The Size of a Cortical Representation

描述（申请人提供）：我们的研究兴趣集中在感觉皮层中感觉上皮的地形图及其可塑性。我们对描绘小（点）刺激下皮层激活的空间范围（例如，所有响应神经元的空间分布）特别感兴趣，因为这是我们理解皮层地图的基础。功能成像方法在表征空间范围方面是有利的，因为它们能够提供快速、高空间分辨率的大皮层区域活动评估。然而，大多数功能成像方法的一个局限性是，它们依赖于大脑激活后的血流动力学事件，因此只能间接地评估潜在的神经元诱发激活的空间范围，因此成像仪缺乏利用成像来评估神经元激活扩散的手段。由于没有直接的方法来验证人类潜在的神经元激活区域的空间范围，成像仪通常采用保守的阈值进行分析，通常强调峰值或峰值附近的激活区域。然而，这种做法可能会导致对皮层功能的偏见和可能扭曲的看法，因为它可能低估了皮层激活的实际规模。为了解决这些问题，我们建议将神经元激活的扩散与相同刺激下同一皮质区域的功能成像成像的扩散直接联系起来。点刺激是须或纯音，皮层激活的扩散分别在成年大鼠体感觉和听觉皮层用本征信号光学成像成像。成像结果将直接与成像后的神经元记录进行比较，在成像皮层内使用电极阵列。反过来，成像和神经元结果也将叠加在同一区域的解剖图上，以突出与活动扩散相关的皮质结构-功能关系。由于功能成像方法可以检测阈上（动作电位）和阈下（局部场电位），因此将记录两种类型的神经元激活的传播并与成像结果进行比较。一旦将神经元扩散映射到成像扩散的规则量化，就可以使用这些规则对整个体感和听觉皮层进行无偏、直接、基于成像的描述。

DESCRIPTION (provided by applicant): Our research interests focus on the topographical mapping of sensory epithelia in sensory cortex and their plasticity. We are particularly interested in delineating the spatial extent of cortical activation (e.g., the spatial spread of all the responding neurons) to small (point) stimulation because it is fundamental to our understanding of cortical maps. Functional imaging methods are advantageous for characterizing the spatial extent because of their ability to provide quick, high spatial resolution assessment of activity from large cortical regions. However, one limitation of most of the functional imaging methods is that they rely on hemodynamic events that follow brain activation and therefore provide only an indirect means for assessing the spatial extent of the underlying neuronal evoked activation and thus imagers lack the means to assess the spread of neuronal activation using imaging. Because there is no direct way to verify the spatial extent of the underlying neuronal activation area in humans, imagers typically apply conservative thresholds for analysis that typically emphasize peak, or near peak activation areas. Such practice, however, may lead to a biased and possibly distorted view of cortical function because it may underestimate the real size of cortical activation. To address these issues, it is proposed to directly relate the spread of neuronal activation to the spread imaged by functional imaging of the same cortical area with the same stimulation. The point stimulation is either a whisker or a pure tone, and the spread of cortical activation is imaged by intrinsic signal optical imaging in the adult rat somatosensory and auditory cortex, respectively. Imaging results will be directly compared to post-imaging neuronal recording using electrode arrays within the imaged cortex. Imaging and neuronal results, in turn, will also be superimposed on the anatomical maps of the same areas to highlight cortical structure-function relationship related to the spread of activity. Because functional imaging methods can detect both suprathreshold (action potentials) and subthreshold (local field potentials), the spread of both types of neuronal activations will be recorded and compared with imaging results. Once the rules of mapping neuronal spread to imaging spread are quantified, it will enable unbiased, direct, imaging-based description of the entire somatosensory and auditory cortices using such rules.