An individual can have very poor conscious memory of a certain traumatic event, but at the same time very strong unconscious emotional memories could be formed through a fear conditioning mechanism. These very resistant-to-extinction fears can become a source of intense anxiety. We have recently identified the gene encoding a protein, called stathmin, needed for the normal function of fear circuits in the brain. Combining behavioral testing and direct recordings of electrical activity of neurons in the amygdala, the brain area playing a key role in fear-related behaviors, we found that in mutant mice, which were deficient in stathmin, both innate (instinctive) and learned fear are significantly reduced. The mutant mice showed that they had difficulties strengthening connections between their nerve cells. This provides a mechanistic explanation for their inability to properly learn fear. Understanding how stathmin controls fear may lead to the design of new treatments for depression, panic and generalized anxiety disorders.

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