Bonhoeffer T, Grinvald A
Rockefeller University, Laboratory of Neurobiology, New York, New York 10021.
Nature. 1991 Oct 3;353(6343):429-31. doi: 10.1038/353429a0.
The mammalian cortex is organized in a columnar fashion: neurons lying below each other from the pia to the white matter usually share many functional properties. Across the cortical surface, cells with similar response properties are also clustered together, forming elongated bands or patches. Some response properties, such as orientation preference in the visual cortex, change gradually across the cortical surface forming 'orientation maps'. To determine the precise layout of iso-orientation domains, knowledge of responses not only to one but to many stimulus orientations is essential. Therefore, the exact depiction of orientation maps has been hampered by technical difficulties and remained controversial for almost thirty years. Here we use in vivo optical imaging based on intrinsic signals to gather information on the responses of a piece of cortex to gratings in many different orientations. This complete set of responses then provides detailed information on the structure of the orientation map in a large patch of cortex from area 18 of the cat. We find that cortical regions that respond best to one orientation form highly ordered patches rather than elongated bands. These iso-orientation patches are organized around 'orientation centres', producing pinwheel-like patterns in which the orientation preference of cells is changing continuously across the cortex. We have also analysed our data for fast changes in orientation preference and find that these 'fractures' are limited to the orientation centres. The pinwheels and orientation centres are such a prominent organizational feature that it should be important to understand their development as well as their function in the processing of visual information.
从软膜到白质相互层叠的神经元通常具有许多共同的功能特性。在整个皮层表面，具有相似反应特性的细胞也聚集在一起，形成细长的条带或斑块。一些反应特性，如视觉皮层中的方向偏好，在皮层表面逐渐变化，形成“方向图”。为了确定等方向域的精确布局，不仅要了解对一种刺激方向的反应，还要了解对多种刺激方向的反应。因此，方向图的精确描绘一直受到技术难题的阻碍，并且在近三十年里一直存在争议。在这里，我们使用基于内在信号的体内光学成像来收集关于一块皮层对许多不同方向光栅的反应信息。这组完整的反应随后提供了关于猫18区一大片皮层中方向图结构的详细信息。我们发现，对一种方向反应最佳的皮层区域形成高度有序的斑块，而不是细长的条带。这些等方向斑块围绕“方向中心”组织，产生类似风车的图案，其中细胞的方向偏好沿着皮层不断变化。我们还分析了数据中方向偏好的快速变化，发现这些“断裂”仅限于方向中心。风车和方向中心是如此突出的组织特征，以至于了解它们的发育以及它们在视觉信息处理中的功能应该很重要。
