The experience of pleasure usually starts below the level of consciousness, but may be stimulated by conscious processes. Reading a particularly poignant passage in a book evokes visual activity in the brain. It activates areas of the brain where conscious and unconscious experience take place. Depending on the nature of the passage, we may experience other sensory perceptions, all without glancing away from what we are reading. The brain generates images, sensations, thoughts, memories, emotions, movement and beliefs without any peripheral input. In fact, the brain may direct the heart rate to increase or decrease, dry the mouth, increase the acid base balance in the bloodstream, flush the skin on the face, or cause other changes in the body completely generated by input from the book. The eyes or other sensory organs are required to start this process, but once it begins the brain is capable of generating great pleasure without any further sensory input and alters the experience of the body.
The brain’s reward circuits are involved in the experience of pleasure. There are two separate, but related phenomena processed in these reward circuits. They are liking and wanting. There is a distinct difference between the two. Liking is associated with pleasure. We can like something and derive pleasure from it, even if we do not want it. This involves the pleasure centers of the brain and causes the release of the pleasure neurotransmitters. These are endorphins, oxytocin, anandamide and GABA. On the other hand, wanting is associated with acquiring something. We may or may not like it. When wanting becomes craving it may lead to addiction. Wanting involves release of the neurotransmitters dopamine and glutamate.