Project - Visual hallucinations in α-synuclein disease

Research Project Abstract

My project focusses on visual hallucinations in α-synuclein disease. The aim is to apply behavioural tasks designed to tap into clinical features linked to visual hallucinations in PDD and DLB. The sensitivity of these tasks will be evaluated and then applied on a “prodromal” RBD group with the goal of predict disease course for this population.

Project tag with a disease

Dementia, PD, DLB, RBD

Research Project Description

Visual Hallucinations in α-synuclein diseases

Currently, visual hallucinations in the synuclein diseases are measured using scales or clinical interview. However, these methods are reliant on reports from the patient or the patient’s caregiver. As these reports are dependent on the patient’s insight, they may not be capturing all visual hallucinations that they are experiencing, especially hallucinations in their mildest form. The aim of my project is to investigate the feasibility and sensitivity of select behavioural tasks designed to measure symptoms that coincide with visual hallucinations. Then I will apply these findings to a prodromal population to see if the tasks are able to predict the prognosis of these individuals. The tasks are as follows:

Sustained Attention Reaction Task (SART)

This is a relatively simple task that requires the patient to maintain their attention on numbers presented to them. They are to press a button for each number they see except for the number three. This task is sensitive to attention impairments, which are theorised to be one of the causes of visual hallucinations.

Mental rotation

This task presents patients with pairs of shapes and requires them to decide if the shapes are mirror images of each other, or a direct copy. To do this, the patient is required to visualise the shape and rotate it until they can decide if the pair is a mirror image or not. This task is designed to measure visuospatial ability, which is severly impaired in DLB patients, who also experience more severe visual hallucinations than Parkinson’s disease patients.

Bistable Percept Paradigm

This task is designed to measure the mildest form of visual hallucinations, misperceptions. It achieves this by presenting patients with ambiguous images which may or may not have a hidden component. Patients are required to identify all the components of the image. The ambiguity and uncertainty of the image encourages patients to list everything they perceive in the image. This may result in the correctly reporting all the components, or incorrectly identifying an aspect that is not in the image or finally missing one of the components. The number of incorrect identifications is related to the severity of visual hallucinations experienced by the patients. While the number of misses made is related to attentional impairment.

Predicting progression of synuclein diseases

Performance from our patient groups in the three behavioural tasks will provide us with a pattern of responding that is unique to patients with PD compared to patients with DLB. The next step of my project is to test a group of REM Behaviour Disorder patients using the same tasks. Individuals with REM Behaviour Disorder have been shown to be a high risk of transition to a more severe synuclein disease such as Parkinson’s disease or dementia with Lewy bodies. I will take the response patterns of the REM Behaviour Disorder patients and match them to patterns obtained from our Parkinson’s disease and dementia with Lewy bodies patients. These patterns should be able to assist the diagnosis of the patient before they become symptomatic. This will allow for treatment to begin at earlier stages, improving the quality of life of these patients for an extended period of time.

Key Publications from this project

Phillips, J. R., Matar, E., Ehgoetz Martens, K. A., Halliday, G. M., Moustafa, A. A., & Lewis, S. J. G. (2019). Evaluating the Sustained Attention Response Task to quantify cognitive fluctuations in dementia with Lewy bodies. J Geriatr Psychiatry Neurol. doi:10.1177/0891988719882093