Polimeni Jonathan R, Granquist-Fraser Domhnull, Wood Richard J, Schwartz Eric L
Department of Electrical and Computer Engineering, Boston University, Boston, MA 02215, USA.
Proc Natl Acad Sci U S A. 2005 Mar 15;102(11):4158-63. doi: 10.1073/pnas.0500291102. Epub 2005 Mar 3.
Neurons in macaque primary visual cortex are spatially arranged by their global topographic position and in at least three overlapping local modular systems: ocular dominance columns, orientation pinwheels, and cytochrome oxidase (CO) blobs. Individual neurons in the blobs are not tuned to orientation, and populations of neurons in the pinwheel center regions show weak orientation tuning, suggesting a close relation between pinwheel centers and CO blobs. However, this hypothesis has been challenged by a series of optical recording experiments. In this report, we show that the statistical error associated with photon scatter and absorption in brain tissue combined with the blurring introduced by the optics of the imaging system has typically been in the range of 250 microm. These physical limitations cause a systematic error in the location of pinwheel centers because of the vectorial nature of these patterns, such that the apparent location of a pinwheel center measured by optical recording is never (on average) in the correct in vivo location. The systematic positional offset is approximately 116 microm, which is large enough to account for the claimed misalignment of CO blobs and pinwheel centers. Thus, optical recording, as it has been used to date, has insufficient spatial resolution to accurately locate pinwheel centers. The earlier hypothesis that CO blobs and pinwheel centers are coterminous remains the only hypothesis currently supported by reliable observation.
猕猴初级视觉皮层中的神经元按其整体地形位置在空间上排列，并至少存在于三个重叠的局部模块化系统中：眼优势柱、方向风车以及细胞色素氧化酶（CO）斑点。斑点中的单个神经元对方向不敏感，风车中心区域的神经元群体表现出较弱的方向调谐，这表明风车中心与CO斑点之间存在密切关系。然而，这一假设受到了一系列光学记录实验的挑战。在本报告中，我们表明，与脑组织中的光子散射和吸收相关的统计误差，加上成像系统光学元件引入的模糊，通常在250微米范围内。由于这些模式的矢量性质，这些物理限制会导致风车中心位置出现系统误差，使得通过光学记录测量的风车中心的表观位置（平均而言）从未处于正确的体内位置。系统位置偏移约为116微米，这足以解释所声称的CO斑点与风车中心的错位。因此，迄今为止所使用的光学记录的空间分辨率不足以精确地定位风车中心。CO斑点与风车中心是共边界的这一早期假设仍然是目前唯一得到可靠观察支持的假设。
