Ding Long, Perkel David J
Department of Neuroscience, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
J Neurosci. 2004 Jan 14;24(2):488-94. doi: 10.1523/JNEUROSCI.4358-03.2004.
Vocal learning in songbirds provides an excellent model for sensorimotor learning in vertebrates, with an accessible, well-defined behavior and discrete neural substrate. The rich behavioral plasticity exhibited by songbirds, however, contrasts starkly with the scarcity of candidate cellular mechanisms. Here, we report for the first time on an activity-dependent form of synaptic plasticity in area X, a component of the song system required for song learning and song maintenance. In slice preparations of zebra finch area X, pairing of high-frequency presynaptic stimulation with postsynaptic depolarization induces Hebbian long-term potentiation (LTP) of the glutamatergic inputs to spiny neurons. This form of LTP requires activation of NMDA receptors and D1-like dopamine receptors. In addition, LTP is observed in birds as young as 47 d after hatching and also in adult birds but not in younger birds, providing evidence of developmental regulation of the onset of synaptic plasticity. These properties make this form of LTP the best known candidate mechanism for reinforcement-based vocal learning in juveniles and song maintenance in adult birds.
鸣禽的发声学习为脊椎动物的感觉运动学习提供了一个极佳的模型，其行为易于观察、定义明确，神经基质也较为离散。然而，鸣禽所展现出的丰富行为可塑性与候选细胞机制的稀缺形成了鲜明对比。在此，我们首次报道了X区（鸣禽学习和维持歌声所需的鸣唱系统的一个组成部分）中一种依赖活动的突触可塑性形式。在斑胸草雀X区的脑片标本中，高频突触前刺激与突触后去极化配对可诱导棘状神经元的谷氨酸能输入产生赫布型长时程增强（LTP）。这种形式的LTP需要NMDA受体和D1样多巴胺受体的激活。此外，在孵化后47天的幼鸟以及成年鸟中均观察到了LTP，但在更年幼的鸟中未观察到，这为突触可塑性起始的发育调控提供了证据。这些特性使这种形式的LTP成为幼鸟基于强化的发声学习以及成年鸟鸣唱维持最知名的候选机制。
