Exploring specific alterations at the explicit and perceptual levels in sense of ownership, agency, and body schema in Functional Motor Disorder: A pilot comparative study with Irritable Bowel Syndrome.

Functional Motor Disorders (FMD) consists in symptoms of altered motor function not attributable to typical neurological and medical conditions. This study aimed to explore explicit and perceptual measures of Sense of Ownership, Agency, and Body Schema in FMD patients, and assess whether these alterations are specific to FMD or shared with other functional disturbances. Twelve FMD patients, ten with Irritable Bowel Syndrome (IBS, a functional gastrointestinal disorder) and fifteen healthy controls (HC) underwent: (i) the Mirror Box Illusion (MBI), requiring participants to perform tapping movements with their dominant hand concealed from sight, while visual feedback was provided by an alien hand under visuo-motor congruency or incongruency conditions; (ii) a Forearm Bisection Task before and after exposure to the MBI, and the Embodiment Questionnaire after the MBI, as perceptual and explicit indices of the embodiment illusion, respectively.

Multisensory conflict affects body schema and reaching space.

Multisensory integration plays a crucial role in building the sense of body ownership, i.e., the perceptual status of one's body for which the body is perceived as belonging to oneself.

Sense of agency in schizophrenia: A reconciliation of conflicting findings through a theory-driven literature review.

The sense of agency is the experience of being the author of self-generated actions and their outcomes. Both clinical manifestations and experimental evidence suggest that the agency experience and the mechanisms underlying agency attribution may be dysfunctional in schizophrenia. Yet, studies investigating the sense of agency in these patients show seemingly conflicting results: some indicated under-attribution of self-agency (coherently with certain positive symptoms), while others suggested over-attribution of self-agency.

Forearm bisection task suggests an alteration in body schema in patients with functional movement disorders (motor conversion disorders).

Objectives: To explore potential alterations of the Body Schema, the implicit sensorimotor representation of one's own body, in patients with Functional Movement Disorders (FMD, Motor Conversion Disorders), characterized by neurological symptoms of altered voluntary motor function that cannot be explained by typical medical conditions. This investigation is prompted by the potential dissociation from their reportedly intact sense of ownership.

Methods: 10 FMD patients and 11 healthy controls (HC) underwent the Forearm Bisection Task, aimed at assessing perceived body metrics, which consists in asking the subject, blindfolded, to repeatedly point at the perceived middle point of their dominant forearm with the index finger of their contralateral hand, and a psychometric assessment for anxiety, depression, alexithymia, and tendency to dissociation.

Sensory Attenuation Deficit and Auditory Hallucinations in Schizophrenia: A Causal Mechanism or a Risk Factor? Evidence From Meta-Analyses on the N1 Event-Related Potential Component.

Background: Sensory attenuation (SA), the dampened perception of self-generated sensory information, is typically associated with reduced event-related potential signals, such as for the N1 component of auditory event-related potentials. SA, together with efficient monitoring of intentions and actions, should facilitate the distinction between self-generated and externally generated sensory events, thereby optimizing interaction with the world. According to many, SA is deficient in schizophrenia.

The influence of arm posture on the Uznadze haptic aftereffect.

The role of arm posture in the Uznadze haptic aftereffect is investigated: two identical test stimuli (i.e., spheres, TS) clenched simultaneously appear haptically different in size after hands have been adapted to two spheres (adapting stimuli, AS) differing in size: the hand adapted to a small AS feels TS bigger than the hand adapted to a big AS.

Sense of body ownership and body agency in schizophrenia.

Recent research suggests that embodiment sensations (sense of body ownership and sense of body agency) are altered in schizophrenia. Using a mirror box illusion setup, we tested if the anomalous embodiment experience depends on deficient processing of visuomotor synchrony, disrupted processing of movement mode, or both. The task required participants to press a lever with their index while looking at the image of the experimenter's hand moving on a similar lever.

I am the metre: The representation of one's body size affects the perception of tactile distances on the body.

Humans must ground the perception of one's body in a mental representation to move in space and interact with objects. This representation can be temporarily altered artificially. In the full-body illusion (FBI), participants see a virtual (or filmed) body receiving a tactile stimulation.

Body-Space Interactions: Same Spatial Encoding but Different Influence of Valence for Reaching and Defensive Purposes.

The space around our body, the so-called peripersonal space, is where interactions with nearby objects may occur. "Defensive space" and "Reaching space", respectively, refer to two opposite poles of interaction between our body and the external environment: protecting the body and performing a goal-directed action. Here, we hypothesized that mechanisms underlying these two action spaces are differentially modulated by the valence of visual stimuli, as stimuli with negative valence are more likely to activate protective actions whereas stimuli with positive valence may activate approaching actions.

Back in control of intentional action: Improvement of ideomotor apraxia by mirror box treatment.

Objectives: A novel method of rehabilitation for ideomotor apraxia (IMA), using a modified version of the mirror box (MB), is proposed. The rationale is based on the theory that disrupted body representation occurs in IMA and that MB training may improve body representation. In the present MB training, patients observed and reproduced movements made by the experimenter in a mirror.

Bliss in and Out of the Body: The (Extra)Corporeal Space Is Impervious to Social Pleasant Touch.

Slow, gentle stimulation of hairy skin is generally accompanied by hedonic sensations. This phenomenon, also known as (positive) affective touch, is likely to be the basis of affiliative interactions with conspecifics by promoting inter-individual bindings. Previous studies on healthy humans have demonstrated that affective touch can remarkably impact behavior.

Psychometric properties of the embodiment scale for the rubber hand illusion and its relation with individual differences.

The Rubber Hand Illusion (RHI) opened the investigation of the sense of body ownership in healthy people. By putting in slight contrast vision touch and proprioception, healthy people embody a fake hand in one's body representation. The easiness of the procedure, typically measured with a set of questions that capture the subjective experience, favoured its blooming.

Behavioral and Physiological Evidence of a favored Hand Posture in the Body Representation for Action.

Motor planning and execution require a representational map of our body. Since the body can assume different postures, it is not known how it is represented in this map. Moreover, is the generation of the motor command favored by some body configurations? We investigated the existence of a centrally favored posture of the hand for action, in search of physiological and behavioral advantages due to central motor processing.

See What You Feel: A Crossmodal Tool for Measuring Haptic Size Illusions.

The purpose of this research is to present the employment of a simple-to-use crossmodal method for measuring haptic size illusions. The method, that we call , was tested by employing Uznadze's classic haptic aftereffect in which two spheres physically identical (test spheres) appear different in size after that the hands holding them underwent an adaptation session with other two spheres (adapting spheres), one bigger and the other smaller than the two test spheres. To measure the entity of the illusion, a three-dimensional visual scale was created and participants were asked to find on it the spheres that corresponded in size to the spheres they were holding in their hands out of sight.

Body illusion and affordances: the influence of body representation on a walking imagery task in virtual reality.

It is well known that our body works as a fundamental reference when we perform visuo-perceptual judgements in spatial surroundings, and that body illusions can modify our perception of size and distance of objects in space. To date, however, few studies have evaluated whether or not a body illusion could have a significant impact on the way individuals perceive to move within the environment. Here, we used a full-body illusion paradigm to verify the hypothesis that an altered representation of the legs of the individuals influences their time-to-walk estimation while imaging to reach objects in a virtual environment.

No efficacy of transcranial direct current stimulation on chronic migraine with medication overuse: A double blind, randomised clinical trial.

Background: Transcranial direct current stimulation was suggested to provide beneficial effects in chronic migraine, a condition often associated with medication overuse for which no long-term therapy is available.

Methods: We conducted a randomised controlled trial to assess long-term efficacy of transcranial direct current stimulation. Adults diagnosed with chronic migraine and medication overuse were assigned to receive in a 1:1:1 ratio anodal, cathodal, or sham transcranial direct current stimulation daily for five consecutive days, along with standardised drug withdrawal protocol.

Sensory- and Action-Oriented Embodiment of Neurally-Interfaced Robotic Hand Prostheses.

Embodiment is the percept that something not originally belonging to the self becomes part of the body. Feeling embodiment for a prosthesis may counteract amputees' altered image of the body and increase prosthesis acceptability. Prosthesis embodiment has been studied longitudinally in an amputee receiving feedback through intraneural and perineural multichannel electrodes implanted in her stump.

A new clinical evaluation of asomatognosia in right brain damaged patients using visual and reaching tasks.

Introduction: The term asomatognosia refers to a unilateral disturbance of body ownership following a cerebrovascular incident. Patients with asomatognosia consider the contralesional limbs as missing or having disappeared from awareness. This neuropsychological disorder modifies body ownership in terms of perceptual experience, visual identification and sense of belonging of contralesional body parts.

Electrophysiological correlates of action observation treatment in children with cerebral palsy: A pilot study.

Action Observation Treatment (AOT) has been shown to be effective in the functional recovery of several clinical populations. However, little is known about the neural underpinnings of the clinical efficacy of AOT in children with Cerebral Palsy (CP). Using electroencephalography (EEG), we recorded µ rhythm desynchronization as an index of sensorimotor cortex modulation during a passive action observation task before and after AOT.

Peripersonal space is diversely sensitive to a temporary vs permanent state of anxiety.

Peripersonal Space (PPS) is the multisensory space immediately surrounding our body. Visual and tactile stimuli here are promptly processed, since their interaction gradually strengthens as the distance between visual stimulus and the body decreases. Recently, a modified version of the Temporal Order Judgment (TOJ) task was proposed to assess PPS based on the spatial congruence between somatosensory and visual stimuli.

The dynamic nature of the sense of ownership after brain injury. Clues from asomatognosia and somatoparaphrenia.

The sense of ownership is the feeling that a body part belongs to ourselves. Brain damage may disrupt this feeling, leading to somatoparaphrenia (SP), i.e.

Defective Embodiment of Alien Hand Uncovers Altered Sensorimotor Integration in Schizophrenia.

The observation that people with schizophrenia misattribute the source of their own actions has led to the hypothesis that they suffer from altered sensorimotor processes underlying sense of agency. Furthermore, rubber hand studies suggest an abnormal experience of embodiment in schizophrenia. However, this latter finding is based on a procedure that elicits ownership sensations for a fake hand by visuo-tactile stimulation, leaving the agency subcomponent of embodiment relatively untouched.

The standard posture of the hand.

Perceived limb position is known to rely on sensory signals and motor commands. Another potential source of input is a standard representation of body posture, which may bias perceived limb position toward more stereotyped positions. Recent results show that tactile stimuli are processed more efficiently when delivered to a thumb in a relatively low position or an index finger in a relatively high position.

Somatosensory cortical representation of the body size.

The knowledge of the size of our own body parts is essential for accurately moving in space and efficiently interact with objects. A distorted perceptual representation of the body size often represents a core diagnostic criterion for some psychopathological conditions. The metric representation of the body was shown to depend on somatosensory afferences: local deafferentation indeed causes a perceptual distortion of the size of the anesthetized body part.

Different tool training induces specific effects on body metric representation.

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.