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

我们已经表明，头部定向主要是由两个独立的途径，即上级丘（SC）-脑桥延髓网状结构-颈部运动神经元和SC-Forel的领域H颈部运动神经元控制。前一种途径主要与头部水平运动的控制有关，后一种途径主要与头部垂直运动的控制有关。本研究用可移动电极记录了猫SC和脑桥延髓网状结构的单个或多个单位的活动，在SC中，浅、中、深层神经元的放电模式不同。一组浅层（I-III层）的神经元在固定目标（凝视放电）后剧烈放电，而中间层（IV层）的神经元在运动到特定视野（运动场）之前会爆发性放电。在注视中心光等待目标出现或注视目标时，许多深层（V-VI）神经元发生紧张性放电，桥延髓网状结构中许多单位显示与头部定向有关的活动。根据其发射模式可将其分为3大类。相位单位以爆发方式击发，在运动开始前20-40 ms开始击发，并在运动结束前停止击发。放电次数与头部运动的最大角速度呈正相关。相位持续单位比相位单位更早地发射，并且在头部运动期间表现出持续的活动，并且随着运动的终止而停止发射。活动度与运动持续时间的关系比与最大角速度的关系更密切。紧张性单位在定向任务的特定阶段表现出持续的活动，即，在注视中心（注视）光、目标光期间或在试验间隔期间。

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.