Neurophysiology of Visual Perception

视觉感知的神经生理学

基本信息

批准号：
8745719
负责人：
David A Leopold
金额：
$ 50.41万
依托单位：
NATIONAL INSTITUTE OF MENTAL HEALTH
依托单位国家：
美国
项目类别：
财政年份：
资助国家：
美国
起止时间：
至
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/8745719
关键词：
Address Affect Area Awareness Basic Science Binocular rivalry Blindness Brain Bypass Cell Nucleus Cerebral cortex Cognition Cognitive Color Conscious Cues Data Dreams Elements Emotions Environment Esthesia Excision Exhibits Eye Face Functional Magnetic Resonance Imaging Goals Hand Head Housing Human Illusions Image Implant Indium Intuition Judgment Laboratories Lead Life Light Location Mammals Maps Medicine Mental disorders Methods Microelectrodes Modeling Monkeys Movement Nature Neurons Neurosciences Paper Pattern Perception Photic Stimulation Primates Process Publishing Pulvinar structure Research Personnel Residual state Retina Retinal Sampling Scotoma Sensory Series Shapes Signal Transduction Social Perception Sorting - Cell Movement Specificity Staging Stimulus Structure Surface System Thalamic structure Time Training Trees Unconscious State V4 neuron Vision Visual Visual Acuity Visual Cortex Visual Illusions Visual Perception Walking Work Writing area V1 area V4 area striata association cortex base computer monitor experience falls follow-up grasp impression injured insight mind control nervous system disorder neurophysiology relating to nervous system research study response segregation sensor transmission process two-dimensional visual stimulus

项目摘要

Nearly half of the cerebral cortex of primates, including humans, is devoted to visual perception. This large proportion reflects the fact that our visual acuity, and the use of vision in our daily life, surpasses that of all other mammals. Why is so much of the brain required to interpret the images falling on the retina? One answer to that question is that vision is, by its nature, an interpretive process and a considerably more difficult problem than one might think. Consider a few moments in the life of a human or any other primate. As we walk or climb through our environment, we turn our heads and move our eyes. We glance three times per second from object to object, in some cases trying to understand the expression on a face, and in others deciding how to shape our hand in order to establish a correct grip. Our own movements cause our retinal image to flit about in a manner that would be impossible to understand if we were to see it on a computer monitor. Nonetheless, our brain is able to interpret this seemlingly incomprehensible sequence of retinal images and integrate it into a stable visual world: Indeed, the retina is only our visual sensor, controlled by the brain to sample data from our environment. It makes no sense to take each snapshot at face value instead the sequence of retinal images is, from the very beginning, interpreted within the context of the movements issued by the brain. Likewise, the brain makes an educated guess on the identity and use of objects, the distance to locations within the scene, the emotions and intentions of people, and a countless number of other features of the world. These qualities are not written into the visual signals themselves, but must be judged based on physical cues, experience, and intuition. In some cases the judgments are unconscious and automatic, whereas in others they are at the fore of our thought processes. In the this we focus on aspects of visual perception that are so immediate and intuitive to us that it is not at all obvious that there is a problem to be solved. In the past year, the laboratory has made headway on three studies related to visual perception. We have also published two studies and a major review in the Annual Review of Neuroscience entitled, Primary visual cortex, awareness and blindsight. In one study, we are investigating activity in a part of the thalamus called the pulvinar during spontaneous changes in visual perception. This project draws upon a phenomenon known as bistable perception, where a given physical stimulus is inherently ambiguous. The brain, seeing ambiguity as a dilemma, lapses into a sequence of spontaneous perceptual reversals. Our study in the pulvinar asks to what extent do visual thalamic neurons respond according to the subjective perception of an observer, even in cases when the stimulus is unchanging? This work follows on a series of previous studies investigating activity throughout the cortex and thalamus during a type of bistable perception called binocular rivalry. Those studies have shown that there is essentially a gradient of perception-related switching throughout the visual cortex, with early areas showing the weakest perceptual correlation and the later areas showing the strongest. The pulvinar receives input from the entire visual cortex, and this input shows some degree of regional segregation. Our aim is therefore to map the subregions of this nucleus during binocular rivalry, as well as other tasks, with the aim of understanding its functional organization with respect to visual perception. During the last year, we have made strong headway on this project, and have collected our first data from the pulvinar. Over the next year, we plan to continue this mapping process so that we will be able to understand the regional specificity of perceptual modulation. The larger goal of this project is to gain insights into the thalamocortical relationship more generally. In the last year, we have also completed two studies related to the contribution of a particular brain area, known as V4, to visual perception. In one project, we have asked investigated the basis of a visual illusion called subjective surface completion. Surface completion is a means by which the brain, upon seeing an array incomplete stimulus elements aligned in just the right way, creates the subjective impression of a surface even though no such surface is physically present. This process is thought to reflect automatic processes by which the brain routinely guesses what is present in a scene. Such guessing is critical in normal vision because, under normal conditions, objects and surfaces are occluded by scene elements. As an analogy, upon viewing a house whose middle portion is blocked by a large tree, the brain understands that the house is a complete and continuous structure that is partly obscured, rather than two half-houses. When certain illusions are optimized, this sort of perceptual completion can be extreme, and it is possible to visually perceive the part of the obscured stimulus that is being completed. This phenomenon raises the question: which neurons in the brain are responsible for this effect? Based on previous work, we gathered that an area known as V4 might contribute to this phenomenon. To address this, we implanted microelectrode arrays in area V4 in two trained monkeys who experienced this visual illusion. We found that V4 neurons exhibited an enhanced, and sometimes rhythmic, response during the illusion compared to similar conditions in which no such illusion was observed. We further discovered that, for a given neuron to participate in this enhancement, the spatial requirements were quite precise. Only when a neurons highest visual sensitivity was directly over the illusory surface was such a modulation observed. The results demonstrate that V4 neurons are directly involved in the interpolative processes involved in subjective surface completion. Moreover, they illustrate that this area, whose neurons normally cover a relatively broad range of visual space, is unexpectedly sensitive to the fine spatial details of the visual stimulus. In another V4 study, we have conducted a follow-up study to an earlier experiment related to the phenomenon of blindsight. We currently have a paper in submission in which we ask the question, to what extent does area V4 respond to visual stimuli when V1 is injured or absent? Under normal conditions, removal of area V1 leads to blindness, but is characterized by some residual, unconscious visual abilities known as blindsight. Our recent findings that fMRI responses in V4 can be observed during blindsight suggest that neurons in this area retain some visual responsiveness. Our present study demonstrates that not only do V4 neurons retain the ability to respond to visual stimuli, but that the residual responses are different in nature than the original responses. Specifically, although much weaker in amplitude, they are more movement sensitive, and to some degree more direction selective, than normal V4 responses. Our findings are in line with the view of the primary visual cortex as the major driver for neural activity in higher cortical areas. At the same time, the presence of weak responses to visual stimulation in the scotoma region supports the notion of V1-bypassing thalamic projections systems as alternative relays for the transmission of information to visual association cortex.

包括人类在内的灵长类动物的大脑皮层中，几乎一半致力于视觉感知。这一很大的比例反映了我们的视力以及在日常生活中视觉的使用超过所有其他哺乳动物的事实。为什么要解释落在视网膜上的图像所需的大脑？这个问题的一个答案是，从本质上讲，愿景是一个解释性过程，并且比人们想象的要困难得多。考虑一下人类或任何其他灵长类动物的生活中的片刻。当我们走路或爬过环境时，我们转过头，移动眼睛。我们每秒从对象到对象三遍，在某些情况下，试图理解脸部的表达，而在其他情况下，我们决定如何塑造我们的手以建立正确的抓地力。我们自己的动作使我们的视网膜图像以某种方式飘动，如果我们要在计算机监视器上看到它，这是不可能理解的。但是，我们的大脑能够解释这种看似难以理解的视网膜图像序列，并将其整合到一个稳定的视觉世界中：的确，视网膜只是我们的视觉传感器，由大脑控制以从我们的环境中进行采样数据。从一开始就将每个快照以面值拍摄，而是在大脑发行的动作的上下文中解释了视网膜图像的顺序是没有意义的。同样，大脑对物体的身份和使用，现场位置的距离，人们的情感和意图以及世界上其他无数其他特征进行了有根据的猜测。这些品质不是写入视觉信号本身的，而必须根据物理线索，经验和直觉来判断。在某些情况下，判断是无意识和自动的，而在其他情况下，它们正处于我们的思维过程中。在这本书中，我们着重于视觉感知的各个方面，对我们如此直接和直观，以至于没有一个问题要解决的问题。在过去的一年中，实验室对与视觉感知有关的三项研究取得了进展。我们还发表了两项研究和一项重大评论，对神经科学的年度综述，标题为“原发性视觉皮层，意识和盲目”。在一项研究中，我们正在研究视觉感知自发变化期间的丘脑一部分的活动。该项目借鉴了一种被称为双态感知的现象，其中给定的物理刺激本质上是模棱两可的。将歧义视为困境，大脑陷入了一系列自发的感知逆转。我们在Pulvinar中的研究询问视觉丘脑神经元在多大程度上根据观察者的主观感知做出反应，即使在刺激不变的情况下？这项工作遵循了一系列先前的研究，研究了整个皮质和丘脑的活性，这是一种称为双眼竞争的双眼感知。这些研究表明，在整个视觉皮层中，基本上存在与感知相关的切换的梯度，早期的区域显示出最弱的感知相关性，而后者的区域显示最强。 Pulvinar从整个视觉皮层接收输入，并且该输入显示一定程度的区域分离。因此，我们的目的是在双眼竞争以及其他任务中绘制该核的子区域，以了解其在视觉感知方面的功能组织。在过去的一年中，我们在这个项目上取得了巨大的进展，并从Pulvinar收集了我们的第一个数据。在明年，我们计划继续进行此映射过程，以便我们能够了解感知调制的区域特异性。该项目的更大目标是更广泛地了解丘脑皮质关系。在去年，我们还完成了两项与特定大脑区域（称为V4）对视觉感知的贡献有关的研究。在一个项目中，我们询问了一个称为主观表面完成的视觉错觉的基础。表面完成是一种手段，通过看到阵列以正确的方式对齐的阵列不完整的刺激元件时，即使没有这种表面存在物理上存在，也会产生表面的主观印象。人们认为这个过程反映了大脑通常猜测场景中存在的东西的自动过程。这种猜测在正常视力中至关重要，因为在正常情况下，物体和表面被场景元素遮住了。作为一个类比，在看一所房屋的中部部分被一棵大树阻塞时，大脑知道房子是一个完整而连续的结构，部分被遮盖了，而不是两个半房子。当优化某些幻想时，这种感知完成可能是极端的，并且可以在视觉上感知到正在完成的掩盖刺激的一部分。这种现象提出了一个问题：大脑中哪些神经元对此作用负责？根据以前的工作，我们收集到一个称为V4的区域可能会导致这种现象。为了解决这个问题，我们将微电极阵列植入了V4区域的两个受过训练的猴子，他们经历了这种视觉幻觉。我们发现，与未观察到这种幻觉相比，V4神经元在幻觉期间表现出增强的，有时甚至有节奏的反应。我们进一步发现，为了使给定的神经元参与这种增强，空间要求非常精确。只有当神经元最高的视觉灵敏度直接在虚幻的表面上时，才观察到这样的调节。结果表明，V4神经元直接参与了参与主观表面完成的插值过程。此外，他们说明该区域的神经元通常涵盖了相对较宽的视觉空间，它对视觉刺激的细节详细说明了敏感。在另一项V4研究中，我们对与盲目现象有关的早期实验进行了后续研究。我们目前有一份提交的论文，我们提出了一个问题，当V1受伤或缺席时，V4面积V4对视觉刺激有何反应？在正常条件下，删除区域V1会导致失明，但其特征是某些残留的无意识视觉能力被称为盲目。我们最近的发现，在盲目的视线期间可以观察到V4中的fMRI响应表明该领域的神经元保留了一些视觉响应能力。我们目前的研究表明，V4神经元不仅保留了对视觉刺激的反应能力，而且剩余反应本质上与原始反应不同。具体而言，尽管幅度较弱，但它们比正常的V4响应更敏感运动敏感，并且在某种程度上更有选择性。我们的发现符合主要视觉皮层作为高层皮质区域神经活动的主要驱动因素。同时，Scotoma区域中对视觉刺激的反应较弱，支持V1-型丘脑投影系统的概念，作为将信息传输到视觉关联皮层的替代继电器。