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Background: Phantom boarder (PB) is the sensation that someone uninvited is in the patient's home despite evidence to the contrary. It is mostly reported by patients with neurodegenerative disorders such as Alzheimer's disease, dementia with Lewy bodies or Parkinson's disease (PD). Presence hallucination (PH) is frequent in neurodegenerative disease, shares several aspects with PB, and is the sensation that someone is nearby, behind or next to the patient (when nobody is actually there). Recent work developed a sensorimotor method to robotically induce PH (robot‐induced PH, riPH) and demonstrated that a subgroup of PD patients showed abnormal sensitivity for riPH. Objective: We investigated if PD patients with PB (PD‐PB) would (1) show elevated sensitivity for riPH that (2) is comparable to that of patients reporting PH, but not PB (PD‐PH). Methods: We studied the sensitivity of non‐demented PD patients in a sensorimotor stimulation paradigm, during which three groups of patients (PD‐PB; PD‐PH; PD patients without hallucinations, PD‐nPH) were exposed to different conditions of conflicting sensorimotor stimulation. Results: We show that PD‐PB and PD‐PH groups had a higher sensitivity to riPH (compared to PD‐nPH). PD‐PB and PD‐PH groups did not differ in riPH sensitivity. Together with interview data, these behavioral data on riPH show that PB is associated with PH, suggesting that both share some underlying brain mechanisms, although interview data also revealed phenomenological differences. Conclusions: Because PD‐PB patients did not suffer from dementia nor delusions, we argue that these shared mechanisms are of perceptual‐hallucinatory nature, involving sensorimotor signals and their integration. [ABSTRACT FROM AUTHOR]

Keywords: Parkinson's disease psychosis; non-motor symptoms; illusions; sensorimotor processing; procedural activities EN Parkinson's disease psychosis non-motor symptoms illusions sensorimotor processing procedural activities 127 129 3 01/05/22 20220101 NES 220101 The presence hallucination (PH) is the sensation that somebody is nearby when no one is actually there. Affecting up to 60% of patients with Parkinson's disease (PD) and occurring early, PHs are clinically relevant for indicating potential negative clinical outcome.1-3 Recently, we have induced PHs safely in patients with PD by generating sensorimotor conflicts while patients repeatedly actuated a robotic device providing tactile feedback.4 Patients with symptomatic PHs were more sensitive to such sensorimotor stimulation than those without. The two patients were recruited in Switzerland from La Tour Hospital (Geneva) and Geneva University Hospital and were identified in the setting of an ongoing study on hallucinations in PD. [Extracted from the article]