NEURAL BASIS OF VOCAL LEARNING

这项研究的长期目标是了解学习和记忆的神经基础，特别是大脑如何在感觉信息的指导下学习复杂的运动行为。鸣禽的发声学习为这一目的提供了一个有用的模型系统，与人类的语音学习特别相关。鸣禽在一段时间内学习复制以前记忆的辅导歌曲，在这个阶段，它们使用自己声音的听觉反馈来改进自己的声音输出，直到它与记忆的歌曲相匹配。这里提出的工作集中在专门用于歌曲学习和产生的大脑区域系统的特定部分，一个被称为前脑前脑通路(AFP)的特殊皮质-基底节回路，因为它在歌曲学习和成人发声可塑性中都扮演着关键但尚不清楚的角色。此外，皮质-基底节环路在进化上保存良好，被认为在许多脊椎动物的运动和强化学习中发挥作用，并且在许多神经精神疾病中是功能障碍的关键部位之一。因为鸣禽AFP是一个控制特定行为的离散的皮质-基底节回路，它可能被证明是一个特别容易处理的系统，可以用来阐明这些通路的非常一般的功能。无论是在正常情况下还是在疾病中。AFP产生对歌曲有选择性的听觉反应，在学习过程中可以参与对歌曲的听觉评估，并在唱歌时显示与运动相关的活动，但这些感觉和运动反应如何相互联系尚不清楚。这个回路的活动在不同的试验中也是非常不同的，这就提出了一个问题，即它如何可靠地编码信息或引导歌曲。在歌唱和歌曲回放过程中，通过来自AFP输出核LMAN的多个神经元的同时记录，第一个目的将检验AFP以分布式“种群”代码的形式编码相关歌曲和歌唱相关信息的假设。进一步的假设是，AFP神经活动的特定模式对正常的歌曲发育至关重要，可能指导着声带运动核RA的连接的形成。这将通过同时记录LMAN和RA中的神经元来进行测试，以便分析它们活动的协方差及其与声音输出的关系。LMAN-RA的相互作用将首先在正常鸟类学习的不同阶段进行研究，然后在AFP活动模式的实验中断后进行研究，以揭示该回路中正常的突触处理以及它如何影响SING运动通路。

The long-term goal of this research is to understand the neural basis of learning and memory, especially how the brain learns complex motor behaviors, guided by sensory information. Vocal learning in songbirds provides a useful model system for this purpose, with special relevance to human speech learning. Songbirds learn to produce a copy of a previously memorized tutor song during a period of "sensorimotoi" learning, in which they use auditory feedback of their own voice to refine their vocal output until it matches the memorized song. The work proposed here focusses on a particular part of the system of brain areas devoted to song learning and production, a specialized cortical-basal ganglia circuit known as the anterior forebrain pathway (AFP), because it plays a crucial but illunderstood role both in song learning and in adult vocal plasticity. Moreover, cortical-basal ganglia circuits, which are well conserved evolutionarily, are thought to function in motor and reinforcement learning in many vertebrates, and to be one critical site of dysfunction in a number of neuropsychiatric disorders. Because the songbird AFP is a discrete cortical-basal ganglia circuit controlling a specific behavior, it may prove a particularly tractable system for elucidating the very general functions of such pathways. both normally and in disease. The AFP develops song-selective auditory responses that could participate in the auditory evaluation of song during learning, and shows motor-related activity during singing, but how these sensory and motor responses relate to each other is not clear. Activity in this circuit is also extremely variable from trial to trial, raising the question of how it could reliably encode information or guide song. With simultaneous recordings from multiple neurons in the output nucleus of the AFP, LMAN, during both singing and song playback, the first aim will test the hypothesis that the AFP encodes relevant song- and singing-related information in the form of a distributed, "population" code. A further hypothesis is that specific patterns of AFP neural activity are critical for normal song development, perhaps guiding the formation of connections in the vocal motor nucleus RA. This will be tested with simultaneous recordings of neurons in both LMAN and RA, so that the covariance of their activity and how it relates to vocal output can be analyzed. LMAN-RA interactions will be studied first in normal birds at different stages of learning, and then after experimental disruptions of the pattern of activity in the AFP, in ways that will shed light both on normal synaptic processing within this circuit as well as on how it influences the song motor pathway.