Perceptual Predictors of Visual Hallucinations in Parkinson's Disease

  • End date
    Sep 2, 2024
  • participants needed
  • sponsor
    Boston University Charles River Campus
Updated on 4 October 2022
motor symptoms


Visual hallucinations (VH) are among the most distressing of the non-motor symptoms of Parkinson's disease (PD). The investigators plan to examine the relation of perceptual variables-basic vision, unusual perceptual experiences-to relevant functional variables such as cognition, mood, and alertness/sleepiness in an online sample of persons with Parkinson's disease (PwPD). It is hypothesized that unusual perceptual experiences will relate significantly to the selected variables. This is an observational study only, and not an interventional study.


Visual Hallucinations (VH) are among the most distressing of the non-motor symptoms of Parkinson's disease (PD), as well as being prevalent, with estimates ranging up to 75%. Researchers have identified numerous correlates of VH in PD including older age, longer and more severe disease, certain dopaminergic medications, mood disturbances, sleep disorders, and altered visual processing. Abnormal visual processing is likely to be an important contributor and may even predict the development of VH. Persons with Parkinson's disease (PwPD) who report VH typically exhibit compromised visuospatial function and visual object perception. Studies using novel behavioral designs have shown abnormal perception of ambiguous or bistable objects in PD-VH. Recently, the investigators demonstrated that PwPD with VH, especially more complex VH, had poorer contrast sensitivity than PwPD without VH, and that their object identification could be normalized with enhanced contrast.

Brain imaging studies have shown structural and functional changes in regions associated with visual processing in PwPD with VH. These studies, coupled with behavioral research pointing to impaired object recognition, have served as the basis for including impaired visual processing (both low-level and high-order visual regions) in theoretical models of VH. Minor hallucinations, too, could be early markers of larger-scale network dysfunction, cognitive impairment, depression, REM sleep behavior disorder, and formed (complex). Because of this possible predictive relation, the investigators include minor hallucinations when referring to VH.

An intriguing question is whether perception-based, non-pharmacological interventions may change the type or reduce the frequency of occurrence of VH in PD. A necessary first step before designing perception-based interventions is to identify markers: perceptual abnormalities that may correlate with, and possibly predict, the development of VH. A potential perceptual marker that has gained traction with researchers studying VH is the response to pareidolic images. These are images that are not meant to represent particular objects, faces, or scenes, but are nevertheless interpreted as being meaningful by persons with PD and especially those with PD-VH. The tendency to see meaning in meaningless images-pareidolia-- has been demonstrated in PD-VH and related disorders and been proposed as a marker for VH, which generally cannot be made to appear on-demand in the lab.

For this study, the investigators propose to conduct an online study of PwPD (proposing a total of 60 participants) to examine the relations among variables that may relate to VH in PD. Participants will be recruited via online research platforms such as the Fox Trial Finder, as in our previous studies. Those PwPD who express interest will be sent a link to the online assessments (Qualtrics). The investigators will collect demographic and health information, followed by questionnaires assessing unusual perceptual experiences, mood, motivation, sleep, fatigue and quality of life. This is an observational study only, and not an interventional study.

Condition Parkinson's Disease, Visual Hallucination
Clinical Study IdentifierNCT05483036
SponsorBoston University Charles River Campus
Last Modified on4 October 2022


Yes No Not Sure

Inclusion Criteria

Participants must be at least 40 years old
Have a self-reported diagnosis of idiopathic PD
Be proficient English speakers
Have functional vision
Have internet access, and access to a desktop computer or laptop

Exclusion Criteria

Self-reported poor vision (non-functional range)
Lack of access to internet and either a desktop computer or laptop
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