Visual snow syndrome (VSS) affects about 2-3% of the world’s population and causes people to see static, flickering dots and flashing lights – when their eyes are both open and closed. IoPPN researchers, part-funded by NIHR Maudsley Biomedical Research Centre , have used a novel approach which combines PET imaging and fMRI to show that the patterns of activity in two brain chemical systems – glutamate and serotonin – are different in people with VSS compared to those without the condition. The f