Adaptation and Visual Coding

描述（由申请人提供）：视觉系统通过适应过程不断重新校准，适应过程根据环境或观察者的变化调整灵敏度。这些适应性调整在整个视觉系统中起作用，因此深刻地影响了视觉感知的大多数方面。大多数先前的视觉适应研究都集中在从毫秒到分钟的短时间尺度上的敏感性变化。然而，有越来越多的理论论据和经验证据表明，这些快速调整叠加在反应变化，影响视觉编码更长的持续时间。这些长期形式的适应可能是设置视觉系统的基线操作状态的主要机制，并且可能对于补偿视觉编码对于在整个生命周期中发生的视觉系统的光学和神经特性的逐渐但显著的变化特别重要。然而，对于更长时间尺度上的适应的性质或特性，或者它们可以适应视觉刺激的哪些属性，几乎一无所知。本研究将通过一系列的研究对长期视觉适应进行系统的研究， 长期敏感性调节的机制和部位及其对视觉感知和视觉表现的影响。具体目标1将探讨适应环境的平均颜色或观察者的光谱灵敏度变化的影响，以及这些影响如何从视网膜和皮层部位的灵敏度变化中产生。具体目标2将测试颜色的长期反应变化是否也表现为其他刺激属性，包括调节对比度和模糊感知的皮层机制以及面部识别的高级后效。这些实验将有助于揭示长期适应是否在校准视觉反应中起着一般或专门的作用。目标3将测试反应的功能形式在短时间尺度和长时间尺度上是否不同，从而测试它们是否被设计为适应刺激的不同方面的视觉编码。最后，目标4将探讨长期适应优化视觉编码的后果。这些实验将包括改变图像的颜色特征，以模拟它们在理论上完全适应的情况下应该如何出现，然后测试观察者对这些预适应图像中的信息的反应。这些研究的结果将有助于揭示适应过程的机制、性质和后果，这些适应过程可能在正常视觉功能中发挥核心作用，但在很大程度上尚未探索。

DESCRIPTION (provided by applicant): The visual system is continuously recalibrated through processes of adaptation that adjust sensitivity in response to changes in the environment or the observer. These adaptive adjustments operate throughout the visual system and thus profoundly influence most if not all aspects of visual perception. Most prior studies of visual adaptation have focused on sensitivity changes over short times scales ranging from milliseconds to minutes. However, there are increasing theoretical arguments and empirical evidence that these rapid adjustments are superimposed on response changes that influence visual coding over much longer durations. These long-term forms of adaptation may be the primary mechanisms for setting the baseline operating states of the visual system, and may be especially important for compensating visual coding for the gradual but pronounced changes in optical and neural properties of the visual system that occur throughout the lifespan. Yet almost nothing is known about the nature or properties of adaptation at longer timescales, or about which attributes of the visual stimulus they can adjust to. The proposed research will provide a systematic investigation of long-term visual adaptation through a series of studies that will probe the mechanisms and sites of long-term sensitivity adjustments and their consequences for visual perception and visual performance. Specific Aim 1 will probe the effects of adaptation to changes in the average color of the environment or in the spectral sensitivity of the observer, and how these effects arise from sensitivity changes at both retinal and cortical sites. Specific Aim 2 will test whether the long-term response changes demonstrated for color are also manifest for other stimulus attributes, including the cortical mechanisms mediating contrast and blur perception as well as high-level aftereffects for face recognition. These experiments will help to reveal whether long-term adaptation plays a general or specialized role in calibrating visual responses. Aim 3 will test whether the functional form of the response changes differs at short and long timescales, and thus whether they are designed to adapt visual coding for different aspects of the stimulus. Finally, Aim 4 will explore the consequences of long-term adaptation for optimizing visual coding. These experiments will include altering the color characteristics of images to simulate how they should appear under theoretically complete adaptation, and then testing how well observers can respond to information in these pre-adapted images. The results of these studies will help to reveal the mechanisms, properties, and consequences of adaptation processes that are likely to play a central role in normal visual function but which remain largely unexplored.