Analysis of information processes in pathways concering in orienting and visual discrimination

结果表明，头部定向主要由两条不同的通路控制，即上丘(SC)-延髓网状结构-颈运动神经元和SC-Forel区H颈运动神经元。前者主要控制头部的水平运动，后者则主要控制头部的垂直运动。在本研究中，用一组可移动电极在猫的头部定向任务中记录了SC和桥延髓网状结构中单个或多个单位的活动，在SC中，浅层、中层和深层神经元的放电模式不同。浅层(I-III层)中的一组神经元在注视目标(凝视发射)后强烈放电，与中层(IV)神经元相反，后者在运动到特定视野(运动场)之前以阵发性放电。许多深层次(V-VI)神经元在注视中心灯等待靶子出现或注视靶子的过程中被强直地放电。桥延髓网状结构中的许多单位显示出与头部定向有关的活动。根据发射模式将其分为3种主要类型。阶段单位以突击方式开火，在移动开始前20-40毫秒开始射击，并在移动结束前停止射击。射击次数与头部运动的最大角速度呈正相关。阶段持续单位比阶段单位更早发射，在头部运动期间表现出持续的活动，并随着运动的终止而停止发射。与最大角速度相比，活动与运动持续时间的关系更为密切。在定向任务的特定阶段，即在注视中心(注视)光、目标光期间或在试验间隔期间，紧张性单位显示出持续的活动。

We have shown that head orienting are principally controlled by two separate pathways, the superior colliculus (SC) -pontomedullary reticular formation-neck motoneurones and SC-Forel's field H neck motoneurones. The former pathway chiefly concerned with control of horizontal head movement, while the latter concerned with the vertical movements. In this study , activities of single or multiple units in the SC and pontomedullary reticular formation were recorded from cats performing headorienting task with an array of movable electrodes implanted chronically.In the SC,firing patterns differed among the neurones in superficial, intermediate and deep layrs. A group of neurones in the superficial layr (layr I-III) fired vigorously after fixating a target (gaze firing), in contrast to intermediate layr (IV) neurones which are known to discharge in bursts before a movement to a particular visual field (movement field) . Many of the deep layr (V-VI) neurones fired tonically during fixating on a center light waiting for the appearance of a target or during fixating on a target.Many units in the pontomedullary reticular formation showed activities related to head orienting. They were classified into 3 major types according to the firing pattern. Phasic units fired in a burst manner, initiated firing 20-40 ms prior to movement onset and stopped firing before the end of movement. The number of firing positively related to the maximal angular velocity of head movement. Phasic sustained units fired eariler than phasic units and showed sustained activity during head movement and ceased firing with termination of movement. The activity was more closely related to the duration of movement than the maximal angular velcity. Tonic units showed sustained activity in a particular phase of orienting task, i.e., during fixating a center (fixation) light, target light or during inter-trial intervals.