Mirror Neurons II


Introduction

This page will provide an overview of the history of the discovery of the mirror neuron, new research that has been done in the mirror neuron field, and information about the mirror neuron controversy. For a more detailed description of the history and anatomical structures involved please see Mirror Neurons by Cassidy under KIN 450 (2010).
Image found at: http://healthyinfluence.com/wordpress/wp-content/uploads/2011/07/Mirror-Neuron-Cartoon.jpg
Image found at: http://healthyinfluence.com/wordpress/wp-content/uploads/2011/07/Mirror-Neuron-Cartoon.jpg


History

Ever wonder why you instinctively cringe when you see someone stub their toe? A group of Italian researchers in Parma, Italy, were the first to discover the neural mechanisms that are involved with this phenomenon. This group was interested in studying motor function of the hand for potential use in rehabilitation for loss of motor function. Using macaque monkeys as subjects, this group examined electronic signals from area F5 to see what happened when various hand actions were performed. Like many other findings in science, the researchers realized after time had gone by that the electrical signals they had been observing were what they later termed mirror neurons firing. After close examination over time, the researchers were shocked to find that when a monkey saw the researchers performing a movement the same area of the brain lit up when the monkey was performing the same reaching movement himself! Several times the monkeys observed various movements similar to the movements they were coaxed to execute, causing their mirror neurons to fire before the researchers caught on to what was going on. This shows that the same neurons in the macaque brain are active when they view someone, a fellow monkey or human, doing an action, as when they perform the same action themselves.6 From these and other experiments that have followed, many believe that mirror neurons are found in the human brain as well.

Possible Functions

The function of mirror neurons is highly complex, and all aspects of their various functions are not completely known. Mirror neurons fire when an action is performed, and when they see this type of action performed as well.6,3 Iacoboni presents research finding that there are two different classifications of mirror neurons. Mirror neurons that fire when observing a movement and then fire when executing the exact same movement are strictly congruent mirror neurons. Those that fire when the observed and performed action is not identical but reaches the same goal are widely congruent mirror neurons. Mirror neurons also fire throughout the whole observation or execution of the movement-they don’t fire along with any specific muscle. These findings agree with the idea that the higher brain centers associated with movement are more geared towards movements as a whole or the goal of a movement rather than specific muscles. Associated with perception and action, Iacoboni argues that mirror neurons are related to visual and tactile receptive fields. He states that mirror neurons create some sort of mapping of potential actions of the body.6
Image found at: http://www.colorado.edu/intphys/Class/IPHY3730/image/figure5i.jpg
Image found at: http://www.colorado.edu/intphys/Class/IPHY3730/image/figure5i.jpg


Another possible function of mirror neurons is their implication for language and language development.The mirror neurons found in Area F5 in the macaque monkey fired during reaching motions or hand movements, but also movements in the face and lips. Smacking of the lips is the main form of communication for the macaque monkeys, so Iacoboni hypothesizes that mirror neurons may play a role in language or communication as well. Further proof for the involvement of mirror neurons in language is that Area F5 is thought to be analogous to Broca’s area in humans.6
Broca's area is located in the inferior left frontal gyrus containing Brodemann's areas 44 and 45. Broca’s area is known to be associated with language development. Lesions in Broca’s area affect language production, a disease called Broca’s Aphasia. Broca's Aphasia entails non-fluent effortful speech with comprehension limited to single words and simple sentences. Repetition ability is impaired and this aphasia is often accompanied by right hemiparesis.8

The discovery of mirror neurons has had a huge impact on how we view the brain and its relation to social interaction. One major change in neuroscience from these discoveries is that perception and action were once viewed as completely different. Now, with mirror neurons firing during the perception and actual performance of an action, perception and action are no longer separable. Marco Iacoboni clearly states the magnanimous impacts of this discovery in his book, “The New Science of How We Connect with Others: Mirroring People”. He writes: “We achieve our very subtle understanding of other people thanks to certain collections of special cells in the brain called mirror neurons. These are the tiny miracles that get us through the day. They are at the heart of how we navigate through our lives. They bind us with each other, mentally and emotionally.”6 Jeremy Rifkin, an economist and activist describes some of these emotional connections from mirror neurons in his video (see additional links for the full video) showing how the discovery of mirror neurons has lead to a different view of humans and their ability to empathize with each other. He accounts mirror neurons to allowing us to feel someone else’s pain, joy, surprise, and fear, as if we were going through the same emotions ourselves. He further goes on to present the idea that at the core of our beings, we are not selfish, but instead our inherent drive is the desire to belong.11 As a believer in Christ, I further apply this knowledge of mirror neurons to be proof of our creation by a detailed, powerful, decisive, purposeful God. I believe that when man was first created, he wasn’t made with an inherent selfishness and desire to be an individual. He was made to belong, and ultimately to love. I do not think it is possible that the intricacy and many functions, still some unknown, of the mirror neuron allowing us to empathize and understand the actions of other people could have just come to be. The remarkable detail and complexity of the brain and the entire human body is proof to me pointing towards our unmistakable creation by the Creator.

Mirror neurons or made up neurons?

Although the majority of evidence presented here is for the presence of mirror neurons and their involvement in various functions, there are some who believe that mirror neurons do not exist, or are not as important as they appear to be stressed in literature. Gregory Hickok from the Department of Cognitive Sciences at the Univeristy of California wrote an article specifically describing eight problems that he sees with the mirror neuron theory. This article is definitely worth taking note of for any mirror neuron enthusiast. Hickok presents clearly and rationally how he believes that mirror neurons do not have the "action understanding" capabilities that many studies have attributed to them. He does not dismiss their presence; he does however, present evidence supporting the idea that many parallels in this field have been drawn without sufficient evidence. One of these parallels that he believes is made without sufficient evidence is the acceptance of the presence of mirror neurons in the human brain based off of discoveries in area F5 in the macaque brain. Hickok argues that taking the idea of mirror neurons found in the macaque brain and then applying it to the human brain is rash. Hickok goes on to argue that not only is there insufficient evidence for the presence of mirror neurons in humans, there is also no backing in research for mirror neurons being associated with higher cognitive functions in humans like empathy and imitation. If the presence of mirror neurons in the human brain is determined based on their presence in the macaque brain, then it makes no sense to associate these neurons with functions that the macaque brain does not have. He does make a valid point; the macaque brain is not known to be able to empathize and imitate, so why would we assume that neurons first found in the macaque brain can do these things in the human brain?5 David Newlin and Rachael Renton, co-authors of a study about possible connections between mirror neurons (if they are present in the human brain) and substance abuse, would probably agree with Hickok. They wrote of studies where the mirror neuron system has been used as foundation for research, "these studies generally assume rather than demonstrate that this [mirror neuron system] is a unique, coherent, and bounded system in the human brain".9 Although I may not agree with everything Hickok presents, his suggestion for researchers in this field to first prove the presence of mirror neurons in the human brain before they use this assumption to prove something else is a wise piece of advice.5

New Research/Literature

One of the widely known experts in the mirror neuron field, Ramachandran conducted a study working with the association found between the Limbic system and the mirror neuron system in Carr et. al's study.1 The Limbic system is connected to the autonomic nervous system, and stimulation can cause psychophysiological changes like heart rate, skin conductance, and respiratory rate. Ramachandran and colleagues used these connections to test the mirror neuron system in humans related to vocal emotions by recording heart rate and skin conductance. These observations were recorded in response to listening to "emotional vocalizations" and thinking about these vocalizations. They hypothesized that changes in heart rate and skin conductance would occur when listening to these vocalizations and when thinking about them. There were seven different recordings that subjects listened to. These recordings expressed happiness, sadness, fear, anger, surprise, disgust, and one control (humming a constant m sound). Subjects listened to the different recordings, with the control first, and 25 second pauses in between each 4-5 second recording. Then the subjects were asked to think about how they would respond in a situation if they were happy, sad, or afraid. Each of these "thinking tasks" had 20 second pauses in between for heart rate and skin conductance to return near baseline. Results showed that there was no increase in heart rate in response to listening to the recordings. They tried to explain this finding by producing research that heart rate is not a stable measure to use to investigate the autonomic nervous system because the heart is under sympathetic and parasympathetic control. They did find, however, a significant increase in skin conductance when completing the thinking tasks. Interestingly, Ramachandran and colleagues presented these two findings as additional proof of the mirror neuron system in humans.10 In my opinion, taking Gregory Hickok's article about problems with associating mirror neurons in humans into account, this is not strong evidence for the mirror neuron system. Nevertheless, Ramachandran et. al certainly bring up an interesting topic in relation to mirror neurons that warrants further study.

It has also been discussed that autism spectrum disorder may have to do with mirror neurons. It is hypothesized that the dysfunction of mirror neurons may be what causes the inability to read social cues and interpret actions of others socially associated with autism.6 Iacoboni discusses a study his wife Mirella Dapretto lead where children (age 12) with autism and non-autistic children observed and imitated “social facial expressions”. Determined from results of functional MRI scans, Dapretto and colleagues observed less mirror neuron activity in children with autism. Furthermore, they found that those with the most severe levels of autism (labeled by a clinical psychologist) had the least amount of mirror neuron activity of all the children.2 Interestingly though, a more recent study conducted in 2010, found no evidence for the dysfunction of the mirror neuron system in autistic children. This study had 20 control and 20 autistic subjects, ranging in age from 11-26. Subjects watched 80 second video clips of a hand moving a chess piece in its palm, then a clip of a moving dot against the same color background as the clip with the hand. The dot was moving at “roughly” the same speed as the hand was moving the chess piece. There was also a video of a static image to create a baseline for each subject. After watching the video of the hand moving the chess piece, subjects were asked to “manipulate the chessman in the same manner as shown in the Hand condition” video. EEG’s from the brain and EMG’s of the hand were recorded for each subject. They found that brain activation between the observation and execution of the motion did not statistically differ between the autistic and non-autistic subjects.4 Although I have not done any research in this field myself, one possible reason as to why Dapretto’s study found differences in mirror neuron activity between autistic and non-autistic subjects may be because her study had to do with social imitation, while Fan’s study just dealt with motor imitation. Needless to say, there is definitely material for further research relating the mirror neuron system to autism.

Another area of research involving mirror neurons involves brain imitation and if mirror neurons are present at birth. Susan Jones of the Department of Psychological and Brain Sciences and Program in Cognitive Science at Indiana University published an overview of the existing research of the development of imitation. She presents two theories of the development of imitation, one being a nativist approach with a mirror neuron system inherited at birth, and another with a dynamic systems approach stating imitation does not present itself till the second year of life. Jones describes how imitation could be a result of other behaviors, stating imitation is "one possible interpretation of behavioral matching and that other interpretations must often be considered". She makes a valid point in her description debating the presence of the mirror neuron system in newborns; mirror neurons first found in monkeys were found during "meaningful" movements. To the best of our knowledge, newborns do not have a concept of meaningful or non-meaningful movements. Newborns are not able to understand their actions yet. In correlation with Hickok and Newlin, Jones encourages the research community to provide a stronger foundation of evidence to support the presence of mirror neurons in the human brain before they are applied to different human brain functions, like imitation.7

Conclusion

In conclusion, the mirror neuron system has many implications for future research and study. Although there is some controversy over the true establishment of this system in the human brain, the literature acquired from research of mirror neurons in humans is helpful for other areas of research. More research needs to be done solidifying the mirror neuron theory in the human brain. This is a very exciting field and should be watched closely by the neuroscience community.

Glossary of Terms

Aphasia: loss or inability to process speech caused by brain damage
Broca's area: inferior left frontal gyrus containing Brodemann's areas 44 and 45; associated with language development
Area F5: area associated with motor function of the hand and mouth in the macaque monkey; where mirror neurons were first discovered
Autism: mental condition where there is great difficulty in formation of friendships, language, and abstract concepts
Limbic system: complex network in the brain associated with emotion
Mirror neuron: special neuron in the brain that fires during perception and execution of a movement

Suggested readings/videos

"RSA animate: the empathic civilization" by John Rifkin


"Mirror, mirror in the brain, what's the monkey stand to gain?"
Allen C. (2010)
A description of how mirror neurons in the brain are observed and the approach to mirror neurons in monkeys is analyzed.

"Imitation, Simulation, and Schizophrenia"
Park S, Matthews N, Gibson C. (2008)
A description of the different theories behind schizophrenia and the possibility of mirror neuron involvement.

“VS Ramachandran: The neurons that shaped civilization”
A video of Ramachandran explaining mirror neurons.

NOVA scienceNOW: Mirror neurons-“Why do we humans get so worked up watching other people?”
A video describing how mirror neurons may be the reason allowing mankind to be empathetic.

“Some speculative hypotheses about the nature and perception of dance and choreography”
Hangendoorn, I. (2004)
Very interesting study about the possible connection between emotion from watching dance and the mirror neuron system.

Quiz

1. What area of the macaque brain were mirror neurons first found?
A. Brodemann's area 4
B. Primary Motor Cortex
C. Broca's Area
D. Supplementary Motor Cortex


2. True or False: The presence of mirror neurons in the human brain is proven through numerous studies and is widely accepted.


3. Short Answer: Studies have been conducted looking for connections between what social disorder and mirror neurons?


4. Mirror neurons are thought to be involved in all of the following EXCEPT:
A. Empathy
B. Imitation
C. Perception of an action
D. Execution of an action
E. Actually, it's all of the above

5. Short answer: What is the difference between mirror neurons and motor neurons?

6. Short answer: Describe how mirror neurons may be the foundation of empathy in human beings.

7. Short answer: Explain how mirror neurons may be involved in language development.

Answers:
1. C
2. False
3. Autism
4. E
5. Mirror neurons fire consistently throughout the entirety of the observation or execution of an action. Also, mirror neurons are thought to also fire to auditory stimuli as well. Motor neurons fire to specific muscles.
6. Mirror neuron theory describes how mirror neurons allow us to experience another's action as it is happening, and their emotions as well. If I can experience someone's sadness when something heartbreaking happens, I can feel a little bit what that person is going through, and support them by their side.
7. Area F5 in the macaque monkey is associated with motor function of the hand and also the mouth. Smacking movements of the lips are one known form of communication between the macaque species. Broca's area in humans is the analogous area to area F5, and Broca's area is known to take part in language and language development in humans. From these associations studies are underway to see if this connection is true.

References

1. Carr L, Iacoboni M, Dubeau M, Mazziotta JC, Lenzi GL. (7 April 2003). Neural mechanisms of empathy in humans: A relay from neural systems for imitation to limbic areas. Proc of Natl Acad Sci USA. (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC154373/?tool=pmcentrez) [12 December 2012].
2. Dapretto M, Davies MS, Pfeifer JH, Scott AA, Sigman M, Bookheimer SY, Iacoboni M. Understanding emotions in others: mirror neuron dysfunction in children with autism spectrum disorders. Nature Neurosci 9(1): 28-30, 2006.
3. Dushanova J, Donoghue J. Neurons in primary motor cortex engaged during action observation. Eur J Neurosci 31(2): 386-398, 2010.
4. Fan Y, Decety J, Yang C, Liu J, Cheng Y. Unbroken mirror neurons in autism spectrum disorders. J of Child Psychol and Psychiatry 51(9): 981-988, 2010.
5. Hickok, G. Eight problems for the mirror neuron theory of action understanding in monkeys and humans. J Cogn Neurosci 21(7): 1229-1243, 2009.
6. Iacoboni M. The new science of how we connect with others: mirroring people. New York: Farrar, Straws, and Giroux, 2008.
7. Jones, SS. The development of imitation in infancy. Phil Trans Royal Soc B 364: 2325-2335, 2009.
8. Kandel ER, Schwartz JH, Jessell TM. Principles of Neural Science. 4th ed. New York: McGraw-Hill, 2000.
9. Newlin DB, Renton RM. A self in the mirror: mirror neurons, self-referential processing, and substance use disorders. Sci Use & Misuse 45:1697-1726, 2010.
10.Ramachandra V, Depalma N, Lisiewski S. The role of mirror neurons in processing vocal emotions: evidence from psychophysiologiccal data. Intl J of Neurosci 119:681-691, 2009.
11.Rifkin J. RSA animate: the empathic civilization. RSA Organization and Cognitive Media. http://www.youtube.com/watch?feature=player_embedded&v=l7AWnfFRc7g [10 December 2011].