Hidden under her bed, sobbing, she tries to reach the emergency services, but the line is cut. You watch the scene, your heart rate accelerates. The stranger quietly climbs the steps one by one … He grabs her leg.

You’re sweating and yet you’re safe, in front of the biggest horror movie cliché. But how do we manage to put ourself in somenone else’s shoes to the point where we seem to live, through the other, the same situation? This is the question I will try to answer.

First, I’m taking you back 30 years ago in Italy. Researchers are studying the macaque motor cortex (the region controlling movements):

Experiment Mirror neurons

When the macaque grabs food, neurons discharge meaning its muscles our contracting in its direction. It’s not surprising.

At the end of the experiment, someone takes the rest of the food to put it away.

Experiment Mirror neurons

To the researchers amazement, a group of neurons activated while the macaque was grabbing food also discharged when the researcher grabed it!

It seems that a group of neurons is activated according to the gesture of the person they observe. As if the monkey’s brain mirrors what’s happening in the brain in front of them : The mirror neurons.

Mirror neurons

It is from this moment that researchs on the subject multiplied in order to better understand their functioning in the monkey’s brain and to know if the human brain also has this type of neuron.

Monkey

Mirror neurons have been studied a lot in the macaque ventral premotor area (F5) since it’s the first place they were found.

F5 monkey brain area Mirror neurons

Over time, they discovered that these neurons, found in several regions of the brain, instead formed a complex neural network. Moreover, this network seems to react specifically to hands and mouth movements observed and executed.

The macaques share 93% of their genes with humans, which makes us very similar. However, we aren’t identical. Therefore, the results obtained in monkeys cannot be directly attributed to humans. Study standards are different with humans and monkeys. It is therefore more difficult to investigate mirror neurons in humans in such a precise manner.

Human

To identify the manifestation of potential mirror neurons in humans, researchers measured neurons activity using electroencephalography.

Electroencephalography: Neuronal activity mesuring method using small electrodes placed on the head. The traces which illustrate the electrical activity of the brain are called electroencephalogram.

Electroencéphaolgraphie

Electroencephalography is used to measure rhythms in the brain. Without going into details, the brain electrical activity is governed by different rhythms. So, when we record them, we get information about what’s going on in a person’s brain. Here, we are mainly interested in mu rhythm. Mu waves look like this:

Research has shown that while a person makes, observes or imagines a movement, the power of mu decreases. This is called mu suppression. It’s believed that mu supression could represent the mirror neurons system activity. It’s therefore by observing mu supressions that we know mirror neurons are active.

Mirror neurons functions

Current research doesn’t reveal exactly what mirror neurons are for. On the other hand, some researchers allowed themselves to put forward some hypotheses about the roles they could play. It is possible that all, some, or none of these functions are actually attributable to mirror neurons.

Imitative learning

Since, by observing a person doing an action, our brain replicates this action at the same time, we could deduce that these neurons are involved in learning these behaviors. Having already, in a certain way, made the gesture in our head would help us to better replicate the same behavior later.

In fact, research has shown that some brain regions are particularly active while we imitate a behavior. To better understand this phenomenon, they asked the participants to either execute a movement with their hand, imitate a hand movement or observe a hand movement. A Broca’s area sub-section, the posterior parietal cortex and the parietal operculum, were more active during imitation than execution and observation.

cerebral regions Mirror neurons

Mirror neurons to predict others intentions

These neural networks could also allow us to predict the next movements a person is about to make. In a study, participants were asked to watch videos where we see a person raising a cup of coffee. The gesture is identical in the 3 videos, but the context is different:

  1. Someone taking a full coffee on a clean table (the participant can therefore predict he raises his coffee to drink it)
  2. Someone taking an empty coffee on a messy table with empty food wrappers (so the participant can predict he wants to throw it away)
  3. Without context (the participant cannot predict anything)

Brain imaging shows greater mirror neurons activation when viewing the first two versions of the video. So, the mirror neurons system seems to react to gestures linked to an intention.

According to this study, the temporo-parietal region, the medial prefrontal cortex and the temporal poles make it possible to better predict the actions observed. By reproducing the actions in these brain regions, it would allow us to better guess what a person is about to do. It can be very helpful in survival situations.

cerebral regions, Mirror neurons
Yawn, Mirror neurons

Communication

Some researchers believe there are mirror neurons in Broca’s area subsection (responsible for language production): the Broca’s area. Indeed, these neurons are activated during mouth and tongue imitation. So, they believe this region could be involved in language development.

Also, they think mirror neurons provide additional support to better understand what we are told. To do so, we would replicate the mouth movements of our interlocutor in our brain as if we were ourselves saying the same words.

Songbirds, Mirror neurons

Mirror neurons behind empathy

In an other study, participants were exposed to bad smells. During this time, researchers were paying attention to their brain imagery. They observed their insula getting activated when they felt disgusted.

insula

Then, they showed them pictures of people feeling disgusted. Then, they observed the same neurons activating than in the first part of the experiment. So, some neurons activate as much when we feel disgusted and when we look at a person being disgusted. Another similar study achieved the same results by causing a little bit of pain to the participants. They found the same activation in some parts of the insula when a person experience pain or see another person experience pain.

Autism, Mirror neurons

In short, current studies show that mirror neurons respond to other people’s mouths and hands movements. These gestures must be motivated by an intention for them to activate this system. These neurons are distributed in several brain regions. Depending on the region, they have a particular function such as predicting actions, empathy, communication, ect. Humans are not the only ones seeming to have mirror neurons. They have been found in other primates, birds and even in dolphins.

There is still a lot of research to do to demystify mirror neurons and better understand their impact on our cognitions and the development of psychopathologies. Unlike the results obtained in macaques, the current results in humans are not unanimous within the scientific community. But whether or not these neurons have all the characteristics we attribute to them, I still consider it very impressive to know we could have neurons which mirror our fellow humans.

English isn’t my first language so there might be some mistakes. If you want, let me know in the comments bellow if you found any so I can fix them. Thank you!

Keep Reading!


Sources

Goldstein, E. B. (2018). Cognitive Psychology (5e éd.). Cengage.

Janilière, H. (18 mai 2017). Pourquoi bailler est-il contagieux?. Sciences et Avenir. https://www.sciencesetavenir.fr/sante/cerveau-et-psy/pourquoi-bailler-est-il-contagieux_100834

Jarder, J. (12 avril 2007). Le macaque partage 93% de ses gènes avec l’homme. Figaro. https://www.lefigaro.fr/sciences/2007/04/13/01008-20070413ARTFIG90017-le_macaque_partage_de_ses_genes_avec_l_homme.php

Jeon, H., & Lee, S. H. (2018). From Neurons to Social Beings: Short Review of the Mirror Neuron System Research and Its Socio-Psychological and Psychiatric Implications.Clinical psychopharmacology and neuroscience : the official scientific journal of the Korean College of Neuropsychopharmacology,16(1), 18–31. https://doi.org/10.9758/cpn.2018.16.1.18

Kilner, J. M., & Lemon, R. N. (2013). What we know currently about mirror neurons.Current biology : CB,23(23), R1057–R1062. https://doi.org/10.1016/j.cub.2013.10.051

(s.d.) Des neurones miroirs à la base de la communication?. Le cerveau à tous les niveaux. https://lecerveau.mcgill.ca/flash/a/a_10/a_10_cl/a_10_cl_lan/a_10_cl_lan.html

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