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Embodied mental rotation is the influence of the body on mental rotation ability. Sports expertise enhances embodied mental rotation ability. However, sport-skill-dependent effects remain unclear. Previous studies refer to the influence of body positions on mental rotation ability. Yet, in sports, the investigation of the effect of simultaneous body and mental rotation movements is essential. Athletes need to constantly mentally and physically adapt to environmental changes and new motor tasks while being in motion themselves. This study aimed to investigate embodied mental rotation ability with simultaneous body and mental rotation in individuals with different sport skills, i.e., in open- and closed-skill sports. Forty-eight men and women, divided into two groups depending on their sport, performed 32 trials of an extended embodied mental rotation task. Simultaneous body and mental rotation were enabled by a novel test method including Virtual Reality. Results revealed shorter response times to the task stimulus in closed-skill sports participants than in open-skill sports participants. This group difference was significant for trials in which rotation directions of the own body and the mental rotation stimulus were aligned. The results might be related to sport-specific skill development processes. Motor imitation skills, as relevant in many closed-skill sports, may facilitate cognitive processes when the motion direction of the own body and of the mental rotation stimulus are aligned. The novel test method identifies potential applications that should be increasingly explored in the future, both for cognitive science and sports research. [ABSTRACT FROM AUTHOR]

Empathy is the ability to perceive and understand others' emotional states generating a similar mental state in the self. Previous behavioural studies have shown that self-reflection can enhance the empathic process. The present event-related potentials' study aims to investigate whether self-reflection, elicited by an introspective self-narrative task, modulates the neuronal response to eye expressions and improves the accuracy of empathic process. The 29 participants included in the final sample were divided into two groups: an introspection group (IG) (n = 15), who received an introspective writing task, and a control group (CG) (n = 14), who completed a not-introspective writing task. For both groups, the electroencephalographic and behavioural responses to images depicting eye expressions taken from the "Reading the Mind in the Eyes" Theory of Mind test were recorded pre- (T0) and post- (T1) 7 days of writing. The main result showed that only the IG presented a different P300 amplitude in response to eye expressions at T1 compared to T0 on the left centre–frontal montage. No significant results on accuracy at T1 compared to T0 were found. These findings seem to suggest that the introspective writing task modulates attention and implicit evaluation of the socio-emotional stimuli. Results are discussed with reference to the hypothesis that such neuronal modulation is linked to an increase in the embodied simulation process underlying affective empathy. [ABSTRACT FROM AUTHOR]

Two decades of research have demonstrated that using a tool modulates spatial representations of the body. Whether this embodiment is specific to representations of the tool-using limb or extends to representations of other body parts has received little attention. Several studies of other perceptual phenomena have found that modulations to the primary somatosensory representation of the hand transfers to the face, due in part to their close proximity in primary somatosensory cortex. In the present study, we investigated whether tool-induced recalibration of tactile perception on the hand transfers to the cheek. Participants verbally estimated the distance between two tactile points applied to either their hand or face, before and after using a hand-shaped tool. Tool use recalibrated tactile distance perception on the hand-in line with previous findings-but left perception on the cheek unchanged. This finding provides support for the idea that embodiment is body-part specific. Furthermore, it suggests that tool-induced perceptual recalibration occurs at a level of somatosensory processing, where representations of the hand and face have become functionally disentangled.

The rubber hand illusion is a perceptual illusion in which participants experience an inanimate rubber hand as their own when they observe this model hand being stroked in synchrony with strokes applied to the person's real hand, which is hidden. Earlier studies have focused on the factors that determine the elicitation of this illusion, the relative contribution of vision, touch and other sensory modalities involved and the best ways to quantify this perceptual phenomenon. Questionnaires serve to assess the subjective feeling of ownership, whereas proprioceptive drift is a measure of the recalibration of hand position sense towards the rubber hand when the illusion is induced. Proprioceptive drift has been widely used and thought of as an objective measure of the illusion, although the relationship between this measure and the subjective illusion is not fully understood. Here, we examined how long the illusion is maintained after the synchronous visuotactile stimulation stops with the specific aim of clarifying the temporal relationship in the reduction of both subjective ownership and proprioceptive drift. Our results show that both the feeling of ownership and proprioceptive drift are sustained for tens of seconds after visuotactile stroking has ceased. Furthermore, our results indicate that the reduction of proprioceptive drift and the feeling of ownership follow similar time courses in their reduction, suggesting that the two phenomena are temporally correlated. Collectively, these findings help us better understand the relationships of multisensory stimulation, subjective ownership, and proprioceptive drift in the rubber hand illusion. [ABSTRACT FROM AUTHOR]

Previous studies have reported (i) freezing-like posturographic correlates in response to painful as compared to non-painful scenes vision (Lelard et al., Front Hum Neurosci 7:4, 2013) and (ii) an increase of this response during the mental simulation as compared to the passive viewing of the painful scenes (Lelard et al., Front Psychol 8:2012, 2017). The main objective of the present study was to explore the modulation of posturographic correlates of painful scenes vision by the level of depicted pain and the influence of mental simulation on this modulation. Thirty-six participants (36.3 ± 11.4 years old) were included in this study. During the experiment, participants had to stand on a posturographic platform. Three types of static visual stimuli were randomly depicting different pain-level situations: no-pain, low-pain, high-pain. In a first run, participants watched these stimuli passively (passive condition); in a second run, they were asked to "imagine that they were personally experiencing the situations they were about to see" (mental simulation condition). For each picture, subjective ratings were recorded for displeasure and desire to avoid at the end of the posturographic session. Results support an approach-type behavior in response to high-pain stimuli in the passive condition which becomes a withdrawal-type behavior in the mental simulation condition. Moreover, this withdrawal-type behavior is modulated by the level of depicted pain and this modulation does not appear for the subjective data. As a conclusion, these results are in accordance with those of previous studies showing the modulation of posturographic correlates of pain perception by mental simulation and report, for the first time, modulation of this effect by the level of depicted pain. The dichotomy of this modulatory effect between subjective and objective data is discussed as well as the finding of an approach-type behavior towards painful stimuli when passively viewing them becoming a withdrawal-type behavior when mental simulation is applied to the same stimuli. [ABSTRACT FROM AUTHOR]

When an individual embodies an avatar, the latter's characteristics or stereotype can change the individual's behavior and attitudes; this is known as the Proteus effect. Here, we looked at whether the embodiment of an avatar resembling an elderly adult (seen from a first-person perspective and facing a virtual mirror) changed mentally represented physical activity in a motor imagery task performed by young adult participants (N = 52). To ensure that the impact of embodiment of an elderly avatar on the motor imagery task was not influenced by a potentially confounded stereotype assimilation effect (due to the mere presence of an avatar), a "young" avatar and an "elderly" avatar were always present together in the virtual environment–even though only one (the self-avatar) was embodied at a given time. We found that it took longer for the participants to perform the motor imagery task with the elderly self-avatar than with the young self-avatar. The more negative the participant's beliefs about motor activity in the elderly, the greater the observed effect of the avatar on motor imagery performance. We conclude that knowledge about the characteristics of an embodied avatar can modify the subject's level of mentally represented physical activity. [ABSTRACT FROM AUTHOR]

This study investigated sex differences in performance and neuronal activity in a mental rotation task with abstract and embodied figures. Fifty-eight participants (26 females and 32 males) completed a chronometric mental rotation task with cube figures, human figures, and body postures. The results are straightforward: depending on angular disparity, participants had a faster reaction time and a higher accuracy rate for embodied stimuli compared to cube figures. The electroencephalogram (EEG) activity pattern showed a higher negative amplitude modulation in the frontal electrodes for females compared to males during the late (400–600 ms) time interval. From 200 to 400 ms after stimulus onset, there was a different activation pattern in the parietal and central electrodes, whereas frontal electrodes did not show differences between embodied and abstract stimuli. From 400 to 600 ms after stimulus onset, there was a different pattern in the central and frontal electrodes but not in the parietal areas for embodied figures in compared to cube figures. Concluding, even though there were no sex differences in the behavioral data, the EEG data did show alterations at the late time interval. Thus, the disparate results regarding sex differences that depend on the type of analysis (behavioral versus neurophysiological) should be more thoroughly investigated. Furthermore, the difference in processing embodied stimuli in an object-based mental rotation task could be confirmed in EEG activity pattern for the first time. [ABSTRACT FROM AUTHOR]

Visual stimulation of a repetitive self-movement image can evoke kinesthetic illusion when a virtual body part is set over the actual body part (kinesthetic illusion induced by visual stimulation, KINVIS). KINVIS induces activity in cerebral network, similar to that produced during motor execution, and triggers motor imagery passively. This study sought to identify a biomarker of KINVIS using event-related desynchronization (ERD) to improve the application of KINVIS to brain–machine interface (BMI) therapy of patients with stroke with hemiparesis. We included healthy adults in whom KINVIS could be induced. Scalp electroencephalograms were recorded during the KINVIS condition, where KINVIS was induced using a self-movement image. The findings were compared to signals recorded during an observation (OB) condition where only the self-movement image was viewed. For the signal intensity of the α- and low β-frequency bands, we calculated ERD during a movie period. The ERD of the α-frequency band in P3 and CP3 during KINVIS was significantly higher than that during OB. Furthermore, using the ERD of the α-frequency band recorded from FC3 and CP3, we could discriminate illusory perception with a 70% success rate. In this study, KINVIS could be detected using the ERD of the α-frequency band recorded from the posterior portion of the sensorimotor cortex. Furthermore, adding ERD recorded from FC3 to that recorded from CP3 may enable the objective discrimination of KINVIS from OB. When applying KINVIS in BMI therapy, the combination ERD of FC3 and CP3 will become a parameter for objectively judging the degree of kinesthetic perception achieved. [ABSTRACT FROM AUTHOR]

Morphology and functional aspects of the tool have been proposed to be critical factors modulating tool use-induced plasticity. However, how these aspects contribute to changing body representation has been underinvestigated. In the arm bisection task, participants have to estimate the length of their own arm by indicating its midpoint, a paradigm used to investigate the representation of the metric properties of the body. We employed this paradigm to investigate the impact of different actions onto tool embodiment. Our findings suggest that a training requiring actions mostly with proximal (shoulder) or distal (wrist) parts induces a different shift in the perceived arm midpoint. This effect is independent of, but enhanced by, the use of the tool during the training and in part influenced by specific demands of the task. These results suggest that specific motor patterns required by the training can induce different changes of body representation, calling for rethinking the concept of tool embodiment, which would be characterized not simply by the morphology of the tools, but also by the actions required for their specific use. [ABSTRACT FROM AUTHOR]

Encoding the position of another person in space is vital for everyday life. Nevertheless, little is known about the specific navigational strategies associated with encoding the position of another person in the wider spatial environment. We asked two groups of participants to learn the location of a target (person or object) during active navigation, while optic flow information, a landmark, or both optic flow information and a landmark were available in a virtual environment. Whereas optic flow information is used for body-based encoding, such as the simulation of motor movements, landmarks are used to form an abstract, disembodied representation of the environment. During testing, we passively moved participants through virtual space, and compared their abilities to correctly decide whether the non-visible target was before or behind them. Using psychometric functions and the Bayes Theorem, we show that both groups assigned similar weights to body-based and environment-based cues in the condition, where both cue types were available. However, the group who was provided with a person as target showed generally reduced position errors compared to the group who was provided with an object as target. We replicated this effect in a second study with novel participants. This indicates a social advantage in spatial encoding, with facilitated processing of both body-based and environment-based cues during spatial navigation when the position of a person is encoded. This may underlie our critical ability to make accurate distance judgments during social interactions, for example, during fight or flight responses. [ABSTRACT FROM AUTHOR]

Mirror visual feedback is used for reducing pain and visually distorting the size of the reflection may improve efficacy. The findings of studies investigating size distortion are inconsistent. The influence of the size of the reflected hand on embodiment of the mirror reflection is not known. The aim of this study was to compare the effect of magnifying and minifying mirror reflections of the hand on embodiment measured using an eight-item questionnaire and on proprioceptive drift. During the experiment, participants ( n = 45) placed their right hand behind a mirror and their left hand in front of a mirror. Participants watched a normal-sized, a magnified and a minified reflection of the left hand while performing synchronised finger movements for 3 min (adaptive phase). Measurements of embodiment were taken before (pre) and after (post) synchronous movements of the fingers of both hands (embodiment adaptive phase). Results revealed larger proprioceptive drift post-adaptive phase ( p = 0.001). Participants agreed more strongly with questionnaire items associated with location, ownership and agency of the reflection of the hand post-adaptive phase ( p < 0.001) and when looking at the normal-sized reflection ( p < 0.001). In conclusion, irrespective of size, watching a reflection of the hand while performing synchronised movements enhances the embodiment of the reflection of the hand. Magnifying and minifying the reflection of the hand has little effect on proprioceptive drift, but it weakens the subjective embodiment experience. Such factors need to be taken into account in future studies using this technique, particularly when assessing mirror visual feedback for pain management. [ABSTRACT FROM AUTHOR]

The dynamic flexibility of body representation has been highlighted through numerous lines of research that range from clinical studies reporting disorders of body ownership, to experimentally induced somatic illusions that have provided evidence for the embodiment of manipulated representations and even fake limbs. While most studies have reported that enlargement of body parts alters somatic perception, and that these can be more readily embodied, shrunken body parts have not been found to consistently alter somatic experiences, perhaps due to reduced feelings of ownership over smaller body parts. Over two experiments, we aimed to investigate the mechanisms responsible for altered somatic representations following exposure to both enlarged and shrunken body parts. Participants were given the impression that their hand and index finger were either longer or shorter than veridical length and asked to judge veridical finger length using online and offline size estimation tasks, as well as to report the degree of ownership towards the distorted finger and hand representations. Ownership was claimed over all distorted representations of the hand and finger and no differences were seen across ownership ratings, while the online and offline measurements of perceived size demonstrated differing response patterns. These findings suggest that ownership towards manipulated body representations is more bidirectional than previously thought and also suggest differences in perceived body representation with respect to the method of measurement suggesting that online and offline tasks may tap into different aspects of body representation. [ABSTRACT FROM AUTHOR]

Recent evidence suggests that interval timing (the judgment of durations lasting from approximately 500 ms. to a few minutes) is closely coupled to the action control system. We used surface electromyography (EMG) and motion capture technology to explore the emergence of this coupling in 4-, 6-, and 8-month-olds. We engaged infants in an active and socially relevant arm-raising task with seven cycles and response period. In one condition, cycles were slow (every 4 s); in another, they were fast (every 2 s). In the slow condition, we found evidence of time-locked sub-threshold EMG activity even in the absence of any observed overt motor responses at all three ages. This study shows that EMGs can be a more sensitive measure of interval timing in early development than overt behavior. [ABSTRACT FROM AUTHOR]

The present study was designed to investigate the incorporation of tools into the human body schema. Previous research on tool use suggests that through physical interaction with a tool, the representation of the body is adjusted to incorporate or 'embody' the tool. The present experiment was conducted to test the limb-specific nature of tool embodiment. Participants were presented with images of a person holding a rake and executed hand- and foot-press responses to colored targets superimposed on the hand, foot, and rake of the image. This task was completed before and after moving a ball around a course with a hand-held rake. Consistent with previous research, a body-part compatibility effect emerged-response times (RTs) were shorter when the responding limb and target location were compatible (e.g., hand responses to targets on the hand) than when they were incompatible (e.g., hand responses to targets on the foot). Of greater theoretical relevance, hand RTs to targets presented on the hand were shorter than those to targets on the rake prior to experience, but were not different after completing the rake task. The post-experience similarity in hand RTs emerged because there was a significant reduction in RTs to targets on the rake following use. There was no significant pre-/post-experience change in hand RTs to targets on the hand or, importantly, for any response executed by the foot. These results provide new evidence that a tool is embodied in a limb-specific manner and is represented within the body schema as if it was an extension of the limb. [ABSTRACT FROM AUTHOR]

The sense of body-ownership involves the integration of vision and somatosensation. In the rubber hand illusion (RHI), watching a rubber hand being stroked for a short time synchronously as one's own unseen hand is also stroked causes the observers to attribute the rubber hand to their own body. The RHI may elicit proprioceptive drift: The observers' sense of their own hand's location drifts toward the external proxy hand. The current experiments examined the possibility of observing, not the proprioceptive drift, but the actual drift 'movement' during RHI induction. The participants' hand, located on horizontally movable board, tended to move toward the rubber hand only while they observed synchronous visuo-tactile stimulation. Furthermore, even when the participants' hand was located on a fixed, unmovable board (that is, the conventional RHI paradigm), participants automatically administered the force toward the rubber hand. These findings suggest that since awareness of our own body and action are fundamental to self-consciousness, these components of 'minimal self' are closely related and integrated into 'one agent' with a unified awareness of the body and action. [ABSTRACT FROM AUTHOR]

Mental rotation of the hands classically induces kinesthetic effects according to the direction of the rotation, with faster response times to the hands' medial rotations compared with lateral rotations, and is thus commonly used to induce engagement in motor imagery (MI). In the present study, we compared the performances of table tennis players (experts on hand movements), who commonly execute and observe fast hand movements, to those of soccer players (non-experts on hand movements) on a mental rotation task of hands. Our results showed a significant effect of the direction of rotation (DOR) confirming the engagement of the participants in MI. In addition, only hand movement experts were faster when the task figures corresponded to their dominant hand compared with the non-dominant hand, revealing a selective effect of motor expertise. Interestingly, the effect of the DOR collapsed in hand movement experts only when the task figures corresponded to their dominant hand, but it is noteworthy that lateral and medial rotations of the right-hand stimuli were not faster than medial rotations of the left-hand stimuli. These results are discussed in relation to possible strategies during the task. Overall, the present study highlights the embodied nature of the mental rotation task of hands by revealing selective effects of motor expertise. [ABSTRACT FROM AUTHOR]

The goal of this study was to elucidate the underlying mechanisms of hand and tool grasping control. We assumed that there is a single principle-governing grasping control irrespective of its effectors and that the degree of prior experience of the effector determines the smoothness of aperture control. Eight participants performed a reach-to-grasp task with four different effectors: index finger and thumb, middle finger and thumb, chopsticks, and a scissor-like tool. Although we employed different effectors with large mechanical variations and different degrees of prior use, maximum grip aperture was scaled as a function of object size and appeared at almost the same timing in all four types of grasping movements. Moreover, reaching time did not substantially differ among grasping conditions. However, plateau duration of the aperture profile differed by effector. Plateau duration was the longest in the unfamiliar scissor-like tool grasping condition. There was no difference between the unfamiliar hand-use grasp with the thumb and the middle finger and the familiar tool-grasp with chopsticks. The familiar hand-use grasp with the thumb and the index finger had the shortest plateau duration. These results supported the idea that there is an effector-independent continuity between hand-use and tool-use in motor control as a function of prior degree of use, rather than the conventionally assumed dichotomy between them. [ABSTRACT FROM AUTHOR]

Does mental rotation depend on the readiness to act? Recent evidence indicates that the involvement of motor processes in mental rotation is experience-dependent, suggesting that different levels of expertise in sensorimotor interactions lead to different strategies to solve mental rotation problems. Specifically, experts in motor activities perceive spatial material as objects that can be acted upon, triggering covert simulation of rotations. Because action simulation depends on the readiness to act, movement restriction should therefore disrupt mental rotation performance in individuals favoring motor processes. In this experiment, wrestlers and non-athletes judged whether pairs of three-dimensional stimuli were identical or different, with their hands either constrained or unconstrained. Wrestlers showed higher performance than controls in the rotation of geometric stimuli, but this difference disappeared when their hands were constrained. However, movement restriction had similar consequences for both groups in the rotation of hands. These findings suggest that expert's advantage in mental rotation of abstract objects is based on the readiness to act, even when physical manipulation is impossible. [ABSTRACT FROM AUTHOR]

Studies of embodied cognition have demonstrated the engagement of the motor system when people process action-related words and concepts. However, research using transcranial magnetic stimulation (TMS) to examine linguistic modulation in primary motor cortex has produced inconsistent results. Some studies report that action words produce an increase in corticospinal excitability; others, a decrease. Given the differences in methodology and modality, we re-examined this issue, comparing conditions in which participants either read or listened to the same set of action words. In separate blocks of trials, participants were presented with lists of words in the visual and auditory modality, and a TMS pulse was applied over left motor cortex, either 150 or 300 ms after the word onset. Motor evoked potentials (MEPs) elicited were larger following the presentation of action words compared with control words. However, this effect was only observed when the words were presented visually; no changes in MEPs were found when the words were presented auditorily. A review of the TMS literature on action word processing reveals a similar modality effect on corticospinal excitability. We discuss different hypotheses that might account for this differential modulation of action semantics by vision and audition. [ABSTRACT FROM AUTHOR]

The cognitive representation of numbers has been studied with chronometric methods but these cannot resolve the current debate about the metrical structure of the “mental number line”. We recorded spatial behaviour as blindfolded adults described the locations of numbers (e.g., “where is 3?”) by pointing and the lengths of magnitudes (e.g., “how much is 56?”) by gesturing. Their unconstrained spatial behaviour revealed idiosyncratic spatial associations for numbers and largely supports a linear representation of magnitudes. [ABSTRACT FROM AUTHOR]