Hallucinations associated with brain hyperactivity in people with macular degeneration

University of Queesnland
New research from the University of Queensland has shown for the first time that visual hallucinations in people with macular degeneration are associated with abnormally heightened activity in the visual cortex of the brain.
The findings, published in the journal Current Biology, could improve diagnosis of such hallucinations.
Macular degeneration is a retinal eye disease that causes progressive deterioration of the central region of the retina, leading to visual loss in the centre of the field of vision, while peripheral vision usually remains unaffected. In Australia, MD is the leading cause of legal blindness in people over the age of 40.
Curiously, many people who develop MD go on to develop a condition known as Charles Bonnet Syndrome, in which they experience hallucinations as the brain adjusts to significant vision loss. The hallucinations can be simple geometric patterns, or much more complex scenes involving animals, people and places.
Why some people with MD experience hallucinations while others do not has remained unclear, but there have been suggestions that the activity levels—or ‘excitability’ – of certain visual regions of the brain could play a role.
To address this, Professor Jason Mattingley and his team from The University’s Queensland Brain Institute and School of Psychology stimulated the peripheral visual fields of study participants and found that individuals with hallucinations do indeed show significantly heightened activity in particular parts of their visual system. We used electroencephalography (EEG) to measure brain electrical activity in three groups: a group with  and Charles Bonnet hallucinations, a group with macular degeneration and no hallucinations, and a control group of visually-healthy elderly people,” Dr. David Painter—the paper’s first author—said.
“Their task was to look at letters appearing on the screen in their periphery, and we flashed checkerboards at unique frequencies on the screen….
Read more: https://medicalxpress.com/news/2018-10-hallucinations-brain-hyperactivity-people-macular.html
Source: Medical Xpress