DAOIB for the Treatment of Brain Fog

Inclusion Criteria: * "post-COVID-19 condition" defined by WHO (symptoms present at three months after SARS-CoV-2 infection and last for at least 2 months which cannot be explained by an alternative diagnosis)(Cabrera Martimbianco, Pacheco et al. 2021) and COVID-induced cognitive impairments * physically healthy and have all laboratory assessments (including urine/blood routine, biochemical tests, and electrocardiograph) within normal limits * have sufficient education to communicate effectively and are capable of completing the assessments of the study Exclusion Criteria: * history of significant cerebrovascular disease * Hachinski Ischemic Score \> 4 * major neurological, psychiatric or medical conditions other than long COVID-induced cognitive impairments * memantine use (memantine is an NMDAR partial antagonist) * substance (including alcohol) abuse or dependence * delusion, hallucination or delirium symptoms * severe visual or hearing loss * inability to follow the protocol