顶下叶在汉语声调感知中的作用:fNIRS导航的TMS研究OACHSSCD

The left inferior parietal lobe(IPL)is a critical brain region for categorical perception of speech,and some studies have shown that it is involved in the categorical perception of Chinese tones.However,its specific role in tone perception remains unclear. The current study manipulated both tonal categories(intercategory vs.intracategory)and acoustic features(large vs.small acoustic intervals)in successively presented stimulus pairs to examine whether the IPL is sensitive to acoustic features or to the abstract representation of tonal categories during Chinese tone perception.Experiment 1 used functional near-infrared spectroscopy(fNIRS)to localize functional activation in the IPL during tone perception.Experiment 2 used transcranial magnetic stimulation(TMS)to virtually impair the IPL and establish a causal neural link between the IPL and tonal categorical perception. Experiment 1 showed that the dorsal IPL channel was sensitive to tonal categories,exhibiting more robust IPL activation induced by intercategory stimulation than intracategory stimulation.This region was also sensitive to acoustic intervals,with stronger activation induced by small acoustic intervals than by large ones.In Experiment 2,the dorsal and ventral IPL channels were virtually disrupted separately using TMS.When the dorsal IPL channel was inhibited,its sensitivity to tonal categories disappeared.In contrast,the ventral IPL channel and the left premotor cortex(PMC)channel were sensitive to acoustic intervals,with stronger activation induced by large acoustic intervals than by small ones.However,when TMS inhibited the ventral IPL channel,only functional compensation in the left inferior frontal gyrus channels showed sensitivity to tonal categories and induced greater intracategory activation than intercategory stimulation did. In summary,these findings demonstrate a critical role of the left dorsal IPL in the categorical perception of Chinese tone.In contrast,the ventral IPL plays an essential gating role in the dorsal stream of speech perception.The results enrich the neurophysiological model of speech perception from a tonal language perspective,elucidating the collaborative mechanism between dorsal and ventral speech streams in categorical perception.