Evaluating the Impact of Non-Invasive Brain Stimulation on Learning and Consolidation of Phonologically Similar Novel Spoken Words - PROJECT SUMMARY/ABSTRACT In the United States, nearly one in five older youth struggles with basic reading skills (NCES; PIAAC, 2019). Because of their low literacy levels, these individuals are placed at greater risk for unemployment and poor health outcomes compared to their typically developing peers (Miller, McCardle, & Hernandez, 2010). These struggles with reading may be due to a brain-based difficulty in learning new words, which is a critical skill for reading and language development (Perfetti, 2007). We have previously reported behavioral evidence that children and youth with reading disabilities experience difficulties learning and remembering phonologically similar spoken pseudowords (e.g., pibu in relation to pibo or dibu; Malins et al., 2020), which can be taken as evidence of unstable phonological representations for newly learned words (Magnuson et al., 2011). Despite these previous behavioral findings, we do not yet understand how language-related networks in the brain contribute to these observed word learning difficulties, especially in older youth who have struggled with reading for many years. The objective of this proposal is to use non-invasive brain stimulation (i.e., repetitive transcranial magnetic stimulation, or rTMS) to evaluate a causal model of word learning and processing, thereby providing a better understanding of its underlying neural mechanisms. In the proposed study, using a within-subjects design, participants will complete a visual phonological discrimination task and spoken artificial lexicon learning and, as well as a novel word retention task following application of rTMS (either active stimulation or sham) to a dorsal stream node of the reading network in the brain. Participants will consist of two groups of learners between the ages of 16 and 21: 20 older youth with typically developed reading abilities (OYTD), and 20 older youth with reading difficulties (OYRD). We hypothesize that: (1) inhibition of the left dorsal stream will impact subsequent learning, processing, and retention of phonologically similar pseudowords; (2) the impact of dorsal stream inhibition on word learning behavior will be associated with baseline levels of variability in neural activity (Hancock, Pugh, & Hoeft, 2017). For the OYTD group (Aim 1), we predict that dorsal stream inhibition will result in slower phonological processing, slower growth in word learning accuracy, and poorer retention, specifically for phonologically related pseudowords. In contrast, for the OYRD group (Aim 2), we predict that dorsal stream inhibition will result in faster phonological processing and growth in word learning accuracy, as well as improved retention specifically for phonologically related pseudowords. To better understand the nature of these effects, we will perform exploratory analyses (Aim 3) to evaluate associations between baseline neural activation variability during a functional magnetic resonance imaging task and individual differences in the magnitude of modulatory effects observed in Aims 1 and 2. Completion of these aims will lay a foundation for future proposals that will use rTMS as an adjunct to improving learning potential during treatment for persistent reading difficulties.
