If you grow up in a community that regularly consumes spicy food, you will dislike and reject it as an infant. But by about age five, you will likely have developed a palate for the pain. Oddly, this appears to be a very human phenomenon. No matter how you train rats or mice, they innately avoid spicy food, as a rule. However, whether or not you enjoy spicy food, there are dozens of examples of humans exposing themselves to painful or unpleasant experiences for the rush. This intentional exposure to pain is known as masochism, and has a lot to do with reward systems in the brain.
How can we experience pain as pleasurable, or get a sense of relief from it? Aren’t pain and pleasure diametrically opposed? Firstly, we need to discuss what pleasure looks like in the brain and how we trigger it. The ventral tegmental area (VTA) is a region at the top of the brainstem that becomes triggered in response to a “pleasurable” stimulus. This activation sends signals forward to the Nucleus Accumbens (NAcc) via dopamine neurons. This modulates the salience of your experience, or how much you pay attention to it. This activation can be in response to your vices such as alcohol, gambling, and orgasming, or through your virtues such as meditation, learning, and helping others.
“When people’s brains were scanned during this painful event, there was dopamine release in the NAcc.”
In a University of Michigan study, participants were subjected to an injection-induced aching of the jaw. When people’s brains were scanned during this painful event, there was dopamine release in the NAcc, which was proportional to the participant’s rating of how painful the experience was. This would imply that dopamine is not a molecule of pleasure, which it is often cited as, rather a molecule of attention. However, there appears to be a complex positive feedback loop when it comes to pain, dopamine, and endorphins.
A popular example of endorphin release in a painful context is exercise. When we exercise, our brain’s pituitary gland releases endorphins. Endorphins are pain-killers produced by the body that work by inhibiting pain signals. This turning down of cells’ signals in response to endorphin release has off-target effects on inhibitory neurons, specifically in the VTA leading to dopamine release. This is central to the pain-pleasure loop, in which the release of endorphins in response to pain could be the culprit that induces the NAcc activation seen in the previous study. Bizarrely, many types of pain, such as the pain of social rejection, can release endorphins in this manner.
“This turning down of cells’ signals in response to endorphin release has off-target effects on inhibitory neurons.”
It was discovered in the early 2000s that people with a gene that caused a beta-endorphin peptide deficiency have an increased vulnerability to alcoholism. Many alcoholics drink to soothe symptoms of anxiety and depression. Perhaps these symptoms come from a failure in their endogenous reward system. It is possible that people who report masochistic tendencies are at the opposite end of a spectrum of endorphin production to alcoholics. Perhaps, overproduction of endorphins can lead to an individual getting an emotional release from pain that is similar to what alcoholics get from drinking. But this is merely speculative, and most scientific institutions seem unlikely to fund the study of BDSM anytime soon. These apparently counter-intuitive behaviours could be entirely learnt, but it seems that on a neurobiological level, the systems of pain and pleasure are inextricably linked.