Poster C46, Wednesday, August 21, 2019, 10:45 am – 12:30 pm, Restaurant Hall
Was the ship thinking or was the sheep sinking? A tDCS study in speakers of English as a second language
Katy Borodkin1, Tamar Gassner1;1Department of Communication Disorders, Sackler Faculty of Medicine, Tel Aviv University
Background. Second language speakers find non-native contrasts (e.g., ship/sheep or think/sink) challenging to perceive and subsequently pronounce correctly. However, musical training can improve these skills (Slevc & Miyake, 2006). Neuroimaging studies suggest that music and speech processing may be linked through a shared neural substrate, located in the left planum temporale (Elmer, Meyer, & Jäncke, 2011). The present study was devised to further examine the neural mechanisms mediating the effects of musical training on second language speech perception and production using transcranial direct current stimulation (tDCS). Method. The training experiment included 20 participants (10 men), aged 26-38. They were native Hebrew speakers who learned English mainly in school and did not have extensive musical training. Participants were randomly assigned to the experimental group (active stimulation, n = 10) or control group (sham stimulation, n = 10). The participants and the experimenter were blinded to group assignment (double-blind design). All participants underwent a 20-min feedback-based musical training combined with anodal (1.5 mA) or sham tDCS over the left posterior superior temporal gyrus (pSTG) (electrode site CP5 according to the EEG 10–20 system). The reference electrode was placed above the contralateral orbit (both electrodes size: 35 cm2). Prior to and following the training, musical skills were tested as well as discrimination and pronunciation skills in English. In a follow-up experiment (listeners experiment), training-induced changes in English pronunciation was assessed by 30 native English speakers (16 men, aged 18-61) using an identification task. Participants in the listeners experiment were unaware of the training experiment procedures. Results. All participants, regardless of tDCS groups, showed an improvement in musical skills following training, as evidenced in reduced reaction times. In contrast, tDCS had a differential effect on speech processing skills in English. Following training, participants in the active stimulation group, but not the control group, showed better discrimination skills (as indexed by increased accuracy) and pronunciation skills in English (as manifested by reduced identification times of listeners who were English native speakers). Discussion. We conclude that musical skills were affected by musical training but not by tDCS stimulation over the left pSTG, since improvement was observed in both tDCS groups. On the other hand, discrimination and pronunciation skills in English as a second language were improved only in active stimulation but not sham stimulation group. These findings do not provide evidence that the left pSTG (of which the planum temporale is a part) is the shared neural substrate for processing music and speech sounds. They do suggest that this region plays an important role in perception and production of speech sounds and that tDCS can be utilized to improve these skills, which are often difficult to master, in second language speakers. References Elmer, S., Meyer, M., & Jäncke, L. (2011). Neurofunctional and behavioral correlates of phonetic and temporal categorization in musically trained and untrained subjects. Cerebral Cortex, 22(3), 650-658. Slevc, L. R., & Miyake, A. (2006). Individual differences in second-language proficiency: Does musical ability matter? Psychological Science, 17(8), 675-681.
Themes: Multilingualism, Speech Motor Control
Method: Neurostimulation