Upper Limb Electromyographic Responses to Motor Imagery and Action Observation in Acquired Brain Injury.

Acquired Brain Injuries are one of the leading causes of mortality and disability worldwide. One of the most frequent sequelae is motor impairment of the upper limbs, which affects people's functionality and quality of life. Following the discovery of mirror neurons, new techniques were developed based on the mechanisms of neuronal plasticity, such as motor imagery (MI) and action observation (AO). We propose a protocol using electromyographic recordings of forearm muscles in people who have suffered a stroke during an MI task and an AO task. Three different experimental conditions will be studied during the electromyographic recordings: control recording, recording during MI, and recording during AO. Understanding the muscle activation in each technique will allow us to develop future protocols and intervention plans, improving the quality of care for people who have suffered a stroke.

Effects of mirror neuron activation therapies on functionality in older adults: Systematic review and meta-analysis.

PURPOSE: To identify the effects of mirror neuron activation (MNAT) combined or not with physical exercise (PE) in healthy older adults, on functionality, balance, gait velocity and risk of falls. METHODS: A systematic electronic search was performed in PubMed/MEDLINE, Cochrane, and Embase databases. RESULTS: Thirteen randomized controlled trials were included in the qualitative analysis, and eleven in the quantitative analysis. All studies showed fair to high quality and the most frequent high-risk bias was "Blinding of participants and personnel". Compared to the control condition, higher improvement was shown in older people who received MNAT, on functionality (1.57 [0.57, 2.62], balance (1.95 [1.32, 2.572]), and gait velocity (1.20 [0.30, 2.11]). Compared to PE, MNAT combined with PE does not improve functionality. More studies are needed to assess MNAT effectiveness in the rest of the outcomes. CONCLUSIONS: Neuron system activation through MNAT improves relevant abilities in older adults, with better results when including functional activities. However, the beneficial effects on these variables of adding MNAT to a PE program are controversial.

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.

Facial emotional congruence in healthy adults and patients suffering from a psychiatric or neurological disorder.

The production of facial emotions is an important conveyor of social communication. The present review of the literature concerns the congruence of facial emotions, that is the facial muscular activation that takes place in response to the emotional facial expression perceived in others. Although scientific interest in facial emotions has increased exponentially in the last few years, the production of facial emotions is still underexplored as compared to emotional perception. Several studies, mainly conducted with electromyography, have shown that facial emotional congruence exists in a robust way, largely for anger and happiness. While facial emotional congruence was long considered as innate and automatic, recent work has demonstrated that several sociocultural factors may influence or reduce this ability, challenging its automaticity. From a neuroanatomical point of view, studies have clearly highlighted the implication of mirror neurons but our knowledge is still limited because of the few methodologies assessing this system and the lack of homogeneity between the protocols used. Many explanatory, and probably not mutually exclusive, theories of emotional facial congruence have been put forward. In experimental neuropsychology, emotional facial congruence has seldom been investigated but the few available results suggest an impairment in psychiatric and neurological patients. In view of the important role of emotional facial productions in human relations and social interactions, new methods for easy clinical assessment need to be designed for the diagnosis and the cognitive care of these abilities. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Recomendaciones para aplicar la terapia de observación acción en accidente cerebrovascular. Revisión de la literatura / Recommendation for appliying action observation therapy in stroke. Literature review

Objetivos: unificar los criterios para la aplicación clínica de la terapia de observación de acción en accidente cerebrovascular. Métodos: realizamos una revisión bibliográfica en los meses de febrero y marzo de 2023, incluyendo siete artículos que cumplían los criterios de selección. Resultados: tras analizar los estudios, la mayoría utiliza la terapia de observación acción para tratar pacientes con accidente cerebrovascular sin otras patologías añadidas, realizando valoración del miembro superior parético, con proyección de vídeos, y ejecución de las actividades o actos motores tras su visualización. Conclusiones: se unifican los criterios con el uso de la técnica en pacientes con un primer accidente cerebrovascular unilateral, sin patologías añadidas que afecten a su aplicación; valorando las capacidades y funcionalidad de los pacientes; visualizando vídeos de actos motores o tares funcionales proyectados en primera persona, y ejecutando las tareas observadas, con el apoyo verbal o físico del terapeuta si es necesario.(AU)

Objective: unify the criteria for the clinical application of action observation therapy in stroke. Methods: we carried out a bibliographic review in the months of February and March 2023, including seven articles that met the selection criteria. Results: after analyzing the studies, the majority use action observation therapy to treat patients with stroke without other added pathologies, carrying out assessment of the paretic upper limb, with video projection, and execution of the activities or motor acts after viewing them. Conclusions: the criteria are unified with the use of the technique in patients with a first unilateral stroke, without additional pathologies that affect its application; assessing the abilities and functionality of patients; viewing videos of motor acts or functional tasks projected in first person, and executing the observed tasks, with the therapist's verbal or physical support if necessary.(AU)

Are there dedicated neural mechanisms for imitation? A study of grist and mills.

Are there brain regions that are specialized for the execution of imitative actions? We compared two hypotheses of imitation: the mirror neuron system (MNS) hypothesis predicts frontal and parietal engagement which is specific to imitation, while the Grist-Mills hypothesis predicts no difference in brain activation between imitative and matched non-imitative actions. Our delayed imitation fMRI paradigm included two tasks, one where correct performance was defined by a spatial rule and another where it was defined by an item-based rule. For each task, participants could learn a sequence from a video of a human hand performing the task, from a matched "Ghost" condition, or from text instructions. When participants executed actions after seeing the Hand demonstration (compared to Ghost and Text demonstrations), no activation differences occurred in frontal or parietal regions; rather, activation was localized primarily to occipital cortex. This adds to a growing body of evidence which indicates that imitation-specific responses during action execution do not occur in canonical mirror regions, contradicting the mirror neuron system hypothesis. However, activation differences did occur between action execution in the Hand and Ghost conditions outside MNS regions, which runs counter to the Grist-Mills hypothesis. We conclude that researchers should look beyond these hypotheses as well as classical MNS regions to describe the ways in which imitative actions are implemented by the brain.

Differential responses in the mirror neuron system during imitation of individual emotional facial expressions and association with autistic traits.

The mirror neuron system (MNS), including the inferior frontal gyrus (IFG), inferior parietal lobule (IPL) and superior temporal sulcus (STS) plays an important role in action representation and imitation and may be dysfunctional in autism spectrum disorder (ASD). However, it's not clear how these three regions respond and interact during the imitation of different basic facial expressions and whether the pattern of responses is influenced by autistic traits. Thus, we conducted a natural facial expression (happiness, angry, sadness and fear) imitation task in 100 healthy male subjects where expression intensity was measured using facial emotion recognition software (FaceReader) and MNS responses were recorded using functional near-infrared spectroscopy (fNIRS). Autistic traits were measured using the Autism Spectrum Quotient questionnaire. Results showed that imitation of happy expressions produced the highest expression intensity but a small deactivation in MNS responses, suggesting a lower processing requirement compared to other expressions. A cosine similarity analysis indicated a distinct pattern of MNS responses during imitation of each facial expression with functional intra-hemispheric connectivity between the left IPL and left STS being significantly higher during happy compared to other expressions, while inter-hemispheric connectivity between the left and right IPL differed between imitation of fearful and sad expressions. Furthermore, functional connectivity changes during imitation of each different expression could reliably predict autistic trait scores. Overall, the results provide evidence for distinct patterns of functional connectivity changes between MNS regions during imitation of different emotions which are also associated with autistic traits.

Non-shared coding of observed and executed actions prevails in macaque ventral premotor mirror neurons.

According to the mirror mechanism the discharge of F5 mirror neurons of a monkey observing another individual performing an action is a motor representation of the observed action that may serve to understand or learn from the action. This hypothesis, if strictly interpreted, requires mirror neurons to exhibit an action tuning that is shared between action observation and execution. Due to insufficient data it remains contentious if this requirement is met. To fill in the gaps, we conducted an experiment in which identical objects had to be manipulated in three different ways in order to serve distinct action goals. Using three methods, including cross-task classification, we found that at most time points F5 mirror neurons did not encode observed actions with the same code underlying action execution. However, in about 20% of neurons there were time periods with a shared code. These time periods formed a distinct cluster and cannot be considered a product of chance. Population classification yielded non-shared coding for observed actions in the whole population, which was at times optimal and consistently better than shared coding in differentially selected subpopulations. These results support the hypothesis of a representation of observed actions based on a strictly defined mirror mechanism only for small subsets of neurons and only under the assumption of time-resolved readout. Considering alternative concepts and recent findings, we propose that during observation mirror neurons represent the process of a goal pursuit from the observer's viewpoint. Whether the observer's goal pursuit, in which the other's action goal becomes the observer's action goal, or the other's goal pursuit is represented remains to be clarified. In any case, it may allow the observer to use expectations associated with a goal pursuit to directly intervene in or learn from another's action.

Reflexive structure of the conscious subject and the origin of language codes.

The code paradigm in biological and social sciences arises to Aristotle. For conscious activity, Aristotle introduced the notion of reflexive self-awareness in sense perception. This reflexive process generates the codes that signify sensual perceptive events and constrain human behavior. Coding systems grow via the generation of hypertextual statements reflecting new meanings in the process defined by Marcello Barbieri as a codepoiesis. It results in the establishment of higher-level codes (metacodes) forming the semiotic screen that has a nature of the set of perceived objects internalized by the conscious subject in encoding the symbolic actions. The characteristic feature of the semiotic screen consists in its property of being shared between the communicating agents. A sufficient complexity of nervous system, through the appearance of mirror neurons that are fired both when a subject executes certain action and when he observes another subject performing a similar action, represents a prerequisite for the emergence of reflexive codes in evolution. The codes appearing as a result of reflexive awareness and establishing different sociotypes, span from the symbolic systems of art and music through the common language to the formal language of logic and mathematics. Social dynamics is based on the implementation of reflexive coding activity and results in the growth and decay of social systems and civilizations.

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.

Aggression: The dark side of mirror neurons sheds light on their functions.

Mirror neurons have been found mainly in neocortical structures of primates and rodents; however, their functions are still debated. A new study has discovered mirror neurons for aggressive behaviors in the ventromedial hypothalamus of mice, an evolutionarily ancient structure, highlighting a new function key for survival.

To see is to experience: Aggression neurons light up when witnessing a fight.

Fighting is an intense experience not only for the executors but also for the observers. In the current issue of Cell, Yang et al. identified hypothalamic aggression mirror neurons, activated during both physical fighting and witnessing a fight, possibly representing a neural mechanism for understanding social experiences in other minds.

Effects of integrated action and sensory observation therapy based on mirror neuron and embodied cognition theory on upper limb sensorimotor function in chronic stroke: a study protocol for a randomised controlled trial.

INTRODUCTION: This study protocol aims to explore the effectiveness and neural mechanism of the integration of action observation therapy (AOT) and sensory observation therapy (SOT) for post-stroke patients on upper limb sensorimotor function. METHODS AND ANALYSIS: This is a single-centre, single-blind, randomised controlled trial. A total of 69 patients with upper extremity hemiparesis after stroke will be recruited and randomly divided into an AOT group, a combined action observation and somatosensory stimulation therapy (AOT+SST) group, and a combined AOT and SOT (AOT+SOT) group in a 1:1:1 ratio. Each group will receive 30 min of daily treatment, five times weekly for 4 weeks. The primary clinical outcome will be the Fugl-Meyer Assessment for Upper Extremity. Secondary clinical outcomes will include the Box and Blocks Test, modified Barthel Index and sensory assessment. All clinical assessments and resting-state functional MRI and diffusion tensor imaging data will be obtained at pre-intervention (T1), post-intervention (T2) and 8 weeks of follow-up (T3). ETHICS AND DISSEMINATION: The trial was approved by the Ethics Committee of Yueyang Hospital of Integrated Traditional Chinese and Western Medicine, Shanghai University of Chinese Traditional Medicine (Grant No. 2020-178). The results will be submitted to a peer-review journal or at a conference. TRIAL REGISTRATION NUMBER: ChiCTR2000040568.

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.

Transdiagnostic investigation into the relationship between mirror neuron system activity, echo-phenomena, and theory of mind in major psychoses.

The association between social cognition and putative mirror neuron system (MNS)-activity in major psychoses might be contingent upon frontal dysregulation. We used a transdiagnostic ecological approach to enrich a specific behavioral phenotype (echophenomena or hyper-imitative states) across clinical diagnoses (mania and schizophrenia) to compare behavioral and physiological markers of social cognition and frontal disinhibition. We examined 114 participants with schizophrenia (N = 53) and mania (N = 61) for the presence and severity of echo-phenomena (echopraxia, incidental, and induced echolalia) using an ecological paradigm to simulate real-life social communication. Symptom severity, frontal release reflexes, and theory of mind performance were also assessed. In a proportion of these participants with (N = 20) and without (N = 20) echo-phenomena, we compared motor resonance (motor evoked potential facilitation during action observation compared to static image viewing) and cortical silent period (CSP) as putative markers of MNS-activity and frontal disinhibition, respectively, using Transcranial Magnetic Stimulation. While the prevalence of echo-phenomena was similar between mania and schizophrenia, incidental echolalia was more severe in mania. Participants with echo-phenomena (compared to those without) had significantly greater motor resonance with singlepulse (not with paired-pulse) stimuli, poorer theory of mind scores, higher frontal release reflexes but similar CSP, and greater symptom severity. None of these parameters significantly differed between participants with mania and schizophrenia. We observed relatively better phenotypic and neurophysiological characterization of major psychoses by categorizing participants based on the presence of echophenomena than clinical diagnoses. Higher putative MNS-activity was associated with poorer theory of mind in a hyper-imitative behavioral state.

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.