Cortical Networks of color/shape integration in grapheme/color synesthesia

描述(由申请人提供)：本提案旨在澄清字素-颜色通感领域的两个中心问题。字素-颜色联结者在观看或思考字母或数字等字素时，会体验到一致和自动的颜色感知。中心问题是1)字素-颜色联觉是否依赖于大脑皮层区域之间的直接解剖投影或间接功能连接；2)联觉知觉需要注意的程度。通感研究者之间存在着争论，他们中的一些人认为通感是早期发育过程中皮质修剪不完全的结果(例如，Maurer&Mondloch，2005；Ramachandran&Hubbard，2001)，另一些人则认为，通感是由于对通常在所有成年人中被抑制的连接的去抑制(例如，Grossenbacher&Lovelace，2001)。越来越多的融合功能和解剖学证据支持参与颜色选择性视区V4(Hubbard，Arman，Ramachandran，&Boynton，2005)；Weiss&Fink，2008)以及顶下区(例如，Rouw&Scholte，2007；Nunn等人，2002)。同样，对角回的TMS可靠地减少了联觉知觉(Esterman，Verstinen，Ivry，&Robertson，2006；Mgueton，Tsakanikos，Walsh，&Ward，2007)。这个不断增长的证据语料库一致地确认了顶叶皮质和V4区在联觉知觉中的作用，但还没有研究澄清这两个区域可能如何相互作用。为了理解联觉，并解决正在进行的关于额外连接或非继承性反馈(或两者兼而有之)的争论，有必要绘制通感体验过程中涉及的功能回路图，并将其与视网膜视觉皮质和解剖连接(DTI)区域的准确测量共同登记。我们将对从V1到IPS的视觉区域进行视网膜定位，并测量这些区域内的解剖和功能连接。然后，使用从以前的通感工作中发展出来的心理物理学范式，我们将测试涉及字素-颜色联觉的皮质网络，并定量测量它们对注意的依赖性。更广泛地说，这项建议解决了知觉绑定和特征整合的广泛问题，这是知觉、认知神经科学和心理学领域的核心问题。通感知觉不会取代诱导器，而是作为一种额外的特征添加到诱导器中。这种联觉的同时也很可能是由注意力调节的(参见Mattingley，2009年的综述)。正如Robertson(2003)所提出的，联觉为实验测试和隔离知觉绑定机制和特征整合提供了一个理想的模型，因为主观联觉体验可以被测量为对单个特征(即通感颜色)的纯粹孤立的现象学经验，而所有刺激属性(即刺激亮度、颜色、大小、物体类型等)都可以被测量。保持可测量的恒定。 公共卫生相关性：这项建议寻求促进对颜色/形状整合的皮质网络的科学理解，并将通过测试字素-颜色联会来研究这一点；在字素-颜色联会中，字母和数字等形式触发自动颜色感知，并在整个成年生活中保持一致。字素-颜色联觉是一种发育现象，大脑中的颜色系统被字母和数字形状激活，尽管这不是一个健康问题，但它曾多次被误诊为精神问题。目前的项目旨在提供科学证据，帮助医学界和公众将这种现象理解为正常视力的一种变体。

DESCRIPTION (provided by applicant): This proposal seeks to clarify two central issues in the field of grapheme-color synesthesia. Grapheme-color synesthetes experience consistent and automatic color percepts when viewing or thinking of graphemes such as letters or numbers. The central issues are 1) whether grapheme-color synesthesia relies on direct anatomical projections or indirect functional connectivity between cortical regions and 2) to what extent synesthetic percepts require attention. A debate exists amongst synesthesia researchers, some of whom suggest that synesthesia results from incomplete cortical pruning during early development (e.g., Maurer & Mondloch, 2005; Ramachandran & Hubbard, 2001) and others who suggest it results from disinhibition of connections normally suppressed in all adults (e.g., Grossenbacher & Lovelace, 2001). A growing body of convergent functional and anatomical evidence supports the involvement of color-selective visual area V4 (Hubbard, Arman, Ramachandran, & Boynton, 2005); Weiss & Fink, 2008) and also inferior parietal areas (intraparietal sulcus and angular gyrus, e.g., (Rouw & Scholte, 2007; Nunn et al., 2002). Likewise, TMS to the angular gyrus reliably diminishes synesthetic percepts (Esterman, Verstynen, Ivry, & Robertson, 2006; Muggleton, Tsakanikos, Walsh, & Ward, 2007). This growing corpus of evidence has consistently identified both parietal cortex and area V4 in synesthetic perception but no study has clarified how these two areas might interact if at all. To understand synesthesia and to resolve the ongoing debate of extra connections or disinherited feedback (or both) it is necessary to map the functional circuit involved during synesthetic experience and co-register it with accurate measurements of retinotopically defined areas of visual cortex and anatomical connectivity (DTI). We will retinotopically localize visual areas from V1 through IPS and measure both anatomical and functional connectivity within these regions. Then, using a psychophysical paradigm developed from previous work on synesthesia, we will test the cortical networks involved in grapheme-color synesthesia and quantitatively measure their dependence on attention. More generally, this proposal addresses the broad issues of perceptual binding and feature integration, core issues in the field of perception and cognitive neuroscience and psychology. Synesthetic percepts do not replace their inducers and instead are added to them as an extra feature. This synesthetic concurrent is also most likely mediated by attention (see Mattingley, 2009 for a review). As suggested by Robertson (2003), synesthesia offers an ideal model for experimentally testing and isolating perceptual binding mechanisms and feature integration because a subjective synesthetic experience can be measured as a purely isolated phenomenological experience of a single feature (i.e., synesthetic color) while all stimulus properties (i.e., the stimulus luminance, color, size, object type, etc.) remain measurably constant. PUBLIC HEALTH RELEVANCE: This proposal seeks to advance the scientific understanding of cortical networks of color/shape integration and will investigate this by testing grapheme-color synesthetes; a population in which forms such as letters and numbers trigger automatic color percepts that remain consistent throughout adult life. Grapheme-color synesthesia is a developmental phenomenon in which color systems in the brain are activated by letter and number shape, and although this is not a health issue, it has been "misdiagnosed" as a psychiatric problem on several occasions. The current project is designed to provide scientific evidence that will help the medical profession as well as the public understand this phenomenon as a variant of normal vision.