DOCTORAL DISSERTATION RESEARCH: Hemispheric Specialization of the Processing of Linguistic Pitch Contrasts

研究表明，大脑的两个半球具有不同的功能。例如，左脑被认为专门负责语言处理，而艺术/创造能力则由右脑专门处理。本论文将评估两种可能的音高加工半球专门化解释。第一种解释是功能解释，它指出音调加工的半球专门化是由音调对比的功能决定的。例如，较具语言性的音高对比(例如，语言音调、重音和语调)由左半球处理，而较少语言的音调对比(例如，音乐)由右半球处理。第二种解释是声学解释，认为声学关联决定大脑半球的专门化，因此，所有音高的处理，无论功能如何，都是由大脑的一个半球执行的。因此，语调和音乐中使用的音高可能由右脑或左脑处理。为了评估这两种解释，我们将进行三组涉及语言语调知觉(或语言音高对比)的实验。语调被定义为在单词层面上用来表示意义的音调模式(例如，在汉语中，/ma/以高音发音表示母亲；相同音节在以下降音调说时表示‘马’)。第一个实验将以大脑受损的个体为受试者；左半球或右半球受损的患者将被要求识别语言音调。第二个实验是两耳分听实验，它将只向听力正常的受试者的一只耳朵呈现语言音调，并评估哪只耳朵/大脑半球的组合更能检测到这些音调。第三个实验将使用神经成像技术来直接检查听力正常的受试者在听语言音调时哪个大脑半球活跃。世界上大多数语言(尽管不是英语)都使用语言音调。更好地了解大脑是如何处理语言语调的，不仅有助于我们了解语言处理和语言的普遍性，还可能有助于我们开发治疗技术，帮助恢复许多脑损伤患者的口头交流技能。

Research studies have shown that the two hemispheres of the brain have different functions. For example, the left hemisphere has been argued to specialize language processing while artistic/creative abilities are specialized by the right hemisphere. This dissertation will evaluate two possible accounts for hemispheric specialization of pitch processing. The first account is a functional account which states that hemispheric specialization of pitch processing is determined by the function of pitch contrasts. For example, pitch contrasts that are more linguistic (e.g. linguistic tone, stress, and intonation) are processed by the left hemisphere, and pitch contrasts that are less linguistic (e.g. music) are processed by the right hemisphere. The second account is an acoustic account which states that acoustic correlates determine hemispheric specialization, and therefore, all processing of pitch, regardless of function, is carried out by one hemisphere of the brain. Thus, pitch used in both intonation and music might be processed by the right hemisphere or the left hemisphere.Three sets of experiments involving the perception of linguistic tone (or linguistic pitch contrast) will be conducted in order to evaluate these two accounts. Linguistic tone is defined as pitch pattern that is used to signal meaning at the word level (e.g. in Chinese, /ma/ spoken with a high pitch means 'mother'; the same syllable means 'a horse' when spoken with a falling pitch). The first experiment will use brain-damaged individuals as subjects; patients with either left-hemisphere or right-hemisphere damage will be asked to identify linguistic tones. The second experiment is a dichotic listening experiment which will present linguistic tones to only one ear of normal-hearing subjects and assess which ear/hemisphere combination better detects these tones. The third experiment will use neuroimaging technique to examine directly which cerebral hemisphere is active when normal-hearing subjects are listening to linguistic tones.Most languages of the world (although not English) utilize linguistic tones. A better understanding of how the brain processes linguistic tones will not only help us to understand language processing and the universality of language, but may also help us to develop therapeutic techniques to help rehabilitate the oral communication skills of many brain damaged patients.