The mirror-neuron system (original) (raw)

The mirror neuron system Annual Rev

Neurosci, 2004

I Abstract A category of stimuli of great importance for primates, humans in particular, is that formed by actions done by other individuals. If we want to survive, we must understand the actions of others. Furthermore, without action understanding, social organization is impossible. In the case of humans, there is another faculty that depends on the observation of others' actions: imitation learning. Unlike most species, we are able to learn by imitation, and this faculty is at the basis of human culture. In this review we present data on a neurophysiological mechanism-the mirror-neuron mechanism-that appears to play a fundamental role in both action understanding and imitation. We describe first the functional properties of mirror neurons in monkeys. We review next the characteristics of the mirror-neuron system in humans. We stress, in particular, those properties specific to the human mirror-neuron system that might explain the human capacity to learn by imitation. We conclude by discussing the relationship between the mirror-neuron system and language.

THE MIRROR SYSTEM HYPOTHESIS: FROM A MACAQUE-LIKE MIRROR SYSTEM TO IMITATION

The Evolution of Language - Proceedings of the 6th International Conference (EVOLANG6), 2006

The Mirror System Hypothesis (MSH) of the evolution of brain mechanisms supporting language distinguishes a monkey-like mirror neuron system from a chimpanzee-like mirror system that supports simple imitation and a human-like mirror system that supports complex imitation and language. This paper briefly reviews the seven evolutionary stages posited by MSH and then focuses on the early stages which precede but are claimed to ground language. It introduces MNS2, a new model of action recognition learning by mirror neurons of the macaque brain to address data on audio-visual mirror neurons. In addition, the paper offers an explicit hypothesis on how to embed a macaque-like mirror system in a larger human-like circuit which has the capacity for imitation by both direct and indirect routes. Implications for the study of speech are briefly noted.

Is human imitation based on a mirror-neurone system? Some behavioural evidence

Experimental Brain Research, 2002

Recently, a population of neurones was discovered in the monkey’s (Macaca nemestrina) ventrolateral part of the pre-motor cortex (area F5). It is specialised for recognising object-oriented actions, regardless of whether these actions are performed or observed by the monkey. The latter observation led to the term mirror-neurones, and because these cells respond to both observed and executed actions, it seems likely that neurones of that type became co-opted during hominid evolution to serve the imitative behaviours that are so prevalent in our species. There is recent physiological evidence that Broca’s area, the human (Homo sapiens) homologue of monkey’s area F5, is involved in the imitation of finger movements. However, concluding that human imitation is based on a mirror-neurone system is premature, because: (1) imitation in monkeys does not reach the same level as in humans or apes and (2) monkeys’ mirror-neurones are specialised for object-oriented actions. This specialisation has not yet been demonstrated in adult humans. We investigated the role of objects in human imitation behaviour in a response time experiment. Subjects had to imitate downward movements of an index finger. In one condition, the observed finger touched one of two dots either ipsi- or contralaterally. In the other condition, the very same movements had to be imitated. However, there were no dots on the table. The presence of dots had a decisive influence on error patterns and on response times, but did not influence the movement proper. Dots specifically reduced the onset latency of ipsilateral finger movements and they specifically increased the use of the wrong finger, when contralateral movements were required. In general, results showed that objects also drive human imitation behaviour. Hence, it is very likely that imitation emerged from the mirror-neurone system of the common ancestor of monkeys and humans.

From monkey mirror neurons to primate behaviours: possible 'direct' and 'indirect' pathways

Philosophical Transactions of the Royal Society B: Biological Sciences, 2009

The discovery of mirror neurons (MNs), deemed to be at the basis of action understanding, could constitute the potential solution to the 'correspondence problem' between one's own and others' action that is crucial for of imitative behaviours. However, it is still to be clarified whether, and how, several imitative phenomena, differing in terms of complexity and cognitive effort, could be explained within a unified framework based on MNs. Here we propose that MNs could differently contribute to distinct imitative behaviours by means of two anatomo-functional pathways, subjected to changes during development. A 'direct mirror pathway', directly influencing the descending motor output, would be responsible for neonatal and automatic imitation. This proposal is corroborated by some new behavioural evidences provided here. During development, the increased control of voluntary movements and the capacity to efficiently suppress automatic motor activation during action observation assign to the core MNs regions essentially perceptuo-cognitive functions. These functions would be exploited by an 'indirect mirror pathway' from the core regions of the MN system to prefrontal cortex. This latter would play a key role in parsing, storing and organizing motor representations, allowing the emergence of more efficient and complex imitative behaviours such as response facilitation and true imitation.

Why the Mirror Neurons Cannot Support Action Understanding

After the discovery of the " mirror " neurons in primates, some researchers tended to explain action understanding as a result of functioning of these units. The proponents of the traditional view on the nature of this cognitive and social phenomenon assume that the mirror neurons do not provide action understanding or provide it only partly. There exist empirical data that cannot be explained through the mirror neuron model of understanding others' actions. Analyzing the mirror neuron data, I revise their function and propose an alternative role of this type of neurons. At first, goals and intentions of the executor's action are coded outside the mirror neuron system. If the action is important for the observer and can be useful in his own motor repertoire, his/her mirror neuron system implicitly reproduces the action, retrieving the kinematics and sensory consequences the observer experienced in the past while executing the same action. Thus, the implicit reproduction facilitates the observer to execute this action either immediately or in the future. More likely, precisely this, but not action understanding, is the function of the mirror neurons.

The mirror neuron system and action recognition

Brain and Language, 2004

Mirror neurons, first described in the rostral part of monkey ventral premotor cortex (area F5), discharge both when the animal performs a goal-directed hand action and when it observes another individual performing the same or a similar action. More recently, in the same area mirror neurons responding to the observation of mouth actions have been also found. In humans, through an fMRI study, it has been shown that the observation of actions performed with the hand, the mouth and the foot leads to the activation of different sectors of BrocaÕs area and premotor cortex, according to the effector involved in the observed action, following a somatotopic pattern which resembles the classical motor cortex homunculus. These results strongly support the existence of an execution-observation matching system (mirror neuron system). It has been proposed that this system is involved in action recognition. Experimental evidence in favor of this hypothesis both in the monkey and humans are shortly reviewed.

Mirror neurons and imitation: A computationally guided review

Neural Networks, 2006

Neurophysiology reveals the properties of individual mirror neurons in the macaque while brain imaging reveals the presence of 'mirror systems' (not individual neurons) in the human. Current conceptual models attribute high level functions such as action understanding, imitation, and language to mirror neurons. However, only the first of these three functions is well-developed in monkeys. We thus distinguish current opinions (conceptual models) on mirror neuron function from more detailed computational models. We assess the strengths and weaknesses of current computational models in addressing the data and speculations on mirror neurons (macaque) and mirror systems (human). In particular, our mirror neuron system (MNS), mental state inference (MSI) and modular selection and identification for control (MOSAIC) models are analyzed in more detail. Conceptual models often overlook the computational requirements for posited functions, while too many computational models adopt the erroneous hypothesis that mirror neurons are interchangeable with imitation ability. Our meta-analysis underlines the gap between conceptual and computational models and points out the research effort required from both sides to reduce this gap. q

Sensorimotor learning configures the human mirror system

Current Biology, 2007

Cells in the ''mirror system'' fire not only when an individual performs an action but also when one observes the same action performed by another agent [1-4]. The mirror system, found in premotor and parietal cortices of human and monkey brains, is thought to provide the foundation for social understanding and to enable the development of theory of mind and language [5-9]. However, it is unclear how mirror neurons acquire their mirror properties-how they derive the information necessary to match observed with executed actions [10]. We address this by showing that it is possible to manipulate the selectivity of the human mirror system, and thereby make it operate as a countermirror system, by giving participants training to perform one action while observing another. Before this training, participants showed event-related muscle-specific responses to transcranial magnetic stimulation over motor cortex during observation of little-and indexfinger movements . After training, this normal mirror effect was reversed. These results indicate that the mirror properties of the mirror system are neither wholly innate [14] nor fixed once acquired; instead they develop through sensorimotor learning . Our findings indicate that the human mirror system is, to some extent, both a product and a process of social interaction.

The mirror-neurons system: data and models

Progress in brain research, 2007

In this chapter we discuss the mirror-neurons system, a cortical network of areas that enables individuals to understand the meaning of actions performed by others through the activation of internal representations, which motorically code for the observed actions. We review evidence indicating that this capability does not depend on the amount of visual stimulation relative to the observed action, or on the sensory modality specifically addressed (visual, acoustical). Any sensorial cue that can evoke the ''idea'' of a meaningful action activates the vocabulary of motor representations stored in the ventral premotor cortex and, in humans, especially in Broca's area. This is true also for phonoarticulatory actions, which determine speech production. We present also a model of the mirror-neurons system and its partial implementation in a set of two experiments. The results, according to our model, show that motor information plays a significant role in the interpretation of actions and that a mirror-like representation can be developed autonomously as a result of the interaction between the individual and the environment.