Neural Control of Vocal Production in Tone-Deafness

描述(由申请者提供)：尽管我们都知道有一个或多个人不能合拍，但这种障碍的神经关联以及它可能揭示的沟通控制模式仍然难以捉摸。除了不能合拍唱歌外，音聋的一个特征标志是超过一个半音的异常大的心理物理音调辨别阈值。无法辨别细微的音调差异可能是这种疾病的一种附带现象，也可能与推测的听觉-运动功能障碍有关，后者是导致声调产生障碍的基础。来自形态计量学、功能成像和事件相关电位(ERP)研究的先导数据和先前的数据表明，参与听觉反馈控制和声音-运动映射的区域存在功能和结构异常，而不是初级听觉皮质功能障碍。考虑到不能唱歌可能反映了听觉-运动整合中的问题，包括前馈和反馈控制机制，本理论框架允许我们将现有的言语感知和产生模型推广到唱歌领域，作为语调言语的一个例子。我们的一般假设是，音聋是涉及听觉反馈和声调产生前馈控制的大脑区域网络功能障碍的结果。我们计划通过首先确定声性耳聋的行为和神经基础来检验这一假设。通过结合神经成像和心理物理的音调产生实验，包括使用音调变化的听觉反馈，我们将测试负责听觉反馈控制和声音-运动映射的神经机制以及这两个系统的相互作用(目标1)。然后，我们将使用一种新的非侵入性脑刺激方法(经颅直流电刺激-TDC)(目标2)，通过创造暂时性的局部功能障碍来逆向工程感知运动通路。根据飞行员的音调产生结果，大脑刺激可以在正常人中暂时导致音聋，从而使我们能够使用从第一个目标开始的实验中评估的心理物理措施来评估我们的地区性假设。研究音聋的神经关联，并在正常受试者中建立音聋的等价物，将为研究正常语言和紊乱语言以及非语言交流中大脑中听觉和运动系统的相互作用提供新的见解。

DESCRIPTION (provided by applicant): Although we all know one or more individuals who can't sing in tune, the neural correlates of this disorder and what it might reveal about models of communication control remain elusive. In addition to an inability to sing in tune, one characteristic marker of tone-deafness is an abnormally large psychophysical pitch discrimination threshold of more than one semitone. The inability to discriminate fine pitch differences may be an epiphenomenon of the disorder, or it could be related to the presumed auditory-motor dysfunction that underlies disabled production of vocal pitch. Pilot and previous data from morphometric, functional imaging, and Event- Related Potential (ERP) studies point towards functional and structural abnormalities in regions involved in auditory feedback control and sound-motor mapping, rather than dysfunctions in primary auditory cortex. In considering that the inability to sing might be reflective of problems in auditory-motor integration including feedforward and feedback control mechanisms, the present theoretical framework allows us to generalize existing models of speech perception and production to the domain of singing as an instance of "intoned-speech". Our general hypothesis is that tone-deafness is a result of dysfunction in a network of brain regions involved in auditory feedback and feedforward control of vocal pitch production. We plan to test this hypothesis by first identifying the behavioral and neural substrates of tone-deafness. By combining neuroimaging and psychophysical experiments of pitch production, including the use of pitch- shifted auditory feedback, we will test the neural mechanisms responsible for auditory feedback control and sound-motor mapping as well as the interaction of these two systems (Aim 1). We will then reverse-engineer the perceptuomotor pathway by creating temporary regional dysfunctions using a new method of non-invasive brain stimulation (transcranial direct current stimulation - TDCS) (Aim 2). Based on pilot pitch production results, brain stimulation can temporarily induce tone-deafness in normal individuals, thus allowing us to assess our regional hypotheses using psychophysical measures that have been evaluated in experiments from the first aim. Examining the neural correlates of tone-deafness and creating a tone-deaf equivalent in normal subjects will offer new insights into the interactions of auditory and motor systems in the brain in normal and disordered speech as well as in non-speech communication.