This platform protocol is designed to be flexible so that it is suitable for a wide range of settings within health care systems, for remote settings, and in community settings where it can be integrated into COVID-19 programs and subsequent treatment plans.

This protocol is a prospective, multi-center, multi-arm, randomized, controlled platform trial evaluating potential interventions for PASC-mediated cognitive dysfunction. The hypothesis is that PASC-associated dysfunction in cognitive domains, such as executive function and attention, may be improved by interventions that selectively focus on enhancing those domains.

This design seeks to evaluate each intervention relative to the Active Comparator. The BrainHQ (alone) arm is important because the intervention is commercially available, accessible, relatively inexpensive, and does not require trained personnel to administer. BrainHQ has been also been proven effective in other studies of cognitive dysfunction such as studies in aging, mild cognitive impairment, traumatic brain injury, among others. The BrainHQ + PASC CoRE arm and the BrainHQ + tDCS arms are suspected to provide cognitive improvements beyond BrainHQ alone through different mechanisms. Both PASC CoRE and tDCS have extensive prior use and have demonstrated utility in improving aspects of cognitive function in other clinical settings..

Participants will be randomized to one of the intervention appendices that are actively enrolling at the time of randomization. Intervention appendices may be added or removed according to adaptive design and/or emerging evidence. Various interventions will be studied.

Participants will be randomized equally across the five arms:

1. Active Comparator (video games)
2. BrainHQ
3. BrainHQ + PASC CoRE
4. BrainHQ + tDCS-active
5. BrainHQ + tDCS-sham

Inclusion Criteria:

1. See NCT05965752 for RECOVER-NEURO: Platform Protocol level inclusion criteria which applies to this appendix

Exclusion Criteria:

1. See NCT05965752 for RECOVER-NEURO: Platform Protocol level exclusion criteria which applies to this appendix

Additional Appendix (Sub-study) Level Exclusion Criteria:

1. Presence of metal objects in the head or neck
2. Skin disorders or skin-sensitive areas near tDCS stimulation locations that would interfere with electrode placement or increase the risk of stimulation-induced damage, at the investigator's discretion

The investigators will share the summary of results on the study website: https://recovercovid.org/

Participants assigned to control will be considered part of pooled analyses if the intervention was active at the time of their enrollment and the participants were eligible to receive that intervention. This will result in approximately a 1:1 allocation ratio for any intervention to pooled control.

Sites will be informed to which intervention appendix participants are randomized, but, when applicable, not whether the participants are allocated to the active intervention arm or control arm within that appendix. The participants and investigators will be blinded throughout the study, when possible.

If open intervention appendices do not have the ability to pool controls but have independent controls, at the second stage participants will be randomized in a 1:1 ratio to intervention vs control inside the specific intervention appendix the participants were randomized to at the first stage of the randomization procedure.