Editing Mirror neuron (section)

==In humans==
[[Image:Gray728.svg|thumb|280px|Diagram of the brain, showing the locations of the frontal and parietal lobes of the [[cerebrum]], viewed from the left. The inferior frontal lobe is the lower part of the blue area, and the superior parietal lobe is the upper part of the yellow area.]]

It is not normally possible to study single neurons in the human brain, so most evidence for mirror neurons in humans is indirect. Brain imaging experiments using [[functional magnetic resonance imaging]] (fMRI) have shown that the human [[Inferior frontal gyrus|inferior frontal cortex]] and [[superior parietal lobule|superior parietal lobe]] are active when the person performs an action and also when the person sees another individual performing an action. It has been suggested that these brain regions contain mirror neurons, and they have been defined as the human mirror neuron system.<ref>{{cite journal | vauthors = Iacoboni M, Woods RP, Brass M, Bekkering H, Mazziotta JC, Rizzolatti G | title = Cortical mechanisms of human imitation | journal = Science | volume = 286 | issue = 5449 | pages = 2526–2528 | date = December 1999 | pmid = 10617472 | doi = 10.1126/science.286.5449.2526 | author-link4 = Harold Bekkering }}</ref> More recent experiments have shown that even at the level of single participants, scanned using fMRI, large areas containing multiple fMRI voxels increase their activity both during the observation and execution of actions.<ref name="GazzolaKeysers2009" />

Neuropsychological studies looking at lesion areas that cause action knowledge, pantomime interpretation, and biological [[motion perception]] deficits have pointed to a causal link between the integrity of the inferior frontal gyrus and these behaviours.<ref>{{cite journal | vauthors = Saygin AP, Wilson SM, Dronkers NF, Bates E | title = Action comprehension in aphasia: linguistic and non-linguistic deficits and their lesion correlates | journal = Neuropsychologia | volume = 42 | issue = 13 | pages = 1788–1804 | year = 2004 | pmid = 15351628 | doi = 10.1016/j.neuropsychologia.2004.04.016 | s2cid = 11622224 | citeseerx = 10.1.1.544.9071 }}</ref><ref name="pmid20957578">{{cite journal | vauthors = Tranel D, Kemmerer D, Adolphs R, Damasio H, Damasio AR | title = Neural correlates of conceptual knowledge for actions | journal = Cognitive Neuropsychology | volume = 20 | issue = 3 | pages = 409–432 | date = May 2003 | pmid = 20957578 | doi = 10.1080/02643290244000248 | s2cid = 16131 }}</ref><ref name="pmid17660183">{{cite journal | vauthors = Saygin AP | title = Superior temporal and premotor brain areas necessary for biological motion perception | journal = Brain | volume = 130 | issue = Pt 9 | pages = 2452–2461 | date = September 2007 | pmid = 17660183 | doi = 10.1093/brain/awm162 | doi-access = free }}</ref> [[Transcranial magnetic stimulation]] studies have confirmed this as well.<ref name="pmid16527749">{{cite journal | vauthors = Pobric G, Hamilton AF | title = Action understanding requires the left inferior frontal cortex | journal = Current Biology | volume = 16 | issue = 5 | pages = 524–529 | date = March 2006 | pmid = 16527749 | doi = 10.1016/j.cub.2006.01.033 | doi-access = free | bibcode = 2006CBio...16..524P }}</ref><ref>{{cite journal | vauthors = Candidi M, Urgesi C, Ionta S, Aglioti SM | title = Virtual lesion of ventral premotor cortex impairs visual perception of biomechanically possible but not impossible actions | journal = Social Neuroscience | volume = 3 | issue = 3–4 | pages = 388–400 | year = 2008 | pmid = 18979387 | doi = 10.1080/17470910701676269 | s2cid = 37390465 }}</ref> These results indicate the activation in mirror neuron related areas are unlikely to be just epiphenomenal.

A study published in April 2010 reports recordings from single neurons with mirror properties in the human brain.<ref name="Keysers 2010">{{cite journal | vauthors = Keysers C, Gazzola V | title = Social neuroscience: mirror neurons recorded in humans | journal = Current Biology | volume = 20 | issue = 8 | pages = R353–R354 | date = April 2010 | pmid = 21749952 | doi = 10.1016/j.cub.2010.03.013 | s2cid = 3609747 | hdl = 20.500.11755/351f0172-b06b-41de-a013-852c64e197fa | doi-access = free | bibcode = 2010CBio...20.R353K | hdl-access = free }}</ref> Mukamel ''et al.'' (Current Biology, 2010) recorded from the brains of 21 patients who were being treated at Ronald Reagan UCLA Medical Center for intractable [[epilepsy]]. The patients had been implanted with intracranial depth electrodes to identify seizure foci for potential surgical treatment. Electrode location was based solely on clinical criteria; the researchers, with the patients' consent, used the same electrodes to "piggyback" their research. The researchers found a small number of neurons that fired or showed their greatest activity both when the individual performed a task and when they observed a task. Other neurons had anti-mirror properties: they responded when the participant performed an action, but were inhibited when the participant saw that action.

The mirror neurons found were located in the supplementary motor area and medial temporal cortex (other brain regions were not sampled). For purely practical reasons, these regions are not the same as those in which mirror neurons had been recorded from in the monkey: researchers in Parma were studying the ventral premotor cortex and the associated inferior parietal lobe, two regions in which epilepsy rarely occurs, and hence, single cell recordings in these regions are not usually done in humans. On the other hand, no one has to date looked for mirror neurons in the supplementary motor area or the medial temporal lobe in the monkey. Together, this therefore does not suggest that humans and monkeys have mirror neurons in different locations, but rather that they may have mirror neurons both in the ventral premotor cortex and inferior parietal lobe, where they have been recorded in the monkey, and in the supplementary motor areas and medial temporal lobe, where they have been recorded from in human – especially because detailed human fMRI analyses suggest activity compatible with the presence of mirror neurons in all these regions.<ref name="GazzolaKeysers2009" />

Another study has suggested that human beings do not necessarily have more mirror neurons than monkeys, but instead that there is a core set of mirror neurons used in action observation and execution. However, for other proposed functions of mirror neurons the mirror system may have the ability to recruit other areas of the brain when doing its auditory, somatosensory, and affective components.<ref name="pmid21782846">{{cite journal | vauthors = Molenberghs P, Cunnington R, Mattingley JB | title = Brain regions with mirror properties: a meta-analysis of 125 human fMRI studies | journal = Neuroscience and Biobehavioral Reviews | volume = 36 | issue = 1 | pages = 341–349 | date = January 2012 | pmid = 21782846 | doi = 10.1016/j.neubiorev.2011.07.004 | s2cid = 37871374 }}</ref>

===Development===
Human infant data using eye-tracking measures suggest that the mirror neuron system develops before 12&nbsp;months of age and that this system may help human infants understand other people's actions.<ref name="pmid16783366">{{cite journal | vauthors = Falck-Ytter T, Gredebäck G, von Hofsten C | title = Infants predict other people's action goals | journal = Nature Neuroscience | volume = 9 | issue = 7 | pages = 878–9 | date = July 2006 | pmid = 16783366 | doi = 10.1038/nn1729 | s2cid = 2409686 }}</ref> A critical question concerns how mirror neurons acquire mirror properties. Two closely related models postulate that mirror neurons are trained through [[Hebbian theory|Hebbian]]<ref name="pmid15491904">{{cite journal | vauthors = Keysers C, Perrett DI | title = Demystifying social cognition: a Hebbian perspective | journal = Trends in Cognitive Sciences | volume = 8 | issue = 11 | pages = 501–507 | date = November 2004 | pmid = 15491904 | doi = 10.1016/j.tics.2004.09.005 | s2cid = 8039741 }}</ref> or [[Associative learning]]<ref>{{cite journal | vauthors = Heyes C | title = Causes and consequences of imitation | journal = Trends in Cognitive Sciences | volume = 5 | issue = 6 | pages = 253–261 | date = June 2001 | pmid = 11390296 | doi = 10.1016/S1364-6613(00)01661-2 | s2cid = 15602731 }}</ref><ref name="pmid16126449">{{cite journal | vauthors = Brass M, Heyes C | title = Imitation: is cognitive neuroscience solving the correspondence problem? | journal = Trends in Cognitive Sciences | volume = 9 | issue = 10 | pages = 489–95 | date = October 2005 | pmid = 16126449 | doi = 10.1016/j.tics.2005.08.007 | s2cid = 1594505 }}</ref><ref name=Heyes2010/> (see [[Associative Sequence Learning]]). However, if premotor neurons need to be trained by action in order to acquire mirror properties, it is unclear how newborn babies are able to mimic the facial gestures of another person (imitation of unseen actions), as suggested by the work of [[Andrew N. Meltzoff|Meltzoff]] and Moore. One possibility is that the sight of tongue protrusion recruits an [[innate releasing mechanism]] in neonates. Careful analysis suggests that 'imitation' of this single gesture may account for almost all reports of facial mimicry by new-born infants.<ref>{{cite journal | vauthors = Anisfeld M |year=1996 |title=Only tongue protruding modeling is matched by neonates |journal=Developmental Review |volume=16 |issue=2 |pages=149–161 |doi=10.1006/drev.1996.0006}}</ref>