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Implementing the Concept of Mirror Neurons into an Exercise Setting Also includes How to Coach Someone to Change Their Body Language.

This is a very interesting article on implementing the concept of mirror neurons into an exercise setting. The author helps people who have injuries, say an injured knee. The author discusses what he feels are some of the controversial claims of mirror neuron researchers. He then goes on to suggest how to use what he feels is truth about mirror in exercise routines/physical therapy. He explains step by step how he has his clients watch videos to improve their exercising results. I have yellow highlighted the interesting parts. I was excited to see that the author’s step by step coaching regime is very similar to the regime that I have been using in my coaching with clients who want to improve their body language, first impressions, public speaking and interview techniques for many years. I have highlighted this coaching approach in green.
 Implementing the concept of mirror neurons into an exercise setting
Posted on January 5, 2014
From Wikipedia:
“A mirror neuron is a neuron that fires both when an animal acts and when the animal observes the same action performed by another.”
If I drink a beer neuron X fires. If neuron X also fires when I watch someone else drink a beer, X is a mirror neuron.
In the neuroscience world, mirror neurons are all the rage. You name it, and people have come up with a possible application. Speech therapy, autism, empathy, evolution, the list is extensive. However, it doesn’t take much scrolling to get to the section in Wikipedia titled, “Doubts concerning mirror neurons.”
“According to scientists such as Hickok, Pascolo, and Dinstein, it is not clear whether mirror neurons really form a distinct class of cells (as opposed to an occasional phenomenon seen in cells that have other functions), and whether mirror activity is a distinct type of response or simply an artifact of an overall facilitation of the motor system.”
Perhaps neuron X fires when I drink a beer and when I watch someone drink a beer, but maybe that’s 5% of what X does. Maybe X also spends 95% of its time on cell communication. Rather than call X a mirror neuron, it’d be more appropriate to say X is a “Communicative cell which also has mirroring properties.”
What you find is much of the media, and the scientists, purporting mirror neuron applications are making a lot of unsubstantiated claims.
First, the majority of mirror neuron research has been done on monkeys, not humans.
Second, there’s zero evidence for some of the touted benefits. Scientists have claimed mirror neurons are what help us understand actions. In regards to autism, perhaps a lack of mirror neurons, or a dysfunction in them, is part of the ailment? Say someone makes a gesture at you. According the theory, your mirror neurons for that gesture fire, causing you to understand what that person is doing. Issues with your mirror neurons = issues understanding. And what’s a hallmark of autistics? Trouble understanding social cues.
Greg Hickok of UC Irvine has a lengthy, head spinning, evisceration of the idea mirror neurons provide action understanding hereFortunately, he has some lighter reading on this topic in his blog tooAn easy refutation for mirror neurons providing understanding is using the condition Apraxia. From the National Institute of Health:
Apraxia is a disorder of the brain and nervous system in which a person is unable to perform tasks or movements when asked, even though:
·         The request or command is understood
·         They are willing to perform the task
·         The muscles needed to perform the task work properly
·         The task may have already been learned
So, Apraxia is a condition in which the person is unable to perform a task despite being able to understand the task. They have neurons which fire when it comes to understanding the task, but not when it comes to completing the task. If the mirror neuron theory of action understanding help up, this would be impossible. As the same neurons which understand the task are supposed to be the same neurons which complete the task.
A simpler example: Your dog can understand when you throw a ball for them to fetch; they know to chase it. Yet, your dog can’t throw a ball like you can. The dog has neurons to understand your action of throwing, but these are not the same neurons which help it throw a ball, because for the dog, those neurons don’t exist.
When it comes to action understanding, something else, a lot of something else, is responsible besides mirror neurons.
It seems easy enough until you realize neuroscientists have spent over a decade arguing about this. Now, I’m no neuroscience expert, but with all the people I’ve trained through the years, I know a little bit about how people understand and learn actions.
I feel like anyone who has coached people move in any capacity gets the following: Someone doesn’t merely watch a task then understand it, at least not without prior experience with that task. They watch it; maybe gain some understanding, then perform it; maybe gain some understanding, then get feedback, gain some more understanding, and so on.
Say you’re in the gym and someone is learning a new exercise. Does anyone expect this person to watch the new exercise then fully understand it? Where you demonstrate it for them, then are so confident they understand things, you walk away knowing they’ll have good form? Of course not. You demonstrate it, they do it, you give them feedback, and so on.
This seems to be a big part of how we grow up and comprehend the world. I wrote about this in my post on Dr. Drew’s book, The Mirror EffectThe idea is as we grow up our parents, or whomever is around us a lot, provides a great deal of our understanding of well, practically everything. (I think this is so interesting.)
If a kid is in pain, how does he or she even know what pain is? Sure, there’s some innate component, but think about it. A kid is running around, trips and bumps his head. He gets up, looks around, and overreacting mom comes rushing over freaking out “OH MY GOD ARE YOU OK?!” The baby learns based off what they see; what’s mirrored to them.
In other words: kid bumps his head, mom demonstrates what happened is a painful event, kid tries being in pain (they cry), mom gives feedback (“I know, I know, that must of hurt”).
Watch what happens in the following video. Notice when mom isn’t giving predictable responses -many of which have been learned at this point, the baby freaks out:
This is a long way of endorsing how trainers, therapists, teachers, whatever, should be showing how to do something before asking someone else to do it. When it comes to learning, visuals seem to be how we learn best. It’s better to show what smiling is than to only ask someone to smile…It’s better to show what a lunge is than to only ask someone to lunge.
So, mirror neurons aren’t why we understand tasks. What do they do then? In fact, do these things even exist?
-
Are mirror neurons real?
As I mentioned, an issue with the mirror neuron world is the majority of the research has been on monkeys. There is research on humans though. Here are some papers that have helped me wrap my head around this:
Notice the titles and the dates. In 2008 mirror neurons were found in humans. In April 2009 we found no evidence for them. Then a few months later we found evidence for them. And I’m only picking a few studies.
On top of this, these studies are insanely hard reads. This is partly because it is high level stuff, and partly because academics of this sort like to write in the manner of, “SPEAK ENGLISH!!!”
Because of the above, in combination with my remedial knowledge of this stuff, I’m not going to delve into these studies. Here are some major points:
-One of the confounding issues is which area of the brain is looked at. Not all studies look in the same area. “Why don’t they all look at the entire brain to simplify this?” Apparently, when you look at only one area you get a much better idea of what’s going on than when you look at multiple areas. Some scientists have different hunches as to where the mirror neurons lay. So, that’s one reason they decide to direct their research in certain brain areas. There’s a race to find these things and each scientist thinks they have the fastest route.
-Not all studies assess the same movements. From a different paper, What we currently know about mirror neurons:  
“Mirror neurons were originally defined as neurons which ‘‘discharged both during monkey’s active movements and when the monkey observed meaningful hand movements made by the experimenter.” Thus, the key characteristics of mirror neurons are that their activity is modulated both by action execution and action observation, and that this activity shows a degree of action specificity.”
The last part is the most important. In order for mirror neurons to fire, specific actions have to happen. This is what the researchers call “Goal oriented actions.” Think the difference between reaching for a piece of food and randomly moving the arms. The first is goal oriented; the second is not. Mirror neurons fire in the former; they don’t for the latter.
-The last study, which found mirror neurons, seems to be the best out of the group. They used goal directed actions and they looked in a place where it makes sense mirror neurons would be.
Let’s bring back the criticism quote from the beginning:
“According to scientists such as Hickok, Pascolo, and Dinstein, it is not clear whether mirror neurons really form a distinct class of cells (as opposed to an occasional phenomenon seen in cells that have other functions), and whether mirror activity is a distinct type of response or simply an artifact of an overall facilitation of the motor system.”
This still holds. What the studies show is cells appear to have the ability to mirror, but we don’t know if there are neurons whose sole function is to do this. For our purposes, does this even matter? If there is a mechanism for mirroring; there is real world application to be had.
Some understanding of why the brain is doing this can help with our application.
-
What do mirror neurons really do?
Remember, Hickok has been one of main critics of the role of mirror neurons, BUT, he believes they exist. His criticism is aimed at what other scientists have proposed their role to be. Therefore (from his blog),
“I’d like to propose the idea mirror neurons take sensory input for a motor purpose.
Can we learn something from the behavior of dogs? If you’ve played fetch with a dog you may have noticed that it quickly learns to anticipate the consequences of throwing actions. For example, it is not hard to fool a naive dog who plays a lot of fetch with a fake throw. Even though the ball isn’t flying through the air the dog may nonetheless take off in chase.
Presumably, the animal has learned to recognize throwing actions. This is interesting because dogs can’t throw and so can’t have throwing mirror neurons. This is also interesting because somehow the action observation, throwing, is triggering an action execution, chasing, in the dog. This tells us that and action observation-execution sensory-motor circuit exists in the animal.
There may even be “chase” cells in the dog’s motor cortex that fire both during action observation and action execution.
Put more succinctly in a paper from him- (Mis)understanding mirror neurons:
“Observed actions can serve as important inputs to action selection, including but not necessarily limited to, mirror actions. “
As a dog, you have a mirror system for certain movements. Your owner throws a ball, your mirror system fires, reflecting the throwing motion, which signals you to chase after the ball. The sensory input is you seeing the throw, the motor response is you chasing the ball. Sensory input => Motor response.
If you’re a human though: You still have a mirror system for certain movements; you watch someone throw a ball, your mirror system fires, reflecting the throwing motion, which can possibly signal you to also throw a ball. 
If you’re a dog, your brain can mirror the action, your body cannot. If you’re a human, your brain can mirror the action, and so you can your body. If you’re a dog, you can’t form a motor response which mirrors the sensory input. You have the neurons to mirror a throwing a motion; you don’t have the neurons to respond with a throwing motion. If you’re a human, you do.
What’s crucial here, I believe, is it appears if you are able to generate a motor response that mirrors the sensory input, the brain circuitry is the same. This is referred to as producing the same neural substrate.
For example, you watch someone throw a ball, your brain fires in the “throw a ball” manner, producing the “throw a ball” neural substrate. Whether you watch someone throw a ball or throw a ball yourself, this neural substrate is the same. So, watching someone throw a ball can help you throw a ball as the brain is practicing the same circuitry. Whether your own body moves or not, your brain is practicing the movement. If you’re a dog, this isn’t true. But we’re not worried about dogs.
We now have our framework for real world application.
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Implementation
Think of athletes. When trying to change their technique, what do they often do? They watch film. Usually a combination of themselves to understand their flaws, along with watching whatever it is they’re trying to attain.
Say you think Roger Federer has perfect forehand technique, and your forehand technique is lacking. You may watch film of Federer to pick up on his technique. We now have an idea why this works: the mirror system. Watching his forehand technique produces a similar circuitry in your brain, as if you actually swung your racquet.
There’s another perk of learning this way- it’s less intense. As a baseball pitcher, you can’t work on your technique through actual throwing indefinitely. You can’t throw everyday, all day. You’ll overtrain, burn out, get hurt, lose strength, etc.
I wrote about this in How many sets and reps to correct muscular imbalances? I used strength and hypertrophy in that post to exemplify there is an optimal amount of volume when trying to get attain something, such as getting stronger and bigger. Go above or below this threshold and you run the risk of attenuating gains. You can’t always be “on.”
The brain however, is always on. So, using our mirror system enables us extra practice without the expense of hampering gains. We’re still using the brain, but we leave the musculoskeletal system alone.
“Isn’t this mental imagery / visualization?”
Not quite!
This is where the work of Lorimer Moseley and the NOIgroup comes in handy. They have a great resource, The Graded Motor Imagery Handbook. They talk about how different levels of imagery elicit different levels of brain activation. Visualization / motor imagery, imagining yourself doing a movement, elicits the greatest level of brain activation without actually moving.
Contrast this with observing people (mirror system), which is, they think (we don’t know for sure yet), the lowest level of brain activation.
So, compared to motor imagery, we’re activating less of the brain.
“Isn’t that bad?”
When you put things into the context of an exercise program, no. I think it’s actually good. Just like the muscles, it’s not like the brain can be on 24/7. Using observation allows us to practice at the lowest intensity level possible.
Speaking of context, let’s remember we’re using all this in the realm of teaching people how to move differently. We’re usually trying to get people out of habits that have been ingrained for a long time. In my experience, people have a very hard time initially knowing when they’re moving better. They just don’t know where there body is in space. They forget their knees are caving in, how they’re standing, their elbow positioning, whatever it is. They need constant reminder and feedback of how to move differently.
Let’s say this population uses motor imagery. Instead of squatting, they’re imagining themselves squat. How does anyone know if their form is bad? There’s no way to give them feedback. If I’m working with someone I can’t let them know their knees are caving if their knees aren’t actually moving!
This is important because we don’t want them getting better at a dysfunctional movement. And, in motor imagery, the brain is firing almost as much as if they were actually moving. You might not be able to see the dysfunction, yet they could still be practicing the dysfunction in their head.
Therefore, I believe using observation is better. Here’s how I do it:
  • In a corrective setting, from Monday – Sunday I outline what to do for people. 6 of those 7 days involves actual exercise. 3 of the 6 days are dedicated to one workout, workout “A”; the other 3 of the 6 days are dedicated to the other workout, workout “B.” This fits in line with the optimal frequency to train muscle groups for beginners.
  • One of the 7 days there is no regular exercise. Instead, I have the person focus on their activities of daily living. They’re going to be moving during the day; let’s do it well.  I also have them watch videos of the proper form of certain exercises, and I have them observe other people’s movement dysfunctions which are similar to theirs.
Let me use a recent example; someone with a common issue. Alex is someone presenting with knee pain. His femurs tend to rotate inwards too much, and his lower leg tends to rotate outwards too much. His knees turn in too much; his feet turn out too much.
On Monday, Thursday and Saturday, he has various exercises aimed at working on this. On Tuesday, Friday and Sunday, he also has various exercises working on this, but these 3 days of exercise are different than Monday, Thursday and Saturday. This way we’re not working the exact same muscles and movements more than 3 days per week.
On Wednesdays, when there is no prescribed exercise, Alex works on his ADLs (he also does this the rest of the week), which are aimed at his movement dysfunction.
Next, he watches some of his prescribed exercises to further ingrain proper form. He might watch the ones which have been the hardest for him to nail down, the ones I think have most benefit, or the ones which tend to give him pain. This way he gets to watch people do a movement which may give him pain, in a pain free manner.
Finally, he watches other people throughout the day. Observing others who 1) Have the same issue and 2) Don’t have the same issue. Paying close attention to the differences between these groups. Now his observation has a goal. It’s not random people watching; it’s people watching with a specific focus. The idea being he wants to “mirror” the better movement and learn to avoid the improper. He takes his sensory input -watching good and bad movement at the lower body, and uses that to form a motor response -his own good movement of the lower body.
This way, 7 days per week, Alex is working on moving better. Whether it’s through actually moving better throughout the day, specific exercises, watching other people, all week he’s doing it.
As you can see, I’m only prescribing this with people one day per week. The person can do it more throughout the week, and I think that’s a good idea, but there’s only so much time I can expect out of clients. Because I’m getting used to this myself too, this seemed like a nice way to start things.
In terms of research to back this up, Moseley’s group has had some good success clinically, but haven’t really studied something of this nature yet. There are a ton of studies illustrating the benefits of using motor imagery in conjunction to physical therapy, but again, this isn’t really motor imagery, and I’ve only seen studies on neurological patients.
As far as I know, the only population trying something like this is athletes, which is a good thing. I’m not big on training people like athletes, but it’s uncanny how often the athletes are ahead of the researchers.
Peyton Manning recently had to sit out of practice due to an ankle injury. He needed to give his soft tissue some time to relax. But, he knows his brain is always on. That’s why you still see him doing mental reps:

Hard to argue with the results. Sensory input -watching film and reading pictures => Motor output -destroying defenses (except when it’s cold). Maybe Eli should work on his mirror system more. BOOM! Hall of famer my ass!



Patti Wood, MA, Certified Speaking Professional - The Body Language Expert. For more body language insights go to her website at www.PattiWood.net. Check out Patti's website for her new book "SNAP, Making the Most of First Impressions, Body Language and Charisma" at www.snapfirstimpressions.com. Also check out Patti's YouTube channel at http://youtube.com/user/bodylanguageexpert.

Mirror Neurons and How They Effect Understanding and Empathy and How Damage to Mirror Neuron Relates to Autism.

Below is a literature review of the research on Mirror Neurons  I have yellow highlighted the interesting parts.
Mirror neurons and their clinical relevance
Giacomo Rizzolatti*, Maddalena Fabbri-Destro and Luigi Cattaneo  About the authors
Correspondence *Department of Neuroscience, University of Parma, 39 via Volturno, 43100 Parma, Italy

Email
 
giacomo.rizzolatti@unipr.it
Summary
One of the most exciting events in neurosciences over the past few years has been the discovery of a mechanism that unifies action perception and action execution. The essence of this 'mirror' mechanism is as follows: whenever individuals observe an action being done by someone else, a set of neurons that code for that action is activated in the observers' motor system. Since the observers are aware of the outcome of their motor acts, they also understand what the other individual is doing without the need for intermediate cognitive mediation. In this Review, after discussing the most pertinent data concerning the mirror mechanism, we examine the clinical relevance of this mechanism. We first discuss the relationship between mirror mechanism impairment and some core symptoms of autism. We then outline the theoretical principles of neurorehabilitation strategies based on the mirror mechanism. We conclude by examining the relationship between the mirror mechanism and some features of the environmental dependency syndromes.
  • The mirror mechanism is a neural system that unifies action perception and action execution
  • The mirror mechanism is organized into two main cortical networks, the first being formed by the parietal lobe and premotor cortices, and the second by the insula and anterior cingulate cortex
  • The role of the mirror mechanism is to provide a direct understanding of the actions and emotions of others without higher order cognitive mediation
  • Limited development of the mirror mechanism seems to determine some of the core aspects of autism spectrum disorders
  • The recently demonstrated link between limited development of the mirror mechanism and that of some aspects of the motor system suggests that rehabilitation in children with austism spectrum disorder should take into account both motor and cognitive strategies
  • The use of action-observation-based protocols could represent a new rehabilitation strategy to treat motor deficits after stroke


Review criteria
PubMed was searched using Entrez for articles published up to September 2008. The search term was "mirror neuron" OR "mirror neurons" OR "mirror neuron system" OR "mirror system". Owing to limitations on the number of references, we cited only articles that we judged to be most important from a theoretical or clinical point of view.
Keywords:
Introduction
Traditionally, it has been assumed that the understanding of actions performed by others depends on inferential reasoning.1, 2, 3 Theoretically, when we witness the actions of others, the information could initially be subjected to sensory processing and then be sent to higher order 'association' areas where it is elaborated on by sophisticated cognitive mechanisms and compared with previously stored data. At the end of this process, we would know what others are doing.4
It is possible that this cognitive operation might indeed occur in some situations when the behavior of the observed person is difficult to interpret.5, 6, 7 However, the ease with which we usually understand what others are doing suggests that an alternative mechanism might be involved in action perception. The essence of this alternative system is that actions performed by others, after being processed in the visual system, are directly mapped onto observers' motor representations of the same actions. The observers are aware of the outcomes of their own actions, so the occurrence of a neural pattern similar to that present during their own voluntary motor acts will enable them to understand the actions of others.
Evidence in favor of the existence of this direct sensory–motor mapping mechanism came from the discovery of a set of motor neurons, known as mirror neurons, that fire both when a monkey performs a given motor act and when it observes another individual performing an identical or similar motor act.8, 9 In this article, we will first review the basic properties of this mechanism, which is known as the mirror mechanism. We then examine the relevance of the mirror mechanism for the interpretation of clinical syndromes such as autism, and for the development of motor rehabilitations strategies.
Mirror neurons in the monkey
Mirror neurons were originally discovered in the ventral premotor cortex (area F5) of the macaque monkey.8, 9 The defining characteristic of these neurons is that they discharge both when the monkey performs a motor act and when the monkey, at rest, observes another individual (a human being or another monkey) performing a similar motor act (Figure 1). The degree of similarity that is required between executed and observed motor acts in order to trigger a given mirror neuron varies from one neuron to another. For most mirror neurons, however, the relationship between the effective observed and executed motor acts is based on their common goal (e.g. grasping), regardless of how this goal is achieved (e.g. using a two-finger or a whole-hand prehension). Importantly, mirror neurons do not discharge in response to the presentation of food or other interesting objects.
Figure 1 A cytoarchitectonic map of the monkey cortex and an example of a mirror neuron.
Figure 1 : A cytoarchitectonic map of the monkey cortex and an example of a mirror neuron. Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, or to obtain a text description, please contact npg@nature.com
The upper part of the figure shows the activity of a mirror neuron recorded from area F5. The neuron discharges both when the monkey grasps an object (A) and when it observes the experimenter grasping the object (B). (C) The cytoarchitectonic parcellation of the agranular frontal cortex and the parietal lobe. PE, PEc, PEip, PF, PFG and PG are parietal areas. An enlargement of the frontal region (inset on the left) shows the parcellation of area F5 into three parts: F5c, F5p and F5a. The mirror neurons are typically found in F5c. The inset on the right shows the areas buried within the intraparietal sulcus. Abbreviations: AI, inferior arcuate sulcus; AIP, anterior intraparietal area; AS, superior arcuate sulcus; C, central sulcus; FEF, frontal eye field; IO, inferior occipital sulcus; IP, inferior precentral sulcus; L, lateral sulcus; LIP, lateral intraparietal area; Lu, lunate sulcus; MIP, medial intraparietal area; P, principal sulcus; STS, superior temporal sulcus; VIP, ventral intraparietal area. Permission obtained from Elsevier Ltd © Rizzolatti G and Fabbri-Destro M (2008) Curr Opin Neurobiol 18: 179–184.

Mirror neurons have also been described in the PFG and anterior intraparietal areas of the inferior parietal lobule (IPL; Figure 1). The general properties of parietal mirror neurons seem to be similar to those of mirror neurons in the premotor cortex. Like the latter neurons, the parietal mirror neurons code for the goals of motor acts rather than the movements from which they are constructed.8, 9
The PFG and anterior intraparietal areas are both connected with the F5 area and the cortex of the superior temporal sulcus. Neurons in the superior temporial sulcus have complex visual properties, and some respond to the observation of motor acts done by others.10, 11 However, they lack the motor properties that are defining features of mirror neurons, and cannot, therefore, be considered to be part of the mirror system.
The organization of the cortical motor system
To understand the functional role of mirror neurons in the premotor cortex and IPL, it is necessary to frame them within the modern conceptualization of the organization of the cortical motor system. Clear evidence exists that most of the parietal and frontal motor areas code for motor acts (i.e. movements with a specific goal) rather than mere active displacement of body parts.12, 13, 14, 15, 16, 17, 18 Even in the primary motor cortex, approximately 40% of neurons code for motor acts.15, 18
Studies in which the properties of single neurons were studied in a naturalistic context have been particularly important for establishing this new view on cortical motor organization.12 These studies showed that many neurons discharge when a motor act (e.g. grasping) is performed with effectors as different as the right hand, the left hand, or the mouth. Furthermore, for the vast majority of neurons, the same type of movement (e.g. an index finger flexion) that is effective at triggering a neuron during one particular motor act (e.g. grasping) is not effective during another motor act (e.g. scratching). By using motor acts as classification criteria, premotor neurons have been subdivided into various categories such as 'grasping', 'reaching', 'holding', and 'tearing' neurons.
Recently, evidence was provided that both inferior parietal and premotor (area F5) neurons are organized in motor chains.19, 20 Grasping neurons recorded from these areas were tested in two main conditions (Figure 2). In one condition, a monkey reached and grasped a piece of food located in front of it and brought it to its mouth. In the other condition, the monkey reached and grasped an object and placed it into a container. The results showed that the majority of the recorded neurons discharged with a different intensity according to the final goal of the action (e.g. eating or placing) in which the grasping motor act was embedded ('action-constrained' neurons). This 'chained' organization seems to be particularly well adapted for providing fluidity to action execution. Individual neurons not only code for specific motor acts, but, by virtue of being wired to neurons that code for the subsequent motor acts, they facilitate the activity of these downstream neurons, thereby ensuring smooth execution of the intended action.
Figure 2 Action-constrained neurons in the monkey IPL.
Figure 2 : Action-constrained neurons in the monkey IPL. Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, or to obtain a text description, please contact npg@nature.com
(A) Apparatus and paradigm used for a task designed to demonstrate action-constrained neurons. The monkey starts from the same position in all trials, reaches for an object (1) and brings it to the mouth (2a) or places it into a container (2b). (B) Activity of three IPL neurons during the motor task in conditions 2a (grasp to place) and 2b (grasp to eat). Raster histograms are synchronized with the moment when the monkey touched the object to be grasped. Unit 67 fires during grasping to eat and not during grasping to place. Unit 161 is selective for grasping to place. Unit 158 does not show any task preference. (C) Visual responses of IPL mirror neurons during the observation of grasping to eat and grasping to place performed by an experimenter. Unit 87 is selective for grasping to eat, unit 39 is selective for grasping to place and unit 80 does not display any task preference. Abbreviation: IPL, inferior parietal lobule. Permission obtained from American Association for the Advancement of Science © Fogassi L et al. (2005) Science 308: 662–667.

The functional role of the mirror neurons
The existence of a class of motor neurons that discharge during the observation of actions done by others is not as bizarre as it might initially seem. While it is true that an action done by others could be recognized by inference on the basis of previous visual experience without involving the motor system, visual perception per se does not provide the observer with the experiential aspects of the action. Furthermore, the mirror system provides a particularly efficient way to establish links between the observed action and other actions with which it is functionally related.21
Evidence in favor of the notion that mirror neurons mediate action understanding came from experiments in which monkeys were not allowed to see the actions performed by others, but were given clues for understanding them. In one series of experiments, monkeys were presented with noisy motor acts (e.g. peanuts breaking, tearing a piece of paper), which they could either both see and hear or only hear.22 The researchers found that many mirror neurons in area F5 responded to the sound of the motor act, even when it was not visible.
In another series, F5 'grasping' and 'holding' mirror neurons were tested both when the monkey observed the experimenter grasping a piece of food and when the monkey was prevented from seeing the experimenter's hand movements by use of a black screen.23 Despite the fact that the monkey could not see the hand–object interaction (the visual triggering feature of the recorded neurons) in the latter condition, many mirror neurons in F5 were active in this situation. The neurons typically began to discharge at the beginning of the hand-reaching movement, indicating that the monkey had a representation of the action performed behind the screen, even when it could not see the performed motor act.
The activity of mirror neurons per se describes only what is happening in the precise moment of occurrence of the observed actions. There is, however, a broader function of mirror neurons. This function is related to the recent discovery that most action-constrained neurons (see above) have mirror properties and selectively discharge when the monkey observes motor acts embedded in a specific action (e.g. grasping for eating but not grasping for placing; see Figure 2).19 The activation of action-constrained mirror neurons, therefore, codes not only 'grasping', but 'grasping for eating' or 'grasping for placing'. This coding implies that when the monkey observes grasping done by another, it is able to predict, on the basis of contextual cues (e.g. repetition, presence of specific objects), what will be the individual's next motor act. In other words, the monkey is able to understand the intentions behind the observed motor act.
The mirror system in humans
Understanding of goals and intentions
A large number of studies based on noninvasive electrophysiological (e.g. EEG, magnetoencephalography [MEG]) or brain imaging (e.g. PET, functional MRI [fMRI]) techniques have demonstrated the existence of the mirror mechanism in humans.8, 9 Brain imaging studies have enabled the mirror areas to be located. These studies showed that the observation of transitive actions done by others results in an increase in blood oxygen level-dependent (BOLD) signal not only in visual areas, but also in the IPL and the ventral premotor cortex, as well as the caudal part of the inferior frontal gyrus (IFG). These latter three areas have motor properties and closely correspond to the areas that contain mirror neurons in the monkey (Figure 3).
Figure 3 The parietofrontal mirror system in humans.
Figure 3 : The parietofrontal mirror system in humans. Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, or to obtain a text description, please contact npg@nature.com
Lateral view of the human cerebral cortex showing Brodmann cytoarchitectonic subdivision. The areas in yellow correspond to areas that respond to the observation and execution of hand motor acts. The left-hand panel shows an enlarged view of the frontal lobe. The possible homology between monkey and human premotor cortex is indicated by arrows. Note that in monkeys area F5 consists of three subareas: F5c, F5p and F5a. Area 44 is considered to be the most likely human homolog of area F5. Abbreviations: C, central sulcus; FEF, frontal eye field; IF, inferior frontal sulcus; IP, inferior precentral sulcus; PMd, dorsal premotor cortex; PMv, ventral premotor cortex; PrePMd, pre-dorsal premotor cortex; SF, superior frontal sulcus; SP, upper part of the superior precentral sulcus. Permission obtained from Elsevier Ltd © Rizzolatti G and Fabbri-Destro M (2008) Curr Opin Neurobiol 18: 179–184.

Both the premotor and the parietal areas of the human mirror system show a somatotopic organization.24 Observation of motor acts done with the leg, hand or mouth activates the precentral gyrus and the pars opercularis of the IFG in a medial-to-lateral direction, as in the classical homunculus model of Penfield25 and Woolsey.26 In the IPL, mouth motor acts are represented rostrally, hand and arm motor acts are represented caudally, and leg motor acts are represented even more caudally and dorsally, extending into the superior parietal lobule.
Most studies on the mirror mechanism in humans have investigated transitive movements such as grasping. In a recent fMRI study in which volunteers were asked to observe video clips showing a hand transport movement without an effector–object interaction, activations were found in the dorsal premotor cortex and also in the superior parietal lobule, with the activation extending into the intraparietal sulcus.27 This finding indicates that the human brain is endowed with a reaching mirror mechanism that is anatomically separated from the mirror mechanism that codes for the distal motor act.
As in the monkey, the parietal and frontal mirror areas in humans code mostly for the goals of motor acts. Gazzola et al.28 instructed volunteers to observe either a human or a robot arm grasping objects. In spite of differences in shape and kinematics between the human and robot arms, the parietofrontal mirror network was activated in both conditions. Further evidence in favor of goal coding was obtained in an fMRI study based on repetition suppression29—a technique that exploits the trial-by-trial reduction of a physiological response to repeated stimuli. The results showed that repeated presentation of the same goal caused suppression of the hemodynamic response in the left intraparietal sulcus, but this region was not sensitive to the trajectory of the agent's hand.
The study of aplasic individuals born without arms and hands provided further evidence in favor of a goal-coding mirror mechanism.30 During MRI scanning, two aplasic individuals and a group of nonaplasic volunteers were instructed to watch videos showing hand actions. All participants also made actions with their feet, mouths, and, in the case of the nonaplasic volunteers, hands. The results showed that in aplasic individuals, the observation of hand motor acts, which they had never themselves performed, activated the mirror areas. The communality of goals between the never-executed hand motor acts and those performed with the mouth and feet was the most probable explanation for this activation.
Growing evidence exists that, in addition to goal coding, the human mirror mechanism has a role in the ability to understand the intentions behind the actions of others. In an fMRI study, volunteers observed motor acts (e.g. grasping a cup) embedded in specific contexts (a condition in which the agent's intention could be easily understood) or devoid of context (a condition in which the agent's intention was ambiguous).31 The results showed that the mirror network was active in both conditions. However, the understanding of intention produced a stronger signal increase in the caudal IFG of the right hemisphere.
The importance of the mirror system in understanding the intentions of others was confirmed by a repetition-suppression fMRI experiment.32 Participants were asked to observe repeated movies showing either the same movement or the same action outcome regardless of the executed movement. The result showed activity suppression in the right IPL and the right IFG when the outcome was the same.
Movement, emotions and language
As we have discussed, the mirror mechanism located in the parietal and frontal areas codes mostly for the goals of observed motor acts. However, studies that involved transcranial magnetic stimulation (TMS) have shown that the human motor system also responds to the observation of movements devoid of a goal.33, 34 This 'movement mirror mechanism' seems to be extremely sensitive to movement kinematics. Dayan et al.35 studied brain responses to the observation of curved hand movements that either obeyed or disobeyed the law—known as the 2/3-power law—that describes the coupling between movement curvature and velocity. Mirror hand areas were more active during the observation of movements that obeyed this law than during other types of motion.
The mirror mechanism is located not only in centers that mediate voluntary movement, but also in cortical areas that mediate visceromotor emotion-related behaviors.36, 37 Brain imaging studies showed that when an individual feels or observes emotions in others caused by disgusting stimuli or stimuli representing pain, there is activation in two structures: the cingulate cortex and the insula. Interestingly, the same voxels are activated in these two structures in both 'feeling' and 'observing' conditions. This finding strongly suggests that feeling emotions and recognizing them in others are mediated by the same neural substrate.
It should be made clear that the anterior insula, where the aforementioned activations were found, has a dysgranular–agranular structure,38 and is, therefore, cytoarchitectonically similar to motor areas. Electrical stimulation of the insula in the monkey produces movements of various body parts, accompanied by a variety of visceromotor responses.39, 40 Similar effects have also been described in humans.41, 42 It is, therefore, appropriate to define these structures as 'mirror areas' in which the motor response includes a visceral component.
In humans, the mirror mechanism is also located in Broca's area, which is involved in language processing and speech production. Evidence for a mechanism that translates heard phonemes into the motor programs necessary to produce them has been provided by TMS experiments.43 The mouth motor field was stimulated in volunteers while they heard words containing phonemes requiring tongue movements (e.g. "birra") or not requiring tongue movements (e.g. "baffo"). Motor evoked potentials recorded from the tongue muscles increased with the presentation of verbal material containing a double 'r' relative to those containing a double 'f'.
The mirror system in neurology
The mirror system and autism
Autism spectrum disorder (ASD) is a heterogeneous developmental syndrome characterized by a marked impairment in social interaction and communication.44 Communication deficits include disturbances in most domains of language and are not limited to its pragmatic aspects.45 Impairment in the domains of affective links and emotion recognition is another important component of ASD.46 A restricted repertoire of activity and interests, repetitive motion, and hypersensitivity to certain sounds are other symptoms that are often present in ASD.
Autism affects a variety of nervous structures, from the cerebral cortex to the cerebellum and brainstem.47 However, in a context of a broader neurodevelopmental deficit, a set of ASD symptoms (impairment in communication, language and emotion, as well as in the capacity to understand others) seems to match the functions mediated by the mirror mechanism. A hypothesis has, therefore, been advanced that this set of deficits might depend on an impairment of the mirror mechanism,48, 49 and there is growing evidence to support this view.50, 52, 53
One classical EEG observation is that mu rhythm (an EEG rhythm recorded from the motor cortical areas) is blocked when a person makes a voluntary movement. This rhythm is also suppressed when a person observes another person performing a movement. Oberman et al.50 used this phenomenon to test the mirror mechanism in children with ASD. The results showed that although individuals with ASD exhibited a suppression of mu rhythm during voluntary movements, this suppression was absent when they watched some one else performing the movement (Figure 4). Martineau et al.54 have reported similar observations.
Figure 4 Absence of mirror EEG responses in autism.
Figure 4 : Absence of mirror EEG responses in autism. Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, or to obtain a text description, please contact npg@nature.com
The charts show suppression of the mu rhythm in controls (A) and patients with autism spectrum disorder (B) during observation of movement of an inanimate object (ball, pale green) or movements made with a hand (hand, green), and during active hand movements made by the individual from whom recordings were being taken (move, red). The bars represent the amount of mu activity in central scalp locations; C3, Cz and C4 refer to scalp coordinates of the 10/20 EEG system. Significant suppression of this activity, indicated by asterisks, is present for the hand observation condition only in controls, showing that patients with autism spectrum disorder fail to respond in a standard way to the observation of other people's actions. Permission obtained from Elsevier Ltd © Oberman LM et al. (2005) Brain Res Cogn Brain Res 24: 190–198.

Oberman et al.55 recently reported an interesting observation concerning the mirror system of children with ASD. The authors investigated how familiarity between an observing individual and a person performing a movement modulates the entity of mu rhythm suppression. Typically developing children and children with ASD viewed video clips showing the hand of a stranger performing a grasping action, the hand of a child's guardian or sibling performing the same action, and the participant's own hand performing the action. The study revealed that mu suppression depended on the familiarity of the observer with the agent, and that children with ASD showed mu suppression when a familiar person performed the action but not when it was performed by an unfamiliar person.
An fMRI study has provided strong evidence in favor of a deficit of the mirror mechanism in ASD. High-functioning children with ASD and matched controls were scanned while they imitated and observed emotional expressions. The results showed a markedly weaker activation in the IFG in children with ASD than in typically developing children. Most interestingly, the degree of activation was inversely related to symptom severity.53
Impaired motor facilitation during action observation has been reported in individuals with ASD by use of TMS.52 Furthermore, unlike typically developing individuals, children with ASD tend not to imitate other individuals in a mirror fashion when viewing them face-to-face.56 This imitation peculiarity is probably attributable to a deficit in the ability of the mirror mechanism to superimpose another person's movements on one's own.
Deficits in the mirror mechanism in ASD have also been addressed from another perspective.57 Typically developing children and children with ASD were tested while they observed an experimenter either grasping a piece of food for eating or grasping a piece of paper to place it into a container (Figure 5). The EMG activity of the mylohyoid muscle, which is involved in opening of the mouth, was recorded. The results showed that observation of food grasping produced activation of the mylohyoid muscle in typically developing children, but not in children with ASD. In other words, whereas the observation of an action done by another individual intruded into the motor system of a typically developing observer, this intrusion was lacking in children with ASD. This finding indicates that, in this disorder, the mirror system is silent during action observation, and that the immediate, experiential understanding of the intentions of others is absent.
Figure 5 Motor behavior in typically developing children and children with ASD.
Figure 5 : Motor behavior in typically developing children and children with ASD. Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, or to obtain a text description, please contact npg@nature.com
This experiment was designed to assess whether an action-constrained motor organization is present in typically developing children and children with ASD.57 (A) Schematic representation of the tasks. The individual reaches for an item on a plate and either brings it to their mouth or puts it into a container placed on their shoulder. Time course for typically developing children (B) and children with ASD (C) of the rectified electromyographic activity of mouth-opening muscles during the execution (left side) and observation (right side) of the 'bringing-to-the-mouth' action (red line) and of the 'placing' action (blue line). All curves are aligned with the moment of object lifting from the touch-sensitive plate (time = 0). The results demonstrate a lack of anticipatory motor activity during execution and a lack of mirror motor activation during observation of a given action in children with ASD. Abbreviations: ASD, autism spectrum disorder; EMG, electromyography.

Both children with ASD and typically developing children were also asked to perform the two actions described above (grasp to eat and grasp to place) while the EMG activity of the mylohyoid muscle was recorded.57 In typically developing children, the muscle became active as soon they moved the arm to reach the food. By contrast, no mylohyoid muscle activation was observed during food reaching and grasping in children with ASD; activation of the muscle was evident only when these children brought the food to their mouths. These data indicate that children with ASD are not only unable to organize their own motor acts into a unitary action characterized by a specific intention, but that they also show a deficit in the mirror mechanism, as reflected in the absence of motor activation of the muscles involved in an observed action.
These findings show an apparent contradiction between the cognitive capacities of children with ASD to report the purpose of an experimenter's action and their lack of motor resonance with the action. To clarify this incongruity, a further experiment was performed in which typically developing children and children with ASD observed an actor performing goal-directed motor acts and were asked to report what the actor was doing and why he was doing it (Rizzolatti G et al., unpublished data). These tasks test two different abilities: the ability to recognize a motor act (e.g. grasping an object) and the ability to understand the intention behind it (e.g. grasping to eat). The results showed that both typically developing children and children with ASD were able to recognize what the actor was doing, but children with ASD failed to recognize why the act was being performed. Children with ASD systematically attributed to the actor the intention that could be derived by the semantics of the object—for example, an intention to cut when scissors were shown—regardless of how the object was grasped. This finding indicates that children with ASD interpret the behavior of others on the basis of the standard use of objects rather than the actual behavior of a person performing a task. Children with ASD, therefore, seem to lack the ability to read the intentions of others on the basis of behavior.
The mirror mechanism and motor rehabilitation
As well as having a role in action understanding, the mirror mechanism also modulates the motor behavior of the observer. This function forms the basis for the imitation of simple motor acts58 and for learning through imitation.59 Particularly interesting from a clinical point of view was the demonstration that the mirror mechanism is involved in the building of motor memories. The most convincing evidence for such a role came from studies by Stefan et al.60, 61 that involved TMS. The authors showed that when participants simultaneously performed and observed congruent movements, the learning of these movements was potentiated with respect to learning through motor training alone. These findings indicate that the coupling of observation and execution strongly facilitates the formation of motor memories.
Could this mechanism be exploited for motor rehabilitation? Many current behavioral neurorehabilitation techniques use strategies that induce long-term plasticity in the motor cortex either by depressing activity on the unaffected side or by potentiating activity on the affected side.62 The possibility that plasticity might be induced in the motor cortex by coupling action observation and execution represents the theoretical basis of a recent study that examined the effect of an 18-day cycle of active motor training with the paretic limb in two groups of patients with chronic stabilized stroke in the middle cerebral artery territory.63 The test group was required to perform hand motor acts prompted by movies showing similar motor acts, whereas the control group performed the same motor training without any visual cues. Functional assessment of the upper limb showed a significant improvement in the test group relative to the control group.
The mirror mechanism probably also forms the neurophysiological basis for 'mirror therapy' (the word 'mirror' being used here in its literal sense), which has been shown to improve upper-limb function in patients with stroke.64, 65 In mirror-therapy protocols, the patients are required to perform movements with their nonparetic hand while watching the hand and its reflection in a parasagittal mirror. This procedure gives a visual illusion of movement of the paretic hand. The generation of cortical plasticity and the consequent rehabilitative results strongly suggest a role in patient improvement for a mechanism that matches seen and executed actions, thereby implicating the mirror mechanism in this process.66
Deficits in the control of mirror mechanisms
Clinical observations have shown that frontal lesions can cause a series of disturbances characterized by the appearance of forced motor behavior triggered by external stimuli.67 Among these manifestations, imitation behavior is particularly interesting in relation to the mirror mechanism. The main feature of this syndrome is the spontaneous imitation of motor acts done by others, and it is considered to be part of the so-called 'environmental dependency syndrome'.68 The condition arises from unilateral, or, more frequently, bilateral prefrontal lesions.68, 69 Imitation behavior is generally attributed to an imbalance between exogenously and endogenously determined behaviors. The observation of actions done by others leads to the coding of potential motor acts in the parietal and premotor mirror areas by means of the mirror mechanism. These potential motor acts typically do not determine overt movements in the healthy adult brain because the manifestation of these acts is suppressed by the frontal lobe. Damage to this lobe would destroy this control mechanism, thereby transforming the potential motor acts into actual motor behavior. In view of the temporal latency between observation and imitation that patients often show, an additional mechanism could be also involved, but the essence of the phenomenon seems to depend on a release of potential motor acts.
Echopraxia is a term that describes forced and uncritical imitation of behaviors. The exogenously triggered behavior is sustained through endogenous mechanisms, resulting in its perseveration. In view of the simplicity of the imitated behaviors, combined with the total lack of criticism of the patient to the imitated behavior, echopraxia is perceived as a distinct disorder from imitation behavior. Echopraxia can arise in the context of basal ganglia dysfunction, as well as after frontal lobe damage. It is probable, however, that in both cases the mechanism that underlies echopraxia is a disinhibition of the mirror areas through loss of suppression by the frontal lobe.70
Conclusions and future prospects
The discovery of the mirror mechanism radically changed our views on how individuals understand actions, intentions and emotions. The identification of this mechanism has had a profound impact on a variety of disciplines, ranging from cognitive neurosciences to sociology and philosophy. Until recently, this discovery had influenced clinical research to a much lesser degree. However, it has now provided deeper insights into the interpretation of certain neurological syndromes, such as the environmental dependency syndrome, and has provided a new theoretical basis for establishing rehabilitation techniques in patients with motor deficits following stroke.
Autism is one condition in which the discovery of the mirror neuron mechanism could have important practical implications in the future. Recent experimental data suggest that individuals with ASD have a deficit in representing goal-directed actions, both when the actions are performed and when they are observed. Children with ASD, therefore, show impairments in organizing their own motor acts according to an action goal, as well as in using this motor mechanism to understand the intentions of others. This new view on ASD could be used to establish new rehabilitation strategies based on a motor approach. The rationale of such an approach is that if the motor knowledge of individuals with ASD is improved, their social knowledge and behavior would also be enhanced.
Key points
  • The mirror mechanism is a neural system that unifies action perception and action execution
  • The mirror mechanism is organized into two main cortical networks, the first being formed by the parietal lobe and premotor cortices, and the second by the insula and anterior cingulate cortex
  • The role of the mirror mechanism is to provide a direct understanding of the actions and emotions of others without higher order cognitive mediation
  • Limited development of the mirror mechanism seems to determine some of the core aspects of autism spectrum disorders
  • The recently demonstrated link between limited development of the mirror mechanism and that of some aspects of the motor system suggests that rehabilitation in children with austism spectrum disorder should take into account both motor and cognitive strategies
  • The use of action-observation-based protocols could represent a new rehabilitation strategy to treat motor deficits after stroke
Acknowledgments
This study was supported by European Union Contract 012738, Neurocom, by PRIN 2006 to GR and by Fondazione Monte Parma. MF-D was supported by Fondazione Cassa di Risparmio di Ferrara.
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Competing interests
The authors declared no competing interests.
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Subject areas under which this article appears: Neuropsychiatric disorders




Patti Wood, MA, Certified Speaking Professional - The Body Language Expert. For more body language insights go to her website at www.PattiWood.net. Check out Patti's website for her new book "SNAP, Making the Most of First Impressions, Body Language and Charisma" at www.snapfirstimpressions.com. Also check out Patti's YouTube channel at http://youtube.com/user/bodylanguageexpert.