The COVID-19 virus can cause long-term changes to the nervous system and cognitive functions, particularly for the older adults, who are the most sensitive group, and also at risk of developing dementia. In addition to curing physical symptoms, the effects on mental health and cognitive functioning cannot be overlooked, and with early detection and compensation of cognitive changes, it is possible to prevent subsequent irreversible neurocognitive decline. As early studies have suffered from a number of methodological deficiencies, we will systematically study the cognitive changes caused by the infection, as well as how they can be effectively reversed. In addition to psychological tests and behavioural data, we also study the changes in brain electrical activity (EEG and event-related potential) and brain networks. The elderly with residual post-covid symptoms will be divided into a cognitive and a relaxation training group, and we will test them immediately after the training and subsequently a year later, in order to examine the changes in attention, memory, and executive functions. Based on our results and an evaluation of the effectiveness the trainings, we plan to develop a ‘smart application’ to provide self-help training for those who have experienced either post-covid, or other viral infections causing similar symptoms.