Language differences in the brain network for reading in naturalistic story reading and lexical decision

Abstract

Differences in how writing systems represent language raise important questions about whether there could be a universal functional architecture for reading across languages. In order to study potential language differences in the neural networks that support reading skill, we collected fMRI data from readers of alphabetic (English) and morpho-syllabic (Chinese) writing systems during two reading tasks. In one, participants read short stories under conditions that approximate natural reading, and in the other, participants decided whether individual stimuli were real words or not. Prior work comparing these two writing systems has overwhelmingly used meta-linguistic tasks, generally supporting the conclusion that the reading system is organized differently for skilled readers of Chinese and English. We observed that language differences in the reading network were greatly dependent on task. In lexical decision, a pattern consistent with prior research was observed in which the Middle Frontal Gyrus (MFG) and right Fusiform Gyrus (rFFG) were more active for Chinese than for English, whereas the posterior temporal sulcus was more active for English than for Chinese. We found a very different pattern of language effects in a naturalistic reading paradigm, during which significant differences were only observed in visual regions not typically considered specific to the reading network, and the middle temporal gyrus, which is thought to be important for direct mapping of orthography to semantics. Indeed, in areas that are often discussed as supporting distinct cognitive or linguistic functions between the two languages, we observed interaction. Specifically, language differences were most pronounced in MFG and rFFG during the lexical decision task, whereas no language differences were observed in these areas during silent reading of text for comprehension.

Fig 1. A. Stimuli were presented in intermixed blocks of reading and listening tasks.

Each block lasted about one minute interspersed with 20s rest intervals. In reading block, 25 phrases (range 24–27) were presented continuously with each phrase lasting 2s; B. Examples of story materials. The Chinese story was translated into English phrase by phrase so that the narrative could be presented at the same rate for both groups. C. Very similar patterns of brain activity are engaged by naturalistic reading across languages (top, middle). The group contrast (bottom) revealed regions activated stronger for Chinese in visual cortex and regions for mapping spelling to meaning.

Fig 2. A. Event related designed were conducted for lexical decision task.

Each trial began with a 200ms fixation. The stimulus was presented for 500ms with a blank screen for participants’ response. The mean ITI was 5.3s; B. Examples of each stimulus class designed for manipulating wordlikeness both for Chinese and English characters/words. C. The contrast brain map for Chinese > English.

Fig 3. Brain regions identified as interaction of Task by Language.

The black outlier indicates anatomical mask of bilateral fusiform gyrus. The bar graphes plot each ROI’s activity pattern.

Fig 4. Data from lexical decision (LD) and story reading in ROIs from meta-analyses of Chinese and English reading.

Large language by task interactions are observed in middle frontal gyrus (MFG), and left and right fusiform gyrus (FFG), indicating that language differences are exaggerated by artificial task conditions in these regions. In posterior superior and middle temporal gyri (STG and MTG), only a large main effect of task was found, suggesting that these regions are engaged more strongly by natural reading conditions than lexical decision in both languages.