Object, face, body and scene representations in the human brain

这项研究的目的是了解我们是如何看到我们所看到的：大脑如何分析落在眼睛视网膜上的光线，以揭示一个充满物体、人和事物的世界？ 在过去的一年里，我们专注于(I)感知和(Ii)复杂视觉刺激的记忆，特别是真实世界的视觉场景、物体和人(NCT00001360)。 感知： 真实世界的场景极其复杂和多种多样，但我们能够毫不费力地对它们进行分类，并识别这些场景中的对象和人。虽然之前的研究已经确定了大脑中似乎专门处理人脸、物体和场景的区域，但目前还不清楚这些不同区域的确切作用是什么，它们包含什么信息。 理解大脑中的视觉感知的主要挑战之一是我们所经历的广泛的不同对象和场景。尽管研究的广度很大，但研究往往集中在少数手工选择的物体或场景类别上，但后续的发现有多有代表性就变得不清楚了。为了克服这一挑战，我们开发了一个大型数据库(Things)，其中包含1,854种不同类型的物体，这些物体系统地从美国英语中的具体、可想象和可命名的名词中采样。这个数据库提供了丰富的物体概念和物体图像资源，并为心理学、神经科学和计算机科学领域的系统和大规模自然主义研究提供了工具。 我们使用这个数据库进行了一项使用在线众包的大规模行为实验，对5000多名参与者进行了146万次试验。使用任务的计算模型，我们能够识别出我们对物体的内部心理表征的49个核心维度，提供了对这个表征空间的全面和细粒度的表征。 这些结果为支持我们对物体的理解的认知过程提供了重要的见解。我们现在正在扩展这项工作，通过收集这组不同对象图像的fMRI和脑磁图(MEG)数据来揭示潜在的大脑机制。 内存： 为了理解物体和场景记忆的本质，我们集中讨论了两个具体问题： 1)内侧顶叶皮质的组织 人类内侧顶叶皮质(MPC)参与了记忆回忆、视觉场景加工和导航等多种认知过程。鉴于MPC在历史上被认为基本上独立的认知领域的招募如此多样化，关于其职能和总体组织没有明确的共识也就不足为奇了。在一系列研究中，我们用功能磁共振成像测量大脑活动，同时向参与者展示场景和人物的图像，并要求他们回忆特定的事件(例如刮胡子、去海滩)，以及回忆著名或个人熟悉的地方和人。我们的发现揭示了两个关键的见解。首先，我们发现，在MPC中，从更多知觉相关的表征到更多与从后到前相关的记忆的表征存在明显的梯度。其次，我们发现MPC内不同的分支在回忆人名或地点的过程中表现出不同的活跃程度。 虽然人和地点是我们记忆中最重要的两件事，但我们也可以回忆起特定的物体，在视觉皮质中已经识别出似乎专门处理人脸、场景和物体的不同区域。在后续研究中，我们一直在研究对物体的回忆是否也会在MPC中招募一个单独的区域，以及对物体和场景的回忆所引起的激活与对相同刺激的感知所引起的激活相比如何。 总而言之，这些结果为理解MPC的功能作用及其在认知不同方面的意义提供了一个新的框架。 2)阐明情景记忆的内容 当我们回忆起以前经历过的事件时，我们到底记得什么？我们的记忆是对那一事件的精确、高清晰度的记录，还是那段记忆的低分辨率要点，或者甚至只是对我们所看到的东西的口头描述？回答这个问题是能够梳理记忆机制的一个重要组成部分：什么信息被编码和保持，记忆如何随着时间的推移而衰退，以及从这些记忆中检索到什么信息。 在一系列研究中，我们一直在使用绘画任务来调查真实世界场景的记忆内容。参与者学习场景，然后在延迟一段时间后，根据记忆尽可能详细地画出这些场景。由此产生的基于内存的绘图由数千名在线观察者评分，显示了大量的对象，很少有内存干扰，以及精确的空间信息。我们既研究了年轻志愿者，也研究了声称没有视觉意象(称为失语症)的人。此外，我们还研究了在记忆中发生的一种常见的失真，在这种失真中，场景的边界被延伸或收缩。 我们的发现表明，不仅有可能在自由回忆过程中量化记忆的内容，而且这些记忆包含了我们视觉经验的详细表征(尽管记忆扭曲仍然可能发生)。 阐明大脑如何使我们能够识别物体、场景、面孔和身体，有助于我们深入了解我们对周围世界的内在表征的本质。理解这些表征对于试图确定许多精神健康和神经疾病的潜在缺陷至关重要。

The goal of this research is to understand how we see what we see: how does the brain analyze the light falling on the retina of the eye to reveal a world full of objects, people and things? During the past year we have focused on both (i) perception and (ii) memory of complex visual stimuli, in particular real-world visual scenes, objects and people (NCT00001360). Perception: Real-world scenes are incredibly complex and heterogeneous, yet we are able to categorize them and identify objects and people within those scenes effortlessly. While prior studies have identified brain regions that appear to be specialized for processing faces, object and scenes, it remains unclear what the precise roles of these different regions are and what information they contain. One of the major challenges in understanding visual perception in the brain is the wide range of different objects and scenes that we experience. Despite this breadth, studies often focus on a small number of hand selected object or scene categories, but it becomes unclear how representative any subsequent findings are. To overcome this challenge we developed a large-scale database (THINGS) of 1,854 diverse types of object sampled systematically from concrete picturable and nameable nouns in the American English language. This database provides a rich resource of object concepts and object images and offers a tool for both systematic and large-scale naturalistic research in the fields of psychology, neuroscience, and computer science. We used this database in a large-scale behavioral experiment using online crowdsourcing, sampling 1.46 million trials in more than 5,000 participants. Using a computational model of the task, we were able to identify 49 core dimensions of our internal mental representations of objects, providing a comprehensive and fine-grained characterization of this representational space. These results provide important insights into the cognitive processes supporting our understanding of objects. We are now extending this work to reveal the underlying brain mechanisms by collecting fMRI and magnetoencephalography (MEG) data for this diverse set of object images. Memory: To understand the nature of object and scene memory, we have focused on two specific issues: 1) Organization of the medial parietal cortex Human medial parietal cortex (MPC) has been implicated in multiple cognitive processes including memory recall, visual scene processing and navigation. Given such diverse recruitment of MPC across cognitive domains historically considered largely independent, it is not surprising that there has been no clear consensus with regard to its function and overarching organization. In a series of studies, we measured brain activations with fMRI while we presented participants with images of scenes and people and also asked them to recall specific events (e.g. shaving, going to a beach) as well as recall famous or personally familiar places and people. Our findings revealed two key insights. First, we found an apparent gradient of representation from more perceptually related to more memory related from posterior to anterior within MPC. Second, we found distinct subdivisions within MPC that were active differentially during recall of either people or places. While people and places are two of the most important things we recall from memory, we can also recall specific objects, and separate regions have been identified in visual cortex that appear to be specialized for processing faces, scenes and objects. In follow-up studies we have been addressing whether recall of objects also recruits a separate region in MPC, and how the activations elicited by recall of objects and scenes compares with that elicited by perception of the very same stimuli. Collectively, these results provide a new framework for understanding the functional role of MPC and its significance during different aspects of cognition. 2) Elucidating the content of scene memory When we recall a previously experienced event, what exactly are we remembering? Are our memories a precise, high-definition recording of that event, a low-resolution gist of that memory, or even just a verbal description of what we saw? Answering this question is an essential component of being able to tease apart the mechanisms of memory: what information is encoded and maintained, how memory decays over time, and what information is retrieved from these memories. In a series of studies, we have been investigating the content of memory for real world scenes using a drawing task. Participants study scenes and then after a delay, draw those scenes in as much detail as possible from memory. The resulting memory-based drawings are scored by thousands of online observers, revealing numerous objects, few memory intrusions, and precise spatial information. We have studied both young volunteers as well as people who claim to have no visual imagery (termed aphantasia). Further, we have investigated a common distortion that occurs in memory in which the boundary of the scene is either extended or contracted. Our findings show that not only is it possible to quantify the content of memory during free recall, but that those memories contain detailed representations of our visual experiences (although memory distortions may still occur). Elucidating how the brain enables us to recognize objects, scenes, faces and bodies provides important insights into the nature of our internal representations of the world around us. Understanding these representations is vital in trying to determine the underlying deficits in many mental health and neurological disorders.