Poster C50, Sunday, March 26, 5:00 – 7:00 pm, Pacific Concourse
Attention modulates relative lateralization of N170 for single letters in Japanese Hiragana
Tomoki Uno1, Ayumi Seki2, Tetsuko Kasai2; 1Graduate School of Education, Hokkaido University, 2Faculty of Education, Hokkaido University
Fluent reading requires the integration of letters into a letter string and rapid conversion of letters to sounds, which are considered to be reflected by N170 component of event-related potentials (ERPs). The relative lateralization of N170 is modulated by the transparency of language, suggesting that it reflects early phonological mapping (Maurer & McCandliss, 2007). Moreover, it has been recently reported that the lateralization of N170 might be modulated by the integration of letters and/or attention: single alphabetic letters, and interspaced or unattended Hiragana letter strings elicited atypical N170 distributed over bilateral occipito-temporal sites (Stevens et al., 2012; Okumura et al., 2014, 2015). To explore the essential factors for the lateralization of N170, the present study examined ERPs in response to single letters of transparent Hiragana and alphanumeric symbols in two tasks. In experiment 1, participants responded to the color change of the fixation that was presented 1.21° below letters/symbols. Therefore, they were asked to keep attention away from letters/symbols. In contrast, in experiment 2, participants responded to the color change of letters/symbols. In this task, they had to keep attention on stimuli. As results, unattended single letters elicited greater negative enhancement than symbols at bilateral occipito-temporal scalp sites during 200–240 ms poststimulus (experiment 1). However, we observed left-lateralized N170 (140-200 ms) for attended single letters (experiment 2). These results showed that left-lateralized N170 could be elicited even by single letters when they are transparent and attended, suggesting that it is involved in the phonological mapping facilitated by attention for letters.
Topic Area: LANGUAGE: Lexicon