Neural Substrates Involved in L2 Phonological Processing Are Constrained by L1

1. Neural Substrates Involved in L2 Phonological Processing Are Constrained by L1 Hsin-Chin Chen1, Jyotsna Vaid2, and Heather Bortfeld3 1National Chung Cheng University, 2Texas A&M University, 2University of Connecticut Correspondence: psyhcc@ccu.edu.tw, jvaid@psych.tamu.edu, heather.bortfeld@uconn.edu Introduction Chinese Monolingual (Chen et al., 2006) English Monolingual (Chen et al., 2006) Chinese-English Bilingual Chinese-English Bilinguals • B. English: • The blood flow change of HbO2 in BA 9 (addressed phonology) was significantly larger than that in BA 39/40 (assembled phonology), t(10)=3.47, p<.01. • The HbO2 in BA 9 was significantly larger than that in BA 39/40 starting at 1.0s and lasting to 9.0s. Chinese Reading Chinese Reading English Reading English Reading BA 9 vs. BA39/40 BA 9 vs. BA39/40 BA 9 vs. BA39/40 BA 9 vs. BA39/40 • Recent studies comparing processes of alphabetic vs. logographic scripts provide evidence for shared and orthography-specific regions of neural activity. • Neuroimaging studies have shown that the left dorsal temporoparietal system (BA39/40) is specifically related to mediated grapheme-to-phoneme conversion and fine-grained phonemic processing in alphabetic writing systems, whereas the left middle frontal gyrus at BA9 is more related to “look-up” processes of addressed phonology (Bolger, Perfetti, & Schneider, 2005; Tan, Laird, & Fox, 2005; Chen et al., 2008). • Examining sentence reading in Japanese-English and English-Japanese bilinguals, Nakada, Fujii, and Kwee (2001) suggested that bilinguals tend to use their neural systems responsible for L1 to process their L2. Nakada et al. (2001) suggested that bilingual readers apply L1 neural systems to process L2, even though the neural systems responsible for L1 processing were not supposed to be responsible for L2 processing in monolingual speakers of that language. • Purpose of the Study :We studied neural correlates of word recognition in Chinese-English skilled bilinguals who use fine-grained phoneme processing for their L2 and addressed phonological processing for their L1. Discussion • As shown in Figure 1, Chinese readers showed stronger blood flow change in BA9 than that in BA39/40, whereas English monolingual readers showed stronger blood flow change in BA39/40 than that in BA9 (reanalyzed from the data of Chen, Vaid, & Bortfeld, 2006). • The present results revealed that our Chinese-English bilingual participants processed their L2 (English) applying their L1 neural systems, although the neural systems responsible for Chinese word recognition, according to Perfetti et al. (2007), are not supposed to be the same as those responsible for English word recognition. • These data are compatible with behavioral studies showing an influence of properties of L1 writing systems on L2 reading strategies. However, it is unclear how to reconcile apparent transfer effects in cognitive processing strategies in bilinguals with claims of orthography-specific regions of neural sensitivity (see comments by Tomioka and Paradis, 2002, on Nakada et al., 2001). Figure 1. Mean blood flow changes of oxyhemoglobin concentration on BA9 and BA39/40 in Chinese and English homophone judgment tasks. In x-axis, 0s represented the onset of the stimuli. Results Method • Measures : • Neural activity was assessed using Near-Infrared Spectroscopy (NIRS), an optical imaging hemodynamic technique that provides better temporal resolution than fMRI and better spatial resolution than electrophysiological measures. • Activity was recorded from two brain areas: BA 9 (associated with addressed phonology) and BA 39/40 (associated with assembled phonology). • Probes emitting light at two wavelengths, 690 and 830 nm, were applied; one of these is more sensitive to oxyhemoglobin whereas the other is more sensitive to deoxyhemoglobin. • The raw signals from detectors were sampled at 200Hz. References • Homophone Judgment Task : • English: Mean RT=1117ms • Chinese: Mean RT=958ms • NIRS Data Analysis : • The raw NIRS signals were converted to optical density units digitally low-pass filtered at 1 Hz and high-pass filtered at 0.02 Hz. • Data were analyzed in 17s time epochs including 2s before and 15s after the onset of the word pairs. • A. Chinese: • The blood flow change of HbO2 in BA 9 (addressed phonology) was significantly larger than that in BA 39/40 (assembled phonology), t(10)=2.81, p<.05. • The HbO2 in BA 9 was significantly larger than that in BA 39/40 starting at 5.5s and lasting to 12.5s. • Participants : 11 Chinese-English bilingual readers with more than 12 years of experience in English reading. • Materials and Procedures : • Participants were tested on two homophone judgment tasks (one per language) while behavioral (reaction time) and neuroimaging measures were obtained. • Per task,10 homophonic word pairs with medium to high word frequencies and 10 non-homophone word pairs were selected as the materials. • On each trial, a fixation point was presented first. After participants clicked the mouse, a pair of words was shown for 2s, followed by a 13s blank. • Participants were to decide whether the presented words were homophones. • Bolger, D. J., Perfetti, C. A., & Schneider, W. (2005). Cross-cultural effect on the brain revisited: Universal structures plus writing system variation. Human Brain Mapping, 25, 92-104. • Chen, H.-C., Vaid, J., & Bortfeld, H. (2006, April). Orthography constrains neural substrates involved in phonological processing: An optical imaging study. Poster presented at annual meeting of the Cognitive Neuroscience Society, San Francisco. • Chen, H.-C., Vaid, J., Bortfeld, H., & Boas, D, A. (2008). Optical Imaging of Phonological Processing in Two Distinct Orthographies. Experimental Brain Research, 184, 427-433. • Nakada, T., Fujii, Y., & Kwee, I. L. (2001). Brain Strategies for Reading in the Second Language are Determined by the First Language. Neuroscience Research, 40, 351-358. • Perfetti, C. A., Liu, Y., Fiez, J. Nelson, J., Bolger, D. J., & Tan, L-H. (2007). Reading in two writing systems: Accommodation and Assimilation in the brain’s reading network. Bilingualism: Language and Cognition, 10, 131-146. • Tan, L. H., Laird, L. L., & Fox, P. T. (2005). Neuroanatomical correlates of phonological processing of Chinese characters and alphabetic words: A meta-analysis. Human Brain Mapping, 25, 83-91. • Tomioka N. & Paradis, M. (2002) Cerebral processes involved in reading as a function of the structure of various writing systems. Neuroscience Research, 42: 87-89. Acknowledgement • We thank David Boas for his helpful comments.