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Poster C81, Wednesday, August 21, 2019, 10:45 am – 12:30 pm, Restaurant Hall

Effects of Transcutaneous Vagus Nerve Stimulation on Statistical Language Learning and Phonological Working Memory

Edith Kaan1, Ivette De Aguiar1, Megan S. Nakamura1, Atharva P. Chopde1, Chenyue Zhao1, Damon G. Lamb1, John B. Williamson1, Eric C. Porges1;1University of Florida

Past studies have found that Vagus Nerve Stimulation (VNS) administered to epileptic patients has a positive effect on performance of memory consolidation tasks (Ghacibeh et al., 2006). More recent research has also demonstrated that applying transcutaneous stimulation to the auricular branch of the vagus nerve (tVNS) can also enhance associative learning in humans, in theory via modulation of neurotransmitters related to memory and learning (Jacobs et al., 2015). Presently, very little is known about the effects of tVNS on procedural learning. The current project investigates the effects of tVNS on phonological working memory and statistical (implicit) language learning. Method: We used a within-subject design with two sessions three weeks apart. Sessions 1 and 2 were counterbalanced to be either with tVNS stimulation via the tragus in the left ear, or with a sham (earlobe) stimulation on the left ear. Stimulation was continuous throughout the study, and set at 80% of the level that caused slight discomfort. Participants carried out a phonological working memory task followed by a statistical learning task in each session. In the phonological working memory task (Nittrouer & Miller, 1999) participants were presented first with 8 non-rhyming words, and then 8 rhyming words paired with corresponding pictures. Participants then listened to the 8 words spoken in a random order and were told to choose the corresponding pictures based on the order they heard the words spoken. The statistical learning task was based on Isbilen et al. (2017). Participants listened to an 11 minute sequence of 6 trisyllabic pseudowords presented without boundaries (e.g. modipalatibilomarikibudutagalu…). After the exposure phase, participants completed a forced choice task in which they heard two items, one that matched and one that did not match the transitional probabilities of the stream they just heard, and indicated which sounded more familiar. Next, participants were asked to repeat sequences of six syllables, which were either composed of two words in the pseudo language or of random combinations of syllables. If statistical learning occurred, words should be repeated more accurately than the non-words. Results and Discussion: Data collected thus far (n=5) show a trend towards a positive effect of tVNS on phonological memory for the rhyming condition only. In addition, tVNS seems to be associated with better word versus non-word repetition in the statistical learning task. No systematic differences between sham and tVNS are seen in the alternative forced choice task. If these results persist with more participants, these outcomes suggest that tVNS enhances phonological memory when the task becomes more challenging (phonologically similar materials). We cannot say at this point whether tVNS enhances statistical learning or the retrieval processes involved in conducting the repetition task.

Themes: Phonology and Phonological Working Memory, Control, Selection, and Executive Processes
Method: Neurostimulation

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