基于群体感受野的二阶方向对比刺激视网膜定位
A second-order orientation-contrast stimulus for population-receptive-field-based retinotopic mapping
摘要：
视野或视网膜定位图是功能磁共振成像中最常用的范例之一。它使用由整个视野呈现的位置变化的高亮度对比度视觉模式引起的活动来确定皮层视觉区的空间组织。虽然使用高亮度对比度的优点是它倾向于驱动宽范围的神经元群体-从而导致高信噪比BOLD响应-但这也可能是一个限制，特别是对于试图从BOLD响应中挤出更多信息的方法，例如群体感受野（pRF）映射。在这种情况下，对神经元子集进行更有选择性的刺激-尽管信号减少-可以更好地表征pRF特性。在这里，我们使用了二阶刺激的基础上的局部差异的方向纹理-我们称之为方向对比度-进行视网膜定位映射。在我们的实验中，参与者观看了由前景（一条）和背景组成的Gabor贴片阵列。这些只能区分的基础上，在补丁方向的差异。在我们的分析中，我们比较了使用这种新的方向对比度为基础的视网膜检查（OCR），使用经典的亮度对比度为基础的视网膜检查（LCR）获得的pRF属性。具体而言，在高阶皮层视觉区，如LO，我们的新方法导致非平凡的减少估计人口感受野大小约30%。我们讨论了如何OCR -通过限制感受野散射和减少BOLD位移-可能导致更准确的pRF定位以及。我们的结论是，使用我们的方法，有可能选择性地针对特定的神经元群体，开辟了使用pRF建模来解剖不同视觉区域中更明确定义的神经元群体的响应特性的方法。
英文摘要：
Visual field or retinotopic mapping is one of the most frequently used paradigms in fMRI. It uses activity evoked by position-varying high luminance contrast visual patterns presented throughout the visual field for determining the spatial organization of cortical visual areas. While the advantage of using high luminance contrast is that it tends to drive a wide range of neural populations - thus resulting in high signal-to-noise BOLD responses - this may also be a limitation, especially for approaches that attempt to squeeze more information out of the BOLD response, such as population receptive field (pRF) mapping. In that case, more selective stimulation of a subset of neurons - despite reduced signals - could result in better characterization of pRF properties. Here, we used a second-order stimulus based on local differences in orientation texture - to which we refer as orientation contrast - to perform retinotopic mapping. Participants in our experiment viewed arrays of Gabor patches composed of a foreground (a bar) and a background. These could only be distinguished on the basis of a difference in patch orientation. In our analyses, we compare the pRF properties obtained using this new orientation contrast-based retinotopy (OCR) to those obtained using classic luminance contrast-based retinotopy (LCR). Specifically, in higher order cortical visual areas such as LO, our novel approach resulted in non-trivial reductions in estimated population receptive field size of around 30%. We discuss how OCR - by limiting receptive field scatter and reducing BOLD displacement - may result in more accurate pRF localization as well. We conclude that using our approach, it is possible to selectively target particular neuronal populations, opening the way to use pRF modeling to dissect the response properties of more clearly-defined neuronal populations in different visual areas.
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