Fitzmaurice Marnie C, Ciaramitaro Vivian M, Palmer Larry A, Rosenquist Alan C
Department of Neuroscience, University of Pennsylvania, Philadelphia 19104-6074, USA.
Vis Neurosci. 2003 Nov-Dec;20(6):687-701. doi: 10.1017/s095252380320609x.
Lesion or inactivation of the superior colliculus (SC) of the cat results in an animal that fails to orient toward peripheral visual stimuli which normally evoke a brisk, reflexive orienting response. A failure to orient toward a visual stimulus could be the result of a sensory impairment (a failure to detect the visual stimulus) or a motor impairment (an inability to generate the orienting response). Either mechanism could explain the deficit observed during SC inactivation since neurons in the SC can carry visual sensory signals as well as motor commands involved in the generation of head and eye movements. We investigated the effects of SC inactivation in the cat in two ways. First, we tested cats in a visual detection task that required the animals to press a central, stationary foot pedal to indicate detection of a peripheral visual stimulus. Such a motor response does not involve any components of the orienting response and is unlikely to depend on SC motor commands. A deficit in this task would indicate that the SC plays an important role in the detection of visual targets even in a task that does not require visual orienting. Second, to further investigate the visual orienting deficit observed during SC inactivation and to make direct comparisons between detection and orienting performance, we tested cats in a standard perimetry paradigm. Performance in both tasks was tested following focal inactivation of the SC with microinjections of muscimol at various depths and rostral/caudal locations throughout the SC. Our results reveal a dramatic deficit in both the visual detection task and the visual orienting task following inactivation of the SC with muscimol.
破坏或使猫的上丘（SC）失活会导致动物无法朝向通常能引发快速反射性朝向反应的外周视觉刺激定向。无法朝向视觉刺激可能是感觉障碍（无法检测到视觉刺激）或运动障碍（无法产生朝向反应）的结果。由于上丘中的神经元既可以携带视觉感觉信号，也可以携带参与头部和眼睛运动产生的运动指令，所以这两种机制都可以解释在上丘失活期间观察到的缺陷。我们通过两种方式研究了猫上丘失活的影响。首先，我们在一个视觉检测任务中测试猫，该任务要求动物按下中央的固定脚踏板以表明检测到外周视觉刺激。这样的运动反应不涉及朝向反应的任何组成部分，并且不太可能依赖于上丘的运动指令。这个任务中的缺陷将表明，即使在不需要视觉定向的任务中，上丘在视觉目标的检测中也起着重要作用。其次，为了进一步研究在上丘失活期间观察到的视觉定向缺陷，并直接比较检测和定向性能，我们在标准视野检查范式中测试猫。在整个上丘的不同深度和前后位置通过微量注射蝇蕈醇对上丘进行局灶性失活后，测试了这两个任务中的表现。我们的结果显示，在用蝇蕈醇使上丘失活后，视觉检测任务和视觉定向任务都出现了明显的缺陷。
