One in five adults in the US are unable to adequately comprehend a sentence. Low literacy is a major public health crisis, with no existing solution: findings from the Programme for the International Assessment of Adult Competencies (PIAAC) reveal that there have been no significant improvements to US national statistics on literacy in the past 30 years. Studies of the survey data reveal that adults with low literacy in the US have in-tact but slow word reading processes and vocabulary, and struggle to comprehend sentences and passages. Rates of poor reading comprehension (RC) ability are especially alarming given that RC ability is strongly predictive of educational outcomes, occupation and wage, health literacy/outcomes, and crime. Through these links, the World Literacy Foundation estimates that the literacy crisis accounts for 2% of the US's GDP annually. The current gold-standard interventions for RC ability are behavioral interventions that focus on cognitive skills found to support RC. However, meta-analyses across interventions show minimal raw gains. Brain research has allowed for the identification of "hidden" RC processes that are not captured by behavioral tests These studies have identified a consistent brain pathway that supports positive RC outcomes. This pathway is a compelling target for brain-based interventions. In particular, recent advances in noninvasive brain stimulation interventions provide a promising route for clinically-meaningful, brain-based treatments. However, brain research in RC has not been translated into an effective brain-based intervention. There is an urgent need for a cutting-edge, non-invasive brain stimulation intervention that will transform the way we approach the clinical treatment of poor RC. The current project will integrate our work in the brain network science of RC and breakthroughs in non-invasive stimulation to address these challenges and develop a brain-based RC intervention.

To accomplish this, the proposed study will invite typical adults with a range of RC ability (good and poor) to participate in three visits to the lab. The rationale for examining adults is to that the current study aims to develop a brain-based intervention (i.e. non-invasive brain stimulation) to treat low literacy in adults, as current behavioral interventions in adults are largely unsuccessful. N=225 participants will come in for three visits; for each visit adults will complete behavioral testing, magnet resonance imaging (MRI), and electroencephalography (EEG). Visit 1 will establish baseline behavior and brain measures of the individual (total visit time of 3.5 hours). Visit 2 will include a behavioral and safe, non-invasive stimulation intervention for the individual (total visit of 3 hours). Stimulation will involve two sessions, one while subjects are in the MRI, and one while subjects are having EEG. Visit 2 will also involve behavioral testing to determine intervention effects. Visit 3 will establish prolonged intervention effects using behavior and brain measures of the individual (total visit of 2.5 hours). Participants will be recruited and randomly assigned to receive one of three non-invasive stimulation interventions, and all will receive a canonical behavioral intervention, so that the smallest subgroup in the study will be N=75, which provides sufficient statistical power (see Statistical Design and Power). All subjects will have typical word reading ability (greater than or equal to 15th percentile), and either good (greater than 25th percentile) or poor (less than or equal to 25th percentile) reading comprehension ability. Non-invasive stimulation subgroups include two stimulation groups distinguished only by electrode placement, and one sham control group. Behavioral intervention involves a short paper/pencil reading comprehension intervention. Each intervention subgroup will be randomly assigned, but with the restriction that the distribution of reading comprehension ability is even across subgroups. This will be accomplished while maintaining double-blind procedures. Collection will begin in Summer 2022 and continue through Fall 2025. Adults will be recruited from the Nashville community. Behavioral testing and MRI (with and without stimulation) will occur at the Vanderbilt Institute for Imaging Science (VUIIS). EEG (with and without stimulation) will occur at the Vanderbilt Kennedy Center.