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See Inside April/May/June 2009

Defense Mechanisms: Neuroscience Meets Psychoanalysis

Suppression and dissociation, two psychoanalytic defense mechanisms, are now studied by modern neuroscience

Nothing is so difficult as not ­deceiving oneself. 
—Ludwig Wittgenstein

How much of what you consciously experience in your daily life is influenced by hidden unconscious processes? This mystery is one of the many that continue to confound our understanding of ourselves. We do not know how conscious impulses, desires or motives become unconscious or, conversely, how unconscious impulses, desires or motives suddenly become conscious.

Advances in technologies such as functional magnetic resonance imaging permit scientists to directly measure brain activity. This ability has led to a revival and reconceptualization of key psychoanalytic concepts, based on the idea of inner forces outside our awareness that influence our behavior. According to psychodynamic theory, unconscious dynamic processes defensively remove anxiety-provoking thoughts and impulses from consciousness in response to our conflicting attitudes. The processes that keep unwanted thoughts from entering consciousness are known as defense mechanisms and include repression, suppression and dissociation.

Suppression is the voluntary form of repression proposed by Sigmund Freud in 1892. It is the conscious process of pushing unwanted, anxiety-provoking thoughts, memories, emotions, fantasies and desires out of awareness. Suppression is more amenable to controlled experiments than is repression, the unconscious process of excluding painful memories, thoughts and impulses from consciousness.

If you are grieving over the death of a loved one or the breakup of a relationship, you may consciously decide to suppress thinking about the situation to get on with your life. Or, in another example, you may have an impulse to tell your boss what you really think about him and his abysmal behavior, but you suppress this thought because you need the job. In both cases, the desire is conscious but is thwarted by the exercise of willpower resulting from a rational decision to avoid the action. The impulse or drive may display itself in other ways, however: you may develop a nervous cough around your boss even though you are not sick. Or a suppressed sexual desire may resurface in a careless phrase or slip of the tongue. In general, “forgotten” thoughts, memories and urges can influence behaviors, conscious thoughts and feelings and can express themselves as symptoms or even as mental illness.

Although some claim that suppression is a psychoanalytical myth with no scientific support, fMRI data suggest otherwise. Psychologist Michael C. Anderson, now at St. Andrews University in Scotland, and his colleagues carried out what they call a “think/no-think” experiment to explore the brain basis of memory suppression. Two dozen volunteers had to memorize 48 word pairs (for example, ordeal-roach or steam-train). Subsequently, while lying in a scanner, subjects were shown the first cue word and had to either recall the second, associated word (called the respond condition) or prevent it from entering consciousness (suppress condition). Actively suppressing the matched word while lying in the scanner had the effect of reducing recall of the word afterward (as compared with the respond condition); this result is not just simple forgetting that occurs with the passage of time.

The imaging data that Anderson and his colleagues collected showed that the volunteers suppressed the words by recruiting parts of the brain involved in “executive control,” namely, areas in the prefrontal cortex, to disengage processing in sectors of the brain important for memory formation and retrieval, in particular the hippocampus. This finding is noteworthy because earlier experiments showed that the amplitude of activity in the hippocampus is proportional to memory recall—the stronger the activity, the higher the likelihood of remembering. A second intriguing observation is that the brain is more active when avoiding recalling a memory than during recall itself. People suppress unwanted memories by exerting willful effort that can be tracked in the nervous system in ways only dreamed of by Freud—who was, after all, a neuroscientist by training.

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