Reachability judgments in upper-limb segmentary exclusion syndrome explore action-related aspects of peripersonal space

Peripersonal space (PPS) refers to the multisensory representation of the space surrounding the body and is shaped by motor experience and body representation. Upper limb segmentary exclusion syndrome (UL-SES) is characterized by persistent underuse of a limb segment without identifiable neurological lesion and is associated with altered body perception. We investigated action-related aspects of PPS in UL-SES using a previously validated reachability-judgment task.

Fifteen participants with UL-SES and 30 healthy participants completed a task comparing perceived maximum reachable distance with objective maximum reachable distance. Body representation disturbances were assessed using the Bath CRPS Body Perception Disturbance Scale (BATH). Contrary to our hypothesis, Reachability judgments did not differ between the affected and unaffected sides in UL-SES participants, and no significant group difference was observed between UL-SES and healthy participants.

In healthy participants, reachability overestimation was greater on the dominant than on the non-dominant side, whereas no dominance effect was observed in UL-SES participants. Higher BATH scores were associated with lower signed RJ-error, i.e. reduced overestimation of reachable space, on the affected side. These findings provide no evidence for major alterations in reachability judgments associated with limb exclusion, while suggesting that body representation influences the estimation of action possibilities in individuals with UL-SES.

The authors thank all the participants for their participation in the study, the paramedical staff, Dr Anne Foisneau Lottin and Anne-Gabrielle François of the Louis Pierquin Centre of the Regional Rehabilitation Institute, and the University Institute for Health Engineering (Paris Sorbonne Universities). The author received No Funding for this work. Louis Pierquin Centre of the Regional Institute of Rehabilitation, UGECAM Nord-Est, Nancy, France Pierrick Herbé, Marion Birck, Amélie Touillet, Jonathan Pierret & Jean Paysant Université de Lorraine, DevAH, 54000, Nancy, France Amélie Touillet, Jonathan Pierret & Jean Paysant UPMC Univ Paris 06, CNRS, UMR 7222, INSERM U1150, Institute of Intelligent Systems and Robotics (ISIR), Sorbonne University, Paris, France CNRS, ISM, Aix Marseille Université, Marseille, France The authors declare no competing interests.

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