In 2000, prominent neuroscientist V. S. Ramachandran wrote that mirror neurons would do for psychology what DNA did for biology (Ramachandran: 2000). Although he has since admitted that this was an overstatement, mirror neurons have still contributed a lot to our understanding of how the brain works in social situations- especially those that require empathy. But how?
Our nervous systems have two types of neurons; motor neurons and sensory neurons. Motor neurons are responsible for actions, delivering signals from the brain to effectors such as muscles. Meanwhile, sensory neurons deliver signals from a receptor, such as pain or temperature receptors in the skin, to appropriate areas of the central nervous system. Every organ in the body has a mix of both motor and sensory neurons (Anderton: 2019).
Unlike sensory and motor neurons, mirror neurons have both sensory and motor functions. From initial studies looking at how they operate in monkeys, researchers found that they are activated both when an action is being observed (sensory) and when being executed (motor). This means that similar areas of the brain are activated when a monkey picks up a banana and when they observe another monkey doing so, in turn meaning that motor neurons may play a large role in how we feel empathy.
Further research has confirmed these findings. In a recent study conducted at the Netherlands Institute for Neuroscience for example, researchers found that the anterior cingulate cortex (ACC), which is active while experiencing pain, can also become active when observing others in pain. Showing more activity in those with high levels of empathy and less in those with psychopathy, from studying both rats and humans, the researchers found that the ability to feel pain comes thanks to the presence of mirror neurons in the ACC (Paddock: 2019).
According to V. S. Ramachandran, “It turns out these anterior cingulate neurons that respond to my thumb being poked will also fire when I watch you being poked—but only a subset of them...If I really and truly empathize with your pain, I need to experience it myself. That’s what the mirror neurons are doing, allowing me to empathize with your pain (Marsh: 2012).”
Due to this link between mirror neurons and empathy, some have suggested that autism, a condition characterized by a lack of empathy, may be due to a deficit of mirror neurons in the brain. Although some studies using brain imaging have confirmed this link, others suggest it to be false. A study by New York University for example found no link between faulty mirror neurons and autism after observing brain activity of 13 autistic people and 10 controls while in a functional MRI scanner (Callaway: 2010).
Despite these findings however, UCLA neuroscientist Mirella Dapretto said that its sample size is too small to draw meaningful conclusions and that either way, it does not rule out the idea of autism being caused by malfunctioning motor neurons (ibid.). Yet, as no further study has so far delved into how mirror neurons function in the brains of those with autism, whether or not this is the case remains a mystery.
To conclude, although it seems clear that mirror neurons have some part in promoting empathy, they are not solely responsible for the behavior. Other factors are likely at play too, hence why humans, monkeys and rats, although all have mirror neurons, tend to display different degrees of empathy.
Ramachandran, V. S.: Edge.org
Anderton: Kate: News-Medical.net
Paddock Ph.D, Catharine: Medical News Today
Marsh, Jason: Greater Good Magazine
Callaway, Ewen: New Scientist