Sensorimotor hallucinations in Parkinson’s disease

Abstract

Hallucinations in Parkinson's disease (PD) are one of the most disturbing non-motor symptoms, affect half of the patients, and constitute a major risk factor for adverse clinical outcomes such as psychosis and dementia. Here we report a robotics-based approach, enabling the induction of a specific clinically-relevant hallucination (presence hallucination, PH) under controlled experimental conditions and the characterization of a PD subgroup with enhanced sensorimotor sensitivity for such robot-induced PH. Using MR-compatible robotics in healthy participants and lesion network mapping analysis in neurological non-PD patients, we identify a fronto-temporal network that was associated with PH. This common PHnetwork was selectively disrupted in a new and independent sample of PD patients and predicted the presence of symptomatic PH. These robotics-neuroimaging findings determine the behavioral and neural mechanisms of PH and reveal pathological cortical sensorimotor processes of PH in PD, identifying a more severe form of PD associated with psychosis and cognitive decline.

Thought consciousness and source monitoring depend on robotically controlled sensorimotor conflicts and illusory states

“…Previous work has shown that the robot-induced FoP results from the manipulation of sensory and motor stimuli, which involve tactile stimulation on the back, as well as proprioceptive, tactile, and motor cues (from the upper limb), the congruency of which in the spatial and temporal domains are controlled via the robot. In the current and our previous research Salomon et al, 2020;Bernasconi et al, 2020), two main experimental conditions were used (synchronous and asynchronous sensorimotor stimulation). Both conditions contain a spatial conflict (between the spatial position of the moving hand and the spatial position of the touch cue delivered on the back of the participants), whereas the asynchronous condition also contains an additional spatiotemporal conflict (i.e., movement performed by the hand is delivered to the back of the participants with a delay of 500 ms).…”

“…Finally, we note that the present results cannot be due to differences in motor patterns spontaneously adopted by participants during the synchronous versus the asynchronous stimulation condition. Indeed, data collected with the same robotic system show that there is no difference in the quantity of poking movements performed in the two conditions, and that there is no link between movement characteristics and the induced FoP (Bernasconi et al, 2020).…”

“…Thus, no specific indications can be provided about the critical delay between movement and feedback generating the effect. Other data available as pre-print (Bernasconi et al, 2020) show that the intensity of FoP rises depending on the delay between the moving hand and tactile feedback on the back (i.e., from 0 to 500 ms), with a plateau at 500-ms delay. Third, we did not investigate the involved neural correlates of TI or the FoP, which was outside the scope of the present study.…”