Neural Control of Vocal Production in Tone-Deafness

描述（由申请人提供）：尽管我们都知道一个或多个唱歌不协调的人，但这种疾病的神经关联以及它可能揭示的交流控制模型仍然难以捉摸。除了唱歌不能走调外，音聋的一个特征标志是心理生理上的音高辨别阈值异常大，超过一个半音。无法辨别细微的音高差异可能是这种疾病的附带现象，或者可能与听觉运动功能障碍有关，这种功能障碍是无法产生音高的基础。来自形态测量学、功能成像和事件相关电位（ERP）研究的初步数据和先前数据指出，听觉反馈控制和声音运动映射相关区域的功能和结构异常，而不是初级听觉皮层的功能障碍。考虑到不能唱歌可能反映了听觉-运动整合的问题，包括前馈和反馈控制机制，目前的理论框架允许我们将现有的语言感知和产生模型推广到唱歌领域，作为“语调语音”的一个实例。我们的一般假设是，音调失聪是大脑中与听觉反馈和音调产生前馈控制有关的区域网络功能障碍的结果。我们计划通过首先确定音聋的行为和神经基础来验证这一假设。通过结合音高产生的神经成像和心理物理实验，包括使用音高移位的听觉反馈，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（目的1）。然后，我们将通过使用一种新的非侵入性脑刺激方法（经颅直流电刺激- TDCS）产生暂时的区域功能障碍来逆向工程感知运动通路（目的2）。根据试验音调产生的结果，大脑刺激可以暂时诱导正常人的音调失聪，从而允许我们使用从第一个目标开始的实验中评估的心理物理测量来评估我们的区域假设。检查音聋的神经相关性，并在正常受试者中创建相应的音聋，将为大脑中听觉和运动系统在正常和紊乱语言以及非语言交流中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.