Similarities and differences in brain activation and functional connectivity in first and second language reading:...

It has been evidenced that both similarities and differences exist in the brain network involved in second language reading in comparison to the first language reading. However, very few studies have been done to compare functional connectivity in L1 and L2 reading. Brain activation and functional connectivity during English pseudoword rhyming judgment in a group of late Chinese-English bilinguals (the CE group) were compared to a Chinese word rhyming judgment task in another group of late Chinese-English bilinguals (the CC group). Brain activation analyses revealed that the two groups engaged a similar network and that the only significant group difference was greater involvement of the right middle occipital gyrus in the CC group than in the CE group, due to greater holistic visuospatial processing of Chinese characters. English pseudowords can be read using the same network as Chinese characters, whereas psychophysiological interaction (PPI) analyses revealed different connectivity within the reading network between the two groups. Greater functional connectivity was found between three visuo-orthographic seed regions and the right precentral gyrus in the CC group, suggesting that the sensorimotor patterns of Chinese syllables are activated during Chinese word rhyming judgment. In contrast, we found greater connectivity between the three seed regions and the left postcentral gyrus in the CE group. In addition, the connectivity between one of the three seed regions (i.e. the right middle occipital gyrus) and the left postcentral gyrus was positively correlated with English proficiency in the CE group. This suggests that somatosensory feedback plays a key role in processing the foreign phonemes of English pseudowords and those highly proficient bilinguals tend to rely on this information to a greater degree. We also found that within the CE group, the connectivity between the right middle occipital gyrus and the left inferior parietal lobule was positively correlated with accuracy, and that the connectivity between the right middle occipital gyrus and the left superior temporal gyrus was negatively correlated with reaction time. These results suggest that even if a Chinese network is used in reading English pseudowords, the classic grapheme-phoneme-correspondence regions that are important for native English reading are involved in highly performing bilinguals by connecting them with the visuo-orthographic region.