This study aims to evaluate the representation of action peripersonal space (PPS) in subjects suffering from unilateral segmental exclusion syndrome of the upper limb compared to healthy control subjects. Segmental exclusion is defined by non-use or under-use of a limb segment without central nervous system damage. The study hypothesizes that this syndrome leads to a modification (shrinkage) of the PPS representation. Participants will perform reachability judgments in a Virtual Reality (VR) environment.

Segmental exclusion syndrome often occurs after limb trauma and manifests as a neglect-like behavior of peripheral origin, sometimes associated with Complex Regional Pain Syndrome (CRPS). The study explores whether the lack of limb use affects the representation of peripersonal space (PPS)-the space immediately surrounding the body where interactions with objects occur.

The study is monocentric, observational, with a matched control group. Participants will undergo:

Clinical assessment (questionnaires on pain, anxiety, body perception, and kinesiophobia).

A Virtual Reality (VR) test (approx. 40 minutes). In VR, participants will judge whether a cylinder presented at different distances and angles is reachable without moving (Perceived Reachable Distance - DMA-p). This will be compared to their Real Reachable Distance (DMA-r).

The goal is to measure the error of judgment to assess PPS representation and check for correlations with body schema disturbances or functional impairment

Inclusion Criteria (patients):

• Age ≥ 18 years.
• Presenting unilateral exclusion symptom of the upper limb or part of the hand evolving for > 3 months.
• No contraindication to force work in daily activities.
• For patients with finger exclusion: at least 2 perturbed items related to exclusion on tests 3 and 4 of the "Bilan 400 points".
• Affiliated to a social security scheme.
• Able to understand simple orders.

Inclusion Criteria (Controls):

• Age ≥ 18 years.
• No history of upper limb impairment with sequelae.

Exclusion Criteria (All):

• Visual impairments.
• Central neurological pathology.
• Unstabilized psychiatric pathology.
• Communication or comprehension difficulties.
• Under legal protection or unable to consent.
• Pregnant or breastfeeding women.
• Cervical pathology contraindicating VR headset use.
• Epilepsy.
• Upper limb pathology unrelated to exclusion.
• Inability to stand for 40 minutes.

he study population consists of two groups recruited at the Institut Régional de Réadaptation (Centre Louis Pierquin, UGECAM Nord-Est) in Nancy, France.

Patients with Exclusion: Participants are selected from patients receiving routine care (full hospitalization or day hospital) at the center. They are identified based on a functional assessment ("Bilan 400 points") showing specific impairments related to unilateral upper limb exclusion evolving for more than 3 months.

Healthy Controls: Asymptomatic volunteers are recruited through the social or family network of the investigators and current participants, as well as via posters displayed in the UGECAM centers.