The MIT Technology Review has a report on a new use for functional MRI: Imaging the Unconscious. One hundred years later, some of Freud’s notions are finally testable:

One of Freud’s theories held that after a traumatic event, people might unconsciously associate a normally benign stimulus, say, a friendly golden retriever, with a previously fearful event, such as getting bitten by a Rottweiler. This theory seems to be true in the case of post-traumatic stress disorder (PTSD). Harmless sights and sounds, for instance, such as a bus traveling on down a street, can trigger a panic attack in someone with PTSD who was once involved in a bus crash. Furthermore, the sufferer may not be immediately able to pinpoint the cause of his or her anxiety attack.

Now scientists are using brain imaging techniques to explore how the unconscious fear signal may be turned up in people with PTSD and other anxiety disorders. To study the brain processes underlying anxiety, researchers use functional magnetic resonance imaging (fMRI) to measure a person’s brain activity while he or she looks at threatening signals, such as a picture of a fearful face. These frightening pictures will spark activity in the part of the brain known as the amygdala, which is part of the evolutionarily ancient brain involved in processing emotion and fear. To study the unconscious aspects of fear and anxiety, the researchers flash the ominous picture so quickly that subjects don’t consciously notice it — the brain reacts to the image, even though the person cannot determine whether or not they actually saw it.

It’s not surprising that these researchers are first going after easily reproducible responses, such as fear. As the technology and methodology improve, we expect insights into more complicated phenomena of the psyche.