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Every day, we make thousands of finger movements on the touchscreen of our smartphones. The same movements might be directed at various distal goals. We can type "What is the weather in Rome?" in Google to acquire information from a weather site, or we may type it on WhatsApp to decide whether to visit Rome with a friend. In this study, we show that by watching an agent's typing hands, an observer can infer whether the agent is typing on the smartphone to obtain information or to share it with others. The probability of answering correctly varies with age and typing style. According to embodied cognition, we propose that the recognition process relies on detecting subtle differences in the agent's movement, a skill that grows with sensorimotor competence. We expect that this preliminary work will serve as a starting point for further research on sensorimotor representations of digital actions. [ABSTRACT FROM AUTHOR]

An impressive body of literature in the past 20 years has revealed a possible role played by cortical motor areas in action perception. One question that has been of interest is whether these areas are selectively tuned to process the actions of biological agents. However, no experiments directly testing the effects of the main characteristics identifying a biological agent (physical appearance and movement kinematics) on corticospinal excitability (CS) are present in literature. To fill this gap, we delivered single-pulse transcranial magnetic stimulation to the primary motor cortex and we recorded motor evoked potentials from contralateral hand muscles during observation of point-light-displays stimuli representing a hand having lost its physical appearance (Experiment 1) and kinematics characteristics (Experiment 2). Results showed that physical appearance, natural kinematics, and the possibility to identify the action behind the stimulus are not necessary conditions to modulate CS excitability during stimuli observation. We propose that the involvement of the motor system can be mandatory whenever the perceived movement, executed by a human, by an animal or by an object, is recognized as reproducible in its final outcome (e.g., position in space, direction of movement, posture of a body part, to-be-produced sound, specific interaction with an object, etc.), and that the peculiar relationship existing between others’ actions and the actions executed by the observer could just represent the extreme in which the motor system is able to almost perfectly reproduce the observed stimulus as it unfolds and, consequently, contribute to stimulus perception in the most efficient way. [ABSTRACT FROM AUTHOR]

To verify if the link between observed hand actions and executed foot actions found in aplasics is essentially induced by the constant use of foot substituting the hand, we investigated if the vision of a grasping hand is able to prime a foot response in normals. Participants were required to detect the time-to-contact of a hand grasping an object either with a suitable or a less suitable movement, an experimental paradigm known to induce a priming effect. Participants responded either with the hand or the foot, while having free or bound hands. Results showed that for hand responses motor priming effect was stronger when the hands were free, whereas for foot responses it was stronger when the hands were bound. These data are interpreted as a further evidence that a difficulty to move affects specific cognitive functions and that the vision of a grasping hand may prime a foot response. [ABSTRACT FROM PUBLISHER]

Abstract: The central role of sensory-motor representations in cognitive functions is almost universally accepted. However, determining the link between motor execution and its sensory counterpart and when, during ontogenesis, this link originates are still under investigation. The aim of the present study is to investigate whether at birth this link is already present and 2-day-old newborns are able to discriminate between visual cues indicating goal-directed or non-goal-directed actions. Here, with a preferential looking technique, a hand grasping a ball was the observed movement and we orthogonally manipulated the three factors necessary to successfully reach the goal: (a) presence of the ball, (b) direction of the arm movement, and (c) hand shaping. Results indicated that newborns orient more frequently and look longer at a hand shape for whole hand prehension but only when the movement is directed away from the body and toward the external world. In addition, newborns prefer the away from the body movement only when the object is present. We argue that newborns prefer a movement directed toward the external world only when it may develop into a purposeful movement because of the presence of the to-be-grasped object. Overall, our results support the existence of primitive sensory-motor associations since the first days after birth. [Copyright &y& Elsevier]

Several transcranial magnetic stimulation (TMS) studies have reported facilitation of the primary motor cortex (M1) during the mere observation of actions. This facilitation was shown to be highly congruent, in terms of somatotopy, with the observed action, even at the level of single muscles. With the present study, we investigated whether this muscle-specific facilitation of the observer’s motor system reflects the degree of muscular force that is exerted in an observed action. Two separate TMS experiments are reported in which corticospinal excitability was measured in the hand area of M1 while subjects observed the lifting of objects of different weights. The type of action ‘grasping-and-lifting-the-object’ was always identical, but the grip force varied according to the object’s weight. In accordance to previous findings, excitability of M1 was shown to modulate in a muscle-specific way, such that only the cortical representation areas in M1 that control the specific muscles used in the observed lifting action became increasingly facilitated. Moreover, muscle-specific M1 facilitation was shown to modulate to the force requirements of the observed actions, such that M1 excitability was considerably higher when observing heavy object lifting compared with light object lifting. Overall, these results indicate that different levels of observed grip force are mirrored onto the observer’s motor system in a highly muscle-specific manner. The measured force-dependent modulations of corticospinal excitability in M1 are hypothesized to be functionally relevant for scaling the observed grip force in the observer’s own motor system. In turn, this mechanism may contribute, at least partly, to the observer’s ability to infer the weight of the lifted object. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the present work was to test the ability to predict the instant at which a grasping hand touches an object. Our hypothesis was that, because of the activation of the mirror-neuron system, the same predictive process necessary for action execution should be active during observation. Experimental evidence indicates, however, that not only observed actions but also observed objects automatically activate observer''s motor repertoire. What happens, therefore, if the observed action is different from the one automatically evoked by the vision of the object? To answer this question we presented subjects with two different grasping actions: the one most suitable for the presented object and a less appropriate one. Subjects were required to detect the instant at which the demonstrator''s hand touched the object. In a further condition, subjects were required to detect the outcome of an action performed by a robotic arm moving with constant kinematics. Results showed that while in the case of robot grasping subjects responded before the touch instant, in the case of human grasping the response followed the touch instant, but occurred much earlier than simple reaction times. This demonstrates that subjects were able to predict the outcome of the seen action. The predictive capability was specifically enhanced during observation of the “suitable” grasping. We interpret these results as an indication of the synergic contribution of both object-related (canonical) and action-related (mirror) neurons during observation of actions directed towards graspable objects. [Copyright &y& Elsevier]

Abstract There is growing evidence that observation of actions performed by other individuals activates observer's cortical motor areas. This matching of observed actions on the observer's motor repertoire could be at the basis of action recognition. Here we investigated if action observation, in addition to cortical motor areas, involves also low level motor structures mimicking the observed actions as if they were performed by the observer. Spinal cord excitability was tested by eliciting the H-reflex in a finger flexor muscle (flexor digitorum superficialis) in humans looking at goal-directed hand actions presented on a TV screen. We found that, in the absence of any detectable muscle activity, there was in the observers a significant modulation of the monosynaptic reflex size, specifically related to the different phases of the observed movement. The recorded H-reflex rapidly increased in size during hand opening, it was depressed during hand closing and quickly recovered during object lifting. This modulation pattern is, however, opposite to that occurring when the recorded muscles are actually executing the observed action [Lemon et al. (1995) J. Neurosci., 15, 6145–56]. Considering that, when investigated at cortical level the modulation pattern of corticospinal excitability replicates the observed movements [Fadiga et al. (1995) J. Neurophysiol., 73, 2608–2611], this spinal ‘inverted mirror’ behaviour might be finalised to prevent the overt replica of the seen action. [ABSTRACT FROM AUTHOR]

Already in uterus the hand moves with the typical accelerated-decelerated kinematics of goal-directed actions and, from the twenty-second week of pregnancy, the unborn shows the ability to modulate the velocity of the movement depending on the nature of the target. According to the direct matching hypothesis, this motor knowledge may be sufficient to attune neonates' motion perception-like adults'-to biological kinematics. Using dots configuration motions which varied with respect to the kinematics of goal-directed actions, we observed that two-day-old human newborns did not show any spontaneous preference for either biological accelerated-decelerated motion or non-biological constant velocity motion when these were simultaneously presented in a standard preferential looking paradigm. In contrast, newborns preferred the biological kinematics after the repeated visual presentation of the different motions in a standard infant-control visual habituation paradigm. We propose that present results indicate that the relationship between perception and action does not require only action development but also the accumulation of sufficient perceptual experience. They also suggest a fast plasticity of the sensorimotor system in linking an already acquired motor knowledge with a newly experienced congruent visual stimulation. [ABSTRACT FROM AUTHOR]