Relation of GABA Levels in Visual Cortex to Strength of Interocular Suppression

描述(由申请人提供)：这份R21提案寻求开发分析程序，以便在一大群健康的成年参与者中，将使用磁共振波谱(MRS)获得的结果与使用多项视觉功能测量获得的行为结果相关联。这项研究特别关注枕叶内抑制性神经递质伽马氨基丁酸(GABA)的水平，以及这些水平与多种心理物理指标的关系，这些指标反映了人类视觉中眼间抑制/双眼竞争的深度。这个项目新颖的、未经检验的方面是试图确定知觉抑制的个体差异是否可以被识别出来 在时间上是稳定的，在衡量标准上是一致的，以及GABA水平是否可以预测这种差异。用于解决这些问题的主要分析方法将是结构方程模型(SEM)，它将使我们能够解决三个相互关联的问题：(1)在特定测量的基础上，行为任务绩效的个体差异是否明显？(2)高阶抑制维度是否构成了这些不同心理物理测量之间的相互关联？(3)我们有充分理由相信存在的视觉皮质内GABA水平的个体差异，是否占高阶抑制维度和/或测量特定方差分量的显著比例？结构方程本身是一种成熟的统计技术，用来检验关于个性和气质个体差异的假设，但它并不经常被用来将生物和感知标记联系起来。如果成功，该项目可能为将人类受试者的神经化学数据和行为-认知数据联系起来提供一项突破性技术。作为双目视觉的专家，PI选择在眼间抑制的背景下探索这一未经测试的应用。为了最大限度地增加成功的机会，该项目包括两名共同研究人员，他们都是范德比尔特大学的教职员工，凯文·沃德尔博士(MR光谱专家)和安德鲁·托马尔肯博士(扫描电子显微镜专家)。这项提议虽然是探索性的，但建立在看似合理的联系假说基础上，并确立了眼间抑制方面的个体差异。此外，我们提供的试点数据证实了我们有能力测量和量化使用范德比尔特大学成像科学研究所的设施扫描的人类视觉皮质中的GABA水平。

DESCRIPTION (provided by applicant): This R21 proposal seeks to develop analytic procedures for relating results obtained using magnetic resonance spectroscopy (MRS) to behavioral results obtained using multiple measures of visual function within a large group of healthy, adult participants. The study focuses specifically on levels of the inhibitory neurotransmitter substance gamma amino butyric acid (GABA) within occipital lobe and the relation of those levels to multiple psychophysical measures indexing depth of interocular suppression/binocular rivalry in human vision. The novel, untested aspect of this project is the attempt to identify whether individual differences in perceptual suppression can be identified that are stable across time and consistent across measures and whether GABA levels predict such differences. The primary analytic approach used to address these questions will be structural equation modeling (SEM), which will allow us to address three inter-related questions: (1) Are individual differences in behavioral task performance evident on a measure-specific basis? (2) Does one higher-order dimension of suppression underlie the inter-correlations among these different psychophysical measures? (3) Do individual differences in GABA levels within visual cortex, which we have good reason to believe exist, account for a significant proportion of the variance of the higher-order suppression dimension and/or measure-specific components of variance? SEM itself is a well-established statistical technique for testing hypotheses concerning individual differences in personality and temperament, but it has not been used often to relate biological and perceptual markers. If successful, this project could provide a breakthrough technique for relating neurochemical data and behavioral-cognitive data in human subjects. Being an expert on binocular vision, the PI chose to explore this untested application within the context of interocular suppression. To maximize the chances of success the project includes two co-investigators who are both Vanderbilt University faculty members, Dr. Kevin Waddell (an expert on MR spectroscopy) and Dr. Andrew Tomarken (an expert on SEM). The proposal, while exploratory, is built around plausible linking hypotheses and established individual differences in aspects of interocular suppression. In addition, we present pilot data confirming our ability to measure and quantify GABA levels in visual cortex of humans scanned using the facilities of the Vanderbilt University Institute of Imaging Sciences.