Mirror neurons are neurons that fire in response to observing an action being performed by another. Although this action is not performed by the individual themselves, activity is provoked in such a way that mimics the activity that would be required to produce the observed action. These neurons have principally been linked to brain regions associated with the motor behaviour including the premotor cortex, the supplementary motor area as well as the somatosensory cortex. The key characteristic of mirror neurons is their activation during the execution of a specific behaviour as well as during observation. As the majority of neurons do not appear to respond to both this makes them somewhat unique.
Since the initial studies on mirror neurons, the mirror neuron system has been attributed to underlying a plethora of social behaviours. Among these are empathy, imitation, theory of mind as well as different forms of social learning. Some proponents take these claims a step further. Ramachandran asserts that the mirror neuron system is a highly evolved neural network that developed contemporaneous to man's first use of tools. In this manner, he posits that the development of this network laid the foundation for the emergence of sophisticated human culture.
Central to this position is the idea that the mirror neuron system allows for purposeful imitation. Recognising the behavioural intentions of others facilitates the adoption of new behaviours; for example, Ramachandran argues that this may be a potential explanation for the development of language. His position is not one that claims that mirror neurons are by any extent the sole means by which culture and social behaviour have come to evolve, but that they are necessary rather than causally sufficient. The presence of the mirror neuron system was expedited cultural advancement. All well and good.
However, a recent review of mirror neurons has emphasised that as research is still at an early stage the majority of these claims are highly premature if not completely unfounded. Firstly, the mirror neuron system has often been interpreted as a means of discerning the intentions of another actor. Neurons in the system have been shown to respond differently to two superficially identical actions depending on the goal of the action. For some theorists this poses an immediate problem as it presumes that a specific intention is in-built and apparent in a given action.
Secondly, and more strikingly, the majority of neurological studies on mirror neurons have been carried out on macaque subjects and doubt remains that these findings can be conclusively applied to a human system. The mirror neurons in question can be differentially affected by a whole host of characteristics pertaining to the observed behaviour. Occlusion, perspective and distance have all been shown to affect responsiveness. In addition, some neurons are very much action-specific, others respond to broadly similar activities, and others still are largely unresponsive. This leads to serious speculation as to whether mirror neurons can legitimately comprise a unified system.
Undoubtedly, mirror neuron research has led to interesting debate on the evolution of social behaviour; but this research, as it stands, is quite precarious. It is for this reason that any conclusions about the role of the mirror neuron system, however ardent, are very hasty.