Feeling of presence in dementia with Lewy bodies is related to reduced left frontoparietal metabolism

Real-time fMRI neurofeedback modulates induced hallucinations and underlying brain mechanisms

Hallucinations can occur in the healthy population, are clinically relevant and frequent symptoms in many neuropsychiatric conditions, and have been shown to mark disease progression in patients with neurodegenerative disorders where antipsychotic treatment remains challenging. Here, we combine MR-robotics capable of inducing a clinically-relevant hallucination, with real-time fMRI neurofeedback (fMRI-NF) to train healthy individuals to up-regulate a fronto-parietal brain network associated with the robotically-induced hallucination. Over three days, participants learned to modulate occurrences of and transition probabilities to this network, leading to heightened sensitivity to induced hallucinations after training. Moreover, participants who became sensitive and succeeded in fMRI-NF training, showed sustained and specific neural changes after training, characterized by increased hallucination network occurrences during induction and decreased hallucination network occurrences during a matched control condition. These data demonstrate that fMRI-NF modulates specific hallucination network dynamics and highlights the potential of fMRI-NF as a novel antipsychotic treatment in neurodegenerative disorders and schizophrenia.

Neuroscience robotics for controlled 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 and short-lasting 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 including 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 hallucinations. Enabling the identification of behavioral and a frontotemporal neural biomarkers of hallucinations, under fully controlled experimental conditions and in real-time, this method can be applied in healthy participants as well as patients with schizophrenia, neurodegenerative disease or other hallucinations. The execution of these protocols requires intermediate-level skills in cognitive neuroscience and MRI processing, as well as minimal coding experience to control the robotic device. These protocols take ~3 h to be completed.

Premotor and fronto-striatal mechanisms associated with presence hallucinations in dementia with Lewy bodies

INTRODUCTION

presence hallucinations (PH) are frequent in dementia with Lewy bodies (DLB), but their cortico-subcortical origin is unknown. Recent studies have defined key frontal and temporal areas contributing to the occurrence of PH (PH-network) and tested their relevance in subjects with Parkinson's disease (PD). With the present study, we aimed at disentangling the metabolic and dopaminergic correlates of pH as well as their relation to a recently defined PH brain network in DLB.

METHODS

for the present study, we included 34 DLB subjects (10 with PH (PH + ); 24 without PH (PH-)), who underwent ¹⁸F-FDG PET and ¹²³I-FP-CIT SPECT imaging. We performed ¹⁸F-FDG PET group comparisons, as well as interregional correlation analyses using ¹⁸F-FDG PH-network regions as a seed.

RESULTS

PH + versus PH- had reduced ¹⁸F-FDG uptake in precentral, superior frontal and parietal gyri, involving ventral premotor cortex (vPMC) of the PH-network that showed strongly reduced functional connectivity with bilateral cortical regions. ¹⁸F-FDG vPMC uptake was negatively correlated with caudate ¹²³I-FP-CIT uptake in PH+ (p = 0.028) and interregional correlation analysis seeding from the vPMC showed widespread fronto-parietal ¹⁸F-FDG decreases in PH + .

DISCUSSION

these findings uncover the pivotal role of vPMC (involved in a PH-network) and its cortico-striatal connections in association with PH in DLB, improving our understanding of psychosis in neurodegeneration.