Neural Mechanisms Controlling Velocity and Position Guided Orienting

猫被训练看光点，然后定向到光点，光点从固定点跳到或以斜坡保持的方式移动到新的目标。这两个刺激诱发的位置导向和速度导向定向，分别，因为前者使用的位置和后者的速度信息的光点.速度引导定向具有潜伏期短（50- 80 ms）、速度大（500°/s）的特点。最佳视觉刺激速度为300-600°/s，其振幅、速度和幅度随其他刺激速度的增加而减小.位置引导定向的特点是延迟时间长（150 - 300 ms），速度较慢，约为速度引导定向的一半.上级丘的神经元从视觉刺激开始用约30 ms的lavage激活，并在刺激期间持续。在相同的最佳定向速度下，射击频率最大.两种主要类型的神经元在脑桥延髓网状结构进行了观察。一种类型仅在运动刺激下激活，潜伏期约为40 ms，并在头部运动的中间时间内激活。另一个是在头部运动过程中激活的，与刺激类型无关。这些神经活动很好地解释了这种差异。

Cats were trained to look at a light spot and then to orient to the light spot which jumped to or moved in a ramp-hold manner to a new target from the fixation point. The two stimulus evoked position guided and velocity guided orienting, respectively, since the former use positional and the latter velocity information of the light spot.1. Velocity guided orienting is characterized by short latency (50-80ms) and large velocity (500°/s). Optimal visual stimulus velocity is 300-600°/s and their latencies, velocities and amplitudes decreased with other stimulus velocities.2. Position guided orienting is characterized by long latencies (150 -300 ms) and slower velocities of about half of the velocity guided orienting.3. Neurons in the superior colliculus activated with latencies of about 30 ms from onset of the visual stimulus and lasted during stimulus. Firing frequencies were maximal with the same optimal velocities for orienting.4. Two major types of neurons in the pontomedullary reticular formation were observed. One type activated only with moving stimulus, with latencies of about 40 ms and active up to middle of head movement in time. The other is activated during head movements irrespective of stimulus types. The differenced were well explained by these neural activities.