应用tDCS技术探讨汉语声调加工的大脑偏侧化

【作者】 张若昕；

【导师】 杨剑峰；

【作者基本信息】 陕西师范大学 ， 基础心理学， 2018， 硕士

【摘要】 近年来,汉语声调加工受到了语言认知神经科学的广泛关注。对声调加工的大脑偏侧化有两种理论假说:功能假说认为,声音加工是由自身功能决定的,正如有意义的语言加工为左半球偏侧化,而音乐等信息的加工为右半球偏侧化;而声学假说则认为,声音的声学物理属性决定了其加工的偏侧化模式,如语音中需要进行高时间分辨率加工的辅音与元音的加工为左偏侧化加工,而慢速变化的频谱信息则存在加工的右偏侧化。汉语声调在功能上是语义单元,而在声学特征上是慢速变化的频率信息。因此汉语声调加工的偏侧化研究是当前研究的一个焦点问题,为厘清上述理论假说争论提供可能。本研究采用经颅直流电刺激(tDCS)的神经调适技术,分别刺激大脑左、右半球的颞叶听觉皮层,通过施加微弱直流电刺激来提高(阳极刺激)和抑制(阴极刺激)大脑皮层的神经兴奋性,考察两半球颞叶区域的神经活动与汉语声调感知的因果联系。本研究通过被试声调知觉分类清晰度以及范畴内刺激与范畴间刺激差异大小对被试声调感知能力进行测量。包含前期行为实验与tDCS实验,实验材料使用汉语/i/一声至四声连续变化(共11个声音刺激)的语音刺激,实验包含识别任务与辨别任务:识别任务中要求被试对随机出现的语音刺激判断为汉语一声或四声;辨别任务中要求被试判断前后出现的两个语音刺激是否相同。行为实验确认被试对实验材料的知觉为范畴知觉,并通过辨别任务挑选一组声学物理间隔相等但分别为范畴间与范畴内的刺激。并以此进行下一步的tDCS实验。tDCS实验采用混合实验设计,刺激类型(阳极刺激vs.阴极刺激)作为被试间变量,刺激位置(左侧颞叶区域vs.右侧颞叶区域)与刺激实施(真刺激vs.伪刺激)作为被试内变量,通过声调识别任务与声调辨别任务测量被试声调感知能力,对比阴极刺激组与阳极刺激组被试大脑左右半球接受tDCS真刺激与伪刺激的声调感知结果。结果发现,在声调识别任务中,右侧颞叶接受阳极刺激时被试的声调分类清晰度得到了显著提高,即增强右侧颞叶神经兴奋性提高声调分类清晰度;而在辨别任务中,右侧颞叶接受阴极刺激时被试的分类知觉能力降低,即抑制右侧颞叶神经兴奋性降低了被试对汉语声调的分类能力。结果表明刺激右侧颞叶影响了汉语声调的感知,而刺激左侧颞叶并没有类似效应。研究结果从因果联系的角度为汉语声调感知的右偏侧化提供了直接的证据。更多还原

【Abstract】 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.更多还原