Twick Isabell, Lee John Anthony, Ramaswami Mani
School of Genetics and Microbiology and School of Natural Sciences, Smurfit Institute of Genetics, Trinity College Institute of Neuroscience, Trinity College Dublin, Ireland.
School of Genetics and Microbiology and School of Natural Sciences, Smurfit Institute of Genetics, Trinity College Institute of Neuroscience, Trinity College Dublin, Ireland; National Centre for Biological Science, Bangalore, India.
Prog Brain Res. 2014;208:3-38. doi: 10.1016/B978-0-444-63350-7.00001-2.
A ubiquitous feature of an animal's response to an odorant is that it declines when the odorant is frequently or continuously encountered. This decline in olfactory response, termed olfactory habituation, can have temporally or mechanistically different forms. The neural circuitry of the fruit fly Drosophila melanogaster's olfactory system is well defined in terms of component cells, which are readily accessible to functional studies and genetic manipulation. This makes it a particularly useful preparation for the investigation of olfactory habituation. In addition, the insect olfactory system shares many architectural and functional similarities with mammalian olfactory systems, suggesting that olfactory mechanisms in insects may be broadly relevant. In this chapter, we discuss the likely mechanisms of olfactory habituation in context of the participating cell types, their connectivity, and their roles in sensory processing. We overview the structure and function of key cell types, the mechanisms that stimulate them, and how they transduce and process odor signals. We then consider how each stage of olfactory processing could potentially contribute to behavioral habituation. After this, we overview a variety of recent mechanistic studies that point to an important role for potentiation of inhibitory synapses in the primary olfactory processing center, the antennal lobe, in driving the reduced response to familiar odorants. Following the discussion of mechanisms for short- and long-term olfactory habituation, we end by considering how these mechanisms may be regulated by neuromodulators, which likely play key roles in the induction, gating, or suppression of habituated behavior, and speculate on the relevance of these processes for other forms of learning and memory.
动物对气味剂的反应中一个普遍存在的特征是，当频繁或持续接触该气味剂时，反应会下降。这种嗅觉反应的下降，被称为嗅觉习惯化，在时间或机制上可能有不同的形式。果蝇黑腹果蝇嗅觉系统的神经回路在组成细胞方面定义明确，这些细胞易于进行功能研究和基因操作。这使得它成为研究嗅觉习惯化的特别有用的实验对象。此外，昆虫嗅觉系统与哺乳动物嗅觉系统在结构和功能上有许多相似之处，这表明昆虫的嗅觉机制可能具有广泛的相关性。在本章中，我们将结合参与的细胞类型、它们的连接性以及它们在感觉处理中的作用，讨论嗅觉习惯化的可能机制。我们概述关键细胞类型的结构和功能、刺激它们的机制，以及它们如何转导和处理气味信号。然后我们考虑嗅觉处理的每个阶段如何可能导致行为习惯化。在此之后，我们概述了各种最近的机制研究，这些研究指出在初级嗅觉处理中心触角叶中抑制性突触的增强在驱动对熟悉气味剂反应降低方面起着重要作用。在讨论了短期和长期嗅觉习惯化的机制之后，我们最后考虑这些机制如何可能受到神经调质的调节，神经调质可能在习惯化行为的诱导、门控或抑制中起关键作用，并推测这些过程与其他形式的学习和记忆的相关性。
