The Role of Priors in Hallucinatory Perception in Parkinson's Disease
For patients and families
In plain language
An automatic summary of structured registry data. It is an orientation aid, not a substitute for the official protocol or a physician assessment.
- What is being studied
- This is an observational study: the protocol does not assign a study treatment.
- Who it may be relevant to
- Registry conditions: PARKINSON DISEASE (Disorder). Basic parameters: 18 years — 85 years · All.
- What needs checking
- Age, condition and sex are only basic indicators. Prior treatment, laboratory values and other mandatory requirements appear in the eligibility criteria below.
- Where it takes place
- France
- Next step
- Save the trial, show it to the treating physician, and confirm current recruitment with the study center. Costs, documents and travel →
Unsure about the terms? Read our patient guide →
Official title
Exploratory Study on the Role of Prior Expectations in Hallucinatory Perceptions
Overview
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.
Primary outcome measures
- Effect of Prior Expectations on False Alarm Rates in Parkinson's Disease Patients With and Without Visual Hallucinations [Time frame: Baseline]
Secondary outcome measures (4)
- Comparison of False Alarm Rates Between Parkinson's Patients Without Hallucinations and Healthy Volunteers [Time frame: Baseline]
- Impact of Prior Expectations on Perceptual Confidence in Parkinson's Disease Patients With and Without Visual Hallucinations [Time frame: Baseline]
- Neuropsychological Profile Differences Between Parkinson's Patients With and Without Hallucinations [Time frame: Baseline]
- Beta Power Differences in the Subthalamic Nucleus During False Alarms in Parkinson's Patients With Deep Brain Stimulation [Time frame: Baseline]
Eligibility criteria
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.
Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.
Healthy volunteers: Yes
Study design
- Observational model
- Case-control
Study locations
France · 1 center
- Grenoble University Hospitals — La Tronche
Identifiers
NCT: NCT07427498 · 38RC25.0050 · 101077874 · 2025-A01842-47