for covid—19, according to the latest research in the us. and here in the uk, a new study has found that even mild cases of covid can cause long—term changes to the brain, as our science editor rebecca morelle explains. we are starting to see the precise impacts of covid on the brain, as uk biobank undertakes the world's biggest scanning project. the task is about to start... scientists have compared brain scans recorded before the pandemic with images taken after a covid—19 infection. the scans reveal changes in the brain of the participants who'd had covid. almost all of them, 96%, had had a mild case. the researchers found that on average the overall size of the brain had shrunk by up to 2%. there was a loss of grey matter in the parts of the brain related to the sense of smell and memory. and those who had been infected found it harder to perform complex mental tasks. the scientists have been trying