PSMD1 and COVID-19: To test whether the brain-infiltrating SARS-CoV-2 S1 protein is involved in the neurological problems observed in COVID-19 patients, we directly introduced S1 proteins into the dorsal hippocampus, a brain sub-region critical for cognition and emotion10, of mice and subjected the mice to a series of behavioral tests to measure cognitive and affective brain functions (Fig. 1a).