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

我们已经表明，头部定向主要由两个独立的通路控制，即上丘(SC) -桥髓网状形成-颈部运动神经元和SC- forel的场H颈部运动神经元。前者主要控制头部水平运动，后者主要控制头部垂直运动。在这项研究中，记录了长期植入可移动电极阵列的猫在执行定向任务时SC和桥髓网状结构中单个或多个单元的活动。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）的一组神经元在注视目标（凝视发射）后强烈放电，而中间层（IV层）神经元在运动到特定视野（运动场）之前会突然放电。许多深层（V-VI）神经元在盯着中心光等待目标出现或盯着目标时发出强直放电。桥髓网状结构中的许多单位显示出与头部定向有关的活动。根据射击模式，它们被分为三种主要类型。相位单位以爆发的方式发射，在运动开始前20-40毫秒开始发射，在运动结束前停止发射。射击次数与头部运动最大角速度呈正相关。相持续单位比相持续单位更早发射，在头部运动时表现出持续的活动，在运动结束时停止发射。活动与运动持续时间的关系比与最大角速度的关系更密切。在定向任务的特定阶段，即在注视中心（注视）光、目标光或试验间隔期间，强直单元表现出持续的活动。

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.