Developmental changes in neural circuits for a behavior

描述（由申请人提供）：动物在有限的发展时期与外部世界的互动对其行为能力有深远而持久的影响。虽然感觉经验在学习行为发展中的作用已经确立，但经验塑造这些行为背后的神经回路的机制尚未得到很好的理解。鸣禽和人类一样，在特定的发育时期听到它们的声音后，就学会了它们的物种典型的发声方式，而发声行为是由高度定位的神经回路控制的。我们将使用鸣禽模型系统来研究内源性和经验因素如何调节神经和行为发育。(1)我们将研究神经营养因子（一类特殊的生长因子）在控制声音学习的神经回路中表达的发育变化，以产生关于其位置和作用机制的假设。(2)我们将测试从活跃神经元的轴突末端释放神经营养因子是否可以调节突触后目标神经元的存活和/或分化。(3)我们将研究声音控制回路的电生理学，重点研究神经营养因子生长因子调节兴奋性突触传递的发育变化，以表征神经元之间功能通信的模式。(4)我们将研究发声发育过程中单个神经元轴突末端的形态，以评估发声控制神经回路之间连接的特异性，并研究听觉剥夺导致的发声学习中断对单个轴突发育的影响。(5)我们将评估神经营养因子对单个轴突末端发育的影响，以此作为测试声音控制神经回路中高度有序的连接模式及其所服务的特殊行为如何在发育早期的有限敏感时期出现的一种手段。

DESCRIPTION (provided by applicant): An animal's interactions with its external world during restricted periods of development have a profound and lasting influence on its behavioral capacities. Although the role of sensory experience in the development of learned behaviors is well established, the mechanisms whereby experience shapes neural circuits underlying such behaviors are not well understood. Songbirds, like humans, learn their species-typical vocalizations after hearing them during a specific period of development, and vocal behavior is controlled by highly localized neural circuits. We will use the songbird model system to investigate how endogenous and experiential factors regulate neural and behavioral development. (1) We will examine developmental changes in the expression of neurotrophins, a specific class of growth factors, in neural circuits that control vocal learning in order to generate hypotheses concerning their locus and mechanism of action. (2) We will test whether release of neurotrophins from axon terminals of active neurons can regulate the survival and/or differentiation of their post-synaptic target neurons. (3) We will investigate the electrophysiology of vocal-control circuits, focusing on developmental changes in regulation of excitatory synaptic transmission by neurotrophin growth factors in order to characterize patterns of functional communication between neurons. (4) We will study the morphology of axon terminals of individual neurons during vocal development to assess the specificity of connections among vocal-control neural circuits, and examine the influence of disruptions in vocal learning due to auditory deprivation on development of single axons. (5) We will assess the influence of neurotrophins on the development of individual axon terminals as a means of testing how highly ordered patterns of connectivity within vocal-control neural circuits and the specialized behaviors they subserve emerge during restricted sensitive periods early in development.