Neural mechanisms of olfactory learning in insect 'Microbrain'

本研究旨在揭示昆虫“微脑”的功能组织，揭示昆虫大脑嗅觉学习的神经机制。起初，我为蟑螂和蟋蟀发明了几种嗅觉学习模式。这些包括对单个或群体昆虫的操作性和经典条件反射程序，它们可用于各种分析目的。其次，利用这些行为范式，我们发现蟑螂和蟋蟀具有优异的嗅觉学习能力，具有习得快、保持时间长、通过再训练易于重写的特点。我的一个值得注意的发现是，在早期若虫阶段接受训练的蟋蟀，它们的嗅觉记忆几乎可以保持一辈子，而且这种持久的记忆很容易在随后的重新训练中被改变。第三，我已经获得的证据表明，蟋蟀蘑菇体内的no系统参与了长期嗅觉记忆的形成。最后，通过从颈结体向轴突逆行填充的方法，对蟑螂下行神经元的体塔和树突分布进行了检测，发现下行神经元体塔至少有235对。我提出了一个蟑螂大脑基本组织的模型，基于它们树突的分布，大脑由许多平行的感觉-运动通路组成，其中许多是由通过更高中枢的间接通路发出的信号调节的

The aim of this study was to reveal functional organization of insect "microbrain" and to reveal neural mechanisms of olfactory learning in insect brain. At first, I invented several olfactory learning paradigms for cockroaches and crickets. These included operant and classical conditioning procedures for individual or groups of insects and they could be used for various analytical perposses. Second, using these behavioral paradigms, we showed that cockroaches and crickets have excellent olfactory learning capability characterized by fast acquisition, long retention, and easy re-writing by re-training. One of my notable finding was that crickets that had been trained in early nymphal stage could retain their olfactory memory for practically a lifetime, and that this long-lasting memory could be easily altered by subsequent re-training. Third, I have attained evidence to suggest that the NO-system in the mushroom body of crickets participates in the formation of long-term olfactory memory. Finally, I examined the distribution of somata and dendrites of descending brain neurons of the cockroach by retrogradely filling their axons from the cervical connective, and showed that there were at least 235 pairs somata of descending neurons. I proposed a model for the basic organization of the cockroach brain, on the basis of the distribution of their dendrites, where the brain consists of a number of parallel sensori-motor pathways many of which are modulated by signals from indirect pathways via higher centers