The study of extinction of conditioned fear has made great progress with the use of Pavlovian fear conditioning in rodents. In recent years, however, there has been a shift toward more realistic behavioral scenarios, in which an animal encounters danger while pursuing rewards. Approach-avoidance conflict tasks can reveal different behavioral strategies employing different prefrontal-amygdalo-striatal circuits. Extinction of approach-avoidance conflict is relevant to understanding obsessive compulsive disorder.
Organisms face challenges to survival throughout life. When we freeze or flee in danger, we often feel fear. Tracing the deep history of danger gives a different perspective. The first cells living billions of years ago likely had to detect and respond to danger in order to survive. Life is about not being dead, and behavior is a major way that organisms hold death off. Although behavior does not require a nervous system, complex organisms have brain circuits for detecting and responding to danger, the deep roots of which go back to the first cells. But these circuits do not make fear, and fear is not the cause of why we freeze or flee. Fear is a human invention; a construct we use to account for what happens in our minds when we become aware that we are in harm’s way. This requires a brain that can personally know that it existed in the past, that it is the entity that might be harmed in the present, and that it will cease to exist in the future. If other animals have conscious experiences, they cannot have the kinds of conscious experiences we have because they do not have the kinds of brains we have. This is not meant as a denial of animal consciousness; it is simply a statement about the fact that every species has a different brain. Nor is it a declaration about the wonders of the human brain, since we have done some wonderful, but also horrific, things with our brains. In fact, we are on the way to a climatic disaster that will not, as some suggest, destroy the Earth. But it will make it inhabitable for our kind, and other organisms with high energy demands. Bacteria have made it for billions of years and will likely be fine. The rest is up for grabs, and, in a very real sense, up to us.