Stein B E, Gaither N S
J Neurophysiol. 1983 Jul;50(1):102-24. doi: 10.1152/jn.1983.50.1.102.
The receptive-field properties of single cells in the optic tectum of Iguana iguana were studied using the same procedures as have been used in this laboratory in studying its mammalian homologue, the superior colliculus. Surprisingly, despite some species-specific characteristics, the range of physiological properties of tectal and superior collicular cells appeared to be strikingly similar. This observation is not consistent with the notion that functional differences between these structures evolved as a consequence of the tremendous elaboration of mammalian neocortex and its involvement in sensory processes. The internal organization of visual tectal receptive fields was observed to be very much like that described in mammals. This included a similar distribution of on-off areas, the presence of both spatial summation and spatial inhibition within the excitatory receptive-field borders, suppressive areas just beyond these borders, and a marked tendency for habituation. In addition, many cells showed distinct directional preferences that were strongly influenced by the velocity of movement through the receptive field. Furthermore, the receptive fields of bimodal and trimodal cells showed topographic correspondences as in mammals, although the sizes of the fields were often large, thereby emphasizing the lack of an exact register between modalities. In contrast to the findings in mammals, however, a preference for stationary over moving stimuli was observed in most neurons, and specializations in iguana tectal cells representing the fovea were noted that have not been described in other species. These foveal specializations include a distinct preference for stationary over moving stimuli, the absence of directional selectivity, and the presence of a majority of cells responding at light onset only. It is suggested that the similarities in the organization and response properties of cells of the optic tectum and superior colliculus reflect the retention of ancestral characteristics through various levels of vertebrate evolution. Furthermore, the subtle species differences in the properties of these cells appear to reflect adaptations to specific ecological pressures rather than general evolutionary trends.
使用本实验室研究其哺乳动物同源物上丘时所采用的相同程序，对鬣蜥视顶盖中单个细胞的感受野特性进行了研究。令人惊讶的是，尽管存在一些物种特异性特征，但顶盖和上丘细胞的生理特性范围似乎极为相似。这一观察结果与以下观点不一致，即这些结构之间的功能差异是由于哺乳动物新皮层的巨大进化及其在感觉过程中的参与而产生的。观察到视觉顶盖感受野的内部组织与哺乳动物中所描述的非常相似。这包括开-关区域的相似分布、兴奋性感受野边界内空间总和与空间抑制的存在、这些边界之外的抑制区域以及明显的习惯化倾向。此外，许多细胞表现出明显的方向偏好，这种偏好受到通过感受野的运动速度的强烈影响。此外，双峰和三峰细胞的感受野与哺乳动物一样表现出拓扑对应关系，尽管感受野的尺寸通常较大，从而强调了不同感觉模态之间缺乏精确的对应。然而，与在哺乳动物中的发现相反，在大多数神经元中观察到对静止刺激比对运动刺激更偏好，并且注意到鬣蜥顶盖细胞中代表中央凹的特化，这在其他物种中尚未有描述。这些中央凹特化包括对静止刺激比对运动刺激有明显偏好、缺乏方向选择性以及大多数细胞仅在光开始时做出反应。有人认为，视顶盖和上丘细胞的组织和反应特性的相似性反映了在脊椎动物进化的各个层面上祖先特征的保留。此外，这些细胞特性中的细微物种差异似乎反映了对特定生态压力的适应，而不是一般的进化趋势。
