The Mirror Neuron Mechanism: The Big Bang of Human Evolution - Evolution Essay Example

Abstract

Mirror Neurons is a class of visuomotor neurons (Rizzolatti and Craighero, 2004) that enables humans to understand (Rizzolatti and Craighero, 2004) and eventually imitate (Arbib, 2002) actions perceived on other individuals - The Mirror Neuron Mechanism: The Big Bang of Human Evolution introduction.

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Mirror Neurons provide explanations on the significance of language evolution (Ramachandran, 2006) and empathy and other emotional responses (Rizzolatti and Craighero, 2004); even more recent studies suggest its relationship to autism (Oberman et al, 2005).

Introduction

            The research will primarily focus on the revolutionary concept of the mirror neurons, its discovery, basic properties and the influence that is has created on various fields of expertise.

According to Ramachandran (2006) such a discovery is “the single most important “unreported” (or at least, unpublicized) story of the decade”.  Such is the case because although mirror neurons are discovered by Rizzolatti during the last decade, it hasn’t been given any serious attention until lately.

            In relation with this, the research will also cite relevant implications of the mirror neurons in terms of human emotions, intentions and relationships.  Similarly it will also discuss the relevance of mirror neurons on the evolution of human language from gestures, understanding and imitation.

            The research will also cite one of the most relevant medical cases wherein the mirror mechanism played a vital role– that is autism.

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                                               The Mirror Neuron System

Mirror Neurons Found in Macaque Monkeys

It is Gaucomo Rizzolatti together with Leonardo Fogassi and Vittorio Gallese at the university in Parma, Italy during the 1980’s and the 1990’s who discovered mirror neurons while conducting experiments on macaque monkeys using fMRI , TMS, and EEG (Rizzolatti et. al, 1996, 131-141).  Rizzolatti’s team was studying the neural response of monkeys on certain hand actions like picking some objects etc.  The discovery of the mirror neurons came by accident when during the experiment Rizzolatti’s colleague Fogassi reached for a banana which eventually triggered a similar neural reaction on the monkey even the latter haven’t moved at all.

Mirror Neurons in monkeys are found in the inferior frontal gyrus also known as the refion F5 which includes the Broca’s area (i.e responsible for speech), muscles for facial expression, and pars opercularis (which is said to have the mirror neurons important for imitation); also mirror neurons in monkeys are said to be found on inferior parietal lobule (Rizzolatti and Craighero, 2004).

Mirror Neurons: “Understanding” as its Basic Function

It is argued by Rizzolati and Craighero (2004) that mirror neuron’s basic function based on the study of macaque monkeys is actually “understanding of actions” being done by others and not really “imitation of actions”;  Hence, implying that one will still able to understand the meaning of a certain action even though there are no visual

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references available.   Such claim by Rizzolati and Craighero (2004) was verified through the study of   Kohler et al. (2002) and Umiltà et al. (2001).

Kohler’s study focuses on the audiovisual aspect of the mirror neurons wherein the F5 region on macaque monkeys’ neural responses are studied based on two situations: First is a visual and auditory display of ripping of a piece of paper and the other was an auditory display “alone” of the ripping a piece of paper.  Results of the study appeared that the neural response on visual and auditory display of ripping a piece of paper is similar to the neural response on the auditory display of ripping a piece of paper “alone”.  In addition, it appears that the neural response is weak or is almost void on the auditory display of sounds that are very much different on the original action done (i.e. ripping a piece of paper).    Kohler et al. (2002).

The study of Umiltà et al. (2001) includes testing of a particular object hidden behind a screen.  There are four situations that are observed: The first situation is that a person is holding an object; The second situation is that a person is miming that he is holding an object; The third is that the macaque monkey observes the action of the first and the second situation; and finally the fourth condition is that the monkey observes the first and the second situation but this time, the part wherein the person’s hand picks up the object is hidden behind the screen.   Results of the study by Umiltà et al. (2001) showed that the neural response given the fourth situation is half to that of the third situation hence saying that the macaque monkey understands the “goal” of the action even though there are no visual displays present.

In sum, the study of Kohler et al. (2002) and Umiltà et al. (2001) asserts that even

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though the macaque monkey doesn’t actually see a particular occurrence, it can still understand the goal of the action based on a grounded idea on a previous occurrence.   The previous occurrence based on a visual and auditory display is enough to trigger the mirror neurons and eventually allow understanding.  If by any instance that the same state of affairs happen again, the mirror neurons “predicts” of the goal of the action even in the absence of a visual stimuli   (Rizzolati and Craighero, 2004).

Mirror Neurons in Humans

To illustrate the presence of mirror neurons in humans, the author would quote on the study of Rizzolati and Fadiga (1995) and Ramachandran (2006).

The study of Rizzolati and Fadiga (1995) focuses on “motor-evoked potentials” of volunteers while watching a person who is about to grasp an object versus the potentials seen when the volunteers actually grasped an object themselves.  The result of the study showed that the same potentials are seen given these two different conditions.

However, since the study used functional magnetic-resonance imaging (fMRI) Christian Keysers, PhD (n.d.) suggests that since recording of neural signals from monkeys is very much unlike in imaging, it is highly possible that one cannot really tell if the very neurons which fired given the first condition are the same set of neurons which fired given the second condition.  Such is the case according to Keysers (n.d.) because since the images seen through fMRI are only millimeters away form each other, it is possible that the neural images seen in the observation are not the exact neurons themselves which fired but could only be in Keysers’ term “neighbors”.

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Ramachandran (2006) on the other hand implies the existence of mirror neurons

through the study of patients with “anosognosia”.  People with anosognosia normally have a stroke on the right hemisphere that eventually leads to a left half-body paralysis.  Some cases of patients with anosognosia develop “denial syndromes” wherein not only the latter deny their own paralysis but also the paralysis of those patients that they are with.  Such a situation is “odd” according to Ramachandran (2006) because such people who develop the denial syndrome are “lucid and intelligent”; because of this Ramachandran (2006) leads to the conclusion that there must be damages on these patients’ mirror neurons.

Mirror Neurons: Imitation and the Human Language

            Rizzolatti et. al (2001) emphasized that the “initial basic function” of the mirror system is not imitation rather understanding other people’s actions.   Albeit, Rizzolatti and Craighero (2004) added additional premises to such an assertion: that although it may be not be the case that mirror neurons necessarily and sufficiently imitate actions, it could be possible that they “mediate imitation” (Jeannerod, 1994).

            If a person happens to observe a particular action, the mirror neurons representing that same occurrence would “automatically” fire in his brain as if he is doing the same kind of action; this case is dependent on the premise that the person necessarily knows the result of such an action (example of this would be the case of the macaque monkeys’ observation of paper ripping).  The mirror system would then transform the visual stimuli into “knowledge” (Rizzolatti et. al, 2001).

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            Rizzolatti and Arbib (1998) have also noted that the mirror neurons would allow people to mime, and also comprehend how tongues and lips move – hence allowing language evolution.  In addition, Arbib (2005.) argues that language actually evolved from a “simple gestural protolanguage” (having pantomime as foundation) to a “verbal protolanguage” or a functional language.  This according to Arbib (2005) would explain how babies are able to learn how to speak and in some cases mimic the actions of their parents, like for example sticking out of the tongue (Ramachandran, 2006).

            Such claim is further strengthened by University of Chicago psychologist Bennett Bertenthal, PhD (n.d.) who said that “Speech is an action that involves the tongue, lips and vocal chords. So the fact that these different actions–speech and other instrumental actions–seem to have an overlapping neural basis is fascinating.”

            However, there are two major objections that could be cited against Arbib (2005) and Rizzolatti’s (1998) theory.  Psychologist David McNeill, PhD (2005) asserts that contrary to the Arbib’s claim that verbal language, gesture, etc evolved one after the other McNeill argues that it is highly possible that verbal language, gesture and Broca’s area evolved all at the same time.   According to McNeill (2005) the whole theory of language evolution lies on the idea of how “our preverbal ancestors” are able to consciously understand that they are indeed doing a particular action, how they are able to transform those actions into verbal or linguistic symbols.  Mirror neurons as asserted by McNeill (2005) paved the way for the prehistoric men to be aware that their actions have social significance.

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Mirror Neurons and Emotions

Rizzolatti and Craighero (2004) made a visual mapping of the brain to locate mirror neurons which respond to emotions.  In doing this study, they have taken into consideration two types of factors that may have triggered the release of emotional responses.  One is the “first person recognition” wherein an observer is able to evoke the same type of emotions based on previous experience that he may have during the past.  And the other is what they call as the “cold action” which is relatively objective compared to the former because there are no feelings involved whatsoever.

The study focused on the mechanisms underlying the “direct sensory-motor mapping” which focused on a basic type of human emotion- disgust.  Such emotion according to Rozin et al. (2000) is the most ideal emotion that should be used for testing because it is one of the fundamental tools for survival during prehistoric times.  Disgust has a strong “communicative value” (Rozin et al. 2000) in terms of food for instance, and its use for determining whether the latter is safe to eat or not.

            Results of the studies showed that whenever a person is exposed to disgusting things, the amygdala which is related to “olfactory modality” and the insula which is related not only to “primary cortical area for chemical exteroception (e.g., taste and olfaction) but also for the interoceptive state of the body (“body state representation”)” (Rizzolatti and Craighero, 2004) is trigerred.  And eventually, it appears that the insula has mirror neurons that are triggered whenever someone is disgusted or see someone who is disgusted (Calder et. al, 2000; Adolphs et. al, 2003).

The result of such study explained why people empathize with others and are

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altruistic most of the time.

The very sight of someone who is in pain or suffering triggers the same response on a person who is observing.  Hence it is almost a “natural” response to help people in need because it is in itself a way to satisfy the self- in Rizzolatti’s own terms: “Thus, acting to render others happy – an altruistic behavior – is transformed into an egoistic behavior – we are happy”.

In addition to the theory that mirror neurons are also responsible in eliciting the same emotional response between people, Marco Iacoboni et. al (2005) is interested on how mirror neurons are able to tell people’s intentions in between actions.  The idea that mirror neurons can be used to predict behaviors is also a noteworthy implication of Rizzolatti and Craighero’s research.  Iacoboni et. al (2005) used fMRI to study the response of 23 volunteers who are to watch three different sets of videos.  The first video shows tea cups and cookies properly set on a clean table, which signals that there is a tea party that will be held.  The second video on the other hand shows that the table now becomes messy and there are crumbs scattered on the before neat table- which of course is a sign that the tea party just ended.  The third video however portrayed just an empty cup alone that is away from any context.

By using the fMRI it appears that neural responses are more responsive in the first two videos wherein there is a specific context where the tea cup would apply; consequently, the last video does not have the same response to that of the first two videos.  Because of this Iacoboni et. al (2005) said: “Take all these lines of evidence together, and it seems clear that mirror neurons are one key to understanding how

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human beings survive and thrive in a complex social world”.

Mirror Neurons and Autism

            People with autism normally acted as if they have their own world- most of them are unable to connect with other people.

Ramachandran (2006) theorized that the defects on a person’s mirror neurons may have caused autism.  Corollary to this assertion are Iacoboni et. al (2006) claims that “faulty mirror neurons could cause repetitive behaviors” and in the long run could cause “mental retardation”.

Other researches such as of Théoret et. al (n.d.) gives a more optimistic explanation.  The study shows that autistic people’s neural systems are not “faulty” as what Iacoboni et. al (2006) explained but rather “not active”.  Contrary to the usual neural response of normal people when perceiving occurrences, autistic people are observed to exhibit less mirror neuron firings, hence allowing little understanding and imitation.

However later studies of Iacoboni (n.d.) claims that it could be the case that when autistic people are asked to do specific things, like for example mimicking facial expressions, they could respond to it correctly, however the only thing that makes it different is that autistic people are doing it consciously rather than unconsciously Iacoboni (n.d.).

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Conclusion

Mirror Neurons, a particular class of visuomotor neurons that allows understanding through observation and in the long run imitation, could be one of the most revolutionary discoveries of the last decade; and such a claim is evident on the attempt to use the mirror neuron mechanism on various fields of knowledge: neurology, psychology, medicine, linguistics, evolution and various philosophies.

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