Mirror Neuron System

Biological control of social cognition including the Mirror-Neuron System

This section will look at biological explanations of social cognition.  However, at the outset it is important to bear in mind that different explanations of similar characteristics are not mutually exclusive.  Evidence for biological explanations do not mean other explanations are wrong; they are simply viewing the behaviour at a different level. 

From the point of view of the perspective; it does say ‘including the mirror-neuron system’ and in fact this appears to be the ONLY biological explanation worth mentioning! 

The Mirror-Neuron System

Understanding the behaviour and thoughts of others is a very useful characteristic of any social creature.  All the primates fall into this category as do a few lower species.  In evolutionary terms therefore, if an individual is socially adept then perhaps it has a greater chance of passing on its genes.  Therefore biological mechanisms underlying such a predisposition are likely to be selected for meaning they are likely to be widespread within the gene pool.

 

From a behaviourist point of view, much of our behaviour is copied or learned from others (social learning).  Individuals that are better at interpreting the actions of others will be better placed to copy and more likely to do so if they see others being rewarded for their behaviour (vicarious conditioning). Gallese et al (1996) Measured the brain activity of monkeys performing a grasping action.  Later when monkeys observed other monkeys making the same action their brain activity was the same.  This is the basis of the mirror-neuron system.  Behaviours we perform ourselves result in very similar brain activity to those similar behaviours we observe. The researchers concluded that this system allows for the action and understanding of others’ actions.

Does the mirror-neuron system exist in humans?

Rizzoletti et al (2006) got human participants to either watch the experimenters making various hand gestures or to make the gestures themselves.  Either way the neural activity in the hands was very similar.

PET scans identified the following brain areas as being involved:

Superior Temporal Sulcus (STS)	Responds to seeing body parts move
Inferior Parietal Lobule*(IPL)	Seems similar to the area involved in monkeys
Inferior Frontal Gyrus (IFG)

*such a sexy word!

This provides evidence for a similar system to humans but how can we be sure it acts to help us understand the behaviour of others rather than just copy it?

Umilta et al (2001)… an ingenious experiemt!

The researchers got monkeys to watch experimenters carrying out various actions. 

1. The experimenter is seen to reach for an item of food
2. An item of food is hidden from view behind a screen.  The researcher then reaches for it as in condition 1, but this time cannot be seen accessing the food.

Findings

Even when the food was hidden, more than 50% of the mirror-neurons still fired and half of these did so as strongly was when the food was in view.  Umilta et al concluded that the monkey brains were responding to the understanding of what the action entailed (i.e. getting food) even though the food could not be seen.

As a further test to show that it wasn’t the action per se that was triggering the mirror neurons, there was a third condition in which no food was hidden and the monkeys watched the same action as in condition 2.  This time the mirror neurons did not fire.  Clearly the firing was triggered by the understanding of the action. 

Dinstein et al (2007) measured the activity in five human brain areas, known to be involved in the mirror-neuron system, while they watched or performed an action. 

Although watching and performing an action resulted in the same brain AREAS being excited, the researchers could not say with certainty that it was the same NEURONS that were firing each time.  Scanning techniques are simply not sufficiently sophisticated to measure at this level. 

Autism and the mirror-neuron system

Baron-Cohen’s work suggests that autistic children lack a theory of mind.  If we assume that the mirror-neuron system is the basis of ToM then we would expect autistic children to have a defective MNS.

Depretto et al (2000) compared autistic children with non-autistic children as they either watched or attempted to imitate one of five facial expressions.  Expressions were either anger, fear, happiness, neutrality, or sadness. 

Findings

1. Autistic children showed less activity in the MNS as they watched or copied the expressions
2. The greater the autistic symptoms the lower the level of activity recorded.

However, there are issues with cause and effect.  We cannot be certain that the autism is due to this lowered level of activity.  Lowered activity could be due to the autism or a third factor could be causing both.

However, some autistic children have shown signs of cortical thinning (means exactly what it says on the tin) in areas known to be related to MNS.

But

Autistic children have a whole range of symptoms, only one of which is inability to understand or interpret the actions of others.  It is difficult to see how MNS could explain symptoms such as the savant-like abilities of some autistic children.

The MNS is not defective in all autistic children suggesting more than one cause of the disorder. 

Mirror neurons and autism:
To investigate this connection, Iacoboni et al studied the brain activity of 20 child subjects, half of whom had autism. The subjects saw 80 pictures of faces expressing anger, fear, happiness, sadness, or nothing in particular. The researchers asked some subjects to merely view the faces and others to imitate them.  In the group of autistic children asked to imitate the faces, the researchers found no activity in brain regions associated with mirror neurons.  The more severe the condition, says Iacoboni, the less active the mirror-neuron system seems to be.

 

 

 

 

 

 

 

 

 

Emotion

Is the MNS involved in our ability to understand or empathize with the emotions of those we observe?

Phillips et al (1997) measured activity in two brain structures, the amygdale and the insula, both known to be involved in emotion and particularly in our response to disgust!  Participants were either exposed to disgusting stimuli (in the form of unpleasant smells) or they watched the facial expressions of other people exposed to similarly disgusting things. 

Both brain structures responded in a similar way regardless of whether the disgust was being experienced or observed in others. 

Note: the five main emotions are usually considered to be: love, happiness, anger, sadness, and fear.  However, disgust is often tested experimentally due to fewer ethical issues! 

It is also worth mentioning that the size of the response increased in proportion to the level of disgust evident on faces of those being observed.

In a similar follow up study, participants had electrodes fitted to their hands and they received painful electric shocks while activity was measured in the limbic system.  Later the participants watched as the electrodes were attached to the hands of a loved one.  When told that they would receive the same shock as they had experienced earlier a similar pattern of firing was noted in the same brain structure. 

However, as with earlier studies it is difficult to conclude that the very same neurons are being fired in watching and experiencing; just similar brain areas!

Phillips suggests that our understanding of others’ emotions occurs at two levels:

Cognitive understanding: we see the person being sad, disgusted etc. and have an understanding based on past experience of how this feels. 

Experiential: on observing a sad or disgusted person the sensory input is mapped directly onto a corresponding motor area that mirrors their response in our brain.  We then experience the same emotional response as the person being observed.

If this latter one is the case then we have a biological mechanism for empathy and true appreciation of the feelings of others.  It might also partly explain certain contagious behaviours such as laughing and yawning. 

Overall evaluation of the Mirror-Neuron System

The model does seem to offer a sound biological explanation of our ability to understand others. 

However there are a few issues:

Methods: the fMRI (functional magnetic resonance imaging) technique is unable to measure specific neurons.  Therefore, as already mentioned we cannot be certain that the very same neurons are being fired when we experience and when we observe.

Much of the research has been carried out on monkeys who have nowhere near the same social repertoire as humans.  We therefore must have a more sophisticated MNS or have other, as yet undiscovered, biological systems underpinning theory of mind.

Gopnik is a particularly staunch opponent to the MN theory.  Apart from its basis in animal research she is also opposed to the reductionist nature of the theory.  Can altruistic behaviour and true empathy be reduced to activity in a set of cells?  Similarly Eisenberg (2000) believes that early understanding of another person’s distress may be the result of MNs but a fuller appreciation and true empathy only comes about through perspective taking which she believes involves far more than the simple MNs. 

Gopnik also questions the innate nature of mirror neurons.  Since imitation is present at birth it has led many to assume that we must be born with a mirror-neuron system fully intact (innate).  Gopnik suggests the possibility that mirror neurons arise through experience.  Hebb suggested the theory of cell assemblies, in which neurons that fire together, wire together.  They form a connection.  Mirror neurons therefore may not be present at birth but develop through the process of association due to experience. 

Mirror neurons and language acquisition

Language development is probably the most important of all human abilities and seems to be the one characteristic that sets us apart from all other species.  Non-human animals communicate but practically all impartial research suggests that it is only humans that have the ability to impart information about experiences and acquired knowledge. 

The main language areas in the brain are Wernickes (concerned with the understanding of language) and Broca’s area (concerned with language production), both named after their respective discoverers. 

Attempts to teach language to other species have generally failed, though the Savage-Rumbaughs and others would disagree.  What seems essential to language acquisition is immersion.  Rather than sitting down and being formally taught to acquire language, humans seem to pick it up by watching and listening to others and then imitating.  Clearly mirror neurons would be useful in this process.  Binkofski et al (2000) used brain imaging techniques to show the existence of mirror neurons in Broca’s area.  

 

Latest stuff

One of the main criticisms of research into mirror neurons centres on our inability to measure activity in specific neurons.  Research simply shows that similar regions of neurons fire when observing and actually doing or experiencing.  These regions comprising perhaps half a million neurons! 

However, Iacobani (reported by Slack 2007) measured the activity of individual neurons in the brains of volunteer epileptics.  The researchers were trying to find neurons responsible for triggering seizures.  The volunteers performed simple actions and then observed others performing similar actions.  Meanwhile the activity of 286 individual neurons was recorded by the researchers.  They reported 34 neurons were the same pattern of firing was triggered by both performing an action and watching it being performed by others (mirror neurons).  Interestingly they found different types of MN including one that becomes suppressed when we watch others perform the same action.  The researchers concluded that this might explain why we don’t blindly copy everything that we observe and perhaps how we distinguish between our own behaviour and that of others. 

More primitive motivations, such as hunger, might also govern the mirror system.  In a study by Decety et two groups of subjects were shown a video of a person grasping food.  Some of the subjects had fasted for at least 12 hours before the viewing; others had a meal before the session.  Using functional imaging, the researchers found greater activity in the mirror systems of the hungry subjects. When a blender brain is running on empty it reacts strongly to the site of fresh fruit; when it’s filled to the brim with a smoothie, it’s less interested
The evolutionary benefits of an efficient and well-regulated perception-action system that swings into action shortly after birth are numerous. A glimpse into another person’s emotions might help predict that person’s behavior. Understanding the face of pain from an early age could keep us from touching a hot stove. At a greater social level, a personal insight into the experiences of others could aid cooperation.

 

My Brain’s a Blender (adapted from ScienceDaily, May 6, 2007)  
Psychologists are finding that the mature adult mirror system does indeed seem to regulate itself, particularly when it comes to empathy.  Such checks and balances occur for our own good.  If, through the mirror system, we were able to completely experience the pain of another person, we might constantly feel distressed.
Clarifying this phenomenon might require a temporary substitute for the term “mirror system.”  A regulated mirror system acts not as a complete mirror, merely flipping around another’s emotions, nor as a sponge, expelling only what it soaks up. Perhaps the mind is more like a kitchen blender: We understand the raw feelings of a friend in pain, but instead of devouring them whole we mix, chop, and purée them into a more digestible serving.  Our blender brains enable us to simultaneously provide support and avoid emotional paralysis.
“The best response to another’s distress may not be distress, but efforts to soothe that distress,” (Jean Decety 2006).  “Empathy has a sharing component, but also self-other distinctions and the capacity to regulate one’s own emotions and feelings.”
In one study, writes Decety, researchers showed subjects a video of patients feeling pain as a result of medical treatment. Some subjects imagined themselves in the patient’s position, whereas others merely considered the patient’s feelings.  Patients who put themselves in the painful shoes showed stronger neural responses in regions of the brain involved in experiencing real pain.