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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.

In the study of bodily awareness, the predictive coding theory has revealed that our brain continuously modulates sensory experiences to integrate them into a unitary body representation. Indeed, during multisensory illusions (e.g., the rubber hand illusion, RHI), the synchronous stroking of the participant’s concealed hand and a fake visible one creates a visuotactile conflict, generating a prediction error. Within the predictive coding framework, through sensory processing modulation, prediction errors are solved, inducing participants to feel as if touches originated from the fake hand, thus ascribing the fake hand to their own body. Here, we aimed to address sensory processing modulation under multisensory conflict, by disentangling somatosensory and visual stimuli processing that are intrinsically associated during the illusion induction. To this aim, we designed two EEG experiments, in which somatosensory- (SEPs; Experiment 1; N = 18; F = 10) and visual-evoked potentials (VEPs; Experiment 2; N = 18; F = 9) were recorded in human males and females following the RHI. Our results show that, in both experiments, ERP amplitude is significantly modulated in the illusion as compared with both control and baseline conditions, with a modality-dependent diametrical pattern showing decreased SEP amplitude and increased VEP amplitude. Importantly, both somatosensory and visual modulations occur in long-latency time windows previously associated with tactile and visual awareness, thus explaining the illusion of perceiving touch at the sight location. In conclusion, we describe a diametrical modulation of somatosensory and visual processing as the neural mechanism that allows maintaining a stable body representation, by restoring visuotactile congruency under the occurrence of multisensory conflicts. [ABSTRACT FROM AUTHOR]

This article explores the relationship between sensory perception, multisensory integration, and bodily self-representation. It includes seven novel publications that offer insights into how our brains construct and integrate sensory experiences, reshaping our understanding of perception and consciousness. The studies cover various topics, such as the impact of brain damage on somatosensory processing, rehabilitation techniques, dysregulated eating behaviors, self-face representation in children, naturalistic limb movements, and the neural differences between airplane pilots and non-pilots. The document also discusses a study that used virtual reality tasks to examine the impact of congruent and incongruent sensory-motor interactions on spatial perception, finding that participants exhibited a bias in left-right tactile localization and a shift in the perceived body midline. These findings contribute to our understanding of spatial biases in virtual environments and have implications for bodily perception. [Extracted from the article]

It has been proposed that seeing human movement or activity (M), while trying to say what the static Rorschach inkblot design look like, is accompanied by Mirror Neuron System (MNS)-like mirroring activity in the brain. The present study aimed to investigate whether the Rorschach cards eliciting M responses could affect the excitability of the motor cortex by recording motor evoked potentials (MEPs) elicited by single-pulse TMS over the primary motor cortex (M1). We hypothesized that Rorschach inkblot stimuli triggering the viewer's experience of human movement would increase corticospinal excitability. Twenty-one healthy volunteers (15 women) participated in the preliminary experiment, while another different sample of twenty-two healthy participants (11 women) ranging in age from 21 to 41 years was enrolled in the main experiment. Our results showed that the Rorschach cards known to be associated with a high number of M responses elicited human movement both as automatic internal sensations and as verbal production of responses involving human movement. However, contrary to our hypothesis, the reported internal feeling of human movement had no corresponding physiological counterpart, as the amplitude of MEPs did not increase. Possible and innovative explanations for the involvement of bottom-up and top-down processes were provided. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

To investigate the relationship between the sense of body ownership and motor control, we capitalized on a rare bizarre disorder wherein another person's hand is misattributed to their own body, i.e., a pathological form of embodiment (E+). Importantly, despite E+ is usually associated with motor deficits, we had the opportunity to test two E+ patients with spared motor function, thus able to perform a reaching task. Crucially, these patients had proprioceptive deafferentation, allowing us to purely isolate the embodiment-dependent effect from proprioception-dependent ones that are usually associated in experimental manipulations of body ownership in healthy participants. Previous evidence suggests that the reaching movement vector is attracted towards an embodied hand during the rubber hand illusion (RHI). However, these results are confounded by the spared proprioception, whose modulation alone could explain the effects on reach planning. The neuropsychological approach employed here provides unambiguous evidence about the role of body ownership in reach planning. Indeed, three brain-damaged patients with proprioceptive deafferentation, two E+ and a well-matched control patient without pathological embodiment (E-), and 10 age-matched healthy controls underwent a reaching task wherein they had to reach for a target from a fixed starting point, while an alien hand (the co-experimenter's) was placed on the table. Irrespective of proprioception, damaged in all patients, only in E+ patients reaching errors were significantly more shifted consistently with the pathological belief, i.e., as if they planned movements from the position of the alien (embodied) hand, as compared to controls. Furthermore, with an additional experiment on healthy participants, we demonstrated that reaching errors observed during the RHI correlate with the changes in ownership. In conclusion, our neuropsychological approach suggests that when planning a reach, we do so from where our owned hand is and not from its physical location. [ABSTRACT FROM AUTHOR]

Although clinical neuroscience and the neuroscience of consciousness have long sought mechanistic explanations of tactile-awareness disorders, mechanistic insights are rare, mainly because of the difficulty of depicting the fine-grained neural dynamics underlying somatosensory processes. Here, we combined the stereo-EEG responses to somatosensory stimulation with the lesion mapping of patients with a tactile-awareness disorder, namely tactile extinction. Whereas stereo-EEG responses present different temporal patterns, including early/phasic and long-lasting/tonic activities, tactile-extinction lesion mapping co-localizes only with the latter. Overlaps are limited to the posterior part of the perisylvian regions, suggesting that tonic activities may play a role in sustaining tactile awareness. To assess this hypothesis further, we correlated the prevalence of tonic responses with the tactile-extinction lesion mapping, showing that they follow the same topographical gradient. Finally, in parallel with the notion that visuotactile stimulation improves detection in tactile-extinction patients, we demonstrated an enhancement of tonic responses to visuotactile stimuli, with a strong voxel-wise correlation with the lesion mapping. The combination of these results establishes tonic responses in the parietal operculum as the ideal neural correlate of tactile awareness. [ABSTRACT FROM AUTHOR]

The human face is one of the most salient stimuli in the environment. It has been suggested that even basic face‐like configurations (three dots composing a downward pointing triangle) may convey salience. Interestingly, stimulus salience can be signaled by mismatch detection phenomena, characterized by greater amplitudes of event‐related potentials (ERPs) in response to relevant novel stimulation as compared to non‐relevant repeated events. Here, we investigate whether basic face‐like stimuli are salient enough to modulate mismatch detection phenomena. ERPs are elicited by a pair of sequentially presented visual stimuli (S1‐S2), delivered at a constant 1‐s interval, representing either a face‐like stimulus (Upright configuration) or three neutral configurations (Inverted, Leftwards, and Rightwards configurations), that are obtained by rotating the Upright configuration along the three different axes. In pairs including a canonical face‐like stimulus, we observe a more effective mismatch detection mechanism, with significantly larger N270 and P300 components when S2 is different from S1 as compared to when S2 is identical to S1. This ERP modulation, not significant in pairs excluding face‐like stimuli, reveals that mismatch detection phenomena are significantly affected by basic face‐like configurations. Even though further experiments are needed to ascertain whether this effect is specifically elicited by face‐like configuration rather than by particular orientation changes, our findings suggest that face essential, structural attributes are salient enough to affect change detection processes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract Mutual adaptive timing (MAT), the capacity to adapt one's timing to the timing of a partner, is a form of interpersonal entrainment necessary to play music in ensemble. To this respect, two questions can be advanced. First, whether MAT can be seen also in non-musician populations. This might imply interesting theoretical consequences with respect to the hypothesis of an innate inter-subjective musicality. Second, whether subject's MAT can be influenced by the position of the partner's body. This might imply that MAT modulation is guided by changes in the feeling of body ownership and agency, which in turn would affect subject's cortico-spinal excitability patterns. In order to test these hypotheses, we employed an alternate joint finger tapping task (which can be easily carried out without being expert performers), while single-pulse TMS was delivered on M1. This experimental design allowed us to test MAT in non-musicians and to study cortico-spinal excitability patterns while manipulating partners' body position. Ownership and agency were tested by ad hoc questionnaires. We first found that MAT was present also in a non-musicians population and was not affected by the position of the partner, thus pointing to the universality of such a joint proto-musical competence. Moreover, cortico-spinal excitability was similar when the subject tapped alone ('solo condition') and when the subject tapped with the partner in a position congruent with the subject's body (the 'egocentric condition'). On the contrary, when the subject tapped with the partner placed in front of him (the 'allocentric' condition') cortico-spinal excitability was higher with respect to the solo and egocentric conditions. These results show that, despite the fact that the partner was present both in the egocentric and in the allocentric position, only the allocentric condition was treated as a social ensemble. Interestingly, in the egocentric condition the partner's body seemed to be treated as the subject's 'own' body. The subjective feeling of ownership and agency were coherent with the physiological data. Highlights • Mutual adaptive timing (MAT) was found in pairs of non musicians tapping in alternation. • MAT is not affected by the partners' body position, allocentric (A) or egocentric (E). • In E the other's hand was treated as one's own while in A as social ensemble. • Motor evoked potentials to TMS over M1 were higher in the A condition. [ABSTRACT FROM AUTHOR]