In lieu of an abstract, here is a brief excerpt of the content:

Jacek Debiec and Joseph LeDoux Fear and the Brain FEAR IS A NATURAL PART OF LIFE. IT OCCURS WHENEVER WE ARE THREATENED. Threats come in many forms. A snake on the ground in front of you is a biologically prepared threat, and so is being face-to-face with an angry human. Evolution has put this kind of information into our brains as a way of dealing with recurring and common themes. When we encoun­ ter them we have the familiar fight/flight response. But not all threats are genetically programmed. Most of the things that make us afraid are things we have learned about in our lives. Biological research over the past two decades has made consider­ able progress in understanding how the brain learns about danger. Most o fthis work has been conducted in animals. For some people, words like “biological,” “brain,” and “animals” imply genetic predetermination. But this is not true. First of all, biological does not mean genetic. Nurture is just as much a part of biology as nature. The research we will describe in this paper in fact is all about how we learn to be afraid through expe­ rience. Second, it is important to realize that the brain is a rich source of information about human nature. By studying psychology through the brain, we can discover things about the mind that we cannot learn by studying the mind alone. Third, much of the progress in understand­ ing the brain basis of psychological functions has come from studies of animals . This is certainly true of fear. While animals are not people, the brain and body of animals, like rats, respond similarly to the human brain and body when threatened. Muscles tense. Blood pressure rises. Stress hormones are released. This is all part of the physiological solu­ social research Voi 71 : No 4 : W inter 2004 807 tion of how to rapidly deal with a threat. These responses, however, can also occur in anticipation of something that might happen—in which case we tend to call it anxiety rather than fear. What does the tension of muscles or the rise of blood pressure in a rat have to do with fearful feelings in humans? Actually, quite a lot. Every animal has to have the ability to detect and respond to threats. Otherwise, it could not make it through the day. This is the job of the brain’s defense system. However, a subjective feeling of fear can only occur in animals that have the capacity to be aware of their own brain’s activities. Fear, in other words, is the feeling that results when the defense system is active in a brain that has the capacity for self-awareness . This undoubtedly occurs in humans. W hether it occurs in other creatures is not known, and may be unknowable. But if activation of the defense system is a key component of the neural basis of fearful feelings, and the defense system works similarly in rats and people, then studies of the defense system in rats tells us about an important system underlying human feelings of fear. Even without this theoretical link to fearful feelings, studies of fear behavior in rats are still important. This work, as we will see, has identified a brain region called the amygdala that is essential for fear learning in rats. This same region is known to be altered in fear disor­ ders in humans, including post-traumatic stress disorder (PTSD), panic disorder, and phobia, as well as other conditions, including depression, autism, and schizophrenia. We will summarize in this paper some of what has been discovered about the defense system through studies of fear learning in rats. HO W IS FEAR LEARNING STUDIED IN RATS? Much work on fear has involved fear conditioning, a variant on the conditioning procedures developed by Pavlov (1927). In fear condition­ ing a relatively neutral event (a conditioned stimulus, CS), such as tone or light, is paired with an aversive event (an unconditioned stimulus, US), such as electric shock. After pairing with the US, the CS acquires an ability to elicit behavioral, autonomic, and endocrine responses. These 808 social research responses are expressed automatically in the presence...

pdf

Share