Evolution of Neural Circuits for Locomotion

运动神经回路的进化

• 批准号: 0445768
• 负责人: Paul Katz
• 金额: --
• 依托单位: Georgia State University Research Foundation, Inc.
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-01-15 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0445768&HistoricalAwards=false
• 关键词: Evolution; Neural; Circuits; Locomotion

Award AbstractDifferent species of animals display disparate behaviors that are produced by underlying neural circuits in the brains of each animal. To understand how different behaviors may have evolved, it is necessary to compare how the neural circuits in closely related species differ. The objective of this project is to address three fundamental questions about the evolution of neural circuits underlying behavior: 1) How do similar nervous systems produce different behaviors? 2) Can the same neurons in different species have similar functions even though the behaviors of the animals differ? 3) How do nervous systems in animals of different lineages produce the same behavior? This study addresses these questions by examining phylogenetic changes in identified homologous neurons in nudibranch mollusks, also known as sea slugs. Nudibranchs have simple nervous systems with individually identifiable neurons that underly three different types of locomotor behavior: crawling and two types of swimming: some sea slugs swim by lateral body flexions and others swim by dorsal/ventral body flexions. The divergent swimming behaviors arose independently multiple times in different nudibranch lineages. Studying phylogenetic differences in the functions and properties of identified neurons underlying locomotion will help determine how the behaviors changed during the evolutionary history of these sea slugs and will also provide understanding of how behaviorally relevant neural circuits can change in any creature.Closely-related nudibranchs can exhibit divergent behaviors that are often associated with species-differences in the properties and connections of the underlying neurons. This project compares the neurophysiological properties and synaptic connections of homologous neurons that produce different behaviors in four closely-related species: Tritonia diomedea (a dorsal/ventral swimmer), Melibe leonina and Dendronotus iris (both lateral swimmers), and Tochuina tetraquetra (a non-swimmer). This part of the project will correlate neurophysiology with behavior to determine which features of the neurons or their circuit connections are functionally important. The functions of the neurophysiological properties then will be tested directly using an electrophysiological technique called dynamic clamp to artificially transform the membrane and synaptic properties of homologous neurons. If the properties of neurons can be electrically transformed so their activity more closely resembles that of the homologous neurons in other species and swim behavior typical of that species is produced, then it would be strong evidence that those neural properties play a causal role in the production of behavior.Despite large differences in the behaviors of some closely-related nudibranchs, there likely will be underlying similarities in the functions of identified neurons. The second aim of the project is to look for conserved behavioral functions of homologous neurons in species with divergent behaviors. This will provide a basis for understanding the shared organization of the neural circuits, which forms the foundation upon which the derived behaviors are built.Distantly-related nudibranchs can also display similar behaviors. The phylogenetic distribution of swim behaviors suggests that they arose independently multiple times. The third aim of this project is to test whether independent evolution of the same motor behavior was caused by convergent or parallel evolution. The functions of homologous neurons in nudibranchs of different lineages that exhibit the same swimming behavior will be tested. The species pairs to be examined are Aphelodoris antillensis and Tritonia diomedea, distantly related dorsal /ventral swimmers, and Flabellina iodinea and Melibe leonina, distantly related lateral swimmers. If homologous neurons came to be used in the same way, for the same purpose, independently in different lineages, then it would indicate that the similarity in the swimming behavior arose through parallel evolution. This would suggest that components of neural circuits are like building blocks that can be taken apart and reassembled in the same way. Alternatively, if it is found that the behaviors resemble each other because of convergent evolution, then it would indicate that there are multiple configurations of nervous systems that can produce the same behavioral output. The project is designed to involve undergraduate students in the research plan. Specific mechanisms are in place to enhance the participation of historically under-represented ethnic groups. Plans have been made to use this project as a tool to teach about animal diversity and evolution in secondary schools using Georgia State University's Bio-Bus and to develop public exhibits on sea slugs at the new Georgia Aquarium in Atlanta.

奖项摘要不同物种的动物表现出不同的行为，这些行为是由每种动物大脑中的潜在神经回路产生的。 为了理解不同的行为是如何进化的，有必要比较密切相关物种的神经回路是如何不同的。 这个项目的目标是解决三个关于行为背后的神经回路进化的基本问题：1）相似的神经系统如何产生不同的行为？2)即使动物的行为不同，不同物种的相同神经元是否具有相似的功能？3)不同谱系动物的神经系统如何产生相同的行为？本研究通过检查裸鳃类软体动物（也称为海蛞蝓）中已确定的同源神经元的系统发育变化来解决这些问题。 裸鳃类有简单的神经系统，具有可单独识别的神经元，这些神经元是三种不同类型的运动行为的基础：爬行和两种类型的游泳：一些海蛞蝓通过侧向身体弯曲游泳，另一些则通过背侧/腹侧身体弯曲游泳。不同的裸鳃类谱系多次独立地出现不同的游泳行为。 研究运动神经元的功能和特性的系统发育差异将有助于确定这些海蛞蝓进化史中的行为如何变化，也将有助于了解行为相关的神经回路如何在任何生物中发生变化。该项目比较了四个密切相关的物种中产生不同行为的同源神经元的神经生理学特性和突触连接：Tritonia diomedea（背侧/腹侧游泳者），Melibe leonina和Dendronotus iris（均为侧游泳者）和Tochuina tetraquetra（非游泳者）。该项目的这一部分将把神经生理学与行为联系起来，以确定神经元或其电路连接的哪些特征在功能上是重要的。神经生理学特性的功能然后将使用称为动态钳的电生理学技术直接测试，以人为地改变同源神经元的膜和突触特性。 如果神经元的特性可以被电转化，使它们的活动更接近其他物种的同源神经元，并产生该物种典型的游泳行为，那么这将是强有力的证据，表明这些神经特性在行为的产生中起着因果作用。尽管一些密切相关的裸鳃类动物的行为存在很大差异，在所识别的神经元的功能中可能存在潜在的相似性。该项目的第二个目标是在具有不同行为的物种中寻找同源神经元的保守行为功能。这将为理解神经回路的共享组织提供基础，神经回路是衍生行为的基础。远亲裸鳃类动物也可以表现出类似的行为。游泳行为的系统发育分布表明，它们独立出现多次。本项目的第三个目的是测试同一运动行为的独立进化是由趋同进化还是平行进化引起的。将测试具有相同游泳行为的不同谱系裸鳃类动物中同源神经元的功能。要检查的物种对是Aesthodoris antillensis和Tritonia diomedea，远亲背/腹游泳者，Flabellina iodinea和Melibe leonina，远亲侧游泳者。 如果同源神经元在不同的谱系中以相同的方式、出于相同的目的独立地被使用，那么这将表明游泳行为的相似性是通过平行进化产生的。这表明神经回路的组成部分就像积木一样，可以以同样的方式拆开和重新组装。或者，如果发现行为由于趋同进化而彼此相似，那么这将表明有多种神经系统配置可以产生相同的行为输出。 该项目旨在让本科生参与研究计划。已建立具体机制，以加强历来代表性不足的族裔群体的参与。已计划利用这一项目作为一种工具，利用格鲁吉亚州立大学的生物巴士在中学讲授动物多样性和进化，并在亚特兰大新的格鲁吉亚水族馆举办关于海蛞蝓的公开展览。