Reflecting on Mirror Neurons

13 December 2011

 MRI scan. Wellcome Images
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MRI scan. Wellcome Images

Packed Lunch is not just about science; it is also about the lives of scientists. At a recent event, Lydia Harriss found that happenstance plays a part not only in scientific discoveries but also in scientific careers…

History is littered with stories of great scientific discoveries happening by chance. The haphazard drifting of mould into a dish of bacteria that led to the discovery of penicillin. The sloshing bath water that inspired Archimedes’ principle of displacement. A pocket full of melted chocolate hinting that microwaves could be used to cook food. But the one about the monkey and the peanut? I confess that this particular example of scientific serendipity had passed me by, until I went to a Wellcome Collection Packed Lunch event in which Dr Zarinah Agnew spoke about her research on mirror neurons.

It turns out that mirror neurons, nerve cells found in the brain that are activated when an individual carries out an action or sees someone else performing the same action, were also discovered by chance.

In 1992, researchers in a lab in Italy had just finished their experiments. They had been looking at the electrical activity of a particular neuron inside a monkey’s brain as the animal picked up a peanut. While clearing up, one of the researchers picked up a peanut, causing the same neuron to activate in the monkey’s brain, even though the animal stayed still and was only watching the researcher pick up the peanut.

This ‘mirror’ response was totally unexpected, and since then mirror neurons have generated a great deal of excitement. It’s been suggested that they are able to match an observed action to an executed action, and could be responsible for our ability to understand, recognise and imitate actions. Wilder speculations have included proposals that mirror neurons may play a role in autism, where a person’s ability to understand other people’s actions is affected. For example, ‘broken’ mirror neurons might prevent a person from mentally simulating an action that they’ve seen someone else perform, stopping them from correctly understanding the reason behind it.

Dr Agnew was quick to point out that although these theories linking mirror neurons to autism might be true, they are a massive leap from the evidence we currently have. No direct evidence of mirror neurons has yet been found in humans, as we can’t readily be experimented on with the electrical recording technique used to identify these neurons in monkeys.

During her PhD, Dr Agnew was able to show that human brains do produce a mirror response similar to that seen in monkeys, using magnetic resonance imaging (MRI). MRI is a technique that can measure brain activity by showing which parts of the brain require increased levels of oxygenated blood. She found that a particular region of the human brain becomes active when people both perform and watch an action, such as a hand-wave.

She also discovered that this system is more complicated than previously thought, by showing that mirror responses vary for different kinds of action. This intriguing finding indicates that the brain does not simply simulate every type of action in the same way, but encodes different actions in different ways.

Curiously, Dr Agnew’s first encounter with mirror neurons also happened by chance, when, after finishing her undergraduate degree in neuroscience and frantically looking for a PhD, one of her housemates showed her an article about mirror neurons in a copy of the Economist. Inspired, she scrambled off to write the proposal for her PhD project straight away. It took Dr Agnew a year to search for funding and a supervisor, but once she got her PhD underway, she went on to do exactly what she’d described in her initial proposal. Impressive stuff, given that the path of a PhD is often winding (my own certainly took a few twists and turns), and very few people actually achieve what they set out to do at the start.

Since finishing her PhD, Dr Agnew has moved on to using MRI to look at the links between action and perception in relation to speech, as it’s been suggested that mirror neurons might also be involved in understanding sounds made by the mouth. Describing her research as “a lot more fun than I thought [it would be]… a real adventure”, she shows every sign of continuing on her terrifyingly directed career path.

It seems that the ‘right place, right time’ variety of chance certainly has its part to play in research, but success takes much more than mere luck. From hearing Dr Agnew talk about her own career, it’s clear that determination, ability and passion are essential for making the most of those tantalizing moments of serendipity when they do come along.

Lydia Harriss is a graduate trainee at the Wellcome Trust.