Sharing motor plans while acting jointly: A TMS study.

When acting together, we may represent not only our own individual goals but also a collective goal. Although behavioural evidence suggests that agents' motor plans might be related to collective goals, direct neurophysiological evidence of whether collective goals are motorically represented is still scarce. The aim of the present transcranial magnetic stimulation (TMS) study is to begin to fill this gap. A participant and a confederate were asked to sequentially perform a two-choice reaction time task by acting on pressure sensors. In their own turn, they saw a cue indicating whether to lift their fingers from (or to press them on) a pressure sensor to shoot a ball across the screen as fast as possible. The confederate responded with the right hand, the participant with the left hand. While the confederate acted on the sensor, the participant's motor evoked potentials (MEPs) were collected from the right Extensor Carpi Ulnaris. If participants represent their own and the confederate's actions as being directed to a collective goal, MEPs amplitude should be modulated according to the action the confederate should perform. To test this conjecture, we contrasted three conditions: a Joint condition, in which both players worked together with their collective goal being to shoot the ball to get it to a common target, a Parallel condition, in which the players performed exactly the same task but received independent outcomes for their performance, and a Competitive condition, in which the outcome of the game still depended on the other player performance, but without the collective goal feature. Results showed no MEPs modulation according to the confederate's action in the Joint condition. Post-hoc exploratory analyses both provide some hints about this negative finding and also suggest possible improvements (i.e., adopting a different dependent variable, avoiding task-switching between conditions) for testing our hypothesis that collective goal can be represented motorically.

Emerging of new bioartificial corticospinal motor synergies using a robotic additional thumb.

It is likely that when using an artificially augmented hand with six fingers, the natural five plus a robotic one, corticospinal motor synergies controlling grasping actions might be different. However, no direct neurophysiological evidence for this reasonable assumption is available yet. We used transcranial magnetic stimulation of the primary motor cortex to directly address this issue during motor imagery of objects' grasping actions performed with or without the Soft Sixth Finger (SSF). The SSF is a wearable robotic additional thumb patented for helping patients with hand paresis and inherent loss of thumb opposition abilities. To this aim, we capitalized from the solid notion that neural circuits and mechanisms underlying motor imagery overlap those of physiological voluntary actions. After a few minutes of training, healthy humans wearing the SSF rapidly reshaped the pattern of corticospinal outputs towards forearm and hand muscles governing imagined grasping actions of different objects, suggesting the possibility that the extra finger might rapidly be encoded into the user's body schema, which is integral part of the frontal-parietal grasping network. Such neural signatures might explain how the motor system of human beings is open to very quickly welcoming emerging augmentative bioartificial corticospinal grasping strategies. Such an ability might represent the functional substrate of a final common pathway the brain might count on towards new interactions with the surrounding objects within the peripersonal space. Findings provide a neurophysiological framework for implementing augmentative robotic tools in humans and for the exploitation of the SSF in conceptually new rehabilitation settings.

Reduced readiness potential and post-movement beta synchronization reflect self-disorders in early course schizophrenia.

Disturbances of conscious awareness, or self-disorders, are a defining feature of schizophrenia. These include symptoms such as delusions of control, i.e. the belief that one's actions are controlled by an external agent. Models of self-disorders point at altered neural mechanisms of source monitoring, i.e. the ability of the brain to discriminate self-generated stimuli from those driven by the environment. However, evidence supporting this putative relationship is currently lacking. We performed electroencephalography (EEG) during self-paced, brisk right fist closures in ten (M = 9; F = 1) patients with Early-Course Schizophrenia (ECSCZ) and age and gender-matched healthy volunteers. We measured the Readiness Potential (RP), i.e. an EEG feature preceding self-generated movements, and movement-related EEG spectral changes. Self-disorders in ECSCZ were assessed with the Examination of Anomalous Self-Experience (EASE). Patients showed a markedly reduced RP and altered post-movement Event-Related Synchronization (ERS) in the beta frequency band (14-24 Hz) compared to healthy controls. Importantly, smaller RP and weaker ERS were associated with higher EASE scores in ECSCZ. Our data suggest that disturbances of neural correlates preceding and following self-initiated movements may reflect the severity of self-disorders in patients suffering from ECSCZ. These findings point towards deficits in basic mechanisms of sensorimotor integration as a substrate for self-disorders.

Colors and Handles: How Action Primes Perception.

How deeply does action influence perception? Does action performance affect the perception of object features directly related to action only? Or does it concern also object features such as colors, which are not held to directly afford action? The present study aimed at answering these questions. We asked participants to repeatedly grasp a handled mug hidden from their view before judging whether a visually presented mug was blue rather than cyan. The motor training impacted on their perceptual judgments, by speeding participants' responses, when the handle of the presented mug was spatially aligned with the trained hand. The priming effect did not occur when participants were trained to merely touch the mug with their hand closed in a fist. This indicates that action performance may shape the perceptual judgment on object features, even when these features are colors and do not afford any action. How we act on surrounding objects is therefore not without consequence for how we experience them.

Consciousness and complexity: a consilience of evidence.

Over the last years, a surge of empirical studies converged on complexity-related measures as reliable markers of consciousness across many different conditions, such as sleep, anesthesia, hallucinatory states, coma, and related disorders. Most of these measures were independently proposed by researchers endorsing disparate frameworks and employing different methods and techniques. Since this body of evidence has not been systematically reviewed and coherently organized so far, this positive trend has remained somewhat below the radar. The aim of this paper is to make this consilience of evidence in the science of consciousness explicit. We start with a systematic assessment of the growing literature on complexity-related measures and identify their common denominator, tracing it back to core theoretical principles and predictions put forward more than 20 years ago. In doing this, we highlight a consistent trajectory spanning two decades of consciousness research and provide a provisional taxonomy of the present literature. Finally, we consider all of the above as a positive ground to approach new questions and devise future experiments that may help consolidate and further develop a promising field where empirical research on consciousness appears to have, so far, naturally converged.

Neurotypical individuals fail to understand action vitality form in children with autism spectrum disorder.

Any defects of sociality in individuals diagnosed with autism spectrum disorder (ASD) are standardly explained in terms of those individuals' putative impairments in a variety of cognitive functions. Recently, however, the need for a bidirectional approach to social interaction has been emphasized. Such an approach highlights differences in basic ways of acting between ASD and neurotypical individuals which would prevent them from understanding each other. Here we pursue this approach by focusing on basic action features reflecting the agent's mood and affective states. These are action features Stern named "vitality forms," and which are widely assumed to substantiate core social interactions [D. N. Stern, The Interpersonal World of the Infant (1985); D. N. Stern, Forms of Vitality Exploring Dynamic Experience in Psychology, Arts, Psychotherapy, and Development (2010)]. Previously we demonstrated that, although ASD and typically developing (TD) children alike differentiate vitality forms when performing actions, ASD children express them in a way that is motorically dissimilar to TD children. To assess whether this motor dissimilarity may have consequences for vitality form recognition, we asked neurotypical participants to identify the vitality form of different types of action performed by ASD or TD children. We found that participants exhibited remarkable inaccuracy in identifying ASD children's vitality forms. Interestingly, their performance did not benefit from information feedback. This indicates that how people act matters for understanding others and for being understood by them. Because vitality forms pervade every aspect of daily life, our findings promise to open the way to a deeper comprehension of the bidirectional difficulties for both ASD and neurotypical individuals in interacting with one another.

How Tool-Use Shapes Body Metric Representation: Evidence From Motor Training With and Without Robotic Assistance.

Previous evidence has shown that tool-use can reshape one's own body schema, extending peripersonal space and modulating the representation of related body parts. Here, we investigated the role of tool action in shaping the body metric representation, by contrasting two different views. According to a first view, the shaping would rely on the mere execution of tool action, while the second view suggests that the shaping induced by tool action on body representation would primarily depend on the representation of the action goals to be accomplished. To this aim, we contrasted a condition in which participants voluntarily accomplish the movement by representing the program and goal of a tool action (i.e., active tool-use training) with a condition in which the tool-use training was produced without any prior goal representation (i.e., passive tool-use training by means of robotic assistance). If the body metric representation primarily depends on the coexistence between goal representation and bodily movements, we would expect an increase of the perceived forearm length in the post- with respect to the pre-training phase after the active training phase only. Healthy participants were asked to estimate the midpoint of their right forearm before and after 20 min of tool-use training. In the active condition, subjects performed "enfold-and-push" movements using a rake to prolong their arm. In the passive condition, subjects were asked to be completely relaxed while the movements were performed with robotic assistance. Results showed a significant increase in the perceived arm length in the post- with respect to the pre-training phase only in the active task. Interestingly, only in the post-training phase, a significant difference was found between active and passive conditions, with a higher perceived arm length in the former than in the latter. From a theoretical perspective, these findings suggest that tool-use may shape body metric representation only when action programs are motorically represented and not merely produced. From a clinical perspective, these results support the use of robots for the rehabilitation of brain-damaged hemiplegic patients, provided that robot assistance during the exercises is present only "as-needed" and that patients' motor representation is actively involved.

How action performance affects object perception.

How deep is the linkage between action and perception? Much is known about how object perception impacts on action performance, much less about how action performance affects object perception. Does action performance affect perceptual judgment on object features such as shape and orientation? Answering these questions was the aim of the present study. Participants were asked to reach and grasp a handled mug without any visual feedback before judging whether a visually presented mug was handled or not. Performing repeatedly a grasping action resulted in a perceptual categorization aftereffect as measured by a slowdown in the judgment on a handled mug. We suggest that what people are doing may impact on their perceptual judgments on the surrounding things.

Peripersonal space representation develops independently from visual experience.

Our daily-life actions are typically driven by vision. When acting upon an object, we need to represent its visual features (e.g. shape, orientation, etc.) and to map them into our own peripersonal space. But what happens with people who have never had any visual experience? How can they map object features into their own peripersonal space? Do they do it differently from sighted agents? To tackle these questions, we carried out a series of behavioral experiments in sighted and congenitally blind subjects. We took advantage of a spatial alignment effect paradigm, which typically refers to a decrease of reaction times when subjects perform an action (e.g., a reach-to-grasp pantomime) congruent with that afforded by a presented object. To systematically examine peripersonal space mapping, we presented visual or auditory affording objects both within and outside subjects' reach. The results showed that sighted and congenitally blind subjects did not differ in mapping objects into their own peripersonal space. Strikingly, this mapping occurred also when objects were presented outside subjects' reach, but within the peripersonal space of another agent. This suggests that (the lack of) visual experience does not significantly affect the development of both one's own and others' peripersonal space representation.

Drawn together: When motor representations ground joint actions.

What enables individuals to act together? Recent discoveries suggest that a variety of mechanisms are involved. But something fundamental is yet to be investigated. In joint action, agents represent a collective goal, or so it is often assumed. But how, if at all, are collective goals represented in joint action and how do such representations impact performance? To investigate this question we adapted a bimanual paradigm, the circle-line drawing paradigm, to contrast two agents acting in parallel with two agents performing a joint action. Participants were required to draw lines or circles while observing circles or lines being drawn. The findings indicate that interpersonal motor coupling may occur in joint but not parallel action. This suggests that participants in joint actions can represent collective goals motorically.

The mirror mechanism: a basic principle of brain function.

The mirror mechanism is a basic brain mechanism that transforms sensory representations of others' behaviour into one's own motor or visceromotor representations concerning that behaviour. According to its location in the brain, it may fulfil a range of cognitive functions, including action and emotion understanding. In each case, it may enable a route to knowledge of others' behaviour, which mainly depends on one's own motor or visceromotor representations.

Press to grasp: how action dynamics shape object categorization.

Action and object are deeply linked to each other. Not only can viewing an object influence an ongoing action, but motor representations of action can also influence visual categorization of objects. It is tempting to assume that this influence is effector-specific. However, there is indirect evidence suggesting that this influence may be related to the action goal and not just to the effector involved in achieving it. This paper aimed, for the first time, to tackle this issue directly. Participants were asked to categorize different objects in terms of the effector (e.g. hand or foot) typically used to act upon them. The task was delivered before and after a training session in which participants were instructed either just to press a pedal with their foot or to perform the same foot action with the goal of guiding an avatar's hand to grasp a small ball. Results showed that pressing a pedal to grasp a ball influenced how participants correctly identified graspable objects as hand-related ones, making their responses more uncertain than before the training. Just pressing a pedal did not have any similar effect. This is evidence that the influence of action on object categorization can be goal-related rather than effector-specific.

When a laser pen becomes a stick: remapping of space by tool-use observation in hemispatial neglect.

The role of active tool use in the remapping of space in hemispatial neglect patients has been extensively investigated. To date, however, there is no evidence that observing tool use can play a role in the remapping of space in hemispatial neglect patients. In this study, a patient with a severe hemispatial neglect in near but not far space and twelve healthy controls were asked to bisect near and far lines using a laser pen. The task was performed both before and immediately after sessions in which they merely observed the experimenter bisecting near and far lines with a stick. During the observation session, participants were either holding an identical stick or empty-handed. Results, in both the neglect patient and healthy controls, showed that observing the experimenter bisecting line while holding the same tool, produces a remapping of the far space into the near space. This result was particularly evident in the neglect patient where observing line-bisection task extended the spatial deficit from the near to the far space. Our results provide new empirical support to the idea that the space around us is not mapped in merely metrical terms, rather it seems to be deeply impacted by both action observation and execution.

Understanding action with the motor system.

We challenge Cook et al.'s claim about the vagueness of the notion of action understanding in relation with mirror neurons. We show the multidimensional nature of action understanding and provide a definition of motor-based action understanding, shedding new light on the various components of action understanding and on their relationship. Finally, we propose an alternative perspective on the origin of mirror neurons, stressing the necessity to abandon the dichotomy between genetic and associative hypotheses.

The neural correlates of 'vitality form' recognition: an fMRI study: this work is dedicated to Daniel Stern, whose immeasurable contribution to science has inspired our research.

The observation of goal-directed actions performed by another individual allows one to understand what that individual is doing and why he/she is doing it. Important information about others' behaviour is also carried out by the dynamics of the observed action. Action dynamics characterize the 'vitality form' of an action describing the cognitive and affective relation between the performing agent and the action recipient. Here, using the fMRI technique, we assessed the neural correlates of vitality form recognition presenting participants with videos showing two actors executing actions with different vitality forms: energetic and gentle. The participants viewed the actions in two tasks. In one task (what), they had to focus on the goal of the presented action; in the other task (how), they had to focus on the vitality form. For both tasks, activations were found in the action observation/execution circuit. Most interestingly, the contrast how vs what revealed activation in right dorso-central insula, highlighting the involvement, in the recognition of vitality form, of an anatomical region connecting somatosensory areas with the medial temporal region and, in particular, with the hippocampus. This somatosensory-insular-limbic circuit could underlie the observers' capacity to understand the vitality forms conveyed by the observed action.

How your hand drives my eyes.

When viewing object-related hand actions people make proactive eye movements of the same kind as those made when performing such actions. Why is this so? It has been suggested that proactive gaze when viewing a given hand action depends on the recruitment of motor areas such as the ventral premotor (PMv) cortex that would be involved in the execution of that action. However, direct evidence for a distinctive role of the PMv cortex in driving gaze behavior is still lacking. We recorded eye moments while viewing hand actions before and immediately after delivering repetitive transcranial magnetic stimulation (rTMS) over the left PMv and the posterior part of the left superior temporal sulcus, which is known to be involved in high-order visual action processing. Our results showed that rTMS-induced effects were selective with respect to the viewed actions following the virtual lesion of the left PMv only. This, for the first time, provides direct evidence that the PMv cortex might selectively contribute to driving the viewer's gaze to the action's target. When people view another's action, their eyes may be driven by motor processes similar to those they would need to perform the action themselves.

Impaired vitality form recognition in autism.

Along with the understanding of the goal of an action ("what" is done) and the intention underlying it ("why" it is done), social interactions largely depend on the appraisal of the action from the dynamics of the movement: "how" it is performed (its "vitality form"). Do individuals with autism, especially children, possess this capacity? Here we show that, unlike typically developing individuals, individuals with autism reveal severe deficits in recognizing vitality forms, and their capacity to appraise them does not improve with age. Deficit in vitality form recognition appears, therefore, to be a newly recognized trait marker of autism.

What type of action understanding is subserved by mirror neurons?

The role of the mirror mechanism in cognition remains an intriguing and hotly debated topic in cognitive neuroscience. Since its discovery in the monkey and human brain, many have claimed that the mirror mechanism is critically involved in understanding action. But what does understand mean here? What kind of action understanding, if any, can be ascribed to the mirror mechanism? The aim of the paper is to face these questions by providing a refined notion of both action and action understanding.

Grasping affordances with the other's hand: a TMS study.

The power of an object to afford a suitable act has been shown to depend on its reachability. Nevertheless, most of our perception and action occur in a social context. Little research has directly explored whether the possibility for other people to act upon an object may affect our processing of its affording features. To tackle this issue, we magnetically stimulated the left primary motor cortex and recorded motor-evoked potentials (MEPs) while participants were presented with a handled object (i.e. a mug) close either to them or to a virtual individual such as an avatar. We found highest MEPs both when the mug was near enough to be actually reachable for the participants and also when it was out of reach for them, provided that it was ready to the avatar's hand. We propose that this effect is likely to be due to an interpersonal bodily space representation, which plays critical role in basic social interaction.