Neuroscience of CBS
Research type
Research Study
Full title
The Neurochemistry and Connectivity in the Brain in Charles Bonnet Syndrome
IRAS ID
290078
Contact name
Holly Bridge
Contact email
Sponsor organisation
University of Oxford
Clinicaltrials.gov Identifier
To be provided, In progress
Duration of Study in the UK
1 years, 5 months, 27 days
Research summary
Research Summary
Charles Bonnet Syndrome (CBS) is a condition in which people experience complex visual hallucinations, such as ‘Acrobats balancing on bicycles’ or ‘Spiders crossing meals’. The condition usually occurs in people who have significant vision loss due to eye disease. The aim of this project is to help understand how these hallucinations come about.In the healthy visual system, the eye provides input to a large area of the brain that performs the computations required to allow us to see the world. There are specialised brain regions responsible for processing of faces, objects, motion and colour. When the eye is no longer working, these parts of the brain lose their input and we think this can lead to abnormal activity.
Not all people with eye disease and vision loss develop CBS, so we will use magnetic resonance imaging (MRI) to compare the brains of people with and without the condition. In particular we are interested in measuring the levels of chemicals in the visual areas of the brain to see whether they are disrupted in CBS, leading to the hallucinations. We can also measure how the different areas of the visual brain are connected together and see whether this is altered in CBS, perhaps with increases in the strength of connection between specialised areas. These measures will be related to questionnaires about hallucinations and vision. This will be done by comparing low vision who experience Charles Bonnet visual hallucinations compared to low vision patients who do not have hallucinations. Assessments will take place at the Wellcome Centre for Integrative Imaging (WIN) based at the John Radcliffe Hospital.
The study will provide insight into the role of the brain in generating CBS hallucinations, helping us to design a larger study and eventually to test whether there are interventions to help improve the condition.
Summary of Results
In Charles Bonnet Syndrome (CBS), people with sight loss start to see hallucinations that they know are not real but can be disturbing. In this study we used magnetic resonance imaging (MRI) scanning to measure how the chemistry in the visual brain differs in people with CBS and those who have sight loss but no hallucinations. We also used functional MRI to investigate whether activity to visual images differed between these groups. Surprisingly we did not find any differences in chemistry or functional activity between these groups, suggesting that their brains do not differ greatly. Any differences in how their visual brain works may be too small to measure, or only present when people are actually hallucinating.REC name
Wales REC 6
REC reference
21/WA/0014
Date of REC Opinion
3 Mar 2021
REC opinion
Further Information Favourable Opinion