User:Niubrad

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I'm a neurobiology grad student at San Diego State University. I am currently doing research with mirror neurons, using functional MRI scanning techniques. I also work in a teratology lab where we look for treatments for fetal alcohol spectrum disorders.

Wikipedia is my friend.

^[1]

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 himself performing the action. These neurons have been observed in primates, in some birds, and in humans. In humans, they have been found in Broca's area and the inferior parietal cortex of the brain. Some scientists consider mirror neurons one of the most important findings of neuroscience in the last decade. See for example this^[2] essay by Ramachandran on their potential importance in imitation and language.

Contents 1 Introduction 2 Discovery 3 Specifics of Mirror Neuron Function 4 The significance of mirror neurons 5 Footnotes 6 References 7 External links

[edit] Introduction

In the monkey, mirror neurons are found in the inferior frontal gyrus and inferior parietal lobule. These neurons are active when the monkeys perform certain tasks, but they also fire when the monkeys watch 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.

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,^[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]

Research into all of these possibilities is ongoing.

[edit] 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]

As with many other notable discoveries, mirror neurons were found by chance. Rizzolatti explains; "I think it was Fogassi, standing next to a bowl of fruit and reached for a banana, when some of the neurons reacted. How could this happen, when the monkey did not move? At first we thought it to be a flaw in our measuring or maybe equipment failure, but everything checked out OK and the reactions were repeated as we repeated the movement."^{[citation needed]}

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, evidences from fMRI, TMS and EEG and behavioral strongly suggest the presence of similar systems in human, where brain regions which respond during both action and the observation of action have been identified. Not surprisingly, these brain region closely match those found in the macaque monkey ^[10].

[edit] Specifics of Mirror Neuron Function

Mirror neurons mediate the understanding of other persons behavior: Each time an individual sees an action done by another individual, neurons that represent that action are activated in the observer’s premotor cortex. This automatically induced, motor representation of the observed action corresponds to the same firing neuron when the same action is done by the observer, and whose outcome is known by the acting individual. In this way, the mirror system can transform visual information into knowledge^[11].

Mirror neurons are at the root of action understanding, that is, they will not fire by visualizing an action in ones own mind, instead they will fire when there is sufficient contextual clues that give incite as to what action is taking place. For instance, if an experimenter rips a piece of paper in front of a subject, the mirror neuron might fire in a subsequent trial when then ripping a piece of paper is behind a curtain, because the sound alone may trigger sufficient contextual clues about an action. Another way, a mirror neuron encoded for grasping an object will not fire when an experimenter reaches for a nonexistent object, however the neuron will fire if the experimenter reaches for something (or not something) hidden behind a curtain. This can be explained by the observer, in the first trial, knowing the object is not there, however in the trial where an experimenter is reaching behind a curtain, the observer may try to understand the action as grasping an object, therefore eliciting activation for that particular mirror neuron^[12].

[edit] The significance of mirror neurons

Since the discovery of mirror neurons, grand claims have been made for their importance (e.g. by Ramachandran). In particular, there has been much speculation about the evolution of mirror neurons, and their relationship to language evolution. While mirror neurons are present in macaque monkeys, these monkeys imitate each other's behaviour only as neonates and during a limited temporal window^[13]. In adults, they may enable the monkey to understand what another monkey is doing, or to recognise the other monkey's action.^[14]

In humans, mirror neurons are 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.^[15] However, like many theories of language evolution, there is little direct evidence either way.

Studies also link mirror neurons to understanding goals and intentions. Fogassi et al. (2005)^[16] 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 discharged 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.

[edit] Footnotes

[edit] References

• The others are inside you, article from “Ingeniøren” (original title: “De andre er inden I dig”).
• What do mirror neurons mean…?, workshop sponsored by The European Science Foundation.
• E. Bruce Goldstein. (2002). Sensation and Perception, Wadsworth (p. 321-324)

[edit] External links

• NOVA scienceNOW: Mirror Neurons (including a 14 minute broadcast segment)
• Neuroscience And Bio Behavioural Reviews.
• LiveScience article on mirror neurons in mind reading
• A primer on mirror-neurons and a critical view on their role in imitation