I guess this idea of the Pleasure Pain Principle was founded by Sigmund Freud and is the idea that we naturally seek pleasure and avoid pain. He suggests that pain is the opposite of pleasure. Pavlov’s idea of Classical Conditioning suggests that Pleasure and Pain is based on a reward and punishment system; where we receive pleasure when rewarded and pain when punished; learning by associations, but this is not always true. Some rewards, such as too much admiration causes pain or frustration. His idea of classical conditioning is that some responses involve automatic, pre-programmed responses, whereas operant conditioning involves learned responses.
Pleasure is not always the opposite of Pain. If I have a painful toothache, there is no situation of a Pleasurable Mouth Sensation; it is mainly an automatic normal response to eating, mostly unaware, where enjoyment doesn’t come from using the teeth to chew, but from the taste of the food itself; so in this case, Freud’s Pleasure Pain Principle does not apply, but Pavlov’s Classical Conditioning does. One may find pleasure in eating again after the toothache is fixed, but it is not a long lasting principle that operates in our active memory of how enjoyable it is to eat food with healthy teeth and gums, in fact, the pleasure component may only last a few days, after the pain is gone and then it returns to an automatic process in unawareness. We don’t think about our teeth offering pleasure while in use, but our smiles, a separate expression, does.
Pavlov’s idea says it requires two stimuli to produce the automatic response. In a toothache, the only two stimuli I can consider are Hot, Warm, and Cold liquids or solids, so there are in fact more than two stimuli in a toothache with an automatic pain response. Since his principles or theories involved learned behavior and conditioning, it is not really comparable to a toothache, although it does include stimuli and a pre-programmed response where the pre-programmed original response was not painful and then became painful because of some other change (such as gum disease, cavity, or just an increase in tooth sensitivity).
The University of Michigan’s Health System suggests Dopamine is not only responsible for pleasure, but also pain. Dopamine is the pleasure chemical in the brain. In a study, they injected a needle into a persons jaw, where they observed dopamine release in two other areas of the basal ganglia — the putamen and caudate nucleus — they said it was strongly correlated with the rating of how intense and unpleasant the pain itself was on a scale of 0 to 100. The authors concluded that in some areas of the basal ganglia, dopamine was involved in the assessment of pain itself, while in the ventral area, or nucleus accumbens, it was related to the emotional experience of pain. The article on this study did not say if the increase in Dopamine correlated to the decrease of self-reported pain. The findings of this study only somewhat assist in locating the areas of the Brain that involves the emotional experience related to the pain. What is unclear is their definition of “Emotional Experience” as they do not say if this includes crying, sadness, or happiness. A mild toothache is not typically an emotional experience and those types of responses vary dependent upon age. A baby might have a lower pain tolerance and might cry when they have a toothache, whereas an adult might just have a painful response to the ache and recover until the next time they take a bite or drink.
The British believe they have found the pain centers of the brain. “Pain is a complex, multidimensional experience, which causes activity in many brain regions involved with things like attention, feeling emotions such as fear, locating where the pain is, and so on. But the dorsal posterior insula seems to be specific to the actual ‘hurt level’ of pain itself.” Of course there are studies that refute this theory.
Theories of pain have been debated for centuries, and we still do not know how pain is represented in the brain despite decades of searching for a pain specific brain center. This pursuit for a simple, single pain center however is no longer necessary given the enormity of human neuroimaging data indicating that there is no such dedicated center. Each and every brain area that contains nociceptive neurons also contains non-nociceptive neurons, and neuroimaging has shown that each brain area that responds to noxious stimuli can also respond to non-noxious stimuli.
My own Theory is that the Pain information resides in the areas of the Brain that is responsible for the corresponding organ or body part that is experiencing the pain. In the case of a Toothache, it is the Jaw and Mouth region, and probably offers information in the part of the brain that controls saliva, and possibly much more. It is also related to the specific areas associated with the Toothache Pain, such as a headache in the Right, rear portion of the pain.
If you drew up a map of a toothache pain, you would find it traces from the Tooth, to the Jaw, to the Brain, and possibly the Ears.