Swindale N V, Matsubara J A, Cynader M S
J Neurosci. 1987 May;7(5):1414-27. doi: 10.1523/JNEUROSCI.07-05-01414.1987.
Two-dimensional maps of orientation and direction preference were made in area 18 of the cat's visual cortex using multiple electrode penetrations 150-300 micron apart. The maps were then analyzed by autocorrelation and Fourier transformation. The power spectrum of the orientation map was sharply peaked below the theoretical cutoff frequency for the sampling function (the pattern of electrode penetrations) used to obtain the map. This suggested that it would be possible to interpolate orientation values between the sample points in the cortex. This was done and the resulting fine-grain maps of orientation preference were studied. Empirical testing showed that the interpolated orientation values were accurate to within +/- 30 degrees. Study of the fine-grain maps showed that iso-orientation domains for broad orientation ranges (0 degrees-90 degrees) were branching bands running from an anterolateral to a posteromedial direction across the surface of the cortex with a periodicity of 1.25 +/- 0.13 mm. Domains for smaller orientation ranges (0 degrees-30 degrees) were periodically spaced, but somewhat irregularly shaped patches. The orientation maps contained numerous point singularities where orientation changed discontinuously. These were spaced about 750 micron apart and most were surrounded by a single 180 degrees cycle of orientations. Autocorrelation analysis of the maps of preferred direction revealed local clustering that extended over a distance of 250-300 micron, but spectral analysis failed to reveal any evidence of periodicity. The absence of periodicity was probably due to a relatively large number of 180 degrees reversals in the map of direction preference, which do not affect the continuity of the orientation map and are not sufficiently numerous to destroy local continuity in the direction map. It is shown that the direction map, if it is to be as continuous as possible, must nevertheless contain lines across which direction preference reverses by 180 degrees. These lines run from one orientation singularity to another. Evidence that the direction map approaches this degree of continuity is presented.
使用间距为150 - 300微米的多个电极插入猫的视皮层18区，绘制了方向和方向偏好的二维图谱。然后通过自相关和傅里叶变换对这些图谱进行分析。方向图谱的功率谱在用于获取图谱的采样函数（电极插入模式）的理论截止频率以下急剧峰值。这表明有可能在皮层中的采样点之间插值方向值。进行了插值并研究了由此产生的方向偏好细粒度图谱。实证测试表明，插值后的方向值精确到±30度以内。对细粒度图谱的研究表明，宽方向范围（0度 - 90度）的等方向域是从皮层表面的前外侧向后内侧方向延伸的分支带，周期为1.25±0.13毫米。较小方向范围（0度 - 30度）的域是周期性间隔但形状有些不规则的斑块。方向图谱包含许多方向不连续变化的点奇点。这些奇点相隔约750微米，大多数被单个180度的方向周期包围。对偏好方向图谱的自相关分析揭示了延伸250 - 300微米距离的局部聚类，但频谱分析未能揭示任何周期性证据。缺乏周期性可能是由于方向偏好图谱中相对大量的180度反转，这些反转不影响方向图谱的连续性，并且数量不足以破坏方向图谱中的局部连续性。结果表明，如果方向图谱要尽可能连续，那么它必须包含方向偏好反转180度的线。这些线从一个方向奇点延伸到另一个方向奇点。给出了方向图谱接近这种连续程度的证据。
