By Dov Michaeli
By now every fifth grader has heard about the limbic system in the brain. But in case you already forgot, it is a system of highly interconnected brain structures that integrates stimuli of emotional content and coordinates reactions to those stimuli. For instance, the structure called the amygdala (see picture on the right) receives stimuli that have to do with survival, and it engenders reactions to them, such as fear and aggression (the familiar flight or fight response). The limbic system also contains the nucleus accumbens which has to do with reward. If you are an ape and an attractive female telegraphs her receptivity to sexual intercourse, it makes a certain area in your brain secrete copious amounts of dopamine which in turn arouses the nucleus accumbens, and you.