Pain perception: Ouch, Cupid!

24. June 2011

The heart races, the stomach is tight, one can hardly think of sleeping: heartache. These symptoms are not "just" mentally but also physically perceived as painful, for love sickness and physical pain activate the same areas of the brain.

While chopping onions, the knife-blade slips across and digs deep into the tip of the index finger; The inflamed root of a molar tooth rages and beats; These are both situations which bring about physical pain. Now a completely different scenario: Someone looks at a photo, or hears on the answering machine the voice of his ex-partner, who has recently left him.
What does this have in common with an inflamed molar tooth and a cut to the index finger tip? In neural terms everything, because it also leads to physical pain.

The dimensions of emotional pain

That unpleasant occasions in love affairs hurt just as much as physical suffering is now confirmed in a study by U.S. scientists. It reveals that “heartbreak” pain and physical pain activates the same regions of the brain. Social and emotional rejection gains with these results a further dimension and new meaning, says study leader Prof. Dr. Ethan Kross of the University of Michigan. Previous studies already concluded that between physical and emotional sensations there are parallels. Yet another study showed that the euphoria in the wake of new love stimulates the reward center in the brain and thus can alleviate physical pain. But the social psychologist Professor Kross and his team showed for the first time at the neuronal level why this is so.

Close-matching neural overlap

In the study, forty subjects were included who had experienced within the preceding six months an unwanted and painful end to their relationship. Their average age was 20.78 years. The 21 women and 19 men were recruited, among other places, from a campaign on Facebook. In order to participate in the study, no neurological or psychiatric disease and no chronic pain were allowed to be present. Other criteria of exclusion were the use of psychotropic drugs, antihistamines and steroids.

All study participants had to perform two tasks – one relating to their emotional feelings of rejection and the other to the sensation of physical pain. So that the mental pain load could be collated, the volunteers had to look at some photographs of their former partner, in order to recall the painful experience. Next, they were presented with shots of a friend with whom they recently had a positive experience. For the sensation of physical pain, participants were exposed to thermal stimulation via a cuff on the left forearm.The temperature of the cuff in one test series was so high that it was barely tolerable for the patients. In the other series the cuff was kept pleasantly warm.

As expected, viewing of the ex-partner and the very hot cuff generated significantly higher distress in those subjects than controls (p < 0.001). This was also confirmed by means of measuring brain waves, which the team led by Prof. Kross checked during all these tests. For this purpose, ongoing scans using functional magnetic resonance imaging (fMRI) were compiled. In their analysis it was shown that between the experience of physical and emotional pain there exists a direct and tight neural area of overlap, as the activation which brings about both sensations come from exactly the same brain areas: the secondary somatosensory cortex and the dorsal posterior insula, also known as the insular cortex. Both brain regions are considered responsible for the sensations of the physical pain.

Emotional pain is like physical pain

The Michigan study now shows that these areas of the brain are very likely be able to be activated by painful emotional stimuli and that a response follows at the physical level. Emotional pain differs thus not from physical. That this overlap had not been detected earlier is, in the opinion of Prof. Kross, based on the fact that until now emotional feelings as strong as lovesickness and separation had not been recorded in studies: “The intensity of the examined pain was simply not high enough and did not therefore stimulate the physical pain centers in the brain.”

Somatosensory association

In order to verify the specificity of the brain centers involved in physical sensations of pain, the U.S. scientists compared the results of their fMRI scans with those from meta-analyses. Included in these was data recorded from over five hundred studies of fMRI studies of brain areas for physical pain and negative and positive emotions. Using this comparison, the actual specificity of the two brain areas was able to be confirmed.

“Our data show clearly that the emotional experience of social rejection and loss is directly linked to physical pain,” says Prof. Kross: “An association at a common somatosensory level is presented here, which gives us many new insights”, most notably in the understanding of how love sickness and other emotional distress can lead to such far-ranging physical pain symptoms and various diseases.

The findings from Michigan, beyond that, also provide new evidence that we humans are extremely social creatures – so much so, that social rejection is evaluated by our brain to be as harmful as physical damage.

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Dr Sunil Sewak
Dr Sunil Sewak


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