality as he wanted it to be.'

4) Animal Within - According to Freud, the pleasure principle drives primitive, animal urges. He believed the id was the reason why humans sought instant gratification to their primitive urges of sex and aggression. Modern neuroscience has expanded the concept into at least four classifications

They are the 'seeking' or reward system (which motivates the pursuit of pleasure); the 'anger-rage' system (which governs angry aggression but not predatory aggression); the 'fear-anxiety system; and the 'panic' system (which includes complex instincts such as those that govern social bonding).

The seeking system is a lot like Freud's libido. It is regulated by dopamine and is involved in most forms of craving and addiction.

5) Dreams Have Meaning - Finally, Freud believed that dreams were glimpses into the unconsciousness. Neuroscientists believe that dreaming is generated by the forebrain and that the seeking system 'might be the primary generator of dreams.'

I think it's easy to dub Freud irrelevant to modern neuroscience with all his focus on sex and aggression and odd concepts like his Oedipus complex theory. So many people poke fun at him for outdated ideas - and even the associations listed above are hotly debated among neuroscientists.

Still, I have to admit I find it extremely interesting that some of his ideas are starting to re-emerge in neurocognitive research. One of these days I'll have to pick up Dr. Solms' book, The Brain and the Inner World.