Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA.
Howard Hughes Medical Institute, Janelia Research Campus, Ashburn, VA 20147, USA; The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Curr Biol. 2023 Jul 10;33(13):2742-2760.e12. doi: 10.1016/j.cub.2023.05.064. Epub 2023 Jun 21.
The ability to discriminate sensory stimuli with overlapping features is thought to arise in brain structures called expansion layers, where neurons carrying information about sensory features make combinatorial connections onto a much larger set of cells. For 50 years, expansion coding has been a prime topic of theoretical neuroscience, which seeks to explain how quantitative parameters of the expansion circuit influence sensory sensitivity, discrimination, and generalization. Here, we investigate the developmental events that produce the quantitative parameters of the arthropod expansion layer, called the mushroom body. Using Drosophila melanogaster as a model, we employ genetic and chemical tools to engineer changes to circuit development. These allow us to produce living animals with hypothesis-driven variations on natural expansion layer wiring parameters. We then test the functional and behavioral consequences. By altering the number of expansion layer neurons (Kenyon cells) and their dendritic complexity, we find that input density, but not cell number, tunes neuronal odor selectivity. Simple odor discrimination behavior is maintained when the Kenyon cell number is reduced and augmented by Kenyon cell number expansion. Animals with increased input density to each Kenyon cell show increased overlap in Kenyon cell odor responses and become worse at odor discrimination tasks.
具有重叠特征的感觉刺激辨别能力被认为是在称为扩展层的大脑结构中产生的，在扩展层中，携带感觉特征信息的神经元对更大的一组细胞进行组合连接。50 年来，扩展编码一直是理论神经科学的主要课题，该学科旨在解释扩展电路的定量参数如何影响感觉灵敏度、辨别力和泛化。在这里，我们研究了产生节肢动物扩展层（称为蘑菇体）定量参数的发育事件。我们使用黑腹果蝇作为模型，利用遗传和化学工具来设计对电路发育的改变。这使我们能够产生具有假设驱动的自然扩展层布线参数变化的活体动物。然后，我们测试功能和行为后果。通过改变扩展层神经元（肯尼恩细胞）的数量及其树突复杂性，我们发现输入密度而非细胞数量调节神经元的气味选择性。当肯尼恩细胞数量减少和增加肯尼恩细胞数量扩张时，简单的气味辨别行为得以维持。每个肯尼恩细胞的输入密度增加的动物显示出肯尼恩细胞气味反应的重叠增加，并且在气味辨别任务中变得更差。
