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

描述（由申请人提供）：本R21提案旨在开发分析程序，用于将使用磁共振波谱（MRS）获得的结果与使用一大群健康成人参与者中的多种视觉功能测量获得的行为结果相关联。该研究特别关注枕叶内抑制性神经递质物质γ氨基丁酸（GABA）的水平，以及这些水平与人类视觉中眼间抑制/双眼竞争深度的多个心理物理指标的关系。这个项目的新颖的、未经测试的方面是试图确定是否可以识别感知抑制的个体差异， 是否随时间推移而稳定，并在不同措施之间保持一致，以及GABA水平是否预测了这种差异。解决这些问题的主要分析方法将是结构方程模型（SEM），这将使我们能够解决三个相互关联的问题：（1）行为任务绩效的个体差异是否在特定测量的基础上是明显的？(2)这些不同的心理物理测量之间的相互关联是否存在一个更高阶的抑制维度？(3)我们有充分的理由相信存在的视觉皮层内GABA水平的个体差异是否占高阶抑制维度方差和/或测量特定方差分量的显著比例？SEM本身是一种成熟的统计技术，用于测试有关个性和气质的个体差异的假设，但它并不经常用于将生物和感知标记联系起来。如果成功，该项目将为人类受试者的神经化学数据和行为认知数据的关联提供突破性技术。作为双眼视觉的专家，PI选择在两眼间抑制的背景下探索这种未经测试的应用。为了最大限度地提高成功的机会，该项目包括两名共同研究者，他们都是范德比尔特大学的教员，Kevin Waddell博士（MR光谱学专家）和Andrew Tomarken博士（SEM专家）。该提议虽然是探索性的，但它是建立在合理的联系假设和确定的眼间抑制方面的个体差异基础上的。此外，我们目前的试点数据确认我们的能力，测量和量化GABA水平的视觉皮层的人类扫描使用的设施的范德比尔特大学成像科学研究所。

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.