Masochism activates areas of the cortex involved in empathy, emotions and self-awareness
You don’t come across scientific papers about the neuroscience of masochism very often.
In fact, BDSM is still a taboo subject in science. Researchers only work on issues for which they can get funding. In the USA, Congress has been reluctant to give money to government agencies like the National Institutes of Health (NIH) to do research on sex, much less on “perversions” like BDSM.
That’s why I got so excited when I found this study, done in Germany by scientists from Heidelberg University:
Contextual modulation of pain in masochists: involvement of the parietal operculum and insula. S. Kamping, J. Andoh, I. C. Bomba, M. Diers, E. Diesch and H. Flor. Pain 2016, Vol. 157 Issue 2, Pages 445-45. PDF.
They used functional magnetic resonance (fMRI), a powerful brain imaging technique, to compare the brains of masochists and non-masochists. A clever experimental design combining fMRI with masochistic images and pain let them reach some interesting conclusions.
Questions about masochism
Here are some questions answered by this study:
Are masochist less sensitive to pain?
Does a masochist’s brain respond to BDSM pain (for example, a spanking?) and other forms of pain the same way?
Are there brain areas specifically activated by masochism?
Is masochism addictive?
There were 32 participants in the study: 16 masochists and 16 non-masochists (controls). The masochists were 8 men and 8 women, while the controls were 4 men and 12 women. The masochists were recruited through the internet and in local BDSM meetings. They were further screened using a questionnaire about masochistic activities: they had to consider themselves masochists, prefer the submissive (bottom) role, and more than 50% of their sexual activity had to involve pain.
Excluded from the study were people with mental disorders or chronic pain, and those for whom masochist behavior caused “clinically significant distress” or impaired their social functioning. These exclusion criteria are reasonable, but they may have biased some of the conclusions of the study. For example, I found that masochists with chronic pain successfully use sadomasochism to control the pain caused by their disease - see my survey of 136 masochists. These people seem to be less sensitive to pain than non-masochists, contrary to one of the findings of the study.
The painful stimulus was a laser light applied to the dorsal part of the hand. This produced an intense “pinprick-like” pain of short duration. Participants rated the subjective intensity of the pain using a scale of 0 (no pain) through 10 (“worst pain imaginable”). Laser intensities that gave pain ratings of 3 to 4 were used in the rest of the study.
Another component of the study was masochistic pictures, which were used to evoke erotic feelings in the participants (masochists and controls). Apparently, the scientists didn’t trust themselves to choose the most exciting BDSM pictures, so they recruited 18 additional masochists to pick the 10 best ones. Additionally, three other sets of 10 pictures were used, evoking neutral, positive and negative emotions, respectively.
Pictures were selected for their arousal and valence. In this context, arousal means how much an image captures our attention. Valence refers to whether the picture evokes in us attractiveness (we like it) or averseness (we dislike it). Joy and sexual arousal are emotions with positive valence, whereas fear, sadness, disgust and anger have negative valence. In this study, it was expected that a masochistic picture like a flogging would have positive valence for masochists and negative valence for controls. It would be interesting to know how this is reflected in the activation of different brain areas.
The main part of the study consisted of using functional magnetic resonance (fMRI) to image the brain of the subjects while they were viewing the pictures through goggles and received the painful laser stimulation on the hand. fMRI is based on the fact that when neurons in a brain area are more active, there is more blood flow to that area. Powerful magnetic fields and radiofrequency pulses are used to locate molecules of hemoglobin carrying oxygen in the blood. This way, areas of the brain with increased and decreased blood flow can be identified while the brain does things like feeling pain or getting sexually aroused. Increases and decreases in the blood flow tell us which areas of the brain are more and less active, respectively.
Unlike positron emission tomography (PET) and other brain imaging techniques, fMRI does not require injecting substances to the participants. However, the subjects have to be held immobile inside a huge apparatus that produces the magnetic fields. The fMRI results are shown in tridimensional images of the brain in which brain activity is color-coded: yellow, orange and red show increasing activity, whereas cyan and blue show decreasing brain activity. Grays mean no changes.
A primer about brain areas
To understand the fMRI images, we need to know a bit about the brain areas involved in pain and emotion. So please bear with me while I run you through the brain anatomy that is important for the results of this study.
Cortex means ‘crust’ and is the outer layer of the brain. It is overdeveloped in humans, giving us our extraordinary thinking capacities. During the evolution of apes and hominids, it grew so much that the only way it could get wrapped inside the skull was by developing numerous wrinkles, called gyri. Each gyrus is separated from the next one by a groove called a sulcus.
Apart from them, there are three deep crevices in the cortex, called fissures. The deepest one runs from front to back and divides the brain into the right and left hemispheres. Inside this fissure there are two portions of cortex facing each other. Its deepest part, forming an arch around the center of the brain, is the cingulate cortex. The front part of the cingulate cortex is the anterior cingulate cortex (ACC), which is in charge of making decisions (Engstrom et al., 2014). As we will see, it’s important in pain and masochism.
A second fissure is the central sulcus, which cuts around the sides of the cortex and divides it into frontal and posterior cortex. Roughly speaking, anything forward of the central sulcus has to do with action and anything backwards it has to do with sensation. Thus, the vertical gyrus just forward from the central sulcus - the anterior central gyrus - is the primary motor cortex, which contains a map of all the muscles in the body and executes the last step in processing movement. The vertical gyrus just back from the central sulcus - the posterior central gyrus - is the somatosensory cortex, which contains a map of the whole surface of our skin and is where all tactile and pain sensations terminate. The somatosensory cortex is where we feel where pain is located in the body.
The third fissure is the lateral sulcus, which runs front to back on the side of the brain. The cortex continues inside this fissure and expands inside each hemisphere, forming an island of cortex, which is why it is called the insula - which is Latin for island (Gogolla, 2017). The area of cortex around and inside the lateral sulcus is called the operculum. As we will see, it plays an important role in masochism. The insula is a fascinating brain area because it is where a bunch of our emotions come together. It is responsible for the salience of our sensations: how much a sensation matter to us. For example, pain, itch and sexual pleasure are sensations with high salience.
In humans, the anterior part of the insula is much bigger than in other mammals, even the apes. During human evolution, the function of the anterior insula became different between the brain hemispheres (Craig, 2011). While the posterior insula tells us how we feel at each moment, the right anterior insula is able to imagine how we would feel under certain circumstances (Craig, 2009). It is able to create hypothetical feelings. Hence, it is crucial for empathy - imagining how another person feels - and theory of mind - representing the mental state of another person.
The unpleasantness of pain is processed by the insula, whereas the location of pain is determined by the somatosensory cortex. The drive to do something about the pain comes from the ACC.
Pain sensations from the body travel up the spinal cord and enter the brain, making relays in an area of the brain stem called the parabrachial nucleus, which connects with the amygdala, the part of the brain responsible for fear and anxiety. The pain pathways continue to the thalamus, which is an area in the center of the brain that serves as a relay for all our sensations, except smell. In the thalamus, pain neurons make synapses with neurons going to three areas of the cortex: the somatosensory cortex (where is the pain?), the insula (how bad is the pain?), and the ACC (what am I going to do about the pain?).
I tried to condense that as much as possible, but we need this information to make sense of the findings of this study on masochism.
Hey, who said that neuroscience was easy?
Some interesting findings about the masochists
The masochists showed interest in masochism when they were 17 years old, on average. The earliest was at just 7 years of age and the latest was at 36. Their first masochist activity was when they were 25, on average, with the earliest again happening at 7 and the latest at 47.
This shows that masochistic desires can appear during childhood, even before full-blown sexual desire develops during puberty. A lot of people become masochists when they are teenagers. However, some come to it later in life, perhaps because they are introduced to BDSM by their lovers.
Responses to masochist pictures
Masochistic pictures produced similar levels of arousal (excitement) in masochists (4.3 ± 1.4) and controls (4.2 ± 1.8), on a scale from 1 to 9. However, they had positive valence (attraction) in masochists (6.2 ± 0.9) and negative valence (rejection) in the controls (3.4 ± 1.2), again on a scale from 1 to 9.
Masochists also liked more the images that were more arousing, as shown by a high correlation between the arousal and the valence of the images.
All the other images (neutral, positive and negative) were rated similarly for arousal and valence by the masochists and the controls.
This confirms the assumption of the investigators that masochists like to watch things like floggings or canings, while other people dislike these images. Still, these images are equally impactful to everybody.
Masochists dislike pain outside an erotic context
When pain was applied without showing any pictures, masochists and controls rated the pain similarly for its intensity and unpleasantness.
Without pictures, fMRI showed similar activation of the brain by the pain stimulus in masochists and controls. In both groups, pain activated the brain areas involved in pain: thalamus, primary somatosensory cortex, insula, operculum and ACC. These areas were activated to the same degree in masochists and controls.
This refutes the popular belief that masochists like any kind of pain, in any circumstances. Masochists only like pain when delivered in an erotic setting.
Brain areas activated by masochistic images
In this part of the study, the participants were shown masochistic images without the pain stimulus to see what brain areas were activated. The masochists showed a higher activation of the right ACC and the right anterior insula in response to these images.
I find this fascinating. It shows that what the masochists are doing is imagining the feelings of the submissive partner in the picture using their right anterior insula. The activation of the ACC perhaps represents their desire to be in that situation.
Masochistic images decrease pain in masochists
In this experiment, participants received the laser pain stimulus while viewing the masochistic images. They were asked to rate the intensity and unpleasantness of the pain. Masochists reported less pain intensity (2.2 ± 1.5) than the controls (3.5 ± 2). They also reported the pain as being less unpleasant (1.6 ± 1.2) than the controls (3.2 ± 2.3). These decreases in pain intensity and unpleasantness were as strong as the effect of opioids like morphine.
Therefore, when they are able to eroticize pain, masochists feel pain as being less intense. This indicates that they activate the pain inhibitory pathways that connect the brain stem with the spinal cord, probably the ones that use endorphins. The decrease of pain unpleasantness probably has a different mechanism. This was explored using fMRI in the next experiment.
Brain responses to combinations of masochistic images and pain
Doing fMRI while viewing of masochists images and enduring pain stimulation showed differences between masochists and controls in the activated brain areas. Masochists showed a higher activation of the operculum - the part of the cortex next to the insula -, the superior frontal gyrus and the middle frontal gyrus, two areas of the frontal cortex. The superior frontal gyrus is involved in self-awareness.
In masochists, there was also less functional connectivity between the operculum and the insula, motor cortex, right thalamus and right ACC. This did not happen in the controls. Since the motor cortex and the ACC are involved in the planning of actions, this could mean that masochists do not feel a need to respond to pain. Negative signals from the operculum to the insula may represent the decreased unpleasantness of pain in the masochists.
One surprising negative finding was that fMRI showed that in the masochists there was no activation of the reward pathway of the ventral striatum. This pathway connects the ventral tegmental area (VTA) with the nucleus accumbens, where it releases dopamine. It has been wrongly considered the pleasure pathway, because animals and humans compulsively stimulate it when implanted with electrodes in it. It is also the part of the brain where drugs like opioids and cocaine produce addiction. Today, we know that this pathway does not produce pleasure, but motivation and responses to rewards (Salamone and Correa, 2012). In any case, the fact that this reward pathway is not activated by masochism shows that it is not addictive.
The take-home message is that masochism is an erotic activity that depends on the fetishization of certain relationships, situations, objects and actions. In this BDSM setting, the responses of masochists to pain are dramatically changed, so that they feel less pain and find it less unpleasant (and likely pleasant).
This validates the experiences of masochists when they talk about a BDSM “scene” and “sub space” - an altered state of consciousness brought about by experiencing pain in this setting.
The masochistic experience is not similar to the effect of opioids and other drugs, and does not produce addiction, because it does not activate the dopamine pathway of the striatum (VTA to nucleus accumbens) that mediates the effects of addictive drugs. Instead, it involves the activation of cortical areas of the brain that mediate emotions, empathy, feelings and self-awareness. Therefore, masochism is a complex cognitive and emotional experience anchored in a certain culture and values, and which drives intimate and profound relationships.