Parallel Encoding of Sequence and Structure in a Motor Memory Trace

这个项目的目的是阐明大脑是如何对序列顺序进行编码的。如果你大声朗读这个句子，你会在不到10秒的时间里发出一个精确、有序的序列，其中包括50多种不同的声音。大脑如何存储语音的个体声音，然后如此迅速地以有意义的顺序协调这些声音的产生？对于演奏莫扎特奏鸣曲、鸟鸣或昆虫交配舞蹈的钢琴家，也可能会被问到类似的问题。大脑如何存储这些复杂的行为序列仍是个未知数。利用鸣鸟斑马雀--一种像人类一样学习有意义的声音序列的模式生物--跨学科研究团队将测试这一假设，即大脑通过两种并行运行的独立机制对行为序列进行编码和存储：一种是对声音序列进行编码的机制，另一种是对声音本身进行编码的机制。考虑到动物物种的多样性，它们表现出精细而有意义的行为序列，这些发现将影响包括人类在内的广泛生物的理解。该研究计划协调了来自四个不同学科(神经解剖学、神经生理学、数学和统计学)的教员研究团队的活动，并将为学生提供独特的跨学科培训机会和环境。在几乎所有的动物形式中都可以观察到(并以人类语言为例)行为的一系列秩序包括学习将一组基本的手势单位组织成有目的的行动序列。成年雄性斑马雀(斑腿带喙雀)会产生高度可量化的行为序列(鸟鸣)。此外，运动前皮质区域(HVC，专有名称)被认为编码了巩固的运动前歌曲痕迹。尽管HVC由相似的细胞类型组成，但HVC的内侧和外侧部分被假设为平行编码歌曲的序列(内侧HVC)和音节(横向HVC)。研究小组将测试歌曲的这两个维度是否由生理差异编码：1)内侧和外侧HVC的传入输入，或2)内侧和外侧HVC的内在网络特性(或1和2的组合)。然而，行为中的序列顺序的并行编码应该是分层的，在监督位置上具有序列的轨迹，而不是基本手势单元的轨迹。该团队还将测试从内侧和外侧HVC发出的传出轴突是否在声带运动皮质内以分层方式相互作用。结果将阐明行为顺序的网络体系结构，并提供一个计算平台来理解学习新序列如何塑造这种记忆体系结构。

The purpose of this project is to elucidate how serial order is coded by the brain. If you were to read this sentence aloud, you would utter a precise, ordered sequence of over 50 distinct vocal sounds in less than 10 seconds. How does the brain store the individual sounds of speech and then coordinate the production of these sounds in a meaningful order so quickly? A similar question could be asked about the pianist performing a Mozart sonata, the songs of birds, or the mating dances of insects. How the brain stores these elaborate sequences of behavior remains unknown. Using the songbird zebra finch, a model organism that learns meaningful sequences of vocal sounds like humans do, the interdisciplinary research team will test the hypothesis that the brain encodes and stores sequences of behavior through two separate mechanisms that operate in parallel: one coding mechanism for the sequence of vocal sounds and one for the vocal sounds themselves. Given the diversity of animal species that display elaborate, meaningful sequences of behavior, the findings will influence understanding across a broad array of organisms, including humans. The research plan coordinates the activity of a faculty research team from four different disciplines (Neuroanatomy, Neurophysiology, Mathematics, and Statistics) and will provide students with a unique interdisciplinary training opportunity and environment. Observed in nearly all animal forms (and exemplified by human speech) serial order in behavior consists of learning to organize a set of elemental gestural units into a purposeful sequence of action. Adult male zebra finches (Taeniopygia guttata) produce a highly quantifiable example of serial order in behavior (birdsong). Moreover, a premotor cortical region (HVC, proper name) is known to encode a consolidated premotor trace of song. Although consisting of similar cell types, the medial and lateral portions of HVC are hypothesized to encode the sequence (medial HVC) and syllables (lateral HVC) of song in parallel. The research team will test whether these two dimensions of song are encoded by physiological differences in 1) afferent input to medial and lateral HVC, or 2) the intrinsic network properties of medial and lateral HVC (or a combination of 1 and 2). However, parallel encoding of serial order in behavior should be hierarchical, with traces for sequence in a supervisory position over traces for elemental gestural units. The team will also test whether efferent axons emanating from medial and lateral HVC interact in a hierarchical fashion within vocal-motor cortex. Results will elucidate a network architecture for serial order in behavior and provide a computational platform to understand how learning new sequences shapes such memory architectures.