国际眼科时讯

Proctor Award获奖者专访：视觉环路和阅读环路如何帮助阅读障碍的儿童？丨ARVO2022

2022-05-07 17:36:00
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编者按：视觉环路是视觉生理基础，是传递视觉信息的神经途径。阅读是视觉环路的重要功能，其结构和功能发育与个体学习能力和智力息息相关，但阅读和视觉环路的关系目前仍未完全明确。ARVO 2022会议上，来自斯坦福大学的Brian Wandell教授获得了Proctor Award，并进行了“视觉和阅读的皮质电路”的相关演讲。《国际眼科时讯》于会议现场有幸采访到Brian Wandell教授，分享了其在视觉阅读环路的最新研究，并探讨已有成果和未来可能的发展方向。

人类阅读环路特点：庞大且复杂

迄今为止，科学家初步明确了阅读环路的某些环节。例如，纸张上印刷的文字通过视觉环路，相关文字信息从视网膜传导到早期的视觉皮层，接下来进入大脑的腹侧枕颞部，该部分可能与相关语言皮层相连。目前，除了看单词早期阶段的视觉环路特征，其后期的视觉特征处理网络和特征仍然未知。这些方面人们还可以进一步研究，但在语言和理解方面，一些知识非常复杂。大脑的阅读处理系统非常庞大且有很多部分。

Parts of the reading circuitry are understood. For example, the words start on the printed page (usually), and go through the visual pathways, and those parts from the retina through the early visual cortex we know. We know something about where it goes next into what’s called the ventral occipital temporal part of the brain, but it probably connects to lots of language cortex, and we really don’t know much beyond the early stages of how we see words. For that part we are OK, but when it goes to language and understanding, there is some knowledge, but maybe not appropriate for this particular interview. It is a big complex brain and there are a lot of sections.

发现儿童的阅读环路发育特点，有助于解决儿童阅读障碍

研究团队希望明确关于阅读环路的特点，以帮助父母发现儿童在阅读方面的问题，这也是Brian Wandell教授团队的主要目标。

希望可以观察孩子视觉编码的功能和结构特性，能够告诉家长，儿童今天可能不会阅读，但第二年可能会阅读，一切都会好起来。

知道儿童阅读环路处于正常发展阶段，第二年会发展完善。

可以告诉家长，以前见过类似情况，儿童可能在学习阅读方面有困难，可以通过其他方式（如有声读物、视频等）帮助儿童获得信息和教育。

这是团队的发展目标，大家正在朝着这个方向努力。

The second question is the same question that I had. We would like to learn something about the reading circuitry so that we could help parents. That was really my main goal. Our hope was that we would look at the functional and structural properties of this visual coding and be able to tell the parent, whose child was maybe not reading today but maybe would read next year, that it was going to be OK. Things are developing normally and next year it will be fine. We might tell another parent, we have seen this before, and your child will probably have difficulty ever learning to read, and we should help your child in other ways using audiobooks, videos and other ways to get the information and education. So that’s our goal. I would not say that we have had an impact yet. One of my students (who I would recommend to you for another time), who is at the Stanford Graduate School of Education, continues to try to build on these things.

不同人群之间是否存在视觉环路差异？

人们理解形状和形式的所有思想和能力都始于视觉系统。很明显，盲人不能通过眼睛进行阅读。有趣的是，盲人可以借助盲文作为一种触觉阅读方法。目前已发现，使用盲文的人群与使用文字阅读的人激活了大脑的相同区域——不过不是视觉部分，而是阅读环路过程中的后期部分。深圳神经科学研究所有一个强大的团队，他们研究汉字的阅读与西方文字的阅读是否相同。目前正在进行关于哪些部分是相同的，哪些部分是不同的相关讨论。感兴趣的同道可以在相关方向上进一步探索。欧洲的一些研究人员认为是同一种基本的阅读环路，而深圳的研究学者认为它们有显著差异。Brian Wandell教授曾经在北京参加过一个会议，北京大学的神经外科医生对这个问题很感兴趣，当进行肿瘤或癫痫的切除手术时，他们想要确保尽可能多地保留阅读环路的结构。对于中国人群来说，了解阅读环路的位置是否与西方人群相同，具有重要的现实意义。但目前这个问题还没有完全解决，仍存在争论。

All of our thought and ability to interpret shapes and forms starts in the visual system. So much of reading is seeing words. Clearly if you are blind, you can’t use your eyes to see those words. One of the interesting things is you can use braille in order to read as a tactile method. One of the things we know is that people who use braille do activate the same parts of the brain as people who use words to read - not the visual parts, but the later parts in the process. One of the interesting things your readers might want to know is that there is a strong group at Shenzhen Institute of Neuroscience where they study reading of Chinese characters, and whether the reading of Chinese characters is the same or different from reading Western writing. I would say there is actually a debate about which parts are the same and which parts are different and so forth. You might have a look at that. There are groups in Europe who have argued that it is really basically the same circuitry, while the group in Shenzhen think they have significant differences. I was once at a meeting in Beijing at Peking University I believe, where neurosurgeons were quite interested in this question, because when they do resections for tumors or epilepsies, they want to make sure they don’t remove reading circuitry as much as is possible. Knowing whether for Chinese readers the location of the reading circuitry is the same for Western readers was of practical significance to them. But I don’t think that has been fully resolved yet. There is still an ongoing debate.

阅读环路的结构特点：仍存在谜团，需要进行更多探索

基于视觉白质，人们可以测量白质的组织属性。水分子在不同脑区的进出过程，告诉人们很多关于组织密度和大分子数量的信息。人们可以用扩散来解释这个问题，但目前还缺少一个理论来解释白质的结构特性与灰质的功能反应之间的联系。这是一个很好的问题，但还没有一个明确的答案。这有点类似电子产品的电线，粗电线携带更多的电荷，而小电线携带更少的电荷。大脑的“电线”与实际的电线有所不同，有一些其他的特点。电子产品通常将电线包裹在绝缘体中，与其他电线隔离。而人类大脑的神经网络共享细胞，并不是独立的，它们之间协调信号的能力非常重要，相关内容目前仍在探索中。

In the case of visual white matter, we can measure the tissue properties with the white matter. How water flows in and out of it tells us a lot of information about the density of the tissue and the number of large macromolecules that are there. We can use diffusion for that, but we are missing a theory at this point about how those structural properties of the white matter connect to the functional responses of the grey matter. So, it is a good question, but I can’t say again that there is a crisp answer. It is kind of like having wires for electronics with big thick wires and smaller wires that can carry more charge or less charge. There are other features of the human wires that make them a little different from the electronics. The electronics usually have wires wrapped in an insulator that keeps that wire separated from any other wire. Here, the wires of the human brain actually share cells, so they are not independent. Their ability to coordinate so signals come together or get dispersed in time are important. I wish we had a better theory for that.

fMRI在人类大脑研究中的优势：非侵入性、展示与众不同的个体

功能性核磁共振成像（fMRI）的优点之一是非侵入性，被检查者不需要注入任何东西，更不需要将探针插入大脑。Brian Wandell教授团队体验了几百小时的功能磁共振成像实验，结果并未感到疼痛，而且得到了全脑范围内相当好的空间分辨率的研究结果。现在的测量空间分辨率是毫米（mm）。人们不能同时拥有最大范围的脑区和最细微的空间结构，但可以选择其中之一。很多情况下，fMRI信噪比较低，只需一个人便可以进行操作。在许多医学研究中，需要将研究对象分成两组，每组各100人进行比较。这些研究并没有像人们希望的那样对诊断有所帮助。因为个体之间的差异较大，以至于当阅读环路出现问题时，每个人可能会以不同的方式发生改变，所以这些大样本的群体研究有时是必要的，但并不总是首选。fMRI的另一个优势是，可以展示出与众不同的个体。例如，Brian Wandell教授在演讲中展示了一个没有视交叉的人，而世界上可能没有一百个没有视交叉的人，但人们可以研究这一个人，了解这一个人的反应。如果出现更多的案例，研究人员可以再研究更多的人。

The big strengths of functional MRI are that it is non-invasive - you don’t need to inject anything, you don’t need to put probes into the brain, you can come and go. I’ve been in hundreds of hours of fMRI experiments and it doesn’t hurt. You get a large field of view with pretty good spatial resolution. People are now measuring at sub-millimeter resolution. You can’t have both large field and sub-millimeter, but you can choose one or the other. So it is non-invasive. The signal-to-noise in many cases is good enough that you can use it on a single person. In a lot of medicine, studies take a group of a hundred people and a group of another hundred people and compare them. Those kinds of studies have not been quite as helpful as we would like for diagnosing. Individuals vary so much that when things go badly, they can go badly in different ways in each person, so these group studies are sometimes necessary, but not always preferred. One of the great advantages of fMRI, as I did in my talk today, you can show individuals who are completely unlike any others. For example, I showed a person whose chiasm didn’t cross. There probably aren’t a hundred of them in the world that we know of, but we can study that one person and understand that one person’s responses. We can put them in again if they are ready. That is a great advantage of fMRI.

总的来说，随着神经科学技术手段的发展，人们对大脑、视觉和阅读环路的相关研究会不断发展和完善，以帮助阅读障碍的儿童发现具体原因，寻找合适的干预方案。

专家简介

Brian Wandell教授

斯坦福大学心理学学院

斯坦福大学认知和神经生物学成像中心(MRI服务中心)主任

2013年至2021年，担任吴蔡神经科学研究所(Wu Tsai Neuroscience Institute)副所长

研究以视觉科学为中心，涵盖了视觉障碍、儿童阅读发展、磁共振成像和数字成像的数字成像设备和算法等主题。在视觉神经科学方面的工作使用功能、结构和定量MRI，以及行为测试和建模来理解大脑视觉部分的活动。