A team from the Netherlands Institute for Neuroscience in Amsterdam showed how humans can feel the pain of others: what happens to other people is directly mapped onto neurons in the insula, a region in the brain critical for emotions, according to a study published in the scientific publication eLife.
Sharing pain with others is key to our feeling of empathy and motivates us to help. People differ significantly in this ability to empathise, including patients with some psychiatric disorders who cannot do it at all. This is why the authors wanted to understand how our brain sees and interprets the pain of others.
This is not the first time researchers have attempted to understand empathy. However, previous studies relied on fMRI imaging scans to identify what brain regions activate when we watch somebody in pain. This approach produces limited results because fMRI cannot measure directly the activity of neurons.
To really understand where in the brain we perceive the distress of others, researchers need to introduce electrodes into the brain and directly measure the electrical activity as neurons process information. This is where epilepsy patients come in. Some cannot be treated using only pharmacological treatments. For these patients, surgeons implant electrodes directly into the brains to localise the origin of the epilepsy. This treatment often lasts one week with patients in the hospital while doctors record brain activity and wait for an epileptic event to occur.
During this study, these patients represented a unique opportunity to better understand the human mind: with their consent, patients engaged in a series of psychological tasks while their brain activity was measured through the electrodes they needed for treatment. The team showed participants short videos of a woman experiencing different levels of pain and then measured how strongly the neurons in the insula — a region in the brain involved in controlling emotions — responded to the pain in the video.
“As a neuroscientist, our dream is to understand how neurons make us who we are. What these patients do, by allowing us to record from these electrodes, is to make that dream come true: we could see, in real-time, how the pain of someone else is mirrored in the neurons of an observer. After decades of working on empathy, we could see empathy unfold in the human insula,” said Christian Keysers.
The insula can sense the state of our body and surroundings through information coming from our inner organs, as well as skin, eyes, ears, and nose, and produces what we call emotions. This includes when we experience pain in our own bodies.
Now, the researchers wanted to explore whether this region can also interpret when we see others experience pain. They found that activity in the insula reflected the level of pain from the videos. This is the first time researchers have shown how a region in the brain which is involved in regulating our own pain also contains a way to experience the pain of others. The authors suggested that we can empathise with the pain of others because our brain is capable of transforming their pain into activity in regions involved in our own pain.
What’s more, our brain seems to recognise both pain in the face of the actress in the videos (when the videos focussed only on the face) as well as coming from the body part that was injured (when the videos showed only the hand that was hit by a belt). For the authors, this shows how intricate and flexible this mechanism can be, allowing our brain to fine-tune our perception of pain experienced by others. “Other people’s suffering can be inferred from a variety of indicators: a painful expression, the intensity of the event that inflicts pain in them, etc. With this incredibly valuable data we collected from the patients, we see how the human insula might tune into whichever is available among these various cues when we experience the pain of other people,” said Efe Soyman.
In the future, the authors hope to extend their assessment beyond the insula to develop a complete map of where in the brain we perceive the pain of other people and how that regulates our feeling of empathy.
E Soyman, Bruls R, Ioumpa K, Müller-Pinzler L et al. (2022) Intracranial human recordings reveal association between neural activity and perceived intensity for the pain of others in the insula. eLife 11:e75197. https://doi.org/10.7554/eLife.75197