PARKINSON DISEASE (Disorder)
Conditions
Keywords
Parkinson, hallucination, neuropsychiatry, prior
Brief summary
The goal of this observational study is to better understand the mechanisms of hallucinations in patients with Parkinson's disease. The main question it aims to answer is: Do prior expectations increase the rate of false perceptions during a visual stimulus detection task more in Parkinson's disease patients with visual hallucinations compared to those without? Participants will undertake a computer task involving face detection and a battery of neuropsychological tests.
Detailed description
Understanding why hallucinations happen in Parkinson's disease is crucial for improving the daily lives and care of those affected. Hallucinations are common non-movement symptoms in Parkinson's that can significantly impact how people function, increase the burden on caregivers, and may signal faster cognitive decline. Research shows that what one perceives isn't just based on what senses pick up-it's also shaped by expectations and past experiences. Sometimes, over-relying on these expectations can lead to hallucinations. However, it's still unclear whether this explains why some people with Parkinson's experience hallucinations while others don't. In cognitive science, one way to study hallucinations is by showing people repeated trials where a stimulus is either barely visible or not present at all. The number of times someone reports seeing something when nothing is actually there (called "false alarms") has been linked to the likelihood of experiencing hallucinations in everyday life. To explore this further, researchers use cues that hint at whether a stimulus is likely to appear. Studies have shown that healthy individuals use these cues to guide their perception. Some research even suggests that people with Parkinson's might rely on these cues more strongly, but this hasn't been directly connected to hallucinations yet. This study aims to test whether these cues-by shaping expectations-affect the rate of false alarms more in Parkinson's patients who experience hallucinations compared to those who don't. By understanding why false alarms happen, deeper insights will be gained into visual hallucinations, as well as improved early detection, and ultimately enhanced care. To better understand the brain mechanisms involved, brain activity will be recorded from patients who have deep-brain stimulation electrodes that allow investigators to measure neural signals in a specific brain area called the subthalamic nucleus. This could help uncover how the brain processes these expectations and perceptions.
Interventions
None listed
Sponsors
University Hospital, Grenoble
INSERM U1216 Grenoble Institut des Neurosciences
Study design
Observational model
CASE_CONTROL
Time perspective
PROSPECTIVE
Eligibility
Sex/Gender
ALL
Age
18 Years to 85 Years
Healthy volunteers
Yes
Inclusion criteria
* Adults diagnosed with Parkinson's disease (with or without visual hallucinations) or healthy volunteers. * Age 18 - 85 years. * Consent to participate.
Exclusion criteria
* Currently participating in another clinical or therapeutic trial involving the testing of a drug treatment. * Inability to perform cognitive tests due to: Non-psychiatric (somatic) conditions likely to affect cognitive abilities. Peripheral sensory or motor deficits. Acute clinical conditions (e.g., agitation, impaired consciousness). * Diagnosis of dementia. * Individuals covered by Articles L1121-5 to L1121-8 of the French Public Health Code (Code de la Santé Publique), including: Pregnant women, women in labor, or breastfeeding mothers. Individuals deprived of liberty by judicial or administrative decision. Individuals receiving psychiatric care under Articles L. 3212-1 and L. 3213-1 (excluding those covered by Article L. 1121-8). Individuals admitted to a healthcare or social institution for purposes other than research. Minors or adults under legal guardianship or unable to express consent. \- Individuals with a hierarchical relationship to any professional involved in the study. Only for healthy volunteers: \- Personal history of diagnosed neurological disorders. Post-Inclusion Exclusion: \- Participants included in the study but found to have a MoCA score below 24 will be excluded from the study.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Effect of Prior Expectations on False Alarm Rates in Parkinson's Disease Patients With and Without Visual Hallucinations | Baseline | The primary outcome measures the false alarm rate during a visual stimulus detection task, specifically the percentage of trials in which participants report perceiving a stimulus when none was presented. The study will assess whether prior expectations (cues indicating the likelihood of a stimulus) increase false alarm rates more in Parkinson's disease patients with visual hallucinations compared to those without. The primary statistical analysis will test for an interaction effect (p \< 0.05) between cue (prior expectation), stimulus presence, and group (patients with vs. without hallucinations) using a generalized linear mixed model. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Comparison of False Alarm Rates Between Parkinson's Patients Without Hallucinations and Healthy Volunteers | Baseline | This outcome will test whether prior expectations (cues) affect false alarm rates more in Parkinson's disease patients without hallucinations compared to healthy volunteers. The analysis will use a generalized linear mixed model to assess the presence of an interaction effect (p \< 0.05) between cue, stimulus presence, and group (patients without hallucinations vs. healthy controls). |
| Impact of Prior Expectations on Perceptual Confidence in Parkinson's Disease Patients With and Without Visual Hallucinations | Baseline | This outcome will evaluate whether prior expectations (cues) influence confidence levels more in Parkinson's patients with hallucinations compared to those without. Confidence ratings will be analyzed only for trials where participants report detecting a stimulus. A generalized linear mixed model will test for an interaction effect (p \< 0.05) between cue, stimulus presence, and group (patients with vs. without hallucinations). |
| Neuropsychological Profile Differences Between Parkinson's Patients With and Without Hallucinations | Baseline | This outcome will assess whether there are significant differences in neuropsychological test scores between Parkinson's patients with hallucinations and those without. The results will be interpreted while accounting for multiple comparisons using the False Discovery Rate (FDR). |
| Beta Power Differences in the Subthalamic Nucleus During False Alarms in Parkinson's Patients With Deep Brain Stimulation | Baseline | This outcome will examine whether beta power (recorded via Medtronic's PERCEPT™ device) in the subthalamic nucleus differs between false alarm trials and other trials. Differences will be analyzed using a Student's t-test at each time point within a one-second window following stimulus presentation, with False Discovery Rate (FDR) correction applied to control for multiple comparisons. |
Countries
France
Contacts
CONTACTAnna Castrioto, MD, PhD
CONTACTMichael Pereira, PhD
PRINCIPAL_INVESTIGATORAnna Castrioto
University Hospital, Grenoble
Outcome results
None listed