Testing and surpassing limits of adaptation in visual cortex

大脑有一种改变自身功能的非凡能力。在视觉系统中，这种神经可塑性经常发生，例如当我们从室内移动到室外时。不断变化的环境会极大地影响视觉输入，皮层神经元会改变它们的反应方式，以保持我们的视觉效果。这种类型的神经可塑性，称为视觉适应，在成年人的大脑中很容易发生。然而，其影响往往是短暂的，限制了其在教育、培训和卫生方面的潜在应用。为了理解和克服这一障碍，明尼苏达大学的Stephen Engel博士和他的同事将通过将实验室研究的持续时间延长一个数量级来测试适应的极限。参与者将通过虚拟现实护目镜观察世界，连续适应长达一周的时间，该护目镜显示头戴式摄像机的修改输出。这些实验将测量适应的效果可以持续多久，并测试可能限制这种神经可塑性增长的几个因素。这包括大脑中受益于神经可塑性的部分和可能受到神经可塑性伤害的部分之间的竞争，因为它们依赖于提供输入的大脑区域的稳定性。理解适应应该使它产生有益的神经可塑性，这有很多应用。它可以成为培训行李扫描仪操作员或图像分析师等视觉专家的一部分。它可能成为努力的一部分，以重新布线的病人的大脑患有视觉疾病，如弱视（“懒惰的眼睛”）。这项工作还将测试适用于许多领域的神经可塑性理论。它将为认知神经科学的教学提供教材，并将直接支持对各种研究生和本科生进行尖端方法的培训。成人视皮层可以根据环境的变化显着改变其功能，使其在输入发生巨大变化的情况下仍能发挥最佳功能。至关重要的是，视觉体验环境的时间越长，适应能力就越强，持续时间就越长。这表明，长期暴露于改变的视觉输入可能会在皮层产生持久的变化。技术问题阻碍了在受控条件下长适应持续时间的研究，但仍不清楚某些因素是否“施加制动”，限制了其强度和耐久性。PI开发了克服这一障碍的方法，并检查了4天连续适应的效果，揭示了显着的局限性。赠款的总体目标是了解产生这些限制的制动器。对于整个视觉来说，适应可以产生成本，也可以产生收益，本提案将测试观察到的限制是否是由于它们。第一组实验将测试成本是否限制适应在早期视觉领域，从文献中检查具体的成本，删除它们，并观察是否仍然存在适应的限制。第二组实验将研究长期适应。他们将测试长期适应可以克服限制的假设，通过纠正后期视觉区域的“编码灾难”来降低成本。这项工作将区分适应的主要理论，使用行为和功能磁共振成像（fMRI）数据的定量分析。它也代表了一个重大的经验性进步;数十项研究已经研究了视觉皮层的适应性，但以前的工作没有测量或测试适应性的限制。这项研究的结果可能会影响视觉可塑性重要的各种领域的工作，从教育到军事再到公共卫生。这项工作的结果将被纳入免费分发的教育材料（功能磁共振成像入门课程和文本）。这笔赠款还将为不同群体的学生提供培训机会。

The brain has a remarkable ability to modify its own function. In the visual system such neuroplasticity occurs routinely, for example when we move from indoors to outside. Changing environments affects visual input dramatically, and cortical neurons alter how they respond in order to keep us seeing well. This type of neuroplasticity, called visual adaptation, occurs readily in the adult brain. Its effects tend to be short-lasting, however, limiting its potential applications in education, training, and health. To understand and overcome this roadblock, Dr. Stephen Engel and colleagues at The University of Minnesota will test the limits of adaptation, by extending laboratory studies an order of magnitude in duration. Participants will adapt for up to a week continuously, by viewing the world through virtual reality goggles that display modified output of a head-mounted camera. The experiments will measure how long-lasting the effects of adaptation can become, and test several factors that could be limiting the growth of this type of neuroplasticity. These include competition between the parts of the brain that benefit from neuroplasticity and the parts that could be hurt by it, since they depend upon stability of the brain regions that provide their input. Understanding adaptation should allow it to produce beneficial neuroplasticity, which has many applications. It could become part of training visual experts such as baggage scanner operators or imagery analysts. It could become part of efforts to rewire the brains of patients suffering from visual diseases, such as amblyopia ("lazy eye"). The work will also test theories of neuroplasticity that are applicable in many domains. It will produce educational materials for teaching of cognitive neuroscience, and will directly support the training of a diverse set of graduate and undergraduate students in cutting edge methods.Adult visual cortex can alter its function dramatically in response to changes in the environment, allowing it to function optimally, despite large changes in input. Critically, the longer vision experiences an environment, the stronger and longer lasting adaptation becomes. This suggests that long-term exposure to altered visual input may produce long-lasting changes in cortex. Technical issues have prevented the study of long adapting durations under controlled conditions, however leaving it unknown whether some factors 'put on the brakes', restricting its strength and durability. The PI developed methods to overcome this roadblock, and examined effects of a 4-days of continuous adaptation, revealing significant limits. The general goal of the grant is to understand the brakes producing those limits. For vision as a whole, adaptation can produce costs, as well as benefits, and this proposal will test whether observed limits are due to them. A first set of experiments will test whether costs limit adaptation in early visual areas, examining specific costs from the literature, removing them, and observing whether limits on adaptation remain present. A second set of experiments will examine longer-term adaptation. They will test the hypothesis that long-term adaptation can overcome limits, reducing costs by correcting for a "coding catastrophe" in later visual areas. The work will distinguish between major theories of adaptation, using quantitative analysis of behavioral and functional MRI (fMRI) data. It also represents a major empirical step forward; dozens of studies have examined adaptation in visual cortex, but no previous work has measured or tested adaptation's limits. Results of this research could influence work in a diverse array of fields where visual plasticity is important, from education to the military to public health. Results of the work will be incorporated into educational materials (an introductory fMRI course and text) that will be freely distributed. The grant will also provide training opportunities for a diverse group of students.