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Encyclopedia > Mirror neuron
Locations of mirror neurons
Locations of mirror neurons

A mirror neuron is a neuron which fires both when an animal performs an action and when the animal observes the same action performed by another (especially conspecific) animal. Thus, the neuron "mirrors" the behavior of another animal, as though the observer were itself performing the action. These neurons have been directly observed in primates, and are believed to exist in humans and in some birds. In humans, brain activity consistent with mirror neurons has been found in the premotor cortex and the inferior parietal cortex. Some scientists consider mirror neurons one of the most important findings of neuroscience in the last decade. See for example this[1] essay by Ramachandran on their potential importance in imitation and language acquisition. Image File history File linksMetadata Mirror_neuron. ... Image File history File linksMetadata Mirror_neuron. ... Drawing by Santiago Ramón y Cajal of neurons in the pigeon cerebellum. ... A. A schematic view of an idealized action potential illustrates its various phases as the action potential passes a point on a cell membrane. ... Conspecificity is a concept in biology. ... For the ecclesiastical use of this term, see primate (religion) Families 13, See classification A primate is any member of the biological order Primates, the group that contains all lemurs, monkeys, and apes, including humans. ... Human beings are defined variously in biological, spiritual, and cultural terms, or in combinations thereof. ... For other meanings of bird, see bird (disambiguation). ... The premotor cortex is an area of motor cortex in the frontal lobe of the brain, located in front of the primary motor cortex and behind the prefrontal cortex. ... The parietal lobe is a lobe in the brain. ... Drawing of the cells in the chicken cerebellum by S. Ramón y Cajal Neuroscience is a field that is devoted to the scientific study of the nervous system. ... Vilayanur S. Ramachandran is the director of the Center for Brain and Cognition. ... Language acquisition is the process by which the language capability develops in a human. ...

Contents

Introduction

In the monkey, mirror neurons are found in the ventral premotor cortex (probably the equivalent of the inferior frontal gyrus in humans) and in the anterior inferior parietal lobule. These neurons are active when the monkeys perform certain tasks, but they also fire when the monkeys watches or hears someone else perform the same specific task. Researchers using fMRI, TMS, and EEG have found evidence of a similar system (matching observations with actions), in the human brain. For other uses, see Monkey (disambiguation). ... Inferior frontal gyrus of the human brain. ... The inferior parietal lobule (subparietal district or lobule) lies below the horizontal portion of the intraparietal sulcus, and behind the lower part of the postcentral sulcus. ... Functional Magnetic Resonance Imaging (or fMRI) describes the use of MRI to measure hemodynamic signals related to neural activity in the brain or spinal cord of humans or other animals. ... Transcranial magnetic stimulation (TMS) is the use of powerful rapidly changing magnetic fields to induce electric fields in the brain by electromagnetic induction without the need for surgery or external electrodes. ... Electroencephalography is the neurophysiologic measurement of the electrical activity of the brain by recording from electrodes placed on the scalp or, in special cases, subdurally or in the cerebral cortex. ...


The function of the mirror system is a subject of much speculation. These neurons may be important for understanding the actions of other people, and for learning new skills by imitation. Some researchers also speculate that mirror systems may simulate observed actions, and thus contribute to our theory of mind skills, [2] [3] while others relate mirror neurons to language abilities.[4] It has also been proposed that problems with the mirror system may underlie cognitive disorders, in particular autism.[5][6] To meet Wikipedias quality standards, this article or section may require cleanup. ... Autism is classified by the World Health Organization and American Psychological Association as a developmental disability that results from a disorder of the human central nervous system. ...


Research into all of these possibilities is ongoing.


Discovery

In the 1980s and 1990s, Giacomo Rizzolatti was working with Leonardo Fogassi and Vittorio Gallese at the university in Parma, Italy. These scientists had placed electrodes in the inferior frontal cortex of the macaque monkey to study neurons specialised for the control of hand actions, for example, grabbing objects, picking items up etc. During each experiment, they recorded from a single neuron in the monkey's brain while the monkey was allowed to reach for pieces of food, so the researchers could measure the neuron's response to certain movements.[7] Type Species Simia inuus Linnaeus, 1758 = Simia sylvanus Linnaeus, 1758 Species See text. ... Neurons (also called nerve cells) are the primary cells of the nervous system. ...


This work has since been published [8] and confirmed [9] with mirror neurons found in both inferior frontal and inferior parietal regions of the brain. Recently, evidence from fMRI, TMS and EEG and behavioral strongly suggest the presence of similar systems in humans, where brain regions which respond during both action and the observation of action have been identified. Not surprisingly, these brain regions closely match those found in the macaque monkey [10].


More recently Keysers and colleagues have shown that both in humans and monkeys, the mirror system also responds to the sound of actions [11] [12]


Mirror neurons in monkeys

The only animal where mirror neurons have been studied individually is the macaque monkey. In these monkeys, mirror neurons are found in the inferior frontal gyrus (region F5) and the inferior parietal lobule [13] Type species Simia inuus Linnaeus, 1758 = Simia sylvanus Linnaeus, 1758 Species See text. ...


Mirror neurons are believed to mediate the understanding of other animal's behavior. For example, a mirror neuron which fires when the monkey rips a piece of paper would also fire when the monkey sees a person rip paper, or hears paper ripping (without visual information). These properties have lead researchers to believe that mirror neurons encode abstract concepts of actions like 'ripping paper', whether the action is performed by the monkey or another animal. [14].


The function of mirror neurons in macaques is not known. Adult macaques do not seem to learn by imitation. Recent experiments suggest that infant macaqes can imitate a human's face movements, only as neonates and during a limited temporal window[15]. However, it is not known if mirror neurons underlie this behaviour. A human infant The word Infant derives from the Latin in-fans, meaning unable to speak. ...


In adult monkeys, mirror neurons may enable the monkey to understand what another monkey is doing, or to recognise the other monkey's action.[16]


The mirror neuron system in humans

It is not normally possible to study single neurons in the human brain, so scientists can not be certain that humans have mirror neurons. However, the results of brain imaging experiments have shown that the human inferior frontal cortex and superior parietal lobule is active when the person performs an action and also when the person sees another individual performing an action. Therefore, these brain regions are likely to contain mirror neurons and have been defined as the human mirror neuron system.[17] Human infant data suggest that the mirror neuron system develops before 12 months of age, and that this system helps human infants understand other peoples' actions.[18]


Possible functions of the mirror neuron system

Many different functions for the mirror neuron system have been suggested. These include:


Understanding Intentions Many studies link mirror neurons to understanding goals and intentions. Fogassi et al. (2005)[19] recorded the activity of 41 mirror neurons in the inferior parietal lobe (IPL) of two rhesus macaques. The IPL has long been recognized as an association cortex that integrates sensory information. The monkeys watched an experimenter either grasp an apple and bring it to his mouth or grasp an object and place it in a cup. In total, 15 mirror neurons fired vigorously when the monkey observed the "grasp-to-eat" motion, but registered no activity while exposed to the "grasp-to-place" condition. For four other mirror neurons, the reverse held true: they activated in response to the experimenter eventually placing the apple in the cup but not to eating it. Only the type of action, and not the kinematic force with which models manipulated objects, determined neuron activity. Significantly, neurons fired before the monkey observed the human model starting the second motor act (bringing the object to the mouth or placing it in a cup). Therefore, IPL neurons "code the same act (grasping) in a different way according to the final goal of the action in which the act is embedded" (664). They may furnish a neural basis for predicting another individual’s subsequent actions and inferring intention.


Empathy Mirror neurons have been linked to empathy, because certain brain regions (in particular the anterior insula and inferior frontal cortex) are active when a person experience an emotion (disgust, happiness, pain etc) and when they see another person experience an emotion. [20] [21] [22] However, these brain regions are not quite the same as the ones which mirror hand actions, and mirror neurons for emotional states or empathy have not yet been described in monkeys. More recently, Keysers and colleagues have shown that people that are more empathic according to self-report questionnaires have stronger activations both in the mirror system for hand actions [23] and the mirror system for emotions [24] providing more direct support to the idea that the mirror system is linked to empathy.


Language In humans, mirror neurons have been found in the inferior frontal cortex, close to Broca's area, a language region. This has lead to suggestions that human language evolved from a gesture performance/understanding system implemented in mirror neurons. Mirror neurons certainly have the potential to provide a mechanism for action understanding, imitation learning, and the simulation of other people's behaviour.[25] However, like many theories of language evolution, there is little direct evidence either way. Brocas area is the section of the human brain (in the opercular and triangular sections of the inferior frontal gyrus of the frontal lobe of the cortex) that is involved in language processing, speech production and comprehension. ... Evolutionary linguistics is the scientific study of the history of the origins of language and its development - difficult, because language leaves only vicarious traces in the fossil record. ...


Autism Some researchers claim there is a link between mirror neuron deficiency and autism. In typical children, EEG recordings from motor areas are suppressed when the child watches another person move, and this is believed to be an index of mirror neuron activity. However, this suppression is not seen in children with autism [26]. Also, children with autism have less activity in mirror neuron regions of the brain when imitating [27]. Based on these results, some researchers claim that autism is caused by a lack of mirror neurons, leading to disabilities in social skills, imitation, empathy and theory of mind. This is just one of many theories of autism and it has not yet been proven. Autism is classified by the World Health Organization and American Psychological Association as a developmental disability that results from a disorder of the human central nervous system. ... Autism is classified by the World Health Organization and American Psychological Association as a developmental disability that results from a disorder of the human central nervous system. ...


Theory of Mind In Philosophy of mind, mirror neurons have become the primary rallying call of simulation theorists concerning our 'theory of mind'. 'Theory of mind' refers to our everyday ability to predict and explain quite accurately the mental states of others without direct knowledge of them; for example, how you know a friend is in pain when he says "ouch", or can assume that a person being chased is afraid of the thing after him. According to simulation theory, that knowledge is available because we subconsciously put ourselves in the shoes of the person we're observing and, accounting for relevant differences, imagine what we would do in that scenario.[28][29][30] Mirror neurons have been taken to be the mechanism by which we simulate others in order to better understand them, and therefore their discovery has been taken as a validation of simulation theory (which appeared a decade before the discovery of mirror neurons).[31] A Phrenological mapping of the brain. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...



Gender differences Stronger EEG responses related to the mirror neuron system have been recorded in women compared to men [32]. This finding is consistent with the idea that women tend to be more empathetic, that the mirror neuron system is related to empathy, and that weak responses in the mirror neuron system could be linked to a masculine mind and to autism [33]. However, these ideas have not been tested in full.


Footnotes

  1. ^ V.S. Ramachandran, Mirror Neurons and imitation learning as the driving force behind "the great leap forward" in human evolution. Edge Foundation. Retrieved on 2006-11-16.
  2. ^ Christian Keysers and Valeria Gazzola, Progress in Brain Research, 2006, [1]
  3. ^ Michael Arbib, The Mirror System Hypothesis. Linking Language to Theory of Mind, 2005, retrieved 2006-02-17
  4. ^ Hugo Théoret, Alvaro Pascual-Leone, Language Acquisition: Do As You Hear, Current Biology, Vol. 12, No. 21, pp. R736-R737, 2002-10-29
  5. ^ Oberman LM, Hubbard EM, McCleery JP, Altschuler EL, Ramachandran VS, Pineda JA., EEG evidence for mirror neuron dysfunction in autism spectral disorders, Brain Res Cogn Brain Res.; 24(2):190-8, 2005-06
  6. ^ Mirella Dapretto, Understanding emotions in others: mirror neuron dysfunction in children with autism spectrum disorders, Nature Neuroscience, Vol. 9, No. 1, pp. 28-30, 2006-01
  7. ^ Giacomo Rizzolatti et al. (1996). Premotor cortex and the recognition of motor actions, Cognitive Brain Research 3 131-141
  8. ^ Gallese et al, Action recognition in the premotor cortex, Brain, 1996
  9. ^ Fogassi et al, Parietal Lobe: From Action Organization to Intention Understanding, Science, 2005
  10. ^ Rizzolatti G., Craighero L., The mirror-neuron system, Annual Review of Neuroscience. 2004;27:169-92
  11. ^ Kohler et al., Science, 2002 [2]
  12. ^ Gazzola et al., Current Biology, 2006 [3]
  13. ^ Rizzolatti G., Craighero L., The mirror-neuron system, Annual Review of Neuroscience. 2004;27:169-92
  14. ^ Giacomo Rizzolatti and Laila Craighero Annu. Rev. Neurosci. 2004. 27:169–92
  15. ^ Ferrari PF, Visalberghi E, Paukner A, Fogassi L, Ruggiero A, et al. (2006) Neonatal Imitation in Rhesus Macaques. PLoS Biol 4(9): e302
  16. ^ Giacomo Rizzolatti and Michael A. Arbib, Language within our grasp, Trends in neurosciences, Vol. 21, No. 5, 1998
  17. ^ Marco Iacoboni, Roger P. Woods, Marcel Brass, Harold Bekkering, John C. Mazziotta, Giacomo Rizzolatti, Cortical Mechanisms of Human Imitation, Science 286:5449 (1999)
  18. ^ Terje Falck-Ytter, Gustaf Gredebäck & Claes von Hofsten, Infants predict other people's action goals, Nature Neuroscience 9 (2006)
  19. ^ Fogassi, Leonardo, Pier Francesco Ferrari, Benno Gesierich, Stefano Rozzi, Fabian Chersi, Giacomo Rizzolatti. 2005. Parietal lobe: from action organization to intention understanding. Science 308: 662-667.
  20. ^ Wicker et al., Neuron, 2003 [4]
  21. ^ Singer et al., Science, 2004 [5]
  22. ^ Jabbi, Swart and Keysers, NeuroImage, 2006 [6]
  23. ^ Gazzola, Aziz-Zadeh and Keysers, Current Biology, 2006 [7]
  24. ^ Jabbi, Swart and Keysers, NeuroImage, 2006 [8]
  25. ^ Skoyles, John R., Gesture, Language Origins, and Right Handedness, Psycoloquy: 11,#24, 2000
  26. ^ Oberman LM, Hubbard EM, McCleery JP, Altschuler EL, Ramachandran VS, Pineda JA., EEG evidence for mirror neuron dysfunction in autism spectral disorders, Brain Res Cogn Brain Res.; 24(2):190-8, 2005-06
  27. ^ Mirella Dapretto, Understanding emotions in others: mirror neuron dysfunction in children with autism spectrum disorders, Nature Neuroscience, Vol. 9, No. 1, pp. 28-30, 2006-01
  28. ^ Gazzola, Aziz-Zadeh and Keysers, Current Biology, 2006 [9]
  29. ^ Gordon, R. (1986). Folk psychology as simulation. Mind and Language 1: 158-171
  30. ^ Goldman, A. (1989). Interpretation psychologized. Mind and Language 4: 161–185
  31. ^ Gallese, V., and Goldman, A. (1998). Mirror neurons and the simulation theory of mindreading. Trends in Cognitive Sciences. 2: 493–501
  32. ^ Cheng, Y. W., Tzeng, O. J. L., Decety, J., Imada, T., Hsieh, J. C. 2006. Gender differences in the human mirror system: a magnetoencephalography study. Neuroreport. 2006 Jul 31;17(11):1115-9
  33. ^ Baron-Cohen, S. 2003. The Essential Difference: The Truth about the Male and Female Brain. NY: Basic Books

Empathy Mirror neurons have been linked to empathy, because certain brain regions (in particular the anterior insula and inferior frontal cortex) are active when a person experiences an emotion (disgust, happiness, pain etc) and when they see another person experience an emotion For the Manfred Mann album, see 2006 (album). ... November 16 is the 320th day of the year (321st in leap years) in the Gregorian Calendar, with 45 days remaining. ...


References

  • The others are inside you, article from “Ingeniøren” (original title: “De andre er inden I dig”).
  • E. Bruce Goldstein. (2002). Sensation and Perception, Wadsworth (p. 321-324)

External links


  Results from FactBites:
 
Autism linked to mirror neuron dysfunction (859 words)
Mirror neurons are brain cells in the premotor cortex.
The human mirror neuron system is now thought to be involved not only in the execution and observation of movement, but also in higher cognitive processes – language, for instance, or being able to imitate and learn from others' actions, or decode their intentions and empathize with their pain.
Since autistics' mirror neurons respond to their own motion, the researchers say, perhaps their brains can be induced to perceive their own reflected movements as the movements of another human being.
MirrorNeur (2851 words)
By recording the activity of single neurons in the monkey’s premotor cortex, he found that particular neurons became active when a particular action was performed by the monkey, or when the same action was observed being performed by another monkey.
The neuron in the brain is conceptually no different than a neuron in the fingertip that touches the raisins or a cone cell in the fovea that reacts to a photon reflected from a raisin.
Mirror neurons provide strong evidence against this perspective: actually they corroborate the notion that acting and perceiving are two sides of the same coin.
  More results at FactBites »

 
 

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