When COVID-19 first reared its head back in 2019, it brought with it a slew of strange symptoms beyond just respiratory problems. One of the most puzzling symptoms in those early days was something called “brain fog” — cognitive issues like confusion, forgetfulness, and trouble focusing.

And while other symptoms have changed as the virus mutated, brain fog is still a common complaint of COVID sufferers not only during the initial illness, but extending for months or even years afterwards. Several recent studies have been trying to understand exactly what this virus is doing to our brains — and how to stop it.

Dr. Ziyad Al-Aly, the chief of research and development at the VA St. Louis Health Care System, spoke with Quirks & Quarks host Bob McDonald about what he’s seeing in his research on COVID and the brain. Here is part of their conversation.