Does script format matter for language lateralisation? A functional transcranial Doppler study of Chinese verbal fluency.

Although language production is generally dominated by the left hemisphere, it remains uncertain whether the script format influences the degree of this lateralization. To examine this issue, verbal fluency was assessed in 96 right-handed native Chinese speakers using functional transcranial Doppler sonography (fTCD). The subjects were asked to perform four overt word-generation tasks with four combinations of cue format and fluency type: Pinyin phonological fluency, character phonological fluency, Pinyin semantic fluency, and character semantic fluency. Laterality indices were calculated as the mean left-minus-right middle cerebral artery blood-flow velocity difference across the complete prespecified period of interest from 4 to 14 s after cue onset. All four conditions showed significant left lateralization, with mean LIs of 3.05, 2.60, 2.76, and 2.26 for Pinyin phonological, character phonological, Pinyin semantic, and character semantic fluency, respectively; all ps < .001. Pinyin-cued tasks yielded greater lateralization than character-cued tasks, F(1, 95) = 117.61, p < .001, ηp² = .553, and phonological fluency yielded greater lateralization than semantic fluency, F(1, 95) = 32.81, p < .001, ηp² = .257. The results indicate that verbal fluency is left-dominant in Mandarin, while the script format modulates the degree of hemispheric dominance during lexical retrieval.