Several studies have suggested that COVID-19 patients have long-term structural changes within certain structures in their brains. As an example, an MRI- and DTI-based 3-month follow up study from Lu et al. (2020) found that patients have significantly higher gray matter volumes in their olfactory cortices, hippocampi, insulas, left Rolandic operculum, left Heschl's gyrus, and right cingulate gyrus. General diffusivity had declined. Left hemisphere changes correlated with memory loses, while other right hemisphere changes correlated with smell loss.