A new study published in Nature has provided the clearest evidence yet that Covid-19 can cause regions of the brain to shrink - and lead to cognitive decline - even in people who aren't seriously ill. It's an Oxford University study using data from the UK's biobank, and comparing MRI scans of people before and after catching mild versions of earlier Covid variants. The brain areas most affected are those that are related to smell. Joining us again is Dr Maxime Taquet from Oxford, whom we've chatted with previously. Dr Taquet is an academic clinical fellow in psychiatry at the University of Oxford.