Use TDCS Technology To Explore The Brain Lateralization Of Chinese Tone Processing

The cognitive and neural mechanism of Chinese tone processing has been widely concerned.Two competing hypotheses about hemisphere lateralization for processing lexical tones.The function hypothesis holds that the speech processing is determined by its own function,which is like a meaningful language processing to lateralization of the left hemisphere,while the processing of information such as music is lateralization of the right hemisphere.And acoustic hypothesis is that speech acoustic physical properties of partial lateralization pattern determines the process,such as consonants and vowels which requires high temporal resolution processing and for the left side of the processing,and the slow change of spectrum information processing in the right side of the brain.The two hypotheses are still competing.The tonal language such as Mandarin Chinese has a unique linguistic function:they both have phonological information and acoustic information.Nonetheless,there remains some uncertainty with regard to lateralization of lexical tones processing.To address the problem of causality in lexical tones processing,we used transcranial direct current stimulation(tDCS)to down-regulate(via cathodal stimulation)and up-regulate(via anodal stimulation)excitability in either left or right temporal lobe and measured the effect on performance in a tones identification task and discrimination task in comparison with sham stimulation so that to investigate the lateralization of the perception of Mandarin Chinese lexical tones.The results showed that in identification task,the clarity of perceptual was significantly improved when the right temporal lobe received anodic stimulation.In the discrimination task,the performance of categorical perception was decrease when the left temporal lobe received cathodal stimulation.It was shown that stimulation on the right temporal lobe affected the perception of Chinese tone,while stimulating the left temporal lobe had no similar effect.The results of the study provide direct causality evidence for the lateralization of Chinese tone perception.