Keay K, Westby G W, Frankland P, Dean P, Redgrave P
Department of Psychology, University of Sheffield, U.K.
Neuroscience. 1990;37(3):585-601. doi: 10.1016/0306-4522(90)90093-j.
The previous paper (Redgrave et al., Neuroscience 37, 571-584, 1990) presented anatomical evidence indicating there are at least two largely segregated components of the crossed tecto-reticulo-spinal pathway which project to the periabducens area and caudal medulla. An immediate question arising from this finding is whether tectal cells which project either to the periabducens area or to the caudal medulla have different electrophysiological response properties. An answer to this question would be relevant to the issue of whether different components of the tecto-reticulo-spinal system are specialized for the production of different classes of orienting movement. Accordingly, extracellularly recorded units in the superior colliculus of urethane anaesthetized rats were tested for antidromic activity following electrical stimulation of the periabducens area or the caudal medulla. When antidromic potentials were successfully recorded the sensory properties of the units were tested with a range of unimodal visual, somatosensory and auditory stimuli. The following results were obtained. (i) Tectal cells antidromically activated by stimulation of the caudal medulla were preferentially sensitive to somatosensory stimuli from the perioral region, while cells activated from the periabducens area were more frequently responsive to auditory stimuli. (ii) Tectal fibres activated by stimulation of the caudal medulla had significantly higher conduction velocities than the fibres activated by electrodes in the periabducens region. (iii) More than 90% of antidromically activated cells were located in stratum album intermediale or dorsal stratum profundum. These electrophysiological findings confirm and extend previous anatomical observations which indicate that components of the crossed descending projection of the colliculus may be functionally specialized for the production of different classes of orienting movements.
上一篇论文（雷德格雷夫等人，《神经科学》第37卷，第571 - 584页，1990年）提供了解剖学证据，表明交叉的顶盖 - 网状 - 脊髓通路至少有两个大致分离的组成部分，它们投射到外展神经周围区域和延髓尾部。这一发现引发的一个直接问题是，投射到外展神经周围区域或延髓尾部的顶盖细胞是否具有不同的电生理反应特性。对这个问题的回答将与顶盖 - 网状 - 脊髓系统的不同组成部分是否专门用于产生不同类型的定向运动这一问题相关。因此，在对乌拉坦麻醉的大鼠上丘进行细胞外记录时，在电刺激外展神经周围区域或延髓尾部后，测试了这些神经元的逆向活动。当成功记录到逆向电位后，用一系列单峰视觉、体感和听觉刺激测试了这些神经元的感觉特性。得到了以下结果。（i）通过刺激延髓尾部而被逆向激活的顶盖细胞优先对来自口周区域的体感刺激敏感，而从外展神经周围区域激活的细胞则更频繁地对听觉刺激有反应。（ii）通过刺激延髓尾部而被激活的顶盖纤维的传导速度明显高于在外展神经周围区域由电极激活的纤维。（iii）超过90%的逆向激活细胞位于中间白质层或深层背层。这些电生理发现证实并扩展了先前的解剖学观察结果，表明上丘交叉下行投射的组成部分可能在功能上专门用于产生不同类型的定向运动。
