Ewert J P, Framing E M, Schürg-Pfeiffer E, Weerasuriya A
Abteilung Neurobiologie, Fachbereich Biologie/Chemie, Universität Kassel, Federal Republic of Germany.
J Comp Physiol A. 1990 Sep;167(4):495-508. doi: 10.1007/BF00190820.
The concept of coded 'command releasing systems' proposes that visually specialized descending tectal (and pretectal) neurons converge on motor pattern generating medullary circuits and release--in goal-specific combination--specific action patterns. Extracellular recordings from medullary neurons of the medial reticular formation of the awake immobilized toad in response to moving visual stimuli revealed the following main results. (i) Properties of medullary neurons were distinguished by location, shape, and size of visual receptive fields (ranging from relatively small to wide), by trigger features of various moving configural stimulus objects (including prey- and predator-selective properties), by tactile sensitivity, and by firing pattern characteristics (sluggish, tonic, warming-up, and cyclic). (ii) Visual receptive fields of medullary neurons and their responses to moving configural objects suggest converging inputs of tectal (and pretectal) descending neurons. (iii) In contrast to tectal monocular 'small-field' neurons, the excitatory visual receptive fields of comparable medullary neurons were larger, ellipsoidally shaped, mostly oriented horizontally, and not topographically mapped in an obvious fashion. Furthermore, configural feature discrimination was sharper. (iv) The observation of multiple properties in most medullary neurons (partly showing combined visual and cutaneous sensitivities) suggests integration of various inputs by these cells, and this is in principle consistent with the concept of command releasing systems. (v) There is evidence for reciprocal tectal/medullary excitatory pathways suitable for premotor warming-up. (vi) Cyclic bursting of many neurons, spontaneously or as a post-stimulus sustaining event, points to a medullary premotor/motor property.
编码“指令释放系统”的概念提出，视觉上专门化的下行顶盖（和顶盖前区）神经元汇聚到产生运动模式的延髓回路，并以特定目标组合的方式释放特定的动作模式。对清醒固定蟾蜍内侧网状结构的延髓神经元进行细胞外记录，以响应移动视觉刺激，得到了以下主要结果。（i）延髓神经元的特性通过视觉感受野的位置、形状和大小（范围从相对较小到较宽）、各种移动构型刺激物体的触发特征（包括猎物和捕食者选择性特性）、触觉敏感性以及放电模式特征（迟缓、紧张、预热和周期性）来区分。（ii）延髓神经元的视觉感受野及其对移动构型物体的反应表明顶盖（和顶盖前区）下行神经元的输入汇聚。（iii）与顶盖单眼“小视野”神经元不同，类似延髓神经元的兴奋性视觉感受野更大，呈椭圆形，大多水平定向，且没有明显的拓扑映射。此外，构型特征辨别更敏锐。（iv）在大多数延髓神经元中观察到多种特性（部分显示视觉和皮肤敏感性的组合）表明这些细胞整合了各种输入，这在原则上与指令释放系统的概念一致。（v）有证据表明存在适合运动前预热的顶盖/延髓相互兴奋性通路。（vi）许多神经元的周期性爆发，无论是自发的还是作为刺激后持续事件，都表明具有延髓运动前/运动特性。
