NEURAL CHANGES ASSOCIATED WITH CRITICAL LEARNING PERIODS

描述（改编自申请人的摘要）：鸟类的歌曲学习是一种 研究经验如何影响神经和行为的强大模型 发展 在学习歌曲的过程中，鸟类会记住同种的歌曲， 听觉反馈来塑造他们的发声这些存储的模型。 这 歌曲学习通常仅限于特定物种的敏感期， 这项建议旨在识别鼓励和 限制这种学习。 这些研究集中在两个神经事件， 伴唱学习：密度的发展变化， N-甲基-D-天冬氨酸（NMDA）谷氨酸受体亚型的药理学， 以及在发声运动通路中大量增加的新回路。 NMDA受体与许多经验依赖性 神经可塑性及其激活是记忆所必需的 歌曲学习阶段。 行为药理学和高尔基体染色将是 结合斑胸草雀，以确定是否NMDA受体激活 促使一个鸣唱区域的树突棘减少， 在学习期间。 此外，受体放射自显影将用于确定 1)如果延迟敏感歌曲关闭听觉操纵 学习期同样延长了NMDA受体的发育变化 密度或药理学，2）如果荷尔蒙的操纵，影响歌曲 发育改变NMDA受体表达的发育概况，和 3)如果成年金丝雀重复出现的声音可塑性 伴随着NMDA受体密度或药理学的变化。 第二 一组实验将进一步探索神经元 在发声运动通路中的结合调节行为 可塑性 逆行追踪将用于斑胸草雀， 细胞类型有助于刺激性的相关性之间的数量 与歌曲相关的神经元和学习歌曲的数量。 还有， 蛋黄睾酮水平的测量和操作将用于 评估孵化前激素水平的变化是否与个体 神经元数量或学习能力的差异。 最后，孟加拉成年人 和斑胸草雀将使用胸苷放射自显影进行比较， 逆行追踪以确定HVC神经元中的物种差异 此外，还可以解释不同的物种在发声后退化的差异。 震耳欲聋 许多行为（例如，语言习得，社会依恋， 印记）表现出对它们的敏感性的发展变化， 环境刺激，这些研究将有助于确定神经机制 鼓励学习和限制独特的易感期。

DESCRIPTION (Adapted from applicant's abstract): Avian song learning is a powerful model for studying how experience influences neural and behavioral development. During song learning, birds memorize conspecific songs and use auditory feedback to shape their vocalizations to these stored models. This song learning often is restricted to species-specific sensitive periods, and this proposal is aimed at identifying neural events that encourage and constrain this learning. The studies focus upon two neural events that accompany song learning: developmental changes in the density and pharmacology of the N-methyl-D-aspartate (NMDA) glutamate receptor subtype, and a massive addition of new circuitry within the vocal motor pathway. NMDA receptors have been linked to many instances of experience-dependent neural plasticity and their activation is necessary for the memorization phase of song learning. Behavioral pharmacology and Golgi staining will be combined in zebra finches to determine whether NMDA receptor activation prompts the decline in dendritic spines that occurs in one song region during learning. Also, receptor autoradiography will be used to determine 1) if auditory manipulations that delay closure of the sensitive song learning period similarly extend developmental changes in NMDA receptor density or pharmacology, 2) if hormonal manipulations that affect song development alter the developmental profile of NMDA receptor expression, and 3) if recurring periods of vocal plasticity in adult canaries are accompanied by changes in NMDA receptor density or pharmacology. The second set of experiments will explore further the hypothesis that neuronal incorporation within the vocal motor pathway regulates behavioral plasticity. Retrograde tracing will be used in zebra finches to identify cell types contributing to a provocative correlation between the number of song-related neurons and the amount of song material learned. Also, measurements and manipulations of yolk testosterone levels will be used to assess if variations in prehatch hormone levels relate to individual differences in neuron number or learning capacity. Finally, adult Bengalese and zebra finches will be compared using thymidine autoradiography and retrograde tracing to determine if species differences in HVC neuron addition may account for species differences in vocal deterioration after deafening. Many behaviors (e.g., language acquisition, social attachment, imprinting) exhibit developmental changes in their sensitivity to environmental stimuli, and these studies will help define neural mechanisms that encourage learning and constrain periods of unique susceptibility.