Hierarchical models have been proposed to explain how the brain encodes actions, whereby different areas represent different features, such as gesture kinematics, target object, action goal, and meaning. The visual processing of action-related information is distributed over a well-known network of brain regions spanning separate anatomical areas, attuned to specific stimulus properties, and referred to as action observation network (AON). To determine the brain organization of these features, we measured representational geometries during the observation of a large set of transitive and intransitive gestures in two independent functional magnetic resonance imaging experiments. We provided evidence for a partial dissociation between kinematics, object characteristics, and action meaning in the occipito-parietal, ventro-temporal, and lateral occipito-temporal cortex, respectively. Importantly, most of the AON showed low specificity to all the explored features, and representational spaces sharing similar information content were spread across the cortex without being anatomically adjacent. Overall, our results support the notion that the AON relies on overlapping and distributed coding and may act as a unique representational space instead of mapping features in a modular and segregated manner.

Whether in performing arts, sporting, or everyday contexts, when we watch others move, we tend to enjoy bodies moving in synchrony. Our enjoyment of body movements is further enhanced by our own prior experience with performing those movements, or our \'embodied experience\'. The relationships between movement synchrony and enjoyment, as well as embodied experience and movement enjoyment, are well known. The interaction between enjoyment of movements, synchrony, and embodiment is less well understood, and may be central for developing new approaches for enriching social interaction. To examine the interplay between movement enjoyment, synchrony, and embodiment, we asked participants to copy another person\'s movements as accurately as possible, thereby gaining embodied experience of movement sequences. Participants then viewed other dyads performing the same or different sequences synchronously, and we assessed participants\' recognition of having performed these sequences, as well as their enjoyment of each movement sequence. We used functional near-infrared spectroscopy to measure cortical activation over frontotemporal sensorimotor regions while participants performed and viewed movements. We found that enjoyment was greatest when participants had mirrored the sequence and recognised it, suggesting that awareness of embodiment may be central to enjoyment of synchronous movements. Exploratory analyses of relationships between cortical activation and enjoyment and recognition implicated the sensorimotor cortices, which subserve action observation and aesthetic processing. These findings hold implications for clinical research and therapies seeking to foster successful social interaction.

BACKGROUND: Making sense of others\' actions relies on the activation of an action observation network (AON), which maps visual information about observed actions onto the observer\'s motor system. This motor resonance process manifests in the primary motor cortex (M1) as increased corticospinal excitability finely tuned to the muscles engaged in the observed action. Motor resonance in M1 is facilitated by projections from higher-order AON regions. However, whether manipulating the strength of AON-to-M1 connectivity affects motor resonance remains unclear.
METHODS: We used transcranial magnetic stimulation (TMS) in 48 healthy humans. Cortico-cortical paired associative stimulation (ccPAS) was administered over M1 and the ventral premotor cortex (PMv), a key AON node, to induce spike-timing-dependent plasticity (STDP) in the pathway connecting them. Single-pulse TMS assessed motor resonance during action observation.
RESULTS: Before ccPAS, action observation increased corticospinal excitability in the muscles corresponding to the observed movements, reflecting motor resonance in M1. Notably, ccPAS aimed at strengthening projections from PMv to M1 (PMv→M1) induced short-term enhancement of motor resonance. The enhancement specifically occurred with the ccPAS configuration consistent with forward PMv→M1 projections and dissipated 20 min post-stimulation; ccPAS administered in the reverse order (M1→PMv) and sham stimulation did not affect motor resonance.
CONCLUSIONS: These findings provide the first evidence that inducing STDP to strengthen PMv input to M1 neurons causally enhances muscle-specific motor resonance in M1. Our study sheds light on the plastic mechanisms that shape AON functionality and demonstrates that exogenous manipulation of AON connectivity can influence basic mirror mechanisms that underlie social perception.

This functional magnetic resonance imaging study delves into the impact of experience and pitcher handedness on the pitch-calling behavior of baseball umpires. Expert and intermediate umpires were asked to make ball/strike calls on videotaped pitches of left- and right-handed pitchers and rate their certainty for the call while undergoing scanning. Behavioral results replicated previous findings that expert umpires were more certain but not more accurate or quicker than intermediate umpires, suggesting that, as sports officials, umpires may learn to project confidence to maintain control of the game. At the neural level, expert umpires exhibited more extensive and pronounced activations within the action observation network, dorsal striatum, and cerebellum. These heightened neural responses were probably associated with their enhanced visual processing abilities for pitching action and ball trajectory, honed over years of officiating. Notably, both expert and intermediate umpires exhibited decreased accuracy when judging pitches from left-handed pitchers compared to right-handed ones. These challenges in accuracy corresponded with weaker neural activations in the aforementioned brain regions, implying difficulties in processing specific visual details of the rarely encountered left-handed pitchers. Moreover, slightly longer reaction times and reduced uncertainty were observed particularly for left-handed ball pitches, as revealed by lower activation in the right premotor cortex, highlighting issues with predictive processing. In summary, our findings shed light on the influence of pitcher handedness on the pitch-calling behavior of baseball umpires and extend the current understanding of the perceptual and decision-making behavior of sports officials.

Dual-process theories propose that recognition memory involves recollection and familiarity; however, the impact of motor expertise on memory recognition, especially the interplay between familiarity and recollection, is relatively unexplored. This functional magnetic resonance imaging study used videos of a dancer performing International Latin Dance Styles as stimuli to investigate memory recognition in professional dancers and matched controls. Participants observed and then reported whether they recognized dance actions, recording the level of confidence in their recollections, whereas blood-oxygen-level-dependent signals measured encoding and recognition processes. Professional dancers showed higher accuracy and hit rates for high-confidence judgments, whereas matched controls exhibited the opposite trend for low-confidence judgments. The right putamen and precentral gyrus showed group-based moderation effects, especially for high-confidence (vs. low-confidence) action recognition in professional dancers. During action recognition, the right superior temporal gyrus and insula showed increased activation for accurate recognition and high-confidence retrieval, particularly in matched controls. These findings highlighting enhanced action memory of professional dancers-evident in their heightened recognition confidence-not only supports the dual-processing model but also underscores the crucial role of expertise-driven familiarity in bolstering successful recollection. Additionally, they emphasize the involvement of the action observation network and frontal brain regions in facilitating detailed encoding linked to intention processing.

Observing the actions of others engages a core action observation network (AON) that includes the bilateral inferior frontal cortex (IFC), posterior superior temporal sulcus (pSTS) and inferior parietal lobule (IPL) (Caspers et al., 2010). Each region in the AON has functional properties that are heterogeneous and include representing the perceptual properties of action, predicting action outcomes and making inferences as to the goals of the actor. Critically, recent evidence shows that neural representations within the pSTS are sharpened when attending to the kinematics of the actor, such that the top-down guided attention reshapes underlying neural representations. In this study we evaluate how attention alters network connectivity within the AON as a system. Cues directed participant\'s attention to the goal, kinematics, or identity depicted in short action animations while brain responses were measured by fMRI. We identified those parcels within the AON with functional connectivity modulated by task. Results show that connectivity between the right pSTS and right IFC, and bilateral extended STS (STS+) were modulated during action observation such that connections were strengthened when the participant was attending to the action than goal. This finding is contrasted by the univariate results, which no univariate modulations in these brain regions except for right IFC. Using the functional networks defined by Yeo et al. (2011), we identified the parcels that are modulated by the attention to consist mainly of the fronto-parietal control network and default mode networks. These results are consistent with models of top-down feedback from executive system in the IFC to pSTS and implicates a right lateralized dual pathway model for action observation when focused on whole-body kinematics.

The action observation network (AON) has traditionally been thought to be dedicated to recognizing animate actions. A recent study by Karakose-Akbiyik et al. invites rethinking this assumption by demonstrating that the AON contains a shared neural code for general events, regardless of whether those events involve animate or inanimate entities.

Many studies have shown the effect of dance to the brain. It seems that long-term practice modulates brain plasticity and visuomotor skills, as it activates the Action Observation Network (AON). The aim of this systematic review was to evaluate potential differences in the brain activity (visuomotor skills) between professional dancers and non-dancer adults, measured by electroencephalography (EEG), during the observation of an individual who is dancing (video dance stimuli). This literature search was conducted from February to June 2022, according to the PRISMA guidelines, in the PubMed database using advanced search, mesh terms, and extensive manual search. The included articles were published in English. Specifically, case-control studies were selected, which used healthy adults, professional dancers, and non-dancers as participants, who were exposed to video dance clips and measured by EEG. The articles were excluded if they were based on different type of study, unhealthy population, control group with athletic background, different type of stimuli (rhythmic), or different type of task and procedure. The ratings of quality of evidence were conducted using the Joanna Briggs Institute\'s (JBI) critical appraisal tool. Five case-control studies were included with 193 participants in total, 87% females. The participating groups of professional dancers (n = 12-25) had mean age 25.14 years, with at least 9-19 years of professional training, whereas control groups had the same sample size, mean age of 24.14 years, and no experience in dancing. Most of the studies presented high methodological quality. All studies showed significant differences in dancers\' brain activity, especially regarding the visuomotor skills. The results showed faster activation of AON demonstrated by higher P300 at the frontocentral regions and increased sensitivity of the occipital temporal cortex. Dancers could cope easier with familiar-unfamiliar and effortful-effortless movements. They also demonstrated faster alpha band peak frequency, stronger synchrony over the bands theta, beta, gamma during the audiovisual stimuli, and the ability to encode faster the visual information. The results demonstrate that dancers had better visuomotor skills suggesting dance-enhanced neuroplasticity, as professional dancers processed their actions easier. Dance, which includes visuomotor tasks, could help in prevention, therapy, and rehabilitation of neurodegenerative diseases or movement disorders.

Difficulties in social interactions characterize both autism and schizophrenia and are correlated in the neurotypical population. It is unknown whether this represents a shared etiology or superficial phenotypic overlap. Both conditions exhibit atypical neural activity in response to the perception of social stimuli and decreased neural synchronization between individuals. This study investigated if neural activity and neural synchronization associated with biological motion perception are differentially associated with autistic and schizotypal traits in the neurotypical population. Participants viewed naturalistic social interactions while hemodynamic brain activity was measured with fMRI, which was modeled against a continuous measure of the extent of biological motion. General linear model analysis revealed that biological motion perception was associated with neural activity across the action observation network. However, intersubject phase synchronization analysis revealed neural activity to be synchronized between individuals in occipital and parietal areas but desynchronized in temporal and frontal regions. Autistic traits were associated with decreased neural activity (precuneus and middle cingulate gyrus), and schizotypal traits were associated with decreased neural synchronization (middle and inferior frontal gyri). Biological motion perception elicits divergent patterns of neural activity and synchronization, which dissociate autistic and schizotypal traits in the general population, suggesting that they originate from different neural mechanisms.

The mirror neuron system consists of fronto-parietal regions and responds to both goal-directed action execution and observation. The broader action observation network is specifically involved in observation of actions and is thought to play a role in understanding the goals of the motor act, the intention of others, empathy, and language. Many, but not all, studies have found mirror neuron system or action observation network dysfunction in autism spectrum disorder. The objective of this study was to use observation of a goal-directed action fMRI paradigm to examine the action observation network in autism spectrum disorder and to determine whether fronto-parietal activation is associated with language ability. Adolescents with autism spectrum disorder (n = 23) were compared to typically developing adolescents (n = 20), 11-17 years. Overall, there were no group differences in activation, however, the autism spectrum group with impaired expressive language (n = 13) had significantly reduced inferior frontal and inferior parietal activation during action viewing. In controls, right supramarginal gyrus activation was associated with higher expressive language; bilateral supramarginal and left pars opercularis activation was associated with better verbal-gesture integration. Results suggest that action-observation network dysfunction may characterize a subgroup of individuals with autism spectrum disorder with expressive language deficits. Therefore, interventions that target this dysfunctional network may improve expressive language in this autism spectrum subgroup. Future treatment studies should individualize therapeutic approaches based on brain-behavior relationships.