Neurophysiology of Visual Perception

为了理解我们的视觉，将人类置于适当的植物学背景中是至关重要的：人类是灵长类动物，他们对视觉的主要使用是灵长类动物的典型特征，不同于其他哺乳动物。作为一名感知能力，视觉使个人比他们所处的环境具有巨大的优势，使他们能够从安全的距离远程感知复杂的细节。由于这一背景对我们的研究至关重要，我们最近发表了一篇全面的综述，描述了哺乳动物背景下灵长类视觉的显著特征，从而将人类视觉置于其适当的进化背景中(Leopold，Freiwald和Mitchell，神经系统的进化，编辑)。Kaas，2017)。 我们对视觉感知的大部分研究都集中在我们如何看待形状、物体和场景。从光线进入眼睛的那一刻起，我们的感知就经过了一系列的处理阶段，在灵长类动物异常漫长的发育过程中，通过多年的视觉经验而形成。在我们的实验室里，我们将功能磁共振成像和电生理学结合起来，提出一些问题，比如，鉴于大脑的视网膜图像本质上是二维的，大脑如何创建世界的三维表示？我们如何完成表面，区分前景和背景，并理解真正的运动和由我们自己的眼睛运动引起的运动之间的区别？这些类型的问题在我们的每一条研究路线中都存在。在这里，我们描述了几项专注于特定子问题的研究。 在过去的两年里，我们把研究视觉知觉的重点放在了丘脑大枕核的神秘作用上，它投射到包括初级视觉皮质(V1)在内的多个视觉区域。在一组研究中，我们一直在使用一种新的电极标测方法来研究枕骨的电活动。这个大型项目目前已经产生了两篇正在准备中的论文(Murphy等人)。和(邓等人..我们最近发表了一篇关于枕骨的全面综述论文(Bridge等人，2016)，重点关注其结构和功能的多个方面，包括新假设的瞬时视觉通路，该通路先于传达出生后早期视觉信息的成人膝状体通路。我们最近提交了一项大型合作研究，调查早期消融一个小枕核的作用，以及它的破坏对成年人视觉引导手动行为的影响(Mundinano等人，2017)，正在审查中。 我们还在视觉皮质的活动方面取得了进展，重点关注了V1区的几个特征。在一项目前正在审查中的研究(Cox等人，2017)中，我们研究了短暂注意线索对V1内神经元接受场外活动的影响，结果表明，在有意义的线索呈现后，有效地存在活动眨眼。我们进一步研究了阿尔法信号对尖峰和伽马范围LFP活动的夹带(Dougherty等人，2017年)。我们还发表了一篇论文，表明消融ARE V1不仅没有破坏高阶视觉区域的活动相关性，反而增强了活动相关性(Shapcott等人，2016)。最后，在一项合作研究中，我们发现顶叶皮质受损的人类患者在感知双眼差异方面受到选择性影响(Murphy等人，2016)。 在我们关于视觉感知的研究中，我们对大脑对刺激的反应越来越感兴趣，这些刺激不是简单地在屏幕上闪现，而是随着时间的推移而演变。为此，我们进行了多项研究，让猕猴和绒猴自由观看动态视频刺激。从实验的角度来看，这种类型的实验的数据分析可能是具有挑战性的，因为受试者的眼睛位置存在内在的可变性。在一项研究中，我们系统地检查了受试者眼球运动的区域fMRI反应，并将它们与电影本身对事件的fMRI反应进行了比较(Russ等人，2016)。我们发现这两种情况下的活动模式有很大的不同。在最近的一项研究中，我们使用功能磁共振成像和电生理学来创建一种新的方法，使用功能磁共振成像地图对神经反应进行分类(Park等人，2017年)。这种方法表明，彼此之间数百微米范围内的神经元以非常不同的方式与遥远的大脑区域联系在一起。这些和其他来自自然观察范式的结果提出了一些关于大脑如何解释其视网膜图像的新问题，我们目前正在关注反应的时间动力学，询问神经反应在多大程度上整合了随着时间的推移的时间整合(Russ等人，正在准备中)。

To understand our vision, it is critical to place humans within an appropriate phylogentic context: humans are primates, and their dominant use of vision is typical of primates and different from other mammals. As a sensing faculty, vision places individuals at a great advantage over their environment, allowing them to remotely sense complex details from a safe distance. As this context is critical for our research, we recently published a comprehensive review describing the distinguishing features of primate vision against a mammalian background, and thus placing human vision into its proper evolutionary context (Leopold, Freiwald, and Mitchell, Evolution of Nervous Systems, ed. Kaas, 2017). Much of our research on visual perception centers on how we see shapes, objects, and scenes. From the moment light enters the eyes, our percept is molded by a series of processing stages, crafted through years of visual experience during primates unusually long period of development. In our laboratory, we combine fMRI and electrophysiology to ask questions such as, how does the brain create a three-dimensional representation of the world, given that its retinal images are inherently two-dimensional? How do we complete surfaces, distinguish between foreground and background, and understand the difference between real motion and the motion caused by our own eye movements? These types of questions are present in each of our research lines. Here we described several studies that focus on particular sub-questions. In the past two years, we have placed most of our emphasis studying visual perception on the mysterious role of the large pulvinar nucleus of the thalamus, which projects to multiple visual areas including the primary visual cortex (V1). In one set of studies, we have been investigating electrical activity across the pulvinar using a novel electrode mapping approach. This large project has yielded two papers currently in preparation (Murphy et al. and (Deng et al.. We have recently published a comprehensive review paper on the pulvinar, (Bridge et al., 2016), which focuses on multiple aspects of its structure and function, including a newly hypothesized transient visual pathway that precedes that adult geniculostriate pathway that conveys early postnatal visual information. We have recently submitted a large collaborative study investigating the role of early-life ablation of one small pulvinar nucleus, and the effect of its disruption on visually-guided manual behavior in the adult (Mundinano et al., 2017), under review. We have also made progress on activity in the visual cortex, focusing on several features of area V1. In one study, currently under review (Cox et al., 2017)), we have studied the effects of a brief attentional cue on activity outside neurons receptive fields within V1, with the results suggesting that there is effectively an activity blink just following the presentation of meaningful cues. We further investigated the entrainment of spiking and gamma-range LFP activity by alpha signals (Dougherty et al., 2017). We also published a paper showing that the ablation of are V1 does not disrupt but rather enhances activity correlation in higher-order visual areas (Shapcott et al., 2016). Finally, in a collaborative study, we found that human patients with damage to the parietal cortex were selectively affected in their perception of binocular disparity (Murphy et al., 2016). In our work on visual perception, we have been increasingly interested in the brains responses to stimuli that are not simply flashed on the screen but that rather evolve over time. To this end, we have conducted multiple studies in which macaques and marmosets freely view dynamic video stimuli. From an experimental perspective, data analysis from this type of experiment can be challenging, as there is inherent variability in the subjects eye positions. In one study, we systematically examined the regional fMRI responses to the subjects eye movements, and compared them to the fMRI responses to the events in the movie itself (Russ et al., 2016). We found that the activity patterns under these two conditions were very different. In a very recent study, we used both fMRI and electrophysiology to create a new means to classify neural responses using fMRI maps (Park et al., 2017). This method demonstrated that neurons within hundreds of microns of one another were affiliated in very different ways with distant brain areas. These and other results from the natural viewing paradigm have raised a number of new questions about how the brain interprets its retinal images, and we are currently in the process of focusing on the temporal dynamics of the responses, asking to what extent neural responses integrate temporal integration over time (Russ et al., in preparation).