Roles of the mushroom body in locomotory control in an insect

蘑菇体(MB)是昆虫脑中最明显的神经纤维结构，对各种形式的联想记忆至关重要。为了阐明MB在高级运动控制中的作用，对美洲大蠊输出神经元的活动和MB的细胞结构进行了研究。检测了自由行为蟑螂的MB输出神经元的活动。将直径为17微米的釉质铜丝长期植入MB输出神经纤维内，记录蟑螂在场内自由行走时的单位活动。在记录后，通过传递正电流来浸渍铜离子，以显示电极尖端附近的神经元的轮廓。记录到的神经元可分为：(1)对各种感觉刺激作出反应的感觉单位；(2)在运动过程中活动的运动相关神经元；(3)在感觉刺激和运动动作中活动的感觉运动神经元；(4)在特定运动动作开始之前活动的神经元。本文用还原银染色法和高尔基体染色法研究了蟑螂MB的细胞组织。我发现在MB输出神经束中存在两种大小不同的重复模块亚基。第一个，我称之为薄片，是由200-1000个Kenyon细胞的轴突组成的一个薄(1微米或更小)的网络。这些薄片还被组织成更大的结构组，这里称为板，其宽度为3微米或更大。在输出神经束的整个长度上，共有大约30个大致均匀分布的深色和浅色的板层交替分布。我的结论是，昆虫记忆中心MB包括两种类型的重复模块亚基，哺乳动物的大脑皮层也是如此。

The mushroom body (MB) is the most conspicuous neuropil structure in the insect brain, critical to various forms of associative memory. In order to elucidate the role of the MB in the higher locomotory control, activities of output neurons and the cellular organization of the MB in the cockroach, Periplaneta americana, were studied.1. Activities of MB output neurons of freely behaving cockroaches were examined. Enamel-coated copper wires of 17 mum in diameter were implanted chronically into the MB output neuropil, and unit activity was recorded while the cockroach walked freely in an arena. After the recording, copper ions were impregnated by passing a positive current to reveal profiles of neurons in the vicinity of the electrode tip. The recorded neurons were classified into (1) sensory units which respond to various sensory stimuli, (2) motor-related neurons which are active during locomotory, (3) sensory-motor neurons which are active during sensory stimulation and also during motor action, and (4) neurons whose activity preceded the initiation of specific locomotory action.2. Cellular organization of the cockroach MB was studied by means of reduced-silver and Golgi stainings. I found that two types of repetitive modular subunits with different sizes exist in the MB output neuropil. The first, which I refer to as a sheet, is a thin (1 mum or less) meshwork formed by 200-1000 axons of Kenyon cells. The sheets are further organized into a larger structural grouping, referred to here as a slab, with a width of 3 mum or more. A total of about 30 dark and pale slabs of more or less evenly spaced alternate throughout the length of the output neuropil. I conclude that the MB,insect memory center, consists of two types of repetitive modular subunits, as does the mammalian cerebral cortex.