An observational study in PARKINSON DISEASE (Disorder), sponsored by University Hospital, Grenoble. Recruiting at 2 sites in France. Open to participants aged 18 Years to 85 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-09-30.
Sponsored by University Hospital, Grenoble · Observational
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.
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.
4,573 studies on the registry are indexed under Parkinson Disease; 1,086 are open to participants now.
This study's planned enrollment of 60 is below the median of 96 across 1,085 observational studies indexed under Parkinson Disease.
Browse Parkinson Disease studies →University Hospital, Grenoble is the lead sponsor of 837 studies on the registry; 207 are open to participants now.
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The study will recruit Parkinson's disease patients (disease duration ≥1 year, no major cognitive impairment) from CHU Grenoble-Alpes, including 15 with minor hallucinations (e.g., passage/presence sensations) and 15 with major hallucinations (e.g., complex visual hallucinations). Patients with active psychosis are excluded.
Healthy volunteers (matched by age, gender, and education) will be recruited via ads in senior associations and affiliated institutions (CHUGA, GIN). Matching tolerates ±5 years for age and ±2 years for education; those without a high school diploma will be matched without strict education criteria. Ads may also appear on institutional websites.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Non-psychiatric (somatic) conditions likely to affect cognitive abilities. Peripheral sensory or motor deficits. Acute clinical conditions (e.g., agitation, impaired consciousness).
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 score below 24 will be excluded from the study.
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Short tests of memory and thinking, each scored out of 30. Lower scores suggest more difficulty; criteria give a range, either to include people with memory problems or to leave them out.
MMSE and MoCA
Short tests of memory and thinking, each scored out of 30. Lower scores suggest more difficulty; criteria give a range, either to include people with memory problems or to leave them out.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Patients with Parkinson's disease with hallucinations
Patients with Parkinson's disease without hallucinations
Age and sex matched group of healthy participants
Effect of Prior Expectations on False Alarm Rates in Parkinson's Disease Patients With and Without Visual Hallucinations
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.
Time frame: Baseline
Comparison of False Alarm Rates Between Parkinson's Patients Without Hallucinations and Healthy Volunteers
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).
Time frame: Baseline
Impact of Prior Expectations on Perceptual Confidence in Parkinson's Disease Patients With and Without Visual Hallucinations
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).
Time frame: Baseline
Neuropsychological Profile Differences Between Parkinson's Patients With and Without Hallucinations
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).
Time frame: Baseline
Beta Power Differences in the Subthalamic Nucleus During False Alarms in Parkinson's Patients With Deep Brain Stimulation
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.
Time frame: Baseline
Plan to share: Undecided
No publications or documents are linked to this record.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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