FUNCTIONAL MRI OF LAYER-SPECIFIC CORTICAL MAPS

描述(摘自申请者的摘要)：血氧水平 依赖(BOLD)功能磁共振成像(FMRI)已成为 在体内定位脑功能的重要工具，毫米到 厘米刻度。然而，在这种粗略的规模下，关于 大脑的功能架构必须保持模糊不清。BOLD的适用性 FMRI用于解决精确到亚毫米柱状尺度的问题，是 然而，受到严重质疑，因为尚不清楚是否以及如何 从粗体信号得出的活动在空间上与 下层神经元的电活动。这样做的总体目标是 提案有两个方面。首先，我们的目标是定义和验证神经关联 通过使用合取的单单元录音来实现粗体。为此，我们 假设只有感官之后的早期负面大胆变化 刺激表明神经元在柱状尺度上的活动。这个 另一方面，延迟的积极大胆的变化被假设为 仅指示整体激活本身的模式，但不能 区分电活动列和非活动列。这 假设将通过结合详细的单单元录音来检验 在CAT定向柱中使用超高场(9.4T)功能磁共振研究。在 哺乳动物的大脑皮层，神经元喜欢类似的感受场特性 在垂直和切向上空间聚集成等功能域 通向皮质表面的方向。到目前为止， 单独的大脑皮层地图仅作为所有区域的平均图像进行研究 由于目前的大脑绘图技术的限制，大脑皮层板层。 因此，作为这项研究的第二个目的，我们建议将 通过利用多个皮质图的层流特定的结构 超高场功能磁共振成像(9.4T)在这种柱状规模上的独特优势。 我们假设等功能域的不同组织采取 位于不同的椎板内。因此，空间关系 假设多个皮质映射之间的差异在不同的皮质上是不同的 层次感。我们将利用以下独特优势来检验这一假设 柱状分辨率的超高场fMRI(9.4T)，以产生 方向、眼球优势、方向、 以及猫视皮层的空间频率图。这一点的主要贡献 研究将是：首先，在建立神经元之间的直接关联 活动和BOLD fMRI信号的时空模式一直延伸到 亚毫米刻度。在动物系统中对BOLD的这种直接验证是 当务之急是，随着我们在人类中转向柱状分辨率的大胆功能磁共振成像， 直接验证的手段显然是非常有限的。其次，通过 确定规则，该规则管理多个 普通3维神经电路中的感受场特性， 我们的研究结果将大大有助于我们对这一原则的理解 大脑皮层信息表征本身。

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.