Lui F, Giolli R A, Blanks R H, Tom E M
Department of Anatomy and Neurobiology, California College of Medicine, University of California, Irvine 92717.
J Comp Neurol. 1994 Jun 22;344(4):598-609. doi: 10.1002/cne.903440408.
The primary goal of this study was to determine whether the striate cortex (Oc 1) of the guinea pig projects to the pretectal nucleus of the optic tract (NOT), the first postretinal station of the horizontal optokinetic pathway, and, if so, to analyze the anatomical organization of this cortico-NOT projection. Other goals of this investigation are to identify other pretectal nuclear projections from the visual cortex in the guinea pig, and to determine whether there is any visuotopic organization in this pathway. Axonal tracers (biocytin or 3H-leucine) were injected into the striate cortex (Oc 1), and the tissue processed with histochemical or light autoradiographic techniques. All subcortical terminal labeling is ipsilateral in the basal ganglia and thalamic nuclei. Furthermore, projections are traced to the ipsilateral brainstem, including two areas of the pretectal complex: (1) one in the NOT, extending in some cases to the adjacent lateral portion of the posterior pretectal nucleus (PPN), and (2) one in the pars compacta of the anterior pretectal nucleus (APNc). The terminal fields in the APN are consistently located rostrally in the dorsolateral portion of the nucleus, independently of the injection site in Oc 1, whereas in the NOT the terminal fields shift slightly after injections placed in different locations in the striate cortex. A correlation of the injection sites in Oc 1 and terminal fields in the NOT reveals a loose topographic organization in the cortico-NOT projection; accordingly, the rostrocaudal axis of the striate cortex projects to the lateromedial axis of the NOT, with a 90 degrees rotation, whereas lateral parts of the striate cortex project diffusely throughout the rostrocaudal extent of the NOT. These data show for the first time that the NOT in the guinea pig receives a substantial projection from the visual cortex. Given the fact that in the guinea pig the optokinetic nystagmus shares some of the characteristics found in cat and monkey (i.e., consistent initial fast rise in the slow phase velocity and reduced asymmetry in monocular stimulation), the present findings lend support to the hypothesis that a cortical input to the NOT is a necessary condition for these oculomotor properties to be present.
本研究的主要目的是确定豚鼠的纹状皮质（Oc 1）是否投射到视束前顶盖核（NOT），即水平视动眼反射通路视网膜后的第一个中继站；如果是，则分析这种皮质 - NOT投射的解剖组织结构。本研究的其他目的是确定豚鼠视觉皮质的其他前顶盖核投射，并确定该通路中是否存在任何视拓扑组织。将轴突示踪剂（生物胞素或³H - 亮氨酸）注入纹状皮质（Oc 1），并用组织化学或光镜放射自显影技术处理组织。所有皮质下终末标记在基底神经节和丘脑核中均为同侧。此外，投射追踪到同侧脑干，包括前顶盖复合体的两个区域：（1）一个在NOT，在某些情况下延伸到后顶盖前核（PPN）相邻的外侧部分，（2）一个在前顶盖前核致密部（APNc）。APN中的终末场始终位于该核背外侧部分的前部，与Oc 1中的注射部位无关，而在NOT中，终末场在纹状皮质不同位置注射后会略有移动。Oc 1中的注射部位与NOT中的终末场之间的相关性揭示了皮质 - NOT投射中的一种松散的拓扑组织；因此，纹状皮质的前后轴以90度旋转投射到NOT的内外轴，而纹状皮质的外侧部分则广泛投射到NOT的前后范围。这些数据首次表明豚鼠的NOT接受来自视觉皮质的大量投射。鉴于豚鼠的视动眼性眼球震颤具有猫和猴中发现的一些特征（即慢相速度始终有快速上升且单眼刺激时不对称性降低），目前的研究结果支持了这样一种假设，即皮质向NOT的输入是这些眼动特性存在的必要条件。
