Chinese and Korean characters engage the same visual word form area in proficient early Chinese-Korean bilinguals

Abstract

A number of recent studies consistently show an area, known as the visual word form area (VWFA), in the left fusiform gyrus that is selectively responsive for visual words in alphabetic scripts as well as in logographic scripts, such as Chinese characters. However, given the large difference between Chinese characters and alphabetic scripts in terms of their orthographic rules, it is not clear at a fine spatial scale, whether Chinese characters engage the same VWFA in the occipito-temporal cortex as alphabetic scripts. We specifically compared Chinese with Korean script, with Korean script serving as a good example of alphabetic writing system, but matched to Chinese in the overall square shape. Sixteen proficient early Chinese-Korean bilinguals took part in the fMRI experiment. Four types of stimuli (Chinese characters, Korean characters, line drawings and unfamiliar Chinese faces) were presented in a block-design paradigm. By contrasting characters (Chinese or Korean) to faces, presumed VWFAs could be identified for both Chinese and Korean characters in the left occipito-temporal sulcus in each subject. The location of peak response point in these two VWFAs were essentially the same. Further analysis revealed a substantial overlap between the VWFA identified for Chinese and that for Korean. At the group level, there was no significant difference in amplitude of response to Chinese and Korean characters. Spatial patterns of response to Chinese and Korean are similar. In addition to confirming that there is an area in the left occipito-temporal cortex that selectively responds to scripts in both Korean and Chinese in early Chinese-Korean bilinguals, our results show that these two scripts engage essentially the same VWFA, even at the level of fine spatial patterns of activation across voxels. These results suggest that similar populations of neurons are engaged in processing the different scripts within the same VWFA in early bilinguals.

Figure 1. Schematic depiction of the experimental paradigm.

In block-design runs, subjects viewed Chinese characters, Korean characters, unfamiliar faces and line drawings in separate blocks. In each block 20 stimuli were presented and each stimulus was presented for 250 ms with an inter-stimulus interval of 750 ms. Each run contained 12 blocks with 3 blocks for each category of stimuli.

Figure 2. Selectively activated area for Chinese characters and Korean characters in the left occipito-temporal cortex.

Brain activation maps in Talairach space of each subject show the activation of Chinese characters and Korean characters when contrasted with faces, respectively (q(FDR)<10⁻³). The right side of the image corresponds to the left hemisphere. The cross in each image is centered at the coordinate for the peak category selective response point. The color bar shows the t values.

Figure 3. Correlation coefficients for within-category stimuli (left bar, C-C, K-K, L-L, F-F) and correlation coefficients for between-category stimuli (right bar, C-L, K-L, C-F, K-F, F-L).

The correlation coefficient C-K (middle bar) is not significantly different from the within-category correlations, but significantly different from the between category correlations (p = 0.000).