Hypothalamic neurons that mirror aggression.

Social interactions require awareness and understanding of the behavior of others. Mirror neurons, cells representing an action by self and others, have been proposed to be integral to the cognitive substrates that enable such awareness and understanding. Mirror neurons of the primate neocortex represent skilled motor tasks, but it is unclear if they are critical for the actions they embody, enable social behaviors, or exist in non-cortical regions. We demonstrate that the activity of individual VMHvlPR neurons in the mouse hypothalamus represents aggression performed by self and others. We used a genetically encoded mirror-TRAP strategy to functionally interrogate these aggression-mirroring neurons. We find that their activity is essential for fighting and that forced activation of these cells triggers aggressive displays by mice, even toward their mirror image. Together, we have discovered a mirroring center in an evolutionarily ancient region that provides a subcortical cognitive substrate essential for a social behavior.

Two distinct networks for encoding goals and forms of action: An effective connectivity study.

Goal-directed actions are characterized by two main features: the content (i.e., the action goal) and the form, called vitality forms (VF) (i.e., how actions are executed). It is well established that both the action content and the capacity to understand the content of another's action are mediated by a network formed by a set of parietal and frontal brain areas. In contrast, the neural bases of action forms (e.g., gentle or rude actions) have not been characterized. However, there are now studies showing that the observation and execution of actions endowed with VF activate, in addition to the parieto-frontal network, the dorso-central insula (DCI). In the present study, we established-using dynamic causal modeling (DCM)-the direction of information flow during observation and execution of actions endowed with gentle and rude VF in the human brain. Based on previous fMRI studies, the selected nodes for the DCM comprised the posterior superior temporal sulcus (pSTS), the inferior parietal lobule (IPL), the premotor cortex (PM), and the DCI. Bayesian model comparison showed that, during action observation, two streams arose from pSTS: one toward IPL, concerning the action goal, and one toward DCI, concerning the action vitality forms. During action execution, two streams arose from PM: one toward IPL, concerning the action goal and one toward DCI concerning action vitality forms. This last finding opens an interesting question concerning the possibility to elicit VF in two distinct ways: cognitively (from PM to DCI) and affectively (from DCI to PM).

Anatomo-functional basis of emotional and motor resonance elicited by facial expressions.

Simulation theories predict that the observation of other's expressions modulates neural activity in the same centres controlling their production. This hypothesis has been developed by two models, postulating that the visual input is directly projected either to the motor system for action recognition (motor resonance) or to emotional/interoceptive regions for emotional contagion and social synchronization (emotional resonance). Here we investigated the role of frontal/insular regions in the processing of observed emotional expressions by combining intracranial recording, electrical stimulation and effective connectivity. First, we intracranially recorded from prefrontal, premotor or anterior insular regions of 44 patients during the passive observation of emotional expressions, finding widespread modulations in prefrontal/insular regions (anterior cingulate cortex, anterior insula, orbitofrontal cortex and inferior frontal gyrus) and motor territories (Rolandic operculum and inferior frontal junction). Subsequently, we electrically stimulated the activated sites, finding that (i) in the anterior cingulate cortex and anterior insula, the stimulation elicited emotional/interoceptive responses, as predicted by the 'emotional resonance model'; (ii) in the Rolandic operculum it evoked face/mouth sensorimotor responses, in line with the 'motor resonance' model; and (iii) all other regions were unresponsive or revealed functions unrelated to the processing of facial expressions. Finally, we traced the effective connectivity to sketch a network-level description of these regions, finding that the anterior cingulate cortex and the anterior insula are reciprocally interconnected while the Rolandic operculum is part of the parieto-frontal circuits and poorly connected with the former. These results support the hypothesis that the pathways hypothesized by the 'emotional resonance' and the 'motor resonance' models work in parallel, differing in terms of spatio-temporal fingerprints, reactivity to electrical stimulation and connectivity patterns.

Synergy of the mirror neuron system and the mentalizing system in a single brain and between brains during joint actions.

Cooperative action involves the simulation of actions and their co-representation by two or more people. This requires the involvement of two complex brain systems: the mirror neuron system (MNS) and the mentalizing system (MENT), both of critical importance for successful social interaction. However, their internal organization and the potential synergy of both systems during joint actions (JA) are yet to be determined. The aim of this study was to examine the role and interaction of these two fundamental systems-MENT and MNS-during continuous interaction. To this hand, we conducted a multiple-brain connectivity analysis in the source domain during a motor cooperation task using high-density EEG dual-recordings providing relevant insights into the roles of MNS and MENT at the intra- and interbrain levels. In particular, the intra-brain analysis demonstrated the essential function of both systems during JA, as well as the crucial role played by single brain regions of both neural mechanisms during cooperative activities. Specifically, our intra-brain analysis revealed that both neural mechanisms are essential during Joint Action (JA), showing a solid connection between MNS and MENT and a central role of the single brain regions of both mechanisms during cooperative actions. Additionally, our inter-brain study revealed increased inter-subject connections involving the motor system, MENT and MNS. Thus, our findings show a mutual influence between two interacting agents, based on synchronization of MNS and MENT systems. Our results actually encourage more research into the still-largely unknown realm of inter-brain dynamics and contribute to expand the body of knowledge in social neuroscience.

Grasp-specific high-frequency broadband mirror neuron activity during reach-and-grasp movements in humans.

Broadly congruent mirror neurons, responding to any grasp movement, and strictly congruent mirror neurons, responding only to specific grasp movements, have been reported in single-cell studies with primates. Delineating grasp properties in humans is essential to understand the human mirror neuron system with implications for behavior and social cognition. We analyzed electrocorticography data from a natural reach-and-grasp movement observation and delayed imitation task with 3 different natural grasp types of everyday objects. We focused on the classification of grasp types from high-frequency broadband mirror activation patterns found in classic mirror system areas, including sensorimotor, supplementary motor, inferior frontal, and parietal cortices. Classification of grasp types was successful during movement observation and execution intervals but not during movement retention. Our grasp type classification from combined and single mirror electrodes provides evidence for grasp-congruent activity in the human mirror neuron system potentially arising from strictly congruent mirror neurons.

Effects of a single session action observation training on hand function in healthy young adults: a randomised controlled assessor and participants-blinded trial.

PURPOSE: The aim was to investigate the effects of a single session action observation training (AOT) on hand function and evaluate whether observing self-actions would be more effective than observing someone else. MATERIALS AND METHODS: A total of 60 right-handed healthy young adults, (32 female, 28 males and the mean age was 21.32 ± 1.07 years) were included in the study. The participants were randomly divided into five groups, self-action observation (sAO), observation of a third person (AO), action practice (AP), non-action observation (nAO), and control. A single session was performed for all participants. The primary outcome was the Jebsen Taylor Hand Function Test (JTHFT) assessed by a masked assessor. RESULTS: Significant differences were observed between the sAO and control group in total left side JTHFT performance (p < 0.001). Additionally, there were significant differences between the AO and control group (p < 0.001), and AP and nAO group (p = 0.003) and AP and control group (p < 0.001) in total JTHFT performance change of the left side. Significant differences were found between the sAO and nAO (p = 0.001) and control groups (p < 0.001) in dominant side total JTHFT performance change. No difference between sAO and AP groups were observed (p > 0.05). CONCLUSION: It was observed that a single session of action observation training improved hand function in healthy adults. The better performance achieved in the group watching the self-video may suggest that watching the self-image activates more mirror neurons.

Motor resonance to non-visible postural adaptation: A novel aspect of the mirror mechanism.

The activation of the Mirror Neuron System (MNS) has been described to reflect visible movements, but not postural, non-visible, adaptations that accompany the observed movements. Since any motor act is the result of a well-tailored dialogue between these two components, we decided to investigate whether a motor resonance to nonvisible postural adaptations could be detected. Possible changes in soleus corticospinal excitability were investigated by eliciting the H-reflex during the observation of three videos, corresponding to three distinct experimental conditions: 'Chest pass', 'Standing' and 'Sitting', and comparing its size with that measured during observation of a control videoclip (a landscape). In the observed experimental conditions, the Soleus muscle has different postural roles: a dynamic role in postural adaptations during the Chest pass; a static role while Standing still; no role while Sitting. The H-reflex amplitude was significantly enhanced in the 'Chest pass' condition compared to the 'Sitting' and 'Standing' conditions. No significant difference was found between 'Sitting' and 'Standing' conditions. The increased corticospinal excitability of the Soleus during the 'Chest pass' condition suggests that the mirror mechanisms produce a resonance to postural components of an observed action, although they may not be visible. This observation highlights the fact that mirror mechanisms echo non intentional movements as well and points to a novel possible role of mirror neurons in motor recovery.

Brain-Computer Interface Training of mu EEG Rhythms in Intellectually Impaired Children with Autism: A Feasibility Case Series.

Prior studies show that neurofeedback training (NFT) of mu rhythms improves behavior and EEG mu rhythm suppression during action observation in children with autism spectrum disorder (ASD). However, intellectually impaired persons were excluded because of their behavioral challenges. We aimed to determine if intellectually impaired children with ASD, who were behaviorally prepared to take part in a mu-NFT study using conditioned auditory reinforcers, would show improvements in symptoms and mu suppression following mu-NFT. Seven children with ASD (ages 6-8; mean IQ 70.6 ± 7.5) successfully took part in mu-NFT. Four cases demonstrated positive learning trends (hit rates) during mu-NFT (learners), and three cases did not (non-learners). Artifact-creating behaviors were present during tests of mu suppression for all cases, but were more frequent in non-learners. Following NFT, learners showed behavioral improvements and were more likely to show evidence of a short-term increase in mu suppression relative to non-learners who showed little to no EEG or behavior improvements. Results support mu-NFT's application in some children who otherwise may not have been able to take part without enhanced behavioral preparations. Children who have more limitations in demonstrating learning during NFT, or in providing data with relatively low artifact during task-dependent EEG tests, may have less chance of benefiting from mu-NFT. Improving the identification of ideal mu-NFT candidates, mu-NFT learning rates, source analyses, EEG outcome task performance, population-specific artifact-rejection methods, and the theoretical bases of NFT protocols, could aid future BCI-based, neurorehabilitation efforts.

The Motor Basis for Misophonia.

Misophonia is a common disorder characterized by the experience of strong negative emotions of anger and anxiety in response to certain everyday sounds, such as those generated by other people eating, drinking, and breathing. The commonplace nature of these "trigger" sounds makes misophonia a devastating disorder for sufferers and their families. How such innocuous sounds trigger this response is unknown. Since most trigger sounds are generated by orofacial movements (e.g., chewing) in others, we hypothesized that the mirror neuron system related to orofacial movements could underlie misophonia. We analyzed resting state fMRI (rs-fMRI) connectivity (N = 33, 16 females) and sound-evoked fMRI responses (N = 42, 29 females) in misophonia sufferers and controls. We demonstrate that, compared with controls, the misophonia group show no difference in auditory cortex responses to trigger sounds, but do show: (1) stronger rs-fMRI connectivity between both auditory and visual cortex and the ventral premotor cortex responsible for orofacial movements; (2) stronger functional connectivity between the auditory cortex and orofacial motor area during sound perception in general; and (3) stronger activation of the orofacial motor area, specifically, in response to trigger sounds. Our results support a model of misophonia based on "hyper-mirroring" of the orofacial actions of others with sounds being the "medium" via which action of others is excessively mirrored. Misophonia is therefore not an abreaction to sounds, per se, but a manifestation of activity in parts of the motor system involved in producing those sounds. This new framework to understand misophonia can explain behavioral and emotional responses and has important consequences for devising effective therapies.SIGNIFICANCE STATEMENT Conventionally, misophonia, literally "hatred of sounds" has been considered as a disorder of sound emotion processing, in which "simple" eating and chewing sounds produced by others cause negative emotional responses. Our data provide an alternative but complementary perspective on misophonia that emphasizes the action of the trigger-person rather than the sounds which are a byproduct of that action. Sounds, in this new perspective, are only a "medium" via which action of the triggering-person is mirrored onto the listener. This change in perspective has important consequences for devising therapies and treatment methods for misophonia. It suggests that, instead of focusing on sounds, which many existing therapies do, effective therapies should target the brain representation of movement.

Embodied cognition and mirror neurons: a critical assessment.

According to embodied cognition theories, higher cognitive abilities depend on the reenactment of sensory and motor representations. In the first part of this review, we critically analyze the central claims of embodied theories and argue that the existing behavioral and neuroimaging data do not allow investigators to discriminate between embodied cognition and classical cognitive accounts, which assume that conceptual representations are amodal and symbolic. In the second part, we review the main claims and the core electrophysiological findings typically cited in support of the mirror neuron theory of action understanding, one of the most influential examples of embodied cognition theories. In the final part, we analyze the claim that mirror neurons subserve action understanding by mapping visual representations of observed actions on motor representations, trying to clarify in what sense the representations carried by these neurons can be claimed motor.

Differences in working memory coding of biological motion attributed to oneself and others.

The question how the brain distinguishes between information about self and others is of fundamental interest to both philosophy and neuroscience. In this functional magnetic resonance imaging (fMRI) study, we sought to distinguish the neural substrates of representing a full-body movement as one's movement and as someone else's movement. Participants performed a delayed match-to-sample working memory task where a retained full-body movement (displayed using point-light walkers) was arbitrarily labeled as one's own movement or as performed by someone else. By using arbitrary associations we aimed to address a limitation of previous studies, namely that our own movements are more familiar to us than movements of other people. A searchlight multivariate decoding analysis was used to test where information about types of movement and about self-association was coded. Movement specific activation patterns were found in a network of regions also involved in perceptual processing of movement stimuli, however not in early sensory regions. Information about whether a memorized movement was associated with the self or with another person was found to be coded by activity in the left middle frontal gyrus (MFG), left inferior frontal gyrus (IFG), bilateral supplementary motor area, and (at reduced threshold) in the left temporoparietal junction (TPJ). These areas are frequently reported as involved in action understanding (IFG, MFG) and domain-general self/other distinction (TPJ). Finally, in univariate analysis we found that selecting a self-associated movement for retention was related to increased activity in the ventral medial prefrontal cortex.

The efficacy of graded motor imagery in post-traumatic stiffness of elbow: a randomized controlled trial.

BACKGROUND: Physiotherapy improves the movement range after the onset of post-traumatic elbow stiffness and reduces the pain, which is a factor limiting elbow range of motion. However, no results have been reported for motor-cognitive intervention programs in post-traumatic elbow stiffness management. The objective was to investigate the efficacy of graded motor imagery (GMI) in post-traumatic elbow stiffness. METHODS: Fifty patients with post-traumatic elbow stiffness (18 female; mean age, 41.9 ± 10.9 years) were divided into 2 groups. The GMI group (n = 25) received a program consisting of left-right discrimination, motor imagery, and mirror therapy (twice a week for 6 weeks); the structured exercise (SE) group (n = 25) received a program consisting of range-of-motion, stretching, and strengthening exercises (twice a week for 6 weeks). Both groups received a 6-week home exercise program. The primary outcome was the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire. The secondary outcomes were the active range of motion (AROM), visual analog scale (VAS), Tampa Scale for Kinesiophobia (TSK), muscle strength of elbow flexors and extensors, grip strength, left-right discrimination, and Global Rating of Change. Patients were assessed at baseline, at the end of treatment (12 sessions), and a 6-week follow-up. RESULTS: The results indicated that both GMI and SE interventions significantly improved outcomes (P < .05). After a 6-week intervention, the DASH score was significantly improved with a medium effect size in the GMI group compared with the SE group, and improvement continued at the 6-week follow-up (F1,45 = 3.10, P = .01). The results with a medium to large effect size were also significant for elbow flexion AROM (P = .02), elbow extension AROM (P = .03), VAS-activity (P = .001), TSK (P = .01), and muscle strength of elbow flexors and elbow extensors (P = .03) in favor of the GMI group. CONCLUSION: The GMI is an effective motor-cognitive intervention program that might be applied to the rehabilitation of post-traumatic elbow stiffness to improve function, elbow AROM, pain, fear of movement-related pain, and muscle strength.

[Mirror neurons, neural substrate of action understanding?] / Neurones miroirs, substrat neuronal de la compréhension de l'action?

In 1992, the Laboratory of Human Physiology at the University of Parma (Italy) publish a study describing "mirror" neurons in the macaque that activate both when the monkey performs an action and when it observes an experimenter performing the same action. The research team behind this discovery postulates that the mirror neurons system is the neural basis of our ability to understand the actions of others, through the motor mapping of the observed action on the observer's motor repertory (direct-matching hypothesis). Nevertheless, this conception met serious criticism. These critics attempt to relativize their function by placing them within a network of neurocognitive and sensory interdependencies. In short, the essential characteristic of these neurons is to combine the processing of sensory information, especially visual, with that of motor information. Their elementary function would be to provide a motor simulation of the observed action, based on visual information from it. They can contribute, with other non-mirror areas, to the identification/prediction of the action goal and to the interpretation of the intention of the actor performing it. Studying the connectivity and high frequency synchronizations of the different brain areas involved in action observation would likely provide important information about the dynamic contribution of mirror neurons to "action understanding". The aim of this review is to provide an up-to-date analysis of the scientific evidence related to mirror neurons and their elementary functions, as well as to shed light on the contribution of these neurons to our ability to interpret and understand others' actions.

Enhancing Mirror Therapy via Scaling and Shared Control: A Novel Open-Source Virtual Reality Platform for Stroke Rehabilitation.

Mirror therapy is increasingly used in stroke rehabilitation to improve functional movements of the affected limb. However, the extent of mirroring in conventional mirror therapy is typically fixed (1:1) and cannot be tailored based on the patient's impairment level. Further, the movements of the affected limb are not actively incorporated in the therapeutic process. To address these issues, we developed an immersive VR system using HTC Vive and Leap Motion, which communicates with our free and open-source software environment programmed using SteamVR and the Unity 3D gaming engine. The mirror therapy VR environment was incorporated with two novel features: (1) scalable mirroring and (2) shared control. In the scalable mirroring, mirror movements were programmed to be scalable between 0 and 1, where 0 represents no movements, 0.5 represents 50% mirroring, and 1 represents 100% mirroring. In shared control, the contribution of the mirroring limb to the movements was programmed to be scalable between 0 to 1, where 0 represents 100% contribution from the mirroring limb (i.e., no mirroring), 0.5 represents 50% of movements from the mirrored limb and 50% of movements from the mirroring limb, and 1 represents full mirroring (i.e., no shared movements). Validation experiments showed that these features worked appropriately. The proposed VR-based mirror therapy is the first fully developed system that is freely available to the rehabilitation science community. The scalable and shared control features can diversify mirror therapy and potentially augment the outcomes of rehabilitation, although this needs to be verified through future experiments.

Sensorimotor Expectations Bias Motor Resonance during Observation of Object Lifting: The Causal Role of pSTS.

Transcranial magnetic stimulation studies have highlighted that corticospinal excitability is increased during observation of object lifting, an effect termed "motor resonance." This facilitation is driven by movement features indicative of object weight, such as object size or observed movement kinematics. Here, we investigated in 35 humans (23 females) how motor resonance is altered when the observer's weight expectations, based on visual information, do not match the actual object weight as revealed by the observed movement kinematics. Our results highlight that motor resonance is not robustly driven by object weight but easily masked by a suppressive mechanism reflecting the correctness of weight expectations. Subsequently, we investigated in 24 humans (14 females) whether this suppressive mechanism was driven by higher-order cortical areas. For this, we induced "virtual lesions" to either the posterior superior temporal sulcus (pSTS) or dorsolateral prefrontal cortex (DLPFC) before having participants perform the task. Importantly, virtual lesion of pSTS eradicated this suppressive mechanism and restored object weight-driven motor resonance. In addition, DLPFC virtual lesion eradicated any modulation of motor resonance. This indicates that motor resonance is heavily mediated by top-down inputs from both pSTS and DLPFC. Together, these findings shed new light on the theorized cortical network driving motor resonance. That is, our findings highlight that motor resonance is not only driven by the putative human mirror neuron network consisting of the primary motor and premotor cortices as well as the anterior intraparietal sulcus, but also by top-down input from pSTS and DLPFC.SIGNIFICANCE STATEMENT Observation of object lifting activates the observer's motor system in a weight-specific fashion: Corticospinal excitability is larger when observing lifts of heavy objects compared with light ones. Interestingly, here we demonstrate that this weight-driven modulation of corticospinal excitability is easily suppressed by the observer's expectations about object weight and that this suppression is mediated by the posterior superior temporal sulcus. Thus, our findings show that modulation of corticospinal excitability during observed object lifting is not robust but easily altered by top-down cognitive processes. Finally, our results also indicate how cortical inputs, originating remotely from motor pathways and processing action observation, overlap with bottom-up motor resonance effects.

Largely shared neural codes for biological and nonbiological observed movements but not for executed actions in monkey premotor areas.

The neural processing of others' observed actions recruits a large network of brain regions (the action observation network; AON) in which frontal motor areas are thought to play a crucial role. As the discovery of mirror neurons (MNs) in the ventral premotor cortex, it has been assumed that their activation was conditional upon the presentation of biological rather than nonbiological motion stimuli, supporting a form of direct visuomotor matching. Nonetheless, nonbiological observed movements have rarely been used as control stimuli to evaluate visual specificity, thereby leaving the issue of similarity among neural codes for executed actions and biological or nonbiological observed movements unresolved. Here, we addressed this issue by recording from two nodes of the AON that are attracting increasing interest, namely, the ventrorostral part of the dorsal premotor area F2 and the mesial presupplementary motor area F6 of macaques while they 1) executed a reaching-grasping task, 2) observed an experimenter performing the task, and 3) observed a nonbiological effector moving in the same context. Our findings revealed stronger neuronal responses to the observation of biological than nonbiological movement, but biological and nonbiological visual stimuli produced highly similar neural dynamics and relied on largely shared neural codes, which in turn remarkably differed from those associated with executed actions. These results indicate that, in highly familiar contexts, visuomotor remapping processes in premotor areas hosting MNs are more complex and flexible than predicted by a direct visuomotor matching hypothesis.NEW & NOTEWORTHY Pioneering studies on mirror neurons (MNs) in premotor areas emphasized the absence of response to the sight of nonbiological moving objects, suggesting a match between execution and observation activities. This study shows that although premotor neurons can discriminate between biological and nonbiological observed movements, these visual stimuli rely on largely shared neural codes, which differ strongly from those associated with executed actions.

Is the Putative Mirror Neuron System Associated with Empathy? A Systematic Review and Meta-Analysis.

Theoretical perspectives suggest that the mirror neuron system (MNS) is an important neurobiological contributor to empathy, yet empirical support is mixed. Here, we adopt a summary model for empathy, consisting of motor, emotional, and cognitive components of empathy. This review provides an overview of existing empirical studies investigating the relationship between putative MNS activity and empathy in healthy populations. 52 studies were identified that investigated the association between the MNS and at least one domain of empathy, representing data from 1044 participants. Our results suggest that emotional and cognitive empathy are moderately correlated with MNS activity, however, these domains were mixed and varied across techniques used to acquire MNS activity (TMS, EEG, and fMRI). Few studies investigated motor empathy, and of those, no significant relationships were revealed. Overall, results provide preliminary evidence for a relationship between MNS activity and empathy. However, our findings highlight methodological variability in study design as an important factor in understanding this relationship. We discuss limitations regarding these methodological variations and important implications for clinical and community translations, as well as suggestions for future research.

Very preterm infants displayed similar imitation skills to full-term infants at term equivalent age.

AIM: Very preterm infants are exposed to an atypical environment that could alter their developmental trajectory. We aimed to examine neonatal imitation, a foundation of social cognition, in very preterm and full-term infants. METHODS: In Strasbourg, France, between 2015 and 2018, we prospectively investigated the development of imitation skills. Very preterm (27 to 33 weeks of gestational age, n = 20) and full-term infants (n = 20) were enrolled using four gestures: tongue protrusion, mouth opening, sequential finger movements and hand movements. All testing were performed in infants at term-equivalent age. Two independent and blinded observers coded the behaviour of each infant on video recording. Facial expressions or hand movements, similar to the one presented, were quantified and classified according to their timing. RESULTS: A total of 37 out of 40 infants imitated at least one gesture. The very preterm and term infants did not differ in the presence of imitation or its timing for the four gestures tested. The very preterm infants displayed more imitation abilities for sequential finger movement. Tongue protrusion and sequential finger movement were the particularly strong imitated gesture in both groups. CONCLUSION: These findings are the first to show similar neonatal imitation in term and very preterm infants. Our results may support early parent-infant social interactions.

Neuroscience highlights: The mirror inside our brain.

Over the second half of the 19th century, numerous theories arose concerning mechanisms involved in understanding of action, imitative learning, language development and theory of mind. These explorations gained new momentum with the discovery of the so called "mirror neurons". Rizzolatti's work inspired large groups of scientists seeking explanation in a new and hitherto unexplored area of how we perceive and understand the actions and intentions of others, how we learn through imitation to help our own survival, and what mechanisms have helped us to develop a unique human trait, language. Numerous studies have addressed these questions over the years, gathering information about mirror neurons themselves, their subtypes, the different brain areas involved in the mirror neuron system, their role in the above mentioned mechanisms, and the varying consequences of their dysfunction in human life. In this short review, we summarize the most important theories and discoveries that argue for the existence of the mirror neuron system, and its essential function in normal human life or some pathological conditions.

Effectiveness of Self-Action Observation Therapy as a Novel Method on Paretic Upper Limb and Cortical Excitability Post-Stroke: A Single-Subject Study.

Background: Action Observation Therapy (AOT) is a top-down approach that has been recently introduced in the rehabilitation of neurological disorders mainly after stroke. The main goal of this study was to investigate the effects and feasibility of a new technique in AOT procedure (called self-AOT) following periods of no treatment and routine AOT intervention on upper limb motor function, occupational performance and neurophysiological changes in a stroke patient. Methods: A single-subject A-B-A-C design was used and a 58-year-old woman with a 3-year history of left hemiplegia poststroke participated in this study. In the baseline (A1, A2) phases, the patient received no treatment. In the first intervention (B phase), she received a 4-week AOT, and in the second intervention (C phase), a 4 week of Self-AOT was practiced. In all phases, upper limb motor recovery as a target outcome was evaluated on 4 occasions using the Fugl-Meyer assessment. Upper limb function, dexterity and spasticity were assessed using Action Research Arm Test, Box-Block Test and Modified Modified Ashworth Scale respectively. Occupational Performance/Satisfaction was assessed with Canadian Occupational Performance Measure and to assess neuroplasticity, Motor Evoked Potential was recorded by Transcranial Magnetic Stimulation. Visual analysis, slope, and percentage of non-overlapping data were used for assessing the changes between phases. Results: Percentage of non-overlapping data and slopes indicated that motor recovery had clinically relevant improvements after both interventions compared to baselines. Other outcomes also showed improvements except for spasticity of wrist/elbow flexors and Motor Evoked Potential of opponens indicis. Conclusion: Self-AOT may be as effective as other procedures of AOT for improving upper limb motor function, occupational performance/satisfaction, and cortical excitability post-stroke.