Hallucinations in Parkinson’s disease (PD) are disturbing and frequent non-motor symptoms and constitute a major risk factor for psychosis and dementia. We report a robotics-based approach applying conflicting sensorimotor stimulation, enabling the induction of presence hallucinations (PHs) and the characterization of a subgroup of patients with PD with enhanced sensitivity for conflicting sensorimotor stimulation and robot-induced PH. We next identify the fronto-temporal network of PH by combining MR-compatible robotics (and sensorimotor stimulation in healthy participants) and lesion network mapping (neurological patients without PD). This PH-network was selectively disrupted in an additional and independent cohort of patients with PD, predicted the presence of symptomatic PH, and associated with cognitive decline. These robotics-neuroimaging findings extend existing sensorimotor hallucination models to PD and reveal the pathological cortical sensorimotor processes of PH in PD, potentially indicating a more severe form of PD that has been associated with psychosis and cognitive decline.

Background Minor hallucinations and well‐structured hallucinations are considered in the severity continuum of the psychotic spectrum associated with Parkinson's disease. Although their chronological relationship is largely unknown, the spatial patterns of brain atrophy in these 2 forms of hallucinations partially overlap, suggesting they share similar pathophysiological processes. Functional connectivity studies show that disruption of functional networks involved in perception and attention could be relevant in the emergence of well‐structured hallucinations. However, functional neuroimaging studies in patients with isolated minor hallucinations are lacking. The objectives of this study were to explore the structural and functional changes underlying minor hallucinations. Methods We compared patients with (n = 18) and without (n = 14) minor hallucinations using a multimodal structural (gray‐matter volume voxel‐based morphometry) and functional (seed‐to‐whole‐brain resting‐state functional MRI) neuroimaging study. Results Coincident with previously described structural changes in well‐structured hallucinations in Parkinson's disease, patients with minor hallucinations exhibited gray‐matter atrophy with significant voxel‐wise differences in visuoperceptual processing areas and core regions of the default mode network. Functional connectivity changes consisted of altered connectivity within the default mode network, reduced negative correlation with task‐positive network, and aberrant connectivity between posterior regions of the default mode network and visual‐processing areas. These changes are in accordance with the attentional networks hypothesis proposed for well‐structured hallucinations. Conclusions Although longitudinal studies are needed to assess the potential role of minor hallucinations as an early clinical biomarker of progression to well‐structured hallucinations, the present findings show that the 2 phenomena share similar structural and functional brain correlates. © 2018 International Parkinson and Movement Disorder Society