Department of Neurobiology, Duke University, Durham, North Carolina 27710, USA.
J Neurosci. 2012 Aug 22;32(34):11671-87. doi: 10.1523/JNEUROSCI.1666-12.2012.
Complex brain functions, such as the capacity to learn and modulate vocal sequences, depend on activity propagation in highly distributed neural networks. To explore the synaptic basis of activity propagation in such networks, we made dual in vivo intracellular recordings in anesthetized zebra finches from the input (nucleus HVC, used here as a proper name) and output [lateral magnocellular nucleus of the anterior nidopallium (LMAN)] neurons of a songbird cortico-basal ganglia (BG) pathway necessary to the learning and modulation of vocal motor sequences. These recordings reveal evidence of bidirectional interactions, rather than only feedforward propagation of activity from HVC to LMAN, as had been previously supposed. A combination of dual and triple recording configurations and pharmacological manipulations was used to map out circuitry by which activity propagates from LMAN to HVC. These experiments indicate that activity travels to HVC through at least two independent ipsilateral pathways, one of which involves fast signaling through a midbrain dopaminergic cell group, reminiscent of recurrent mesocortical loops described in mammals. We then used in vivo pharmacological manipulations to establish that augmented LMAN activity is sufficient to restore high levels of sequence variability in adult birds, suggesting that recurrent interactions through highly distributed forebrain-midbrain pathways can modulate learned vocal sequences.
复杂的大脑功能,如学习和调节声音序列的能力,依赖于高度分布式神经网络中的活动传播。为了探索这种网络中活动传播的突触基础,我们对麻醉斑马雀的输入(这里用作专有名词的 HVC 核)和输出[前脑外侧大细胞核(LMAN)]神经元进行了双体内细胞内记录,这是鸣禽皮质基底神经节(BG)通路所必需的,用于学习和调节声音运动序列。这些记录显示了双向相互作用的证据,而不是以前假设的仅从 HVC 到 LMAN 的活动前馈传播。双和三重记录配置和药理学操作的组合用于绘制活动从 LMAN 传播到 HVC 的电路。这些实验表明,活动通过至少两条独立的同侧途径传播到 HVC,其中一条途径涉及通过中脑多巴胺能细胞群的快速信号传递,这让人联想到哺乳动物中描述的反复中皮质环路。然后,我们使用体内药理学操作来证明增强的 LMAN 活动足以恢复成年鸟类中高水平的序列可变性,这表明通过高度分布式前脑-中脑途径的反复相互作用可以调节学习的声音序列。