FUNCTIONAL MRI OF LAYER-SPECIFIC CORTICAL MAPS

描述（改编自申请人摘要）：血氧水平 依赖性（BOLD）功能磁共振成像（fMRI）已成为一种 这是一个重要工具，可以在毫米范围内定位活体大脑功能， 厘米刻度然而，在这个粗略的尺度上， 大脑的功能结构必须保持模糊。BOLD的适用性 功能性磁共振成像解决问题的亚毫米，柱状尺度，是 然而，严重质疑，因为它仍然不知道是否和如何的焦点， 从BOLD信号导出的活动在空间上与 神经元的电活动本报告的总体目标 建议是双重的。首先，我们的目标是定义和验证神经关联 通过使用连接的单个单元记录的粗体。为此我们 假设只有早期的负BOLD改变后，感觉 刺激指示柱状尺度神经元活动。的 另一方面，延迟的正BOLD变化被假设为 仅指示整体激活本身的模式，但不能 区分电活性列和非活性列。这 将通过详细的单个单元记录结合 超高场（9.4T）功能磁共振成像研究在猫方向列。在 哺乳动物皮层，神经元喜欢类似的感受野特性， 在空间上聚集成垂直和切向的等功能域 指向皮质表面。到目前为止， 单独的皮质图仅作为所有区域的平均图像进行了研究。 皮质层，由于目前的脑映射技术的限制。 因此，作为本研究的第二个目的，我们建议将 多个皮质图的特定于椎板的结构， 超高场功能磁共振成像（9.4T）在这种列尺度上的独特优势。 我们假设，不同的组织的isofunctional域采取 在不同的Laminae中。因此，空间关系 假设多个皮质标测图之间的差异在皮质 层次。我们将通过利用以下独特优势来验证这一假设： 超高场fMRI（9.4T）在列分辨率，以产生 定向、眼优势、方向、 和猫视觉皮层的空间频率图。这其中的主要贡献 研究将是：首先，在建立神经元之间的直接相关性， 活动和时空模式的BOLD功能磁共振成像信号下降到 亚毫米尺度在动物系统中对BOLD的这种直接验证是 势在必行，因为我们朝着人类的柱状分辨率BOLD功能磁共振成像， 直接验证的手段显然非常有限。其次通过 确定规则，这些规则管理多个 在一个共同的三维神经回路的感受野特性， 我们的研究结果将大大有助于我们理解的原则 大脑皮层的信息表征

DESCRIPTION(adapted from applicant's abstract): Blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) has become an important tool in localizing brain functions in vivo at millimeter to centimeter scale. At this coarse scale, however, pivotal questions about the brain's functional architecture must remain obscured. The applicability of BOLD fMRI for addressing questions down to the submillimeter, columnar scale, is however, severely questioned, as it remains unknown whether and how the foci of the activity derived from BOLD signals are spatially correlated with the electrical activity of the underlying neurons. The overall objective of this proposal is two-fold. First, we aim to define and validate the neural correlate of BOLD by using conjunctive single unit recordings. To this end, we hypothesize that only the early negative BOLD changes following sensory stimulation are indicative of neuronal activity at a columnar scale. The delayed positive BOLD changes on the other hand, are hypothesized to be indicative only for the pattern of overall activation per se, but incapable of discriminating between electrically active and inactive columns. This hypothesis will be tested by detailed single unit recordings in conjunction with ultra-high field (9.4T) fMRI studies in cat orientation columns. In the mammalian cortex, neurons preferring similar receptive field properties are spatially clustered into iso-functional domains in vertical and tangential directions to the cortical surface. To date, the tangential layout of the individual cortical maps has been studied only as averaged images across all cortical laminae due to the limitations of current brain mapping techniques. Therefore, as the second aim of this study, we propose to label the laminar-specific architecture of the multiple cortical maps by utilizing the unique advantages of the ultra-high field fMRI (9.4T) at this columnar scale. We hypothesize that different organization of iso-functional domains takes places within different laminae. Consequently, the spatial relationships between multiple cortical maps are hypothesized to differ across cortical layers. We will test this hypothesis by utilizing the unique advantages of ultra-high field fMRI (9.4T) at columnar resolution in order to yield the laminar-specific architecture of the orientation, ocular dominance, direction, and spatial frequency maps in cat visual cortex. The main contribution of this study will be: first, in establishing a direct correlation between neuronal activity and the spatio-temporal pattern of the BOLD fMRI signals down to the submillimeter scale. Such a direct validation of BOLD in an animal system is imperative, as we move towards columnar-resolution BOLD fMRI in humans, where the means of a direct validation are evidently very limited. Secondly, by determining the rules, which govern the representation of the multiple receptive field properties within a common 3-dimensional neural circuitry, the results of our study will greatly facilitate our understanding of the principle of cortical information representation per se.