Hua S E, Massone L L, Houk J C
Department of Physiology, Northwestern University Medical School, Chicago, IL 60611.
Neuroreport. 1993 Sep 30;4(12):1319-22. doi: 10.1097/00001756-199309150-00008.
The projection from the retina develops into a precise map of the visual world on the surface of the tectum. The search for molecular position cues that mediate map formation has recently yielded a tectal molecule that exerts a repulsion to fibers from the entire temporal half retina. This molecule appears not to function in the generally accepted gradient manner but instead provides only binary position information, and it is only expressed transiently during early development. Here we describe modeling results that compare the efficacy of binary versus graded position cues in topographic map formation; the model also includes an activity dependent process. We find that binary repulsion is more efficient than graded chemoaffinity in the rapid establishment of map polarity, and transient expression of either cue provides sufficient guidance for precise map formation.
视网膜的投射在顶盖表面形成视觉世界的精确图谱。最近，对介导图谱形成的分子位置线索的研究发现了一种顶盖分子，它对来自整个颞侧半视网膜的纤维产生排斥作用。这种分子似乎并不以普遍接受的梯度方式发挥作用，而是仅提供二元位置信息，并且仅在早期发育过程中短暂表达。在这里，我们描述了建模结果，比较了二元位置线索与梯度位置线索在地形图形成中的功效；该模型还包括一个活动依赖过程。我们发现，在快速建立图谱极性方面，二元排斥比梯度化学亲和性更有效，并且任何一种线索的短暂表达都为精确的图谱形成提供了足够的引导。
