By Miriam Stoppard By and large Long Covid remains a mystery. But piece by piece we’re starting to form a picture. The latest piece of the jigsaw comes from a study by Imperial College London where researchers reveal small deficits in the performance of cognitive and memory tasks in people who had recovered from Covid-19, compared with those who’d never had it. The study also shows that cognitive deficits are worse for people who were hospitalised, who had ongoing long-term symptoms, and who were infected with earlier virus variants. These insights come from the Imperial-led study, called R…