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官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“感觉基元”学习期间学习产生先前记忆的导师歌曲的副本，在此期间，它们使用自己声音的听觉反馈来改进它们的声音输出，直到它与记忆的歌曲相匹配。这里提出的工作集中在一个特定的一部分，专门用于歌曲学习和生产的大脑区域系统，一个专门的皮质基底神经节电路被称为前前脑通路（AFP），因为它在歌曲学习和成人声乐可塑性中起着至关重要的作用，但还不清楚。此外，皮质-基底神经节回路在进化上非常保守，被认为在许多脊椎动物的运动和强化学习中起作用，并且是许多神经精神疾病中功能障碍的一个关键部位。由于鸣禽AFP是一个离散的皮质-基底神经节回路控制特定的行为，它可能被证明是一个特别容易处理的系统，用于阐明这些通路的一般功能。无论是正常还是疾病。AFP发展了歌曲选择性听觉反应，可以参与学习过程中对歌曲的听觉评价，并在唱歌过程中显示运动相关活动，但这些感觉和运动反应如何相互关联尚不清楚。这个回路的活动在不同的试验中也是非常可变的，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。在歌唱和歌曲播放过程中，同时记录来自AFP输出核中的多个神经元，LMAN，第一个目标将测试AFP以分布式“群体”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展至关重要，可能指导发声运动核RA中连接的形成。这将通过同时记录LMAN和RA中的神经元进行测试，以便分析它们的活动的协方差以及它与声音输出的关系。LMAN-RA相互作用将首先在正常鸟类的不同学习阶段进行研究，然后在AFP活动模式的实验中断后，以揭示该回路内正常突触处理以及它如何影响歌曲运动通路的方式进行研究。

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.