Modality- and task-specific brain regions involved in Chinese lexical processing

Abstract

fMRI was used to examine lexical processing in native adult Chinese speakers. A 2 task (semantics and phonology) x 2 modality (visual and auditory) within-subject design was adopted. The semantic task involved a meaning association judgment and the phonological task involved a rhyming judgment to two sequentially presented words. The overall effect across tasks and modalities was used to identify seven ROIs, including the left fusiform gyrus (FG), the left superior temporal gyrus (STG), the left ventral inferior frontal gyrus (VIFG), the left middle temporal gyrus (MTG), the left dorsal inferior frontal gyrus (DIFG), the left inferior parietal lobule (IPL), and the left middle frontal gyrus (MFG). ROI analyses revealed two modality-specific areas, FG for visual and STG for auditory, and three task-specific areas, IPL and DIFG for phonology and VIFG for semantics. Greater DIFG activation was associated with conflicting tonal information between words for the auditory rhyming task, suggesting this region's role in strategic phonological processing, and greater VIFG activation was correlated with lower association between words for both the auditory and the visual meaning task, suggesting this region's role in retrieval and selection of semantic representations. The modality- and task-specific effects in Chinese revealed by this study are similar to those found in alphabetical languages. Unlike English, we found that MFG was both modality- and task-specific, suggesting that MFG may be responsible for the visuospatial analysis of Chinese characters and orthography-to-phonology integration at a syllabic level.

Figure 1

Examples for the meaning task (A) and the rhyming task (B). Rel = related pairs; Unrel = unrelated pairs; Rhy = rhyming pairs; Unrhy = unrhyming pairs.

Figure 2

Experimental timing for the meaning and the rhyming tasks.

Figure 3

Activation map for the meaning task and the rhyming task in the visual modality. Green indicates activation for the meaning task; red indicates activation for the rhyming task; blue indicates overlapping activation for both tasks. FG = fusiform gyrus; IOG = inferior occipital gyrus; MFG = middle frontal gyrus; VIFG = ventral inferior frontal gyrus; Angular = angular gyrus; DIFG = dorsal inferior frontal gyrus.

Figure 4

Activation map for the meaning task and the rhyming task in the auditory modality. Green indicates the activation for the meaning task; red indicates the activation for the rhyming task; blue indicates the overlapping activation for both tasks.

Figure 5

Modality-specific effect in FG and STG. Blue dots mark the peak of ROIs in brain images. *p < .005 between modalities in bar graphs.

Figure 6

Task-specific effects for the rhyming tasks in IPL and DIFG. Blue dots mark the peak of ROIs in brain images. *p < .005 between tasks in bar graphs. Difference in DIFG between word pairs with conflicting tonal information versus those with nonconflicting tonal information is shown in bottom right. Correlation between beta value in DIFG and accuracy for the rhyming task is shown in bottom left.

Figure 7

Task-specific effects for the meaning tasks in VIFG. Blue dots mark the peak of ROIs in brain images. *p < .005 between tasks in bar graphs. Correlation in VIFG between association strength and activation separately for the visual and auditory meaning tasks is shown below.

Figure 8

Modality- and task-specific effects in MFG. Blue dot marks the peak of the ROI in brain images. *p < .05,**p < .01, ***p < .005 in bar graphs.