Exploring the Neurobiology of Empathy, Infant Development, and the Profound Impact of Sharing Pain
What really happens in the brain when you empathise with someone? How does empathy develop from infancy and shape our ability to connect with others? What is so special about empathising with others’
The Mirror Neurone System
Empathy is the ‘ability to share another person’s feelings and emotions as if they were your own’ (Collinsdictionary.com, 2019), and it is grounded in biological mechanisms which determine the extent to which a person has this capacity. The network which is key to understanding the neuroscience behind empathy is the mirror neurone system. Neurones are nerve cells - units of the nervous system which transmit action potentials (electrical impulses) throughout the body in order to convey information.
Diagram 1 - outline of a neurone
The axon of a neurone at rest is around 70 millivolts (mV) more negative than outside. Action potentials are generated in response to a signal, which causes sodium and potassium ions to flow rapidly across the membrane of the axon, ‘depolarising’ it by reversing the electrical potential difference from -70mV to around +40mV. This wave of depolarisation is propagated along the length of the axon, as current flows along it, conveying the action potential towards the axon terminal. The signal is conveyed to the next neurone through the release of neurotransmitters, which are chemicals messengers that either excite or inhibit the activity of the next neurone. A mirror neurone is a specific type of neurone which fires in response to a person observing an action in another person. Remarkably, they fire in the exact same way as the neurones that would fire if the person were to recreate the action being observed. Two main locations of mirror neurones are the sensorimotor system, which is involved in the planning and executing of actions; and the anterior cingulate cortex and insula, which are involved in emotional and cognitive processing and thus empathy. It has been shown that people who are self-reportedly more empathic demonstrate a higher level of activation in their mirror neurones. In a study carried out by Wicker et al., published in 2003, it was found that the neural substrates activated were the same for participants who observed people inhaling different odours (pleasant, neutral and disgusting), and for participants inhaling these different categories of odour themselves, thus supporting the idea that empathy involves the mirroring of observed behaviour in one’s own neural circuits.
Development
In 1949, Donald Hebb suggested a theory which came to be known as the Hebbian theory, and which can be summarised as ‘cells that fire together, wire together’. He suggested that repeated stimulation of two neurones strengthens the connection between them, leading to the capacity for neuroplasticity (the ability of the brain to change and develop in response to various experiences). It is believed that the mirror neurone system develops before 12 months, through Hebbian learning, and is an important part of neural development in infants. The evidence suggests that whilst a preexisting system for facial abilities may be present at birth, the development and refinement of facial movements is modified through social exposure, indicating the role of imitation and thus mirror neurones. As stronger activation of mirror neurones is associated with higher levels of empathy, it can be concluded that Hebbian learning, through strengthening connections between neurones in infants, contributes to their ability to empathise in the future.
Another factor which contributes to the development of empathic behaviour is prior exposure. It was discovered by Hernandez-Lallement et al. that rats who had previously experienced shocks were more likely to exhibit distress at observing other rats experiencing shocks. This idea matches the conclusion of a study published by Greenberg et al. which found that adults who experienced a traumatic event in childhood exhibited a higher level of empathy than other adults.
Empathy for Pain
Some of the key brain regions involved in empathy include the anterior insula and mid-cingulate cortex (MCC). However, Timmers et al. discovered that empathy for pain is different from empathy for other negative feelings, such as anger, fear and disgust. Whilst the anterior insula may be involved in empathy more generally, specifically the bilateral mid-insula responded to empathy for pain. Pain related empathy also activated more of the MCC, leading to the suggestion that empathy for pain could evoke a stronger response than empathy for other negative sentiments.
The mirroring nature of empathy can be seen particularly in a study carried out by Rütgen et al., who demonstrated that participants who experienced first hand pain, and those who experienced empathy from viewing pain in other people, showed a similar reduction in response when given a placebo ‘painkiller’. Thus, analgesic drugs can reduce the ability of a person to empathise with the pain of others.
Conclusion
Empathy is clearly no trivial matter, and the neural circuits involved play a part in many crucial processes such as the development of facial expressions and neuroplasticity. The power of painkillers in modulating empathy for pain carries potential for helping workers who are vulnerable to being affected by the pain of their patients. The reason why empathy for pain appears to be unique compared to other forms of empathy still remains to be discovered, but if anything, it highlights the power of pain, and its role in shaping social interactions within a species.
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