New method for induction and real-time assessment of hallucinations

Although hallucinations are important and frequent symptoms in major psychiatric and neurological diseases, little is known about their brain mechanisms. Hallucinations are unpredictable and private experiences, making their investigation, quantification and assessment highly challenging. A major shortcoming in hallucination research is the absence of methods able to induce specific hallucinations, which resemble clinical hallucinations, can be elicited repeatedly and vary across experimental conditions. By integrating clinical observations and recent advances in cognitive neuroscience with robotics, we have designed a novel device and sensorimotor method able to repeatedly induce a specific, clinically relevant hallucination: presence hallucination. Presence hallucinations are induced by applying specific conflicting (spatiotemporal) sensorimotor stimulation between an upper extremity and the torso of the participant. Another, MRI-compatible, robotic device using similar sensorimotor stimulation permitted the identification of the brain mechanisms of these specific and clinically-relevant hallucinations, affecting many patients suffering from Parkinson’s disease, Dementia with Lewy bodies or schizophrenia. The method has already been applied to patients with schizophrenia (Salomon et al., 2020), patients with Parkinson’s disease (Bernasconi et al., 2021), and patients with Dementia with Lewy bodies (Nicastro et al., 2021).

In the latest report we provide detailed instructions to scientists and clinicians who wish to use our robotic system in their experimental and clinical settings. We suggest that the adaptation and further integration of this robotic procedure to other psychophysical, neuropsychological, clinical and neuroimaging techniques may help early detection of patients (e.g. Parkinson’s disease, dementia with Lewy bodies) at higher risk of psychosis and related cognitive decline.