Summary: Early hallucinations in people with Parkinson’s disease can be an early indicator of faster cognitive decline.
By combining detailed neuropsychological assessments with resting-state electroencephalography (EEG), researchers linked subtle, often underreported hallucinations to an accelerated loss of frontal executive function over subsequent years.
These findings underline the importance of early recognition and clinical attention to hallucinations as potential markers for a more severe progression of Parkinson’s disease.
Key facts
- Early hallucinations in Parkinson’s disease may signal an increased risk of rapid cognitive decline.
- Decline over five years was associated with frontal theta (4–8 Hz) oscillatory activity measured by EEG at the initial visit.
- Minor hallucinations occur in roughly one-third of Parkinson’s patients before motor symptoms begin, suggesting their potential as an early clinical marker.
Source: EPFL
Have you ever had a sudden, strong feeling that someone is standing just behind you, compelling you to turn around, only to find no one there?
This experience is known as a presence hallucination. Presence hallucinations are common but often go unreported by people with Parkinson’s disease, and they can appear early in the disease course.
Patients, caregivers, and clinicians sometimes attribute these experiences to medication or dismiss them as minor, but new evidence suggests they warrant careful attention.
Researchers at EPFL now report that newly diagnosed Parkinson’s patients who experience early hallucinations are more likely to show accelerated cognitive deterioration, particularly in frontal executive functions.
The study is published in the journal Nature Mental Health.
“Early hallucinations should be taken seriously in Parkinson’s disease,” says Olaf Blanke, Bertarelli Chair in Cognitive Neuroprosthetics and head of EPFL’s Laboratory of Cognitive Neuroscience.
“If you have Parkinson’s and notice hallucinations, even mild ones, tell your doctor as soon as possible,” recommends Fosco Bernasconi of EPFL and lead author of the study. “Our results link early hallucinations with later cognitive decline in Parkinson’s; similar relationships may exist in other neurodegenerative disorders, but further research is needed.”
Long-term clinical study design
In a collaboration between EPFL and Sant Pau Hospital in Barcelona, the team followed 75 patients aged 60–70 who had been diagnosed with Parkinson’s disease. Clinicians conducted comprehensive neuropsychological testing to evaluate cognitive function, neuropsychiatric interviews to document hallucination experiences, and resting-state EEG recordings.
Analysis showed that patients reporting early hallucinations experienced a steeper decline in frontal executive function over the following five years. Importantly, the degree of decline correlated with increased frontal theta-band activity measured during the initial EEG—but this relationship held only for patients who already had hallucinations at baseline. Patients who were clinically and demographically similar but did not report hallucinations at onset did not show the same EEG–cognition link.
Implications for earlier detection and intervention
Neurodegenerative diseases such as Parkinson’s are frequently diagnosed when pathology is advanced, limiting the effectiveness of interventions. By identifying early, reliable markers of a more aggressive disease trajectory—like minor hallucinations and associated EEG patterns—clinicians could intervene sooner to slow cognitive and psychiatric symptoms.
Hallucinations are among the lesser-known, yet common, non-motor symptoms in Parkinson’s. About half of patients experience some form of hallucination during the disease course, and roughly one-third report early hallucinations before motor signs like tremor appear. Hallucinatory experiences exist on a spectrum: minor phenomena such as presence hallucinations tend to occur early, while complex visual hallucinations typically emerge later and have already been linked to dementia in Parkinson’s and related disorders such as dementia with Lewy bodies.
Because complex visual hallucinations usually develop at more advanced stages, they are less useful for early risk stratification. Detecting subtle hallucinatory symptoms and their electrophysiological correlates early on could therefore help identify individuals at higher risk for rapid cognitive decline and dementia.
“Finding the earliest signs of dementia allows for earlier management, enabling development of targeted, personalized therapies aimed at modifying disease course and preserving cognitive function,” says Blanke. “Our goal is an early marker that predicts a more severe form of Parkinson’s—one marked by faster cognitive decline—based on proneness to hallucinations.”
“We are also working on neurotechnology approaches to detect risk even before hallucinations appear,” adds Bernasconi, describing ongoing efforts to translate these discoveries into practical, early-detection tools.
About this Parkinson’s disease research news
Author: Hillary Sanctuary
Source: EPFL
Contact: Hillary Sanctuary – EPFL
Image: Image credited to Neuroscience News
Original research: Open access. “Theta oscillations and minor hallucinations in Parkinson’s disease reveal decrease in frontal lobe functions and later cognitive decline” by Olaf Blanke et al., Nature Mental Health
Abstract
Theta oscillations and minor hallucinations in Parkinson’s disease reveal decrease in frontal lobe functions and later cognitive decline
Cognitive decline and hallucinations are common and disabling non-motor symptoms in Parkinson’s disease, typically appearing during later stages. Minor hallucinations, however, can arise early and have been proposed as predictors of future cognitive impairment. Clinical evidence establishing this link has been limited.
This study examined whether patients with Parkinson’s disease who experience minor hallucinations show altered brain oscillations and whether these electrophysiological differences predict progressive cognitive deficits. Using model-driven EEG analysis alongside neuropsychiatric and neuropsychological assessments in 75 patients, the authors found enhanced frontal theta oscillations in those with minor hallucinations and linked these oscillatory changes to reduced frontal–subcortical cognitive functions.
Follow-up neuropsychological testing five years later revealed a stronger decline in frontal–subcortical functions among patients with minor hallucinations, a decline that was anticipated by elevated frontal theta activity measured at the initial assessment. Together, these findings define a combined minor-hallucination and theta-oscillation early marker for cognitive decline in Parkinson’s disease.