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Poster A77, Wednesday, November 8, 10:30 – 11:45 am, Harborview and Loch Raven Ballrooms

A tDCS study of the implicit learning of foreign cognate and non-cognate words

Joshua Payne1, Paul Mullins1, Marie-Josephe Tainturier1;1Bangor University

Some studies suggest that transcranial direct current stimulation (tDCS) over left temporoparietal cortex can enhance the acquisition of new words in healthy adults, as this region is thought to be involved in the acquisition of form-meaning connections. The goal of our study was to extend these findings to a real foreign language and to examine the relative effects of stimulation on cognate and non-cognate words as a function of phonological memory ability. We expected cognate words to be learned and retained more easily and that tDCS would enhance learning, particularly for non-cognates. In addition, we expected tDCS facilitation to be more pronounced for participants with poorer phonological memory. Methods: Thirty-two monolingual English speakers completed three experimental sessions on consecutive days, and a follow-up session one week later. We recorded accuracy and RTs during implicit vocabulary learning tasks, adapted from Flöel et al. (2008), conducted in two consecutive sessions (1mA active vs. sham tDCS). Half of the target Dutch nouns were non-identical cognates (BOOK -> boek) and half matched non-cognates (WINDOW -> raam). Backward translation tasks were used to assess learning and retention, immediately, the following day, and a week following acquisition. tDCS was applied single-blind to the left temporoparietal region, with anode centred over CP5, and a contralateral supraorbital reference. Phonological memory ability was measured using the CTOPP-2. Results: Mixed effects analyses showed significant gains in overall vocabulary acquisition, with a Dutch-English cognate advantage. Performance for cognates in backward translation tasks was stable at all three post-stimulation time points. Non-cognates showed initial increases in performance the day after learning, which decayed a week later. At the group level, performance during and after active tDCS did not differ significantly from sham. We observed a significant interaction between Phonological Memory, Stimulation and Cognate Status. Participants with poorer phonological memory learned more non-cognates during active tDCS versus sham. Unexpectedly, those with higher phonological memory showed an overall decrement in performance during active stimulation. Phonological Memory did not significantly modulate the effect of tDCS on backward translation. Discussion: Even following brief exposure to a FL, phonological form similarity affects how easily meaning can be acquired for translation equivalents in an implicit learning task. We observed specific effects of tDCS for people with lower phonological memory abilities in line with some recent findings in older adults. The novel finding that tDCS negatively impacts performance for participants with higher phonological memory may be due to an overstimulation of temporal cortex in this group, in line with a population coding account of tDCS effects. Response times analysis is in progress, which may be more sensitive to the effects of stimulation for better learners and/or cognate stimuli. Multiple stimulation sessions may also be more effective, particularly in young people. Direct comparison of multiple montages and systematic exploration of multiple tES techniques/parameters (e.g., tRNS, multi-session) would provide insight into potentially subtle neural changes. Manipulation of key psycholinguistic variables, such the phonological similarity manipulation we employed, may highlight the specific role of regions inovlved in lexical processing and language learning.

Topic Area: Phonology and Phonological Working Memory

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