Abstract
Multisensory integration (MSI) deficits in patients with Parkinson's Disease (PD) have recently attracted growing interest in both clinical and research realms, MSI being crucial in maintaining well-coordinated responses to external stimuli. In this framework, we exploited the Rubber Hand Illusion (RHI), an experimental procedure that induces healthy individuals to embody a fake hand by integrating multisensory body-related cues, to address potential alterations of the embodiment phenomenon in PD. Specifically, we leveraged a visuo-tactile (VT; Experiment 1) and a visuo-motor (VM; Experiment 2) RHI version and applied it to 32 PD patients and age-matched controls. Classical RHI measures (i.e., ownership and agency questionnaires, proprioceptive drift) were collected. Questionnaires revealed typical VT- and VM-RHI patterns in patients, although diminished as compared to controls. Crucially, proprioceptive drift showed an abolishment of VM- (but not VT-) RHI effect in patients, advocating for a channel-specific embodiment abnormality that emerged only when the motor system, involved in the pathology, was challenged by the RHI. Interestingly, such a deficit emerged specifically when proprioceptive drift, engaging a motor response, was considered as a measure. We speculatively interpret this finding in light of the neural degeneration of basal ganglia in PD, being these structures engaged in visuo-motor integration.