# EEG changes associated with hallucinations caused by Charles Bonnet Syndrome

## TL;DR

This study identifies changes in brain activity linked to hallucinations in Charles Bonnet Syndrome using EEG.

## Contribution

The first group study to show a repeatable EEG marker for hallucination onset in Charles Bonnet Syndrome.

## Key findings

- Reduced α power in occipital electrodes at hallucination onset compared to offset.
- Intermittent low endogenous alpha may create neural conditions for hallucinations in CBS patients.

## Abstract

Charles Bonnet syndrome (CBS) is characterised by the presence of visual hallucinations following visual loss in many patients. The neuropathophysiology of CBS is poorly understood. We used electroencephalography (EEG) in individuals with frequent hallucinations in order to identify changes in neural activity that co-occur with hallucination onset. We found reduced α power in occipital electrodes at the onset of the hallucinations compared to offset (p < 0.05), suggesting that intermittent periods of low endogenous alpha may create the neural conditions for hallucination to emerge in CBS patients. This is the first group study that shows a repeatable marker of brain activity changes in CBS that occur either at the onset or just prior to the onset of the hallucination. This offers important implications for both research and clinical practice. It could aid in early detection and prediction of hallucination onset and improve our understanding of the neural mechanisms underlying CBS. It also may help reduce stigma around the condition by validating the patient experience through measurable brain changes.