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The peripersonal space (PPS) is a special portion of space immediately surrounding the body, where the integration between tactile stimuli delivered on the body and auditory or visual events emanating from the environment occurs. Interestingly, PPS can widen if a tool is employed to interact with objects in the far space. However, electrophysiological evidence of such tool-use dependent plasticity in the human brain is scarce. Here, in a series of three experiments, participants were asked to respond to tactile stimuli, delivered to their right hand, either in isolation (unimodal condition) or combined with auditory stimulation, which could occur near (bimodal-near) or far from the stimulated hand (bimodal-far). According to multisensory integration spatial rule, when bimodal stimuli are presented at the same location, we expected a response enhancement (response time – RT – facilitation and event-related potential – ERP – super-additivity). In Experiment 1, we verified that RT facilitation was driven by bimodal input spatial congruency, independently from auditory stimulus intensity. In Experiment 2, we showed that our bimodal task was effective in eliciting the magnification of ERPs in bimodal conditions, with significantly larger responses in the near as compared to far condition. In Experiment 3 (main experiment), we explored tool-use driven PPS plasticity. Our audio-tactile task was performed either following tool-use (a 20-minute reaching task, performed using a 145 cm-long rake) or after a control cognitive training (a 20-minute visual discrimination task) performed in the far space. Following the control training, faster RTs and greater super-additive ERPs were found in bimodal-near as compared to bimodal-far condition (replicating Experiment 2 results). Crucially, this far-near differential response was significantly reduced after tool-use. Altogether our results indicate a selective effect of tool-use remapping in extending the boundaries of PPS. The present finding might be considered as an electrophysiological evidence of tool-use dependent plasticity in the human brain.

Circle-line drawing paradigm is used to study bimanual coupling. In the standard paradigm, subjects are asked to draw circles with one hand and lines with the other hand; the influence of the concomitant tasks results in two “elliptical” figures. Here we tested whether proprioceptive information evoked by muscle vibration inducing a proprioceptive illusion (PI) of movement at central level, was able to affect the contralateral hand drawing circles or lines. A multisite 80 Hz-muscle vibration paradigm was used to induce the illusion of circle- and line-drawing on the right hand of 15 healthy participants. During muscle vibration, subjects had to draw a congruent or an incongruent figure with the left hand. The ovalization induced by PI was compared with Real and Motor Imagery conditions, which already have proved to induce bimanual coupling. We showed that the ovalization of a perceived circle over a line drawing during PI was comparable to that observed in Real and Motor Imagery condition. This finding indicates that PI can induce bimanual coupling, and proprioceptive information can influence the motor programs of the contralateral hand.

Recently, a monothematic delusion of body ownership due to brain damage (i.e., the embodiment of someone else's body part within the patient's sensorimotor system) has been extensively investigated. Here we aimed at defining in-depth the clinical features and the neural correlates of the delusion. Ninety-six stroke patients in a sub-acute or chronic phase of the illness were assessed with a full ad-hoc protocol to evaluate the embodiment of an alien arm under different conditions. A sub-group of seventy-five hemiplegic patients was also evaluated for the embodiment of the movements of the alien arm. Fifty-five patients were studied to identify the neural bases of the delusion by means of voxel-based lesion-symptom mapping approach. Our results show that, in forty percent of the whole sample, simply viewing the alien arm triggered the delusion, but only if it was a real human arm and that was seen from a 1st person perspective in an anatomically-correct position. In the hemiplegic sub-group, the presence of the embodiment of the alien arm was always accompanied by the embodiment of its passive and active movements. Furthermore, the delusion was significantly associated to primary proprioceptive deficits and to damages of the corona radiata and the superior longitudinal fasciculus. To conclude, we show that the pathological embodiment of an alien arm is well-characterized by recurrent and specific features and might be explained as a disconnection deficit, mainly involving white matter tracts. The proposed exhaustive protocol can be successfully employed to assess stroke-induced disorders of body awareness, unveiling even their more undetectable or covert clinical forms.

OBJECTIVE It was suggested that the bimanual coupling effect might be linked to motor intentionality and planning, which are the top-down components of motor execution. However, previous results in pathological and healthy individuals have also underlined the pivotal role of bottom-up sensorimotor information. METHOD In this single-case study, the Circles-Lines Coupling Task was administered to a left-parietal-brain-damaged individual. The cerebral lesion caused a central proprioceptive loss, relative to the impaired right hand, when out of the visual control. For the 1st time in literature, we sought to investigate whether the movement of the unaffected hand induced an efficient coupling effect on the movement of the affected one. The bimanual task was performed in the presence and absence of visual input. The patient's performance was compared with that of healthy controls. RESULTS We observed the traditional bimanual coupling effect in healthy controls. Moreover, we also replicated the effect when they performed the task blindfolded. In the case of the patient, both hands showed the typical ovalization of the line trajectory when the task was performed in visual modality. It is interesting that when the patient performed the task blindfolded, the trajectories of the impaired right hand seemed to be not influenced by the concomitant circular movement of the spared left hand. CONCLUSIONS The movement of the unaffected hand induced a bimanual coupling effect on the movement of the affected one only when the visual input was available. In absence of a visual feedback, the aberrant proprioceptive information might preclude the emerging of bimanual coupling, even in the case of a preserved motor intentionality and planning. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Our research focused on the role of vision and proprioception in modulating a defensive reflex (hand blink reflex, HBR) whose magnitude is enhanced when the threatened hand is inside the peripersonal space of the face. We capitalized on virtual reality, which allows dissociating vision and proprioception by presenting a virtual limb in congruent/incongruent positions with respect to the participants' limb. In experiment 1, participants placed their own stimulated hand in far/near positions with respect to their face (postural manipulation task), while observing a virtual empty scenario. Vision was not informative, but the HBR was significantly enhanced in near compared with far position, suggesting that proprioception is sufficient for the HBR modulation to occur. In experiment 2, participants did not perform the postural manipulation but they (passively) observed the avatar's virtual limb performing it. Proprioceptive signals were not informative, but the HBR was significantly enhanced when the observed virtual limb was near to the face, suggesting that visual information plays a role in modulating the HBR. In experiment 3, both participants and avatar performed the postural manipulation, either congruently (both of them far/near) or incongruently (one of them far, the other near). The HBR modulation was present only in congruent conditions. In incongruent conditions, the conflict between vision and proprioception confounded the system, abolishing the difference between far and near positions. Taken together, these findings promote the view that observing a virtual limb modulates the HBR, providing also new evidence on the role of vision and proprioception in modulating this subcortical reflex.

Body ownership (i.e., the conscious belief of owning a body) and sense of agency (i.e., being the agent of one’s own movements) are part of a pre-reflective experience of bodily self, which grounds on low-level complex sensory–motor processes. Although previous literature had already investigated body ownership in obesity, sense of agency was never explored. Here, we exploited the sensory attenuation effect (i.e., an implicit marker of the sense of agency; SA effect) to investigate whether the sense of agency was altered in a sample of 18 individuals affected by obesity as compared with 18 healthy-weight individuals. In our experiment, participants were asked to rate the perceived intensity of self-generated and other-generated tactile stimuli. Healthy-weight individuals showed a significantly greater SA effect than participants affected by obesity. Indeed, while healthy-weight participants perceived self-generated stimuli as significantly less intense as compared to externally generated ones, this difference between stimuli was not reported by affected participants. Our results relative to the SA effect pinpointed an altered sense of agency in obesity. We discussed this finding within the motor control framework with reference to obesity. We encouraged future research to further explore such effect and its role in shaping the clinical features of obesity.

Individuals with autism spectrum conditions (ASC) are less susceptible to multisensory delusions, such as rubber hand illusion (RHI). Here, we investigate whether a monochannel variant of RHI is more effective in inducing an illusory feeling of ownership in ASC. To this aim, we exploit a non-visual variant of the RHI that, excluding vision, leverages only on the somatosensory channel. While the visual-tactile RHI does not alter the perceived hand position in ASC individuals, the tacto-tactile RHI effectively modulates proprioception to a similar extent as that found in typical development individuals. These findings suggest a more effective integration of multiple inputs originating from the same sensory channel in ASC, revealing a monochannel preference in this population.

Professional athletes, compared to beginners, can better predict the outcome of sport-related observed movements, via mirror motor-system modulations (motor resonance). Furthermore, motor-system inhibition occurs when observing other people experiencing pain (pain resonance). Here we investigated whether observing sport-related actions, whose outcome can lead or not to a painful experience, results into different prediction performances depending on expertise and history of injury. Experiment 1 revealed that professional skiers, relative to beginners, show greater prediction accuracy but slower reaction times. Experiment 2 revealed that, among professional skiers, those previously injured, compared to uninjured ones, are slower in predicting the outcome of the observed action when it actually leads to an injury. We hypothesize that such results could be explained by an automatic activation of both motor and pain resonance mechanisms in the onlooker, inducing a sort of experience-dependant freezing response while observing actions likely leading to an injury.

The clinical effects of the Covid-19 pandemic are now the subject of numerous studies worldwide. But what are the effects of the quarantine imposed by the states that implemented the measures of lockdown? The present research aims to explore, in a preliminary way, the major stress-related symptoms during the lockdown, due to Covid-19, in the Italian population. Subjects were asked to fill out a survey, that traced a line identifying the most relevant psychophysiological symptoms that took into account factors such as perceived stress, body perception, perceived pain, quality of sleep, perceptive variations (i.e., olfactory, gustatory, visual, acoustic, and haptic perception). A network approach formulating a hypothesis-generating exploratory analysis was adopted. Main results of the network analysis showed that the beliefs of having had the Covid-19 was related to individual variables (i.e., gender, working in presence, sleep quality, anxiety symptoms), while the familiarity of Covid-19 disease was related to contextual factors (e.g., number of recorded cases in the Region, working in presence). The self-perception of olfactory and perceptive alterations highlighted a great sensorial cross-modality, additionally, the olfactory impairment was related to the belief of having had the Covid-19. Compared to general network data, BAI, perceived stress, anxiety and chronic pain were in relation to daily sleep disturbance. Main study's results show how the management of the Covid-19 stressful representation, in its cognitive aspects, can modulate the psychophysiological responses.

The ability to identify our own body is considered a pivotal marker of self-awareness. Previous research demonstrated that subjects are more efficient in the recognition of images representing self rather than others' body effectors (self-advantage). Here, we verified whether, at an electrophysiological level, bodily-self recognition modulates change detection responses. In a first EEG experiment (discovery sample), event-related potentials (ERPs) were elicited by a pair of sequentially presented visual stimuli (vS1; vS2), representing either the self-hand or other people's hands. In a second EEG experiment (replicating sample), together with the previously described visual stimuli, also a familiar hand was presented. Participants were asked to decide whether vS2 was identical or different from vS1. Accuracy and response times were collected. In both experiments, results confirmed the presence of the self-advantage: participants responded faster and more accurately when the self-hand was presented. ERP results paralleled behavioral findings. Anytime the self-hand was presented, we observed significant change detection responses, with a larger N270 component for vS2 different rather than identical to vS1. Conversely, when the self-hand was not included, and even in response to the familiar hand in Experiment 2, we did not find any significant modulation of the change detection responses. Overall our findings, showing behavioral self-advantage and the selective modulation of N270 for the self-hand, support the existence of a specific mechanism devoted to bodily-self recognition, likely relying on the multimodal (visual and sensorimotor) dimension of the bodily-self representation. We propose that such a multimodal self-representation may activate the salience network, boosting change detection effects specifically for the self-hand.

A challenge for neuroscience is to understand the conscious and unconscious processes underlying construction of willed actions. We investigated the neural substrate of human motor awareness during awake brain surgery. In a first experiment, awake patients performed a voluntary hand motor task and verbally monitored their real-time performance, while different brain areas were transiently impaired by direct electrical stimulation (DES). In a second experiment, awake patients retrospectively reported their motor performance after DES. Based on anatomo-clinical evidence from motor awareness disorders following brain damage, the premotor cortex (PMC) was selected as a target area and the primary somatosensory cortex (S1) as a control area. In both experiments, DES on both PMC and S1 interrupted movement execution, but only DES on PMC dramatically altered the patients’ motor awareness, making them unconscious of the motor arrest. These findings endorse PMC as a crucial hub in the anatomo-functional network of human motor awareness., Here, using electrical stimulation on patients undergoing awake brain surgery, the authors show that disruption of the premotor cortex makes patients unconscious of motor arrest. This finding suggests the premotor cortex is crucial for motor awareness.

Self-harm is considered a pervasive problem in several psychopathologies, and especially in Borderline Personality Disorder (BPD). Self-harming behaviors may be enacted for many purposes for example to regulate emotions and to reduce dissociation. BPD patients often report dissociative episodes, which may be related to an altered body awareness, and in particular to an altered awareness of the sense of agency. The sense of agency draws in part upon perceptions of being in control of our bodies and our physical movements, of being able to act upon environments. In this study, we aim to investigate whether dissociative experiences of BPD patients may be linked to an altered sense of agency and whether self-injurious actions may, through strong sensorial stimulation, constitute a coping strategy for the reduction of the distress associated with these dissociative experiences. A group of 20 BPD patients, of whom 9 presented self-harming behaviors, took part in the study and were compared with an age-matched control group of 20 healthy individuals. Sense of agency was evaluated through the Sensory Attenuation paradigm. In this paradigm, in a comparison with externally generated sensations, the degree to which perceived intensity of self-generated sensations is reduced is considered an implicit measure of sense of agency. As we expected, we found a significant difference in the perceptions of the two groups. The attenuation effect appeared to be absent in the BPD group while it was present in the control group. However, further analysis revealed that those BPD patients who engaged in self-harming behaviors presented a degree of attenuation which was similar to that of the control group. These results confirm the hypothesis that self-injurious actions constitute a coping strategy for increasing the sense of agency. We finally discuss the correlation of these experimental results with some clinical self-evaluation measures assessing dissociation, anxiety, depression, and affective dysregulation.

When body ownership is impaired after brain-damage, the capacity to discriminate between one's own and others' body-parts is lost. Delusional body-ownership has been recently described in patients who misidentify someone else's limb as their own (pathological embodiment) whenever it is positioned in a body congruent position. This delusion can be frequently associated with somatosensory and attentional deficits. Here, we leveraged the phenomenon of tactile extinction, as this clinical sign can be substantially ameliorated when contralesional touches are combined with proximal visual stimulation. Is body ownership a necessary prerequisite to modulate cross-modal processing and thus reducing tactile extinction? Fourteen patients with tactile extinction (TE+) took part in the study: eight of them with pathological embodiment (E+, experimental group) and six of them without pathological embodiment (E-, control group). In two different paradigms, differing for the nature of visuo-tactile stimuli, bilateral tactile stimulation of the patients' hands was combined with visual stimuli occurring on A) their own contralesional (affected) hand, B) the examiner's hand (embodied in E+), or C) a neutral object. In both groups, visual stimuli proximal to the own hand significantly improved contralesional tactile detection, while visual stimuli occurring on the neutral object did not. Crucially, only in E+TE+ patients did visual stimuli on the examiner's (embodied) hand improve contralesional tactile detection. This finding shows that cross-modal visuo-tactile integration is conditional to body-ownership, so that it ameliorates tactile extinction when visual stimuli occur on what is believed to be one's own body. From a clinical point of view, this study suggests that the effectiveness of cross-modal rehabilitative intervention can benefit from a careful evaluation of the patients' sense of body-ownership, so often impaired after brain-damage.

Prismatic adaptation (PA) results from repeated ballistic movements of the dominant arm toward visual targets while wearing prisms shifting the visual field laterally (visuomotor prismatic training [VPT]). Following PA, subjects' pointing movements are deviated contralaterally to prismatic shift (aftereffect). The question of whether spatial attention is also biased in the same direction remains controversial in the scientific literature. To investigate the effect of PA on spatial attention, we asked healthy participants to perform a visual detection threshold task before and after VPT with left- and right-deviating prisms and visuomotor training without prisms. Our results demonstrate that both left and right VPTs modulate visual detection threshold, significantly ameliorating detection accuracy and response times bilaterally. These data indicate that PA modulates visual attention bilaterally and that detection threshold paradigms are sensitive to its effects in the visual domain. We suggest that the described PA effects are mediated by the joint action of attentional and alerting mechanisms. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

From Kant to current perspectives in neuroaesthetics, the experience of beauty has been described as disinterested, i.e. focusing on the stimulus perceptual features while neglecting self-referred concerns. At a neurophysiological level, some indirect evidence suggests that disinterested aesthetic appreciation might be associated with attentional enhancement and inhibition of motor behaviour. To test this hypothesis, we performed three auditory-evoked potential experiments, employing consonant and dissonant two-note musical intervals. Twenty-two volunteers judged the beauty of intervals (Aesthetic Judgement task) or responded to them as fast as possible (Detection task). In a third Go-NoGo task, a different group of twenty-two participants had to refrain from responding when hearing intervals. Individual aesthetic judgements positively correlated with response times in the Detection task, with slower motor responses for more appreciated intervals. Electrophysiological indexes of attentional engagement (N1/P2) and motor inhibition (N2/P3) were enhanced for more appreciated intervals. These findings represent the first experimental evidence confirming the disinterested interest hypothesis and may have important applications in research areas studying the effects of stimulus features on learning and motor behaviour.

Anatomo-clinical evidence from motor-awareness disorders after brain-damages suggests that the premotor cortex (PMC) is involved in motor-monitoring of voluntary actions. Indeed, PMC lesions prevent patients from detecting the mismatch between intended, but not executed, movements with the paralyzed limb. This functional magnetic resonance imaging study compared, in healthy subjects, free movements against blocked movements, precluded by a cast. Cast-related corticospinal excitability changes were investigated by using transcranial magnetic stimulation. Immediately after the immobilization, when the cast prevented the execution of left-hand movements, the contralateral right (ventral) vPMC showed both increased hemodynamic activity and increased functional connectivity with the hand area in the right somatosensory cortex, suggesting a vPMC involvement in detecting the mismatch between planned and executed movements. Crucially, after 1 week of immobilization, when the motor system had likely learned that no movement could be executed and, therefore, predictions about motor consequences were changed, vPMC did not show the enhanced activity as if no incongruence has to be detected. This can be interpreted as a consequence of the plastic changes induced by long-lasting immobilization, as also proved by the cast-related corticospinal excitability modulation in our subjects. The present findings highlight the crucial role of vPMC in the anatomo-functional network generating the human motor-awareness.

Autism spectrum conditions (ASC) are characterized by social-communicative deficits and repetitive stereotyped behaviors. Altered motor coordination is also observed and a dysfunction of motor imagery has been recently reported on implicit tasks. However, no information on explicit motor imagery abilities is available in ASC. Here, we employed a spatial bimanual task to concurrently assess motor coordination and explicit motor imagery in autism. A secondary objective of the study was to evaluate these abilities across two populations of ASC, namely adolescents and adults with ASC. To this aim, we took advantage of the circles-lines task in which where participants were asked to continuously draw: right hand lines (unimanual condition); right hand lines and left hand circles (bimanual condition); right hand lines while imagining to draw left hand circles (imagery condition). For each participant, an Ovalization Index (OI) was calculated as a deviation of the right hand drawing trajectory from an absolute vertical axis. Results showed a significant and similar coupling effect in the bimanual condition (i.e., a significant increase of the OI values with respect to the unimanual condition) in both controls and ASC participants. On the contrary, in the imagery condition, a significant coupling effect was found only in controls. Furthermore, adult controls showed a significantly higher imagery coupling effect in comparison to all the other groups. These results demonstrate that atypical motor imagery processes in ASC are not limited to implicit tasks and suggest that development of neural structures involved in motor imagery are immature in ASC. Autism Res 2018, 11: 376-384. © 2017 International Society for Autism Research, Wiley Periodicals, Inc. Lay summary Autism spectrum conditions (ASC) are characterized by social-communicative and motor coordination difficulties but in many cases also by an impaired capability to imagine movements. In this study we found that while two handed coordination in ASC can be developed as well as in typically developed persons, the development of motor imagery could still be immature in ASC, leading to difficulties in imagining, understanding as well as programming and coordinating complex movements.

There is no consensus on whether, and to what extent, actions contribute to constructing awareness of one's own body. Here we investigated at both physiological and behavioral level whether a prolonged limb immobilization affects body ownership. We tested a group of healthy participants, whose left-hand movements were prevented by a cast for one week, and a control group without any movement restriction. In both groups, we measured the strength of the rubber hand illusion (i.e., proprioceptive shift and questionnaire on ownership) and the physiological parameters known to be modulated by short-term arm immobilization (i.e., resting motor threshold, motor evoked potentials and force parameters) before and after the week of immobilization. Our results showed stronger illusory effects on the immobilized hand on both behavioral indexes and weaker illusory effects on the non-immobilized hand on the questionnaire. Additionally, the increased proprioceptive shift was positively correlated to the motor threshold of the contralateral hemisphere. Our findings show at both behavioral and physiological level that altering those movement-related signals which constantly stem from our own body parts, modulates the experience of those body parts as mine. This, in turn, supports the view of a direct role of actions in the developing and maintaining a coherent body ownership.

The effect of long-term immobilization on the motor system has been described during motor preparation, imagination or execution, when the movement has to be performed. But, what happens when the movement has to be suppressed? Does long-term limb immobilization modulate physiological responses underlying motor inhibition? Event-related potentials (ERPs) were recorded in healthy participants performing a Go/Nogo task, either with both hands free to respond (T1/T4: before/after the immobilization) or when left-hand movements were prevented by a cast (T2: as soon as the cast was positioned; T3: after one week of immobilization). In the right (control) side, N140, N2, and P3 components showed the expected greater amplitude in Nogo than in Go trials, irrespective of the timepoint. On the contrary, in the left (manipulated) side, each component of the ERP responses to Nogo trials showed specific differences across timepoints, suggesting that the inhibition-related EEG activity is significantly reduced by the presence of the cast and the duration of the immobilization. Furthermore, inhibition-related theta band activity to Nogo stimuli decreased at post-immobilization blocked session (T3-blocked). Altogether these findings can be interpreted as a consequence of the plastic changes induced by the immobilization, as also demonstrated by the cast-related corticospinal excitability modulation (investigated by using TMS) and by the decreased beta band in response to Go and Nogo trials. Thus, only if we are free to move, then inhibitory responses are fully implemented. After one week of immobilization, the amount of inhibition necessary to block the movement is lower and, consequently, inhibitory-related responses are reduced.

Phantom limb is a common sensation in amputees, who often report vivid experiences of voluntarily moving their phantom. Previous studies showed that phantom movement can be functionally disentangled from imagined movement comparable to the actual movement of an intact limb. How and to what extent phantom movement and real movement share similar physiological mechanisms? Here, we focused on a specific aspect of motor control, the motor inhibition, and we asked whether inhibitory physiological responses are implemented when a phantom movement has to be suppressed. Sixteen two-handed controls and two left upper-limb amputees (with and without phantom movement) underwent a Go/Nogo paradigm, while event-related potentials (ERPs) were recorded. The task was performed with both the right (intact) and the left (phantom) hand, either in real or imagery conditions. Opposite results between the moving-phantom case and the static-phantom case were found. In the real condition, moving-phantom case showed the classical motor-inhibition related ERP pattern, with large P300 inhibitory wave when the movements of both (right) intact and (left) phantom limbs have to be suppressed. This inhibitory response was not different from that found in controls (who performed the task with an existing hand; real condition), but, crucially, it was significantly different from the imagery condition of controls. Contrariwise, in the static-phantom case, the ERP responses to Nogo trials during the real condition were different from the real condition in controls, but were not different from their imagery condition. Importantly, in the real condition, Nogo-ERP responses were significantly different between the two phantom cases. Taken together, these findings provide compelling evidence that phantom movements share the same neurophysiological correlates of real movements, not only when an action has to be executed, but also when it should be inhibited.

The ability to know where our body parts are located in space (proprioception) is fundamental for both successfully interacting with the external world and monitoring potential threats. In this case-control study, we investigated whether the absence of proprioceptive signals may affect physiological defensive responses. To this aim, a right brain-damaged patient with a left upper-limb proprioceptive deficit (P+ patient) and age-matched healthy controls, underwent the recording of the Hand-Blink Reflex (HBR). This defensive response, elicited by electrical stimulation of the median nerve and recorded from the orbicularis oculi, is modulated by the hand position: it is enhanced when the threatened hand is near to the face, inside the defensive peripersonal-space (DPPS). According to the classical neuropsychological perspective, we used P+ patient as a model to investigate the role of proprioception in HBR modulation, by manipulating the congruity/incongruity between the intended and actual positions of the stimulated hand. P+ patient, with his eyes closed, had to voluntarily place his left hand either far from or near to his face and to relieve the arm’s weight over a supporting device. Then, in congruent conditions, the hand was stimulated in the actual (intended) position. In incongruent conditions, the patient’s hand was moved by the examiner from the intended to the opposite (not-intended) position and then stimulated. We observed an inverse response pattern between congruent and incongruent conditions. In congruent conditions, P+ patient showed an HBR enhancement in near compared to far position, comparable to that found in healthy controls. This suggests that, even in absence of proprioceptive and visual information, the HBR modulation was still present. Conversely, in incongruent conditions, P+ patient showed a greater HBR magnitude for far position (when the hand was actually far, but the patient intended it to be near) than for near position (when the hand was actually near, but the patient intended it to be far). This result suggests that proprioceptive signals are not necessary for HBR modulation to occur. It relies more on the intended than on the actual position of the hand. The role of motor intention and planning in shaping the DPPS is discussed.

Introduction Evidence about altered bimanual coordination has been reported in Parkinson's Disease. However, no previous study has explored such an alteration quantifying the interference effect that the trajectory of each hand might impose on the other one. Thus, in the present research, we applied the traditional Circles-Lines Coupling Task, which allowed assessing the motor coordination of the two hands, in the context of Parkinson's Disease. Methods Thirty-six individuals affected by Parkinson's Disease were consecutively recruited and assigned to two groups according to their symptoms' lateralization. Moreover, eighteen age-matched healthy controls participated in the study. We capitalized on the Circles-Lines Coupling Task, in which the performance during incongruent movements (drawing lines with one hand and circles with the other hand) was compared with the performance during congruent movements (drawing lines with both hands). A bimanual coupling index was computed to compare the interference effect of each hand on the other one. Results In healthy controls, the bimanual coupling index did not differ between the two hands. Crucially, in both groups of individuals affected by Parkinson's Disease, the less affected hand showed a significantly higher bimanual coupling index, due to the abnormal interference exerted by the most affected one, than vice versa. Conclusions Our results highlighted an altered spatial bimanual coupling in Parkinson's disease, depending on the symptoms' lateralization. We offered different explanations of our results according to the theoretical frameworks about the mechanisms subserving bimanual coordination.

Brain-damaged patients with anosognosia for hemiplegia deny their motor deficit and believe they can still move the paralyzed limb. Previous studies suggest that anosognosia can arise from intact motor intentionality and planning for the plegic hand. However, few studies focused on the relationship between this spared intentionality and perception. To further investigate this topic, we used an apparent motion paradigm, where a stimulus generated an ambiguous motion and participants were simply asked to judge its direction (right or left). We confirmed that, when healthy participants are asked to press a key either with their right or left hand, triggering the apparent motion, they show a perceptual bias toward the direction of the moving hand. Both bimanual and unimanual modalities (i.e. key pressing with-both-hands or with-one-hand, respectively) of the same apparent motion paradigm were administered to two groups of healthy participants. Interestingly, only in the bimanual modality, participants showed a significant perceptual bias. Hemiplegic patients with and without anosognosia, were requested to perform the bimanual task. Patients without anosognosia, fully aware of their left motor deficit, only programed right hand movements, behaving similarly to healthy controls performing the unimanual task. On the contrary, in patients with anosognosia, an effective motor intentionality for the left (plegic) hand influenced visual perception, giving rise to similar perceptual bias as that found in healthy controls actually performing bimanual movements. These findings suggest that having a specific motor representation can lead to different outcomes in the perception of the outside world.

Humans experience their own body as unitary and monolithic in nature. However, recent findings in cognitive neuroscience seem to suggest that body awareness has a complex and multifaceted structure that can be dissociated in several subcomponents, possibly underpinned by different brain circuits. In the present paper, we focus on a recently reported neuropsychological disorder of body ownership in which patients misattribute to themselves someone else's arm and its movements. As first, we briefly review the clinical and functional features of this disorder. Secondly, we attempt to explain the nature of the delusion and to gain new hints regarding the mechanisms subserving the construction and the maintenance of the sense of body ownership in the intact brain functioning.

Pain has an inhibitory effect on the corticospinal excitability that has been interpreted as an evolutionary mechanism, directed to down-regulate cortical activity in order to facilitate rapid protective spinal reflexes. Here, we focused on the link between defensive mechanisms and motor system and we asked whether voluntary actions can modulate the corticospinal excitability during painful stimulations. To this aim, we manipulated the volition-related aspects of our paradigm by comparing conditions in which either the participant (self-generated action) or the experimenter (other-generated action) pressed the button to deliver painful high-intensity transcutaneous electric shocks to the right digit V. MEPs to TMS were recorded from the FDI and APB muscles of the stimulated hand. A compelling agent-dependent modulation of the corticospinal excitability was found, showing, in self-generated compared to other-generated actions, a significantly lower inhibitory effect, as measured by greater MEP amplitude. This finding suggests a top-down modulation of volitional actions on defensive mechanisms, promoting the view that predictive information from the motor system attenuates the responses to the foreseeable adverse events generated by one's own actions as compared to unpredictable events generated by someone else's actions.

Pathological embodiment (E+) is a specific contralesional delusion of body ownership, observed following brain damage, in which patients embody someone else's arm and its movements within their own body schema whenever the contralesional 'alien' arm is presented in a body-congruent position (i.e., 1st person perspective and aligned with the patient's shoulder). This disorder is often associated with spatial neglect, a neurological syndrome in which patients are unaware of stimuli presented in the contralesional (often the left) space. Capitalizing on previous evidence demonstrating that prismatic adaptation of the ipsilesional arm to right-deviating prisms is effective in ameliorating neglect symptoms, here we investigated whether such amelioration also occurs in E+ patients with neglect when prismatic training is performed by the 'alien' embodied arm. Four left neglect patients (one with and three without pathological embodiment) underwent visuomotor prismatic training performed by an 'alien' arm. Specifically, while patients were wearing prismatic goggles shifting the visual field rightward, a co-experimenter's left arm presented in a body-congruent perspective was repeatedly moved toward visual targets by another examiner. In a control condition, the co-experimenter's arm was moved toward the targets from a body-incongruent position (i.e., 3rd person perspective). Neglect symptoms were assessed before and after training through paper-and-pencil tasks. In the E+ patient, neglect improved significantly more in 1st than in 3rd person perspective training, suggesting that prismatic adaptation of the 'alien' embodied arm is effective in modulating spatial representation. Conversely, for control E- patients (not embodying the 'alien' arm), we observed more limited improvements following training. These findings indicate that the 'alien' embodied arm is so deeply embedded in the patient body and motor schema that adaptation to prismatic lenses can affect multiple processing stages, from low level sensory-motor correspondences, to higher level body, motor and spatial maps, similarly as it occurs in normal subjects and neglect patients without pathological embodiment.

Amputees with phantom limb sometimes report vivid experiences of moving their phantom. Is phantom movement only "imaginary", or, instead, it has physiological properties comparable to those pertaining to real movements? To answer this question, we took advantage of the intermanual transfer of sequence learning, occurring when one hand motor skills improve after training with the other hand. Ten healthy controls and two upper-limb amputees (with and without phantom-movement) were recruited. They were asked to perform with the right (intact) hand a fingers-thumb opposition sequence either in Naïve condition or after an active (Real condition) or a mental (Imagery condition) training with the left (phantom) hand. In healthy controls, the results showed different effects after active training (i.e., faster movement duration (MD) with stable accuracy) and after mental training (i.e., increased accuracy with stable MD). Opposite results between moving-phantom case and static-phantom case were found. In the Real condition, after an "active" training with her phantom hand, the moving-phantom case showed a faster performance of the intact hand. This transfer effect was not different from that found in healthy controls, actually performing the active training with an existing hand (Real condition), but, crucially, it was significantly different from both Imagery and Naïve conditions of controls. Contrariwise, in the static phantom case, the performance during the Real condition was significantly different from the Real condition of healthy controls and it was not significantly different from their Imagery and Naïve conditions. Importantly, a significant difference was found when the transfer effect in Real condition was compared between the two phantom cases. Taken together, these findings provide the first evidence that a phantom limb can learn motor skills and transfer them to the intact limb.

A fundamental component of the self-awareness is the sensation that we are acting with our own body. Thus, a coherent sense of self implies the existence of a tight link between the sense of body ownership and the motor system. Here, we investigated this issue by taking advantage of a well-known experimental manipulation of body ownership, i.e., the rubber hand illusion (RHI), during which the subjects perceive a fake hand as part of their own body. To test the effect of the motor system down-regulation on the RHI susceptibility, we designed a sham-controlled study, where the primary motor cortex (M1) excitability was modulated by off-line low-frequency repetitive transcranial magnetic stimulation (rTMS). After rTMS (real or sham), subjects underwent the RHI either on the right hand, contralateral to the inhibited hemisphere (Experiment 1), or on the left hand, ipsilateral to the inhibited hemisphere (Experiment 2). Only in Experiment 1, the procedure strengthened the illusory experience, as proved by a significant increase, in rTMS compared to Sham, of both subjective (Embodiment/Disembodiment Questionnaires) and objective (Proprioceptive Drift) RHI measures. This evidence demonstrates that, when the M1 activity is down-regulated, the sense of body ownership is attenuated and the subjects become more prone to incorporate an alien body part. This, in turn, supports the existence of a mutual interaction between the sense of body ownership and the motor system, shedding new light on the construction of a coherent sense of self as an acting body.

Motor imagery (MI) is the mental simulation of an action without any overt movement. Functional evidences show that brain activity during MI and motor execution (ME) largely overlaps. However, the role of the primary motor cortex (M1) during MI is controversial. Effective connectivity techniques show a facilitation on M1 during ME and an inhibition during MI, depending on whether an action should be performed or suppressed. Conversely, Transcranial Magnetic Stimulation (TMS) studies report facilitatory effects during both ME and MI. The present TMS study shed light on MI mechanisms, by manipulating the instructions given to the participants. In both Experimental and Control groups, participants were asked to mentally simulate a finger-thumb opposition task, but only the Experimental group received the explicit instruction to avoid any unwanted fingers movements. The amplitude of motor evoked potentials (MEPs) to TMS during MI was compared between the two groups. If the M1 facilitation actually pertains to MI per se, we should have expected to find it, irrespective of the instructions. Contrariwise, we found opposite results, showing facilitatory effects (increased MEPs amplitude) in the Control group and inhibitory effects (decreased MEPs amplitude) in the Experimental group. Control experiments demonstrated that the inhibitory effect was specific for the M1 contralateral to the hand performing the MI task and that the given instructions did not compromise the subjects' MI abilities. The present findings suggest a crucial role of motor inhibition when a "pure" MI task is performed and the subjects are explicitly instructed to avoid overt movements.

Converging evidence on voluntary actions underlays the existence of a motor monitoring system able to compare the predicted and the actual consequences of our movements. In this context, both the premotor cortex (PMC) and the posterior parietal cortex (PPC) play a role in action monitoring and awareness. The present study explores the role of PMC and PPC in monitoring involuntary muscle contractions induced by transcranial magnetic stimulation (TMS) over the hand motor area. To this aim, the effects of transcranial direct current stimulation (tDCS) over PMC and PPC were examined. Thirty-six healthy subjects were asked to perform a motor monitoring task (i.e., to verbally report hand twitches induced by TMS) after 10 min of tDCS. Through three experiments, the effects of cathodal, anodal and sham tDCS over the left and the right hemispheres were compared. Our results show that cathodal tDCS over the right PMC does not affect the monitoring of involuntary movements. By contrast, tDCS over both the right and the left PPC affects motor monitoring, depending on the current polarity: while cathodal tDCS increases the feeling of phantom-like movements (which actually did not occur), anodal tDCS impairs the ability to detect involuntary hand twitches (which actually took place). These findings show that the PMC is not involved in motor monitoring of involuntary movements; rather, the PPC, where multisensory stimuli converge and are processed, seems to play a crucial role.

In anosognosia for hemiplegia, patients may claim having performed willed actions with the paralyzed limb despite unambiguous evidence to the contrary. Does this false belief of having moved reflect the functioning of the same mechanisms that govern normal motor performance? Here, we examined whether anosognosics show the same temporal constraints known to exist during bimanual movements in healthy subjects. In these paradigms, when participants simultaneously reach for two targets of different difficulties, the motor programs of one hand affect the execution of the other. In detail, the movement time of the hand going to an easy target (i.e., near and large), while the other is going to a difficult target (i.e., far and small), is slowed with respect to unimanual movements (temporal coupling effect). One right-brain-damaged patient with left hemiplegia and anosognosia, six right-brain-damaged patients with left hemiplegia without anosognosia, and twenty healthy subjects were administered such a bimanual task. We recorded the movement times for easy and difficult targets, both in unimanual (one target) and bimanual (two targets) conditions. We found that, as healthy subjects, the anosognosic patient showed coupling effect. In bimanual asymmetric conditions (when one hand went to the easy target and the other went to the difficult target), the movement time of the non-paralyzed hand going to the easy target was slowed by the ‘pretended’ movement of the paralyzed hand going to the difficult target. This effect was not present in patients without anosognosia. We concluded that in anosognosic patients, the illusory movements of the paralyzed hand impose to the non-paralyzed hand the same motor constraints that emerge during the actual movements. Our data also support the view that coupling relies on central operations (i.e., activation of intention/programming system), rather than on online information from the periphery.

Recent studies show that motor responses similar to those present in one's own pain (freezing effect) occur as a result of observation of pain in others. This finding has been interpreted as the physiological basis of empathy. Alternatively, it can represent the physiological counterpart of an embodiment phenomenon related to the sense of body ownership. We compared the empathy and the ownership hypotheses by manipulating the perspective of the observed hand model receiving pain so that it could be a first-person perspective, the one in which embodiment occurs, or a third-person perspective, the one in which we usually perceive the others. Motor-evoked potentials (MEPs) by TMS over M1 were recorded from first dorsal interosseous muscle, whereas participants observed video clips showing (a) a needle penetrating or (b) a Q-tip touching a hand model, presented either in first-person or in third-person perspective. We found that a pain-specific inhibition of MEP amplitude (a significantly greater MEP reduction in the “pain” compared with the “touch” conditions) only pertains to the first-person perspective, and it is related to the strength of the self-reported embodiment. We interpreted this corticospinal modulation according to an “affective” conception of body ownership, suggesting that the body I feel as my own is the body I care more about.

During the rubber hand illusion (RHI), subjects experience an artificial hand as part of their own body, while the real hand is subject to a sort of 'disembodiment'. Can this altered belief about the body also affect physiological mechanisms involved in body-ownership, such as motor control? Here we ask whether the excitability of the motor pathways to the real (disembodied) hand are affected by the illusion. Our results show that the amplitude of the motor-evoked potentials recorded from the real hand is significantly reduced, with respect to baseline, when subjects in the synchronous (but not in the asynchronous) condition experience the fake hand as their own. This finding contributes to the theoretical understanding of the relationship between body-ownership and motor system, and provides the first physiological evidence that a significant drop in motor excitability in M1 hand circuits accompanies the disembodiment of the real hand during the RHI experience. DOI: http://dx.doi.org/10.7554/eLife.14972.001, eLife digest The feeling of body ownership — that the various parts of your body are all part of you — is something that we typically take for granted. However, brain damage can disrupt this sensation and leave individuals convinced that an arm or a leg is no longer their own. Even in healthy people, the ‘rubber hand illusion’ can temporarily produce a similar phenomenon. Individuals watch a lifelike rubber hand being touched while their own hand – which is hidden from view – is touched at the same time. This creates the feeling that the artificial hand has become part of their body, while their real hand is left in a ‘disembodied’ state. How does the brain generate this illusory sense of ownership and accompanying sense of disembodiment? A person’s ability to move their body is thought to contribute to their feeling of body ownership. Therefore, della Gatta, Garbarini et al. asked whether the brain’s ability to move the real hand changes during the rubber hand illusion. In the experiments, the region of the brain that controls hand movement was artificially stimulated in a number of volunteers. When an individual had been primed by the rubber hand illusion to perceive a fake hand as part of their own body, their brain was temporarily less able to activate the muscles of their real hand. This is as if the brain no longer considered the real hand as part of the body. Thus, the altered sense of body ownership experienced during the rubber hand illusion is not a bizarre fantasy, but corresponds to a physiological reaction that accompanies changes in brain activity. The next step is to further define and quantify the relationship between the sense of body ownership and the control of body movement. Specifically, how does activity in the brain areas that control movement contribute to the sense of body ownership? And how do these brain regions communicate with one another to generate a sense of self? DOI: http://dx.doi.org/10.7554/eLife.14972.002

Do conscious beliefs about the body affect defensive mechanisms within the body? To answer this question we took advantage from a monothematic delusion of bodily ownership, in which brain-damaged patients misidentify alien limbs as their own. We investigated whether the delusional belief that an alien hand is their own hand modulates a subcortical defensive response, such as the hand-blink reflex. The blink, dramatically increases when the threated hand is inside the defensive peripersonal-space of the face. In our between-subjects design, including patients and controls, the threat was brought near the face either by the own hand or by another person’s hand. Our results show an ownership-dependent modulation of the defensive response. In controls, as well as in the patients’ intact-side, the response enhancement is significantly greater when the threat was brought near the face by the own than by the alien hand. Crucially, in the patients’ affected-side (where the pathological embodiment occurs), the alien (embodied) hand elicited a response enhancement comparable to that found when the threat is brought near the face by the real hand. These findings suggest the existence of a mutual interaction between our conscious beliefs about the body and the physiological mechanisms within the body.

In Motor Neglect (MN) syndrome, a specific impairment in non-congruent bimanual movements has been described. In the present case-control study, we investigated the neuro-functional correlates of this behavioral deficit. Two right-brain-damaged (RBD) patients, one with (MN+) and one without (MN−) MN, were evaluated by means of functional Magnetic Resonance Imaging (fMRI) in a bimanual Circles-Lines (CL) paradigm. Patients were requested to perform right-hand movements (lines-drawing) and, simultaneously, congruent (lines-drawing) or non-congruent (circles-drawing) left-hand movements. In the behavioral task, MN− patient showed a bimanual-coupling-effect, while MN+ patient did not. The fMRI study showed that in MN−, a fronto-parietal network, mainly involving the pre-supplementary motor area (pre-SMA) and the posterior parietal cortex (PPC), was significantly more active in non-congruent than in congruent conditions, as previously shown in healthy subjects. On the contrary, MN+ patient showed an opposite pattern of activation both in pre-SMA and in PPC. Within this fronto-parietal network, the pre-SMA is supposed to exert an inhibitory influence on the default coupling of homologous muscles, thus allowing the execution of non-congruent movements. In MN syndrome, the described abnormal pre-SMA activity supports the hypothesis that a failure to inhibit ipsilesional motor programs might determine a specific impairment of non-congruent movements.

Previous evidence has shown that active tool-use can reshape one's own body schema, extend peripersonal space and modulate the representation of related body parts. Here we investigate the effect of tool-use training on length representation of the contralesional forearm in brain-damaged hemiplegic patients who manifested a pathological embodiment of other people body parts. Four patients and 20 aged-matched healthy-controls were asked to estimate the mid-point of their contralesional forearm before and after 15. min of tool-use training (i.e. retrieving targets with a garbage plier). In the case of patients, training was always performed by the examiner's (alien) arm acting in two different positions, aligned (where the pathological embodiment occurs; E+ condition) or misaligned (where the pathological embodiment does not occur; E- condition) relative to the patients' shoulder. Healthy controls performed tool-use training either with their own arm (action condition) or observing the examiner's arm performing the task (observation condition), handling (observation with-tool condition) or not (observation without-tool condition) a similar tool. Crucially, in the E+ condition, when patients were convinced to perform the tool-use training with their own paralyzed arm, a significant overestimation effect was found (as in the Action condition with normal subjects): patients mislocated their forearm midpoint more proximally to the hand in the post- than in the pre-training phase. Conversely, in the E- condition, they did not show any overestimation effect, similarly to healthy subjects in the observation condition (neither in the with-tool nor in the without-tool condition significant overestimation effects were found). These findings show the existence of a tight link between spatial, motor and bodily representations and provide strong evidence that a pathological sense of body ownership can extend to intentional motor processes and modulate the sensory map of action-related body parts.

OBJECTIVES Previous findings suggest that, in anosognosic patients, their illusory motor experience is based on a "normal" motor intention and planning for the paralyzed limbs. However, these studies involved proximal muscles (shoulder) that can be mediated by the ipsilateral (intact) cortex more than distal muscles (fingers). In the present study, we asked whether, in anosognosic patients, the spared motor intention for the paralyzed limb can go as far as to influence kinematic parameters of distal movements. METHOD Six hemiplegic patients (1 with and 5 without anosognosia) were required to reach and grasp with both hands targets of the same or different size, attached to a plinth. Maximum grip aperture of the right (intact) hand was recorded using an infrared motion capture system. All patients were evaluated with a specific battery for anosognosia and different neurpsychological test. RESULTS In the patient affected by anosognosia for hemiplegia, the grip aperture of the healthy hand was influenced by the intended (but not executed) movement of the plegic hand when the patient was trying to reach to grasp targets of different size, F(2, 14) = 11.87, p < .001. Patients affected by hemiplegia (without anosognosia) didn't show any interference effect between the plegic and healthy hand even when they were asked to reach to grasp targets of different size. CONCLUSIONS Our results confirm the hypothesis that a spared intention-programming system within the contralateral (damaged) cortex can go as far as to influence distal kinematic parameters of the healthy hand of patients affected by anosognosia for hemiplegia.

A brief overview of the most important cognitive alterations as a consequence of focal brain damage is presented. The discipline that studies the relationship between brain damage and higher cognitive functions is called neuropsychology and is mainly based on correlations between anatomy and function. Leaving aside the importance of the clinical impact that neuropsychology has on patients' treatment, its main experimental aim is to draw inferences from the pathological conditions to normal functions, on the assumption that if the lesion to a particular brain area or circuit has provoked a specific deficit, then that part of the brain is involved in or is necessary for sustaining the normal function. The main classical neuropsychological syndromes related to perceptual, spatial, linguistic, motor, and memory domain will be discussed, with a final part on syndromes in which conscious awareness is specifically altered.

Patients with a neurologically based loss of tactile processing on the contralesional side of the body can firmly deny the deficit (i.e., anosognosia for hemianesthesia). Previous studies attempted to feature the disease in both clinical and anatomo-functional terms. However, the picture is still incomplete and, most importantly, to date it is unclear whether and to which extent it can shed light on the mechanisms subserving tactile processing in the intact brain. Here we will briefly review the literature and we will put forward a possible anatomo-functional interpretation of anosognosia for hemianesthesia.