Listening and reading comprehension in Cantonese-speaking people with right hemisphere versus left-hemisphere damage with aphasia

Background:
Reading in Chinese has been associated with activation of the right hemisphere fusiform gyrus (Conrad, 2016) and occipital cortex, which contribute to the visual and spatial recognition of the visual symbols during the processing of Chinese characters (Clark et al., 1996; Shen et al., 1999). Listening comprehension has been relatively less associated with the right hemisphere activation (Tan et al., 2001). This study compares the reading and listening comprehension among left-brain damaged (LHD) people with aphasia (PWA), individuals with right hemisphere damage (RHD) without aphasia and neurotypical healthy controls (HC) using the newly developed Cantonese Computerized Revised Token Test (CRTT-Cantonese; Bakhtiar et al., 2020) adapted from the English CRTT (McNeil et al. 2015).

Methods:
Thirty-two native Cantonese-speaking PWA, 18 Cantonese speakers with RHD, and 42 HC participated in this study. All participants had more than six years of formal education with no premorbid history of speech, language, hearing or learning disabilities. All the participants completed the Cantonese Aphasia Battery (CAB), Hong Kong Oxford Cognitive Screen (HK-OCS), Snellen visual test, pure tone hearing screening test, and CRTT pretests in the first session. Participants were randomly assigned to perform either the CRTT-Cantonese listening (CRTT-L-Cantonese) or CRTT-Cantonese reading (CRTT-R-WFCantonese) tests across 2 separate sessions with at least one-week interval.

Results:
Linear mixed-effect analysis revealed a significant main effect of group for CRTT-Cantonese subtest scores. Tukey post-hoc pairwise comparisons showed that PWA scored significantly lower than RHD and HC groups (p < .0001), and the RHD group scored significantly lower than HC (p < .05). However, there were no significant interactions between groups and modalities.

Conclusion:
These results demonstrate that the CRTT-L-Cantonese and CRTT-R-WF-Cantonese significantly differentiate the langauge comprehension among three participant groups of PWA, RHD and HC. However, the current findings did not show any diversion among reading and listening comprehension in the RHD group. These results confirm that language comprehension is mainly subserved with left hemisphere langauge network strucutres, which is more damaged in PWA, though it can be affected to a lesser extent in people with RHD. Our newly developed Cantonese Computerized Revised Token Test showed sufficient sensitivity to make this distinction.