Lazar Aurel A, Liu Tingkai, Yeh Chung-Heng, Zhou Yiyin
Bionet Group, Department of Electrical Engineering, Columbia University, New York, NY, United States.
Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, United States.
Front Physiol. 2024 Oct 16;15:1410946. doi: 10.3389/fphys.2024.1410946. eCollection 2024.
Associative memory in the Mushroom Body of the fruit fly brain depends on the encoding and processing of odorants in the first three stages of the Early Olfactory System: the Antenna, the Antennal Lobe and the Mushroom Body Calyx. The Kenyon Cells (KCs) of the Calyx provide the Mushroom Body compartments the identity of pure and odorant mixtures encoded as a train of spikes. Characterizing the code underlying the KC spike trains is a major challenge in neuroscience. To address this challenge we start by explicitly modeling the space of odorants using constructs of both semantic and syntactic information. Odorant semantics concerns the identity of odorants while odorant syntactics pertains to their concentration amplitude. These odorant attributes are multiplicatively coupled in the process of olfactory transduction. A key question that early olfactory systems must address is how to disentangle the odorant semantic information from the odorant syntactic information. To address the untanglement we devised an Odorant Encoding Machine (OEM) modeling the first three stages of early olfactory processing in the fruit fly brain. Each processing stage is modeled by Divisive Normalization Processors (DNPs). DNPs are spatio-temporal models of canonical computation of brain circuits. The end-to-end OEM is constructed as cascaded DNPs. By extensively modeling and characterizing the processing of pure and odorant mixtures in the Calyx, we seek to answer the question of its functional significance. We demonstrate that the DNP circuits in the OEM combinedly reduce the variability of the Calyx response to odorant concentration, thereby separating odorant semantic information from syntactic information. We then advance a code, called first spike sequence code, that the KCs make available at the output of the Calyx. We show that the semantics of odorants can be represented by this code in the spike domain and is ready for easy memory access in the Mushroom Body compartments.
触角、触角叶和蘑菇体萼片。萼片的肯扬细胞（KC）为蘑菇体各部分提供了以一系列尖峰编码的纯净气味剂和气味剂混合物的特征。表征KC尖峰序列背后的编码是神经科学中的一项重大挑战。为了应对这一挑战，我们首先使用语义和句法信息结构对气味剂空间进行显式建模。气味剂语义涉及气味剂的特征，而气味剂句法则与其浓度幅度有关。这些气味剂属性在嗅觉转导过程中是相乘耦合的。早期嗅觉系统必须解决的一个关键问题是如何从气味剂句法信息中分离出气味剂语义信息。为了解决这个分离问题，我们设计了一种气味剂编码机器（OEM），对果蝇大脑早期嗅觉处理的前三个阶段进行建模。每个处理阶段都由归一化除法处理器（DNP）建模。DNP是脑回路规范计算的时空模型。端到端的OEM被构建为级联的DNP。通过广泛建模和表征萼片中纯净气味剂和气味剂混合物的处理过程，我们试图回答其功能意义的问题。我们证明，OEM中的DNP电路共同降低了萼片对气味剂浓度反应的变异性，从而将气味剂语义信息与句法信息分离。然后，我们提出了一种称为首个尖峰序列编码的编码，KC在萼片输出端提供这种编码。我们表明，气味剂的语义可以由尖峰域中的这种编码表示，并且可以在蘑菇体各部分中轻松进行记忆访问。
