Neural mechanisms of color

描述（由申请人提供）：神经活动，感知和认知之间的联系知之甚少。这个提议提出了颜色作为一个模型系统来填补这些知识空白。颜色是视觉体验的一个基本特征，关于来自眼睛的锥信号如何编码并传输到大脑皮层，我们已经知道很多。但令人惊讶的是，人们对解码这些信号以产生感知颜色并指导感知决策的机制知之甚少。已经提出了两种竞争的解码方案：间隔码，其需要具有尖锐的色度调谐的细胞群体，其一起包含所有颜色空间，再加上赢家通吃规则;以及群体码，其需要至少两组颜色调谐的神经元，再加上加权平均规则。目前还不清楚大脑皮层内的哪些神经元群参与其中。一个线索来自恒河猴的下颞叶皮层（IT）损伤，它会导致严重的色盲，类似于人类某些脑中风所伴随的全色盲。IT是涉及对象编码的许多方面的组织的扩展区域，并且IT的功能组织知之甚少。如果没有这些信息，几乎不可能知道哪些神经元最有可能对颜色处理做出贡献。可能的组织模式包括：由独特的专门领域组成的模块模式;分布式处理模式;或由一系列分级阶段组成的混合模式，每个阶段由一整套功能分区组成。目标1要求在警觉的猴子中进行一系列功能性磁共振成像（fMRI）实验，以确定IT中颜色编码区域的分布，它们的功能连接以及与其他功能定义区域的关系 目的2概述了在猴子执行颜色任务时与微刺激配对的IT颜色区域的fMRI引导的微电极记录，以测试神经活动和感知颜色之间的因果关系，并确定两种解码方案中的哪一种，间隔或群体，这项研究将揭示感知和认知从神经回路活动中产生的原理。这些信息是了解损害认知和感知的精神疾病和中风的病因，诊断和治疗所必需的。此外，这项工作将建立人类和猴子之间的高阶区域的关系，这对于使用猴子作为人类视觉和疾病的模型是必要的。

DESCRIPTION (provided by applicant): The links between neural activity, perception and cognition are poorly understood. This proposal advances color as a model system to fill these gaps in knowledge. Color is an essential feature of visual experience, and much is known about how cone signals from the eye are encoded and transmitted to the cortex. But surprisingly little is known about the mechanisms that decode these signals to bring about perceived colors and guide perceptual decisions. Two competing decoding schemes have been proposed: an interval code, which requires a population of cells with sharp chromatic tuning that together encompass all color space, coupled with a winner- take-all rule; and a population code, which needs at minimum two groups of color-tuned neurons, coupled with a weighted-average rule. It is unclear which groups of neurons within the cerebral cortex are involved. One hint comes from lesions of inferior temporal cortex (IT) in rhesus monkeys, which cause profound color blindness similar to the achromatopsia that accompanies certain cerebral strokes in humans. IT is an expansive region of tissue implicated in many aspects of object coding, and the functional organization of IT is poorly understood. Without this information, it is almost impossible to know which neurons are the most likely to be contributing to color processing. Possible organizational schemes include a modular model comprising uniquely specialized areas; a distributed-processing model; or a hybrid model, consisting of a series of hierarchical stages, each comprising a full complement of functional subregions. Aim 1 calls for a battery of functional magnetic resonance imaging (fMRI) experiments in alert monkey that will determine the distribution of color-coding regions in IT, their functional connectivity and relationship to other functionally defined regions to test which model accounts for the organization of IT. Aim 2 outlines fMRI-guided microelectrode recordings of IT color regions paired with microstimulation while monkeys perform color tasks, to test the causal link between neural activity and perceived color, and to determine which of the two decoding schemes, interval or population, is implemented in IT. The research will uncover principles by which perception and cognition emerge from the activity of neural circuits. This information is required to understand the etiology, diagnosis, and treatment of mental illnesses and strokes that impair cognition and perception. Moreover, the work will establish the relationship of higher-order areas between humans and monkeys, which is necessary in order to use monkeys as models of human vision and disease.