Davidson R M, Joly T J, Bender D B
Department of Oral Biology, State University of New York, Buffalo 14226.
Exp Brain Res. 1992;92(2):246-58. doi: 10.1007/BF00227968.
Many cells in the superficial layers of the monkey superior colliculus are sensitive to the relative motion between a small target moving through the classic receptive field and a textured, moving background pattern that fills the visual field beyond the classic receptive field. The cells respond well when motion of the target differs from that of the background, but their responses are suppressed when the target moves in phase with the background. To determine whether this relative motion sensitivity depends on input to the colliculus from visual cortex, we studied colliculus cells in immobilized, anesthetized monkeys after unilateral thermocoagulation, or anesthetic blockade, of the corticotectal tract at the level of the pulvinar. In the colliculus ipsilateral to the corticotectal tract lesions, relative motion sensitivity was significantly reduced when compared either with the colliculus in intact animals or with the colliculus contralateral to the lesion. However, a moving-background stimulus still had a modest suppressive effect compared with a stationary background ("background motion sensitivity"), as is the case for intact animals. Anesthetic blockade of the corticotectal tract had similar effects; relative motion sensitivity, but not background motion sensitivity, was lost following injection of mepivacaine or bupivacaine. Pulvinar cell loss alone, induced by kainic acid injection, had no effect on relative motion sensitivity in the colliculus. The corticotectal tract lesions, but not the anesthetic injections, also had minor effects on flash-evoked responses and spontaneous discharge rates; these effects may reflect a retrograde response of some tectopulvinar cells to injury of their axons by the corticotectal tract lesions. In the colliculus opposite the corticotectal tract lesion, relative motion sensitivity was similar to that in normal animals. However, responses in the presence of a moving background were enhanced, suggesting that removal of cortical input to one colliculus may disinhibit the contralateral colliculus, a phenomenon reminiscent of the Sprague effect in the cat. We conclude that while cortical input to the colliculus may contribute little to the classic receptive field properties of superficial-layer cells, it clearly does contribute to relative motion sensitivity.
猕猴上丘表层的许多细胞对穿过经典感受野的小目标与填充经典感受野之外视野的带纹理移动背景图案之间的相对运动敏感。当目标运动与背景运动不同时，这些细胞反应良好，但当目标与背景同相运动时，它们的反应受到抑制。为了确定这种相对运动敏感性是否依赖于来自视皮层的上丘输入，我们在丘脑枕水平对皮质顶盖束进行单侧热凝或麻醉阻断后，研究了固定化、麻醉的猕猴的上丘细胞。在皮质顶盖束损伤同侧的上丘中，与完整动物的上丘或损伤对侧的上丘相比，相对运动敏感性显著降低。然而，与静止背景相比，移动背景刺激仍有适度的抑制作用（“背景运动敏感性”），完整动物的情况也是如此。皮质顶盖束的麻醉阻断有类似效果；注射甲哌卡因或布比卡因后，相对运动敏感性丧失，但背景运动敏感性未丧失。单独由注射 kainic 酸引起的丘脑枕细胞损失对上丘的相对运动敏感性没有影响。皮质顶盖束损伤而非麻醉注射对闪光诱发反应和自发放电率也有轻微影响；这些影响可能反映了一些顶盖丘脑细胞对皮质顶盖束损伤导致的轴突损伤的逆行反应。在皮质顶盖束损伤对侧的上丘中，相对运动敏感性与正常动物相似。然而，在有移动背景时的反应增强，这表明去除一侧上丘的皮质输入可能会解除对侧上丘的抑制，这一现象让人想起猫的 Sprague 效应。我们得出结论，虽然皮质对上丘的输入可能对表层细胞的经典感受野特性贡献不大，但它显然对相对运动敏感性有贡献。
