The purpose of this study is to compare two approaches to cognitive rehabilitation in adults with post-viral cognitive syndrome, which resulted in brain fog. All participants will be screened for eligibility prior to participation. Most of the procedures will take place over a phone call or secure telehealth platform (i.e., Zoom). However, participants will be asked to visit UAB on three occasions for blood sample collection and brain imaging (about 2 hours each). Online testing will happen one month before treatment, one day before treatment, one day afterwards, and 6 months afterwards. The study will utilize two different forms of rehabilitation training to improve participants' cognitive ability. Participants will be randomized to one of the two treatment groups. The first treatment approach, known as Constraint-Induced Cognitive Therapy (CICT), will feature (A) web-based computer "games" that trains how quickly individuals process information that they receive through their senses; (B) online training on everyday activities with important cognitive components, (C) procedures designed to transfer improvements in cognition from the treatment setting to everyday life, and (D) a non-invasive form of vagus nerve stimulation, also known as trans-auricular VNS (taVNS). The second approach, known as Brain Fitness Training (BFT), will include (A) web-based computer "games" that train reaction time and eye-hand coordination; (B) in-lab training on relaxation, breathing, healthy nutrition, and healthy sleep, (C) education about how relaxation, breathing, nutrition, and sleep are connected to thinking effectiveness, and (D) taVNS. Approximately 30 hours of training will be conducted over a secure telehealth platform (i.e., Zoom) in the span of two- to four- weeks. A typical CICT session will consist of one hour of gaming, with the bulk of the session being spent on cognitive training of the target behaviors and procedures designed to promote transfer of therapeutic gains to daily life. ta-VNS will be administered for 10 minutes before gaming and in-lab target behavior training. A typical BFT session will consist of one hour of gaming, training on healthy lifestyle behaviors (i.e., healthy sleep, nutrition, and relaxation habits), as well as procedures designed to promote transfer of behavior changes to daily life. Ta-VNS will be administered for 10 minutes before gaming and in-lab target behavior training. Training sessions in both conditions will be scheduled based on participants' availability, with the options for sessions scheduled to be as close as every weekday over 2 weeks or as loosely as every other weekday (i.e., over a 4-week span). If a caregiver is available, they will receive training on how to best support participants in their therapeutic program. After the training ends, both groups will receive 4 follow-up phone calls approximately one week apart to promote integration of the gained skills into everyday life. Outcomes measured will include cognitive processing speed, cognitive function on laboratory tests, and spontaneous performance of everyday activities with important cognitive components in daily life.

Inclusion Criteria:

• diagnosis of ME/CFS that preceded cognitive complaints
• mild or greater cognitive impairment
• moderate or greater brain fog
• some impairment in the performance of daily activities
• ≥ 18 years, no upper limit if medically stable
• reside in the community (as opposed to a hospital or skilled nursing facility)
• able to travel to the laboratory on multiple occasions
• has Internet service
• has a personal computer, laptop, or tablet that can access the Internet
• sufficiently fit, from both a physical and mental health perspective, to take part in the study
• adequate sight and hearing to complete the UFOV test
• adequate thinking skills, e.g., ability to follow directions and retain information to complete UFOV and CTAL, as marked by the judgement of the screener that the candidate is able to adequately complete the UFOV and CTAL
• sufficient English proficiency (i.e., ability to speak, understand, read, and write to take part in study activities)

Exclusion Criteria:

• cognitive impairment due to a developmental disability, psychiatric disorder, or substance abuse, or due to another type of brain injury, such as traumatic brain injury, stroke, or a progressive brain disease, such as Alzheimer's Dementia
• current substance abuse disorder
• diagnosis of postural orthostatic tachycardia syndrome (POTS) by a healthcare provider
• prior cognitive processing speed training on DoubleDecision or a similar program
• cannot tolerate taVNS
• prior history of heart attack or other serious cardiac events
• implanted medical device of any type
• vasovagal syncope or history of fainting
• history of seizures or epilepsy
• temporomandibular Joint (TMJ) syndrome or other conditions that cause substantial jaw pain
• history of peripheral nerve injury to the head, neck, or face
• pregnant or breastfeeding
• not able or willing to get an MRI scan
• not able or willing to get a blood draw

We will share baseline, post-treatment, and follow-up scores on the primary outcome on a de-identified basis.

The IPD will be published along with the primary outcome paper as a supplement. The primary outcome paper will describe the study protocol and the statistical analysis plan. We estimate this will take place within two years of the collection of the last data follow-up data point. The data will be available for as long the journal in which the paper appears exists.

Anyone who can access the journal article will be able to access the supplemental data. As noted, we will post scores on the primary outcome on a de-identified basis. Interested parties will be able to access the data by going to the journal website, finding the article, and then downloading the supplement.