Anatomical and physiological studies of mushroom body neurons of an insect.

蘑菇体（MB）是昆虫脑中一个重要的神经元结构，对各种形式的联想记忆起着关键作用。在本研究中，1.研究了自由活动美洲大蠊（Periplaneta americana）的MB输出神经元的活动。将直径为14-20 μm的绝缘铜线长期植入MB输出神经元，在蟑螂自由行走于竞技场的同时，差分记录单位活动。在记录之后，通过使正电流通过来浸渍铜离子以标记电极尖端的位置。在本研究中记录的41个单位分为：（1）感觉神经元，响应视觉，嗅觉和/或触觉刺激，（2）运动相关的神经元，在运动过程中活跃，（3）感觉运动神经元，在感觉刺激和运动过程中也活跃。一些运动相关神经元在特定运动动作开始前表现出活动，持续0.2-1秒。这些结果表明，MB整合了各种感觉和运动信号，并为自主运动行为形成准备信号。用高尔基体染色法和荧光黄注射法研究了蟑螂MB输出神经元的树突形态。一些神经元的树突只与特定的MBs模块化亚基组合相互作用。研究了蟑螂和蟋蟀（Glyllus bimaculatus）将薄荷与奖励和香草与非奖励联系起来的能力。在这两种昆虫中，一次试验就足以改变最初的气味偏好，并且通过三次训练形成的记忆至少保留了七天。结果表明，这两种昆虫都具有良好的气味学习能力，适合作为研究昆虫嗅觉学习神经基础的材料。

The mushroom body (MB) is a conspicuous neuropil structure in the insect brain, and is critical to various forms of associative memory. In the present study,1. Activities of MB output neurons of freely behaving cockroaches, Periplaneta americana, were examined. Insulated copper wires of 14-20 μm in diameter were implanted chronically into the MB output neuropil, and unit activity was differentially recorded while the cockroach walked freely in an arena. After the recording, copper ions were impregnated by passing a positive current to mark the location of electrode tips. The 41 units recorded in the present study were classified into (1 ) sensory neurons which responded to visual, olfactory and/or tactile stimuli, (2) motor-related neurons which were active during locomotion, (3) sensory-motor neurons which were active during sensory stimulation and also during motor action. Some motor-related neurons exhibited activity preceding the initiation of specific locomotory action for 0.2-1 sec. These results suggest that the MB integrate various sensory and motor signals and form preparatory signals for voluntary locomotory actions.2. Dendritic morphology of output neurons of cockroach MB was studied by means of Golgi stainings and by injecting Lucifer Yellow into the neurons. Some neurons had dendrites which interact only with a specific combination of modular subunits of the MBs.3. The ability of cockroaches and crickets (Glyllus bimaculatus) to associate peppermint with reward and vanilla with non-reward was examined. In both insects, a single trial was sufficient to change the initial odor preference, and memory formed by three-time training retained for at least seven days. The results showed that both species have excellent ability to learn odors and are suited as materials to study neural basis of olfactory learning in insects.