Le Doux talks about this too:

http://www.cns.nyu.edu/ledoux/overview.htm

In particular:

> Research into the brain mechanisms of fear help us understand why these emotional conditions [phobias and traumas] are so hard to control. Neuroanatomists have shown that the pathways that connect the emotional processing system of fear, the amygdala, with the thinking brain, the neocortex, are not symmetrical -the connections from the cortex to the amygdala are considerably weaker than those from the amygdala to the cortex. This may explain why, once an emotion is aroused, it is so hard for us to turn it off at will. The asymmetry of these connections may also help us understand why psychotherapy is often such a difficult and prolonged process- it relies on imperfect channels of communication between brain systems involved in cognition and emotion.

These low level basic emotional responses do become automatic due to experience. We can learn to have some control over their expression, however, though it is hard work...

I think that mindfullness helps...