Long abstractThis article argues that mirror neurons originate in sensorimotor associative learning and therefore a new approach is needed to investigate their functions. Mirror neurons were discovered about 20 years ago in the monkey brain, and there is now evidence that they are also present in the human brain. The intriguing feature of many mirror neurons is that they fire not only when the animal is performing an action, such as grasping an object using a power grip, but also when the animal passively observes a similar action performed by another agent. It is widely believed that mirror neurons are a genetic adaptation for action understanding; that they were designed by evolution to fulfill a specific socio-cognitive function. In contrast, we argue that mirror neurons are forged by domain-general processes of associative learning in the course of individual development, and, although they may have psychological functions, they do not necessarily have a specific evolutionary purpose or adaptive function. The evidence supporting this view shows that 1) mirror neurons do not consistently encode action 'goals'; 2) the contingency-and context-sensitive nature of associative learning explains the full range of mirror neuron properties; 3) human infants receive enough sensorimotor experience to support associative learning of mirror neurons ('wealth of the stimulus'); and 4) mirror neurons can be changed in radical ways by sensorimotor training. The associative account implies that reliable information about the function of mirror neurons can be obtained only by research based on developmental history, system-level theory, and careful experimentation. 3 Short abstractMirror neurons have been described as "the neurons that shaped civilization" (Ramachandran, 2009). It is widely assumed that mirror neurons were designed by evolution to enable action understanding. In contrast, we argue that mirror neurons are forged by domain-general processes of associative learning, and do not necessarily have a specific evolutionary purpose or adaptive function. The associative account allows that mirror neurons may have psychological effects or functions. However, it implies that, to get reliable information about the function of mirror neurons, we need a new approach based on developmental history, system-level theory, and careful experimentation. 4Mirror neurons (MNs) were discovered serendipitously in 1992 and given their brilliant name four years later (di Pellegrino, Fadiga, Fogassi, Gallese, & Rizzolatti, 1992;. The striking feature of many MNs is that they fire not only when a monkey is performing an action, such as grasping an object using a power grip, but also when the monkey passively observes a similar action performed by another. Neurons with this capacity to match observed and executed actions, to code both 'my action' and 'your action', were originally found in area F5 of the ventral premotor cortex (PMC) Gallese et al., 1996) and the inferior parietal lobule (IPL) (Bonini et al., 2010;Fogassi et al., 2005) of th...

The temporoparietal junction (TPJ) is a key node within the "social brain". Several studies suggest that the TPJ controls representations of the self or another individual across a variety of low-level (agency discrimination, visual perspective taking, control of imitation) and high-level (mentalizing, empathy) sociocognitive processes. We explored whether sociocognitive abilities relying on on-line control of self and other representations could be modulated with transcranial direct current stimulation (tDCS) of TPJ. Participants received excitatory (anodal), inhibitory (cathodal), or sham stimulation before completing three sociocognitive tasks. Anodal stimulation improved the on-line control of self-other representations elicited by the imitation and perspective-taking tasks while not affecting attribution of mental states during a self-referential task devoid of such a requirement. Our findings demonstrate the efficacy of tDCS to improve social cognition and highlight the potential for tDCS to be used as a tool to aid self-other processing in clinical populations.

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 index-finger movements [11-13]. 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 [15, 16]. Our findings indicate that the human mirror system is, to some extent, both a product and a process of social interaction.

Previous studies using the dot perspective task have shown that adults are slower to verify the number of dots they can see in a picture when a human figure in the picture, an avatar, can see a different number of dots. This "self-consistency effect," which occurs even when the avatar's perspective is formally task-irrelevant, has been interpreted as evidence of implicit mentalizing; that humans can think about the mental states of others via dedicated, automatic processes. We tested this interpretation by giving participants 2 versions of the dot perspective task. In some trials, the avatar was presented as in previous experiments, and in other trials the avatar was replaced by an arrow with similar low-level features. We found self-consistency effects of comparable size in the avatar and arrow conditions, suggesting that self-consistency effects in the dot perspective task are due to domain-general processes such as those that mediate automatic attentional orienting.

The ability to represent mental states (theory of mind [ToM]) is crucial in understanding individual differences in social ability and social impairments evident in conditions such as autism spectrum disorder (ASD). The Reading the Mind in the Eyes Test (RMET) is a popular measure of ToM ability, validated in part by the poor performance of those with ASD. However, the RMET requires recognition of facial emotion, which is impaired in those with alexithymia, which frequently co-occurs with ASD. Thus, it is unclear whether the RMET indexes emotion recognition, associated with alexithymia, or ToM, associated with ASD. We therefore investigated the independent contributions of ASD and alexithymia to performance on the RMET. ASD and alexithymia-matched control participants did not differ on RMET performance, whereas ASD participants demonstrated impaired performance on an alternative test of ToM, the Movie for Assessment of Social Cognition (MASC). Furthermore, alexithymia, but not ASD diagnosis, significantly influenced RMET performance but did not affect MASC performance. These results suggest that the RMET measures emotion recognition rather than ToM ability and support the alexithymia hypothesis of emotion-related deficits in ASD.

Imitative compatibility, or automatic imitation, has been used as a measure of imitative performance and as a behavioral index of the functioning of the human mirror system (e.g., Brass, Bekkering, Wohlschlager, & Prinz, 2000; Heyes, Bird, Johnson, & Haggard, 2005; Kilner, Paulignan, & Blakemore, 2003). However, the use of imitative compatibility as a measure of imitation has been criticized on the grounds that imitative compatibility has been confounded with simple spatial compatibility (Aicken, Wilson, Williams, & Mon-Williams, 2007; Bertenthal, Longo, & Kosobud, 2006; Jansson, Wilson, Williams, & Mon-Williams, 2007). Two experiments are reported in which, in contrast with previous studies, imitative compatibility was measured on both spatially compatible and spatially incompatible trials, and imitative compatibility was shown to be present regardless of spatial compatibility. Additional features of the experiments allowed measurement of the time courses of the imitative and spatial compatibility effects both within and across trials. It was found that imitative compatibility follows a different time course from spatial compatibility, providing further evidence for their independence and supporting the use of imitative compatibility as a measure of imitation

It has been proposed that Autism Spectrum Disorder (ASD) is associated with difficulties perceiving the internal state of one's body (i.e., impaired interoception), causing the socio-emotional deficits which are a diagnostic feature of the condition. However, research indicates that alexithymia – characterized by difficulties in recognizing emotions from internal bodily sensations – is also linked to atypical interoception. Elevated rates of alexithymia in the autistic population have been shown to underpin several socio-emotional impairments thought to be symptomatic of ASD, raising the possibility that interoceptive difficulties in ASD are also due to co-occurring alexithymia. Following this line of inquiry, the present study examined the relative impact of alexithymia and autism on interoceptive accuracy (IA). Across two experiments, it was found that alexithymia, not autism, was associated with atypical interoception. Results indicate that interoceptive impairments should not be considered a feature of ASD, but instead due to co-occurring alexithymia.

A core requirement for imitation is a capacity to solve the correspondence problem; to map observed onto executed actions, even when observation and execution yield sensory inputs in different modalities and coordinate frames. Until recently, it was assumed that the human capacity to solve the correspondence problem is innate. However, it is now becoming apparent that, as predicted by the associative sequence learning model, experience, and especially sensorimotor experience, plays a critical role in the development of imitation. We review evidence from studies of non-human animals, children and adults, focusing on research in cognitive neuroscience that uses training and naturally occurring variations in expertise to examine the role of experience in the formation of the mirror system. The relevance of this research depends on the widely held assumption that the mirror system plays a causal role in generating imitative behaviour. We also report original data supporting this assumption. These data show that theta-burst transcranial magnetic stimulation of the inferior frontal gyrus, a classical mirror system area, disrupts automatic imitation of finger movements. We discuss the implications of the evidence reviewed for the evolution, development and intentional control of imitation.