大脑如何压缩嘈杂世界的新框架
内容总结：
大脑如何压缩嘈杂世界？两位顶尖神经科学家提出全新分类框架
导语： 我们每时每刻都被海量感官信息包围——光子击中视网膜、声波震动耳膜、气味分子结合受体……而大脑之所以能驾驭这股信息洪流，靠的是强大的数据压缩能力。传统神经科学认为，分类发生在感官处理的末端，大脑被动接收信息后进行解码匹配。但这一经典模型面临一个难题：为何同样一组感官信号，在不同情境下会被大脑赋予截然不同的含义？
突破传统：分类不是“档案柜”而是“生存工具”
美国东北大学的情绪神经科学专家丽莎·费尔德曼·巴雷特和麻省理工学院的神经科学家厄尔·米勒日前在《自然综述·神经科学》杂志上联合发表了一项新框架，对大脑如何形成分类提出了颠覆性见解。他们的核心观点出人意料：大脑并非将客观现实映射到分类中，而是为了满足身体的生存需求，主动将分类投射到世界上。
马里兰大学神经科学家路易斯·佩索阿评价道，这是“对分类的全新视角”，尤其强调“维持身体能量约束是构建分类的基础”这一理念“非常值得深入探索”。
观点融合：预测编码与情绪构建论的碰撞
这两位重量级学者多年来虽在同一学术圈却从未直接合作。米勒专注研究大脑高级电信号模式，其工作基于“预测编码”理论——将感知视为大脑预测的产物，而非被动接收感官信号的结果。巴雷特则将预测理念应用于情绪研究，提出“动态平衡”概念：情绪类别如同神经系统生成的预测性“行动计划”，例如心跳加速、呼吸急促时，身体会根据情境判断是“恐惧”还是“兴奋”。
2025年，巴雷特主动联系米勒，提议将双方的洞见整合为新的分类框架。两人一拍即合，米勒回忆称：“我们的讨论让我们意识到彼此理念相通。”
核心机制：身体状态决定分类结果
巴雷特和米勒提出，分类并非仅在特定脑区发生，而是遍布整个神经系统。他们的证据来自多个层面：神经连接的结构更倾向于支持内部预测信号的反馩流动——即使在视觉皮层，90%的突触连接都服务于反馈信号；同时，感官信息在深入大脑的过程中会被高度压缩，最终与身体内部信号汇聚于“边缘核心”——一个整合身体、感官、记忆和高阶认知信息的关键区域。
这一框架能解释为何同一组感官信号在不同情境下被分类为不同事物：如果你又累又饿，一个碰伤的苹果会被分类为急需的食物；而当你精力充沛、能量充足时，同样的苹果只是需要略过的次品。伦敦大学学院的桑德拉·赖纳特指出：“我们的内部状态与感官输入同等重要，甚至更为重要。”
理论意义：分类是神经系统的基本组织原则
巴雷特和米勒呼吁学界超越“档案柜”式的分类模型——即分类像文件一样存储在记忆中待检索。他们主张，从大脑压缩感官信息的结构方式，到预测并预设备身体反应的机制，分类已“内嵌”于神经系统之中，是其基本组织原则，整合记忆、感知和行为，帮助我们在信息丰富的世界中更好地生存。
这一框架将分类的预测来源从传统认为的皮层整合区域，转移至大脑深部的边缘核心系统——该系统与调节体温、心率、饥饿感等基本生理功能的下丘脑紧密相连。巴雷特强调，选择边缘核心作为起点是出于学术讨论的方便：“我们也可以选择其他任何起点。”米勒则补充道：“这不只发生在大脑的一端，而是发生在各个层面、各个地方，是反馈与正向信息流相互作用的结果。”
中文翻译：
大脑如何压缩我们嘈杂世界的新框架
引言
我们生命中的每一刻，身体都浸没在感官信号之中。光子撞击我们的视网膜。压缩的空气波冲击我们的耳膜。挥发性分子与鼻腔中的受体结合，化学物质覆盖我们的味蕾。压力和热量激活我们皮肤中的神经末梢。我们之所以能够驾驭这股洪流，是因为大脑做了大量的数据压缩。通过一种被称为“分类”的过程，大脑将混乱、嘈杂、信息丰富的世界转化为我们能够在经验层面上理解并据此行动的对象、人物、概念和情绪。
在神经科学的传统观点中，分类发生在感觉加工的末端。大脑被动地接收感官细节，然后解码其特征，并将其与记忆中存储的模板进行匹配，就像一位职员在一排神经文件柜中翻找。但这种分类方法难以解释我们为世界特征赋予标签时所展现出的非凡灵活性。在晴朗的日子里，在开阔的街道上，一阵突然的有节奏的“啪嗒”声是鸽子起飞的声音；然而当我们在夜晚走在一条昏暗的小巷里时，同样的声音却是陌生人脚步的拖沓声。大脑如何能在不同情境下以截然不同的方式对相似的感官信号集进行分类？
两位世界顶尖的神经科学家将一种对大脑功能和结构的最新理解带到了这个问题上。在《自然综述·神经科学》的页面上，在东北大学研究情绪心理学和神经科学的莉萨·费尔德曼·巴雷特，与在麻省理工学院研究大脑如何执行目标导向行为的厄尔·米勒，合作提出了一个新的分类观点。他们描述大脑如何每时每刻不断地重建其分类——不仅基于感官和记忆，还基于身体当下的生理需求。
他们框架的核心是一个反直觉的洞见。虽然我们可能觉得自己的分类反映了客观现实，但研究人员认为，大脑是为了响应身体的生存需求而将分类投射到世界上的。在我们甚至还没意识到自己的感官印象之前，大脑就已经在让身体做好准备，以维持为我们生理系统供能的能量资源的方式行事。如此一来，大脑的预测——而非感官信息的累积效应——最终塑造并限制了我们对世界上的对象和特征进行分类的方式。
这两位学者的框架是“对分类的一种全新视角”，马里兰大学的神经科学家路易斯·佩索阿说。他们的观点，即“维持生命的能量约束是构建我们分类方式的基础”，他说，“非常值得深入探究”。
巴雷特和米勒框架中的另一个新点是一个假设：分类并非发生在大脑的某个特定区域，而是遍布整个器官乃至更广。他们认为，要理解生物体如何形成分类，神经科学家必须从头部到脚趾地观察整个神经系统。
重量级联手
多年来，这两位有影响力的神经科学家一直在同一轨道上，却从未直接合作过。
米勒测量大脑中的高级电模式，以更好地理解一种被称为“预测编码”的神经计算模型的驱动机制。预测编码将我们的感知视为大脑预测的产物，而非由它被动接收的感官信号构建出来的场景。
通常，如果我们正在经历一个正常的感官场景（比如说，在家放松），没有任何新奇信息，大脑会生成关于环境的预测信号（称为反馈信号），这些信号将主导传入的感官（或“前馈”）信号。但如果发生了意外事件——一个偏离预测模型的事件——感官前馈信号，比如到达视觉皮层的那些信号，就会与预测反馈信号发生冲突。这种差异产生预测误差。当感官信号违反你的预测模型时，它们可能会以惊讶的感觉进入意识体验。
“你的大脑必须不断地对接下来几秒钟将要发生的事情做出预测，因为它必须过滤掉大部分传入的感官信息，”米勒说。“它无法处理所有信息，所以它主要寻找与预测不匹配的东西，因为那更有信息量。”
在她的工作中，巴雷特将这些预测和预期的想法应用于我们对情绪的理论理解。她工作的核心是“动态平衡”的概念：生物体如何预测性地调节其能量使用。在她看来，情绪类别——恐惧、快乐、愤怒——类似于神经系统生成的预测性“行动计划”，用于激活那些之前对我们有益的行为。例如，一个兴奋的身体状态，心率升高、呼吸加快、肌肉紧绷，在被狗追赶的情境下，会指示“恐惧”这一情绪类别，以激活某些行为并使用我们的能量资源去战斗或逃跑。传统上，人们认为情绪是与生俱来、硬接线在特定回路中的。巴雷特帮助证明了我们是在身体内部信号和外部情境信号的关联中构建情绪类别的。
2025年，巴雷特联系了米勒，想看看他是否有兴趣将他们的想法结合起来，创建一个新的分类框架——一个超越文件柜模型、纳入他们关于预测和动态平衡观点的框架。“即使是真正杰出的科学家，有时也可能被传统思维所引导，而这种思维很难超越，”她说。“他立刻就理解了我的意思。”于是她问他是否愿意一起写一篇论文。米勒同意了。
“在我们的讨论中，很明显我们是一路人，”米勒说。“我喜欢莉萨的一点是，她总是从全局角度思考……我们俩都不怕说出与主流观点相悖的话。”
生机勃勃的分类
作为动物，我们的任务是在变化中生存——无论是我们所处环境的变化，还是我们自身身体的变化。因为我们的能量、时间和计算资源有限，理解每种情况的每个细节是不可能的。这意味着我们必须走捷径才能活下来。
分类就在此时登场。“类别是在特定情境中不同事物被视为相似或等同的事件，”巴雷特说。类别可能基本到“食物”、“威胁”或“配偶”。人类拥有形成更精细类别——包括高度抽象的类别——的非凡能力：去一趟哲学系，你会听到诸如“正义”、“真理”和“美”这样的类别。
分类的功能，巴雷特说，是利用与新情境相似的过往经验来实施维持身体系统运转的行为。“苹果”这个类别可能通过物理特征来定义——光滑、圆形、红色、手掌大小——但它也包括一套我们应如何与之互动的行为策略：“适合食用”或“腐烂时扔掉”。
“关于分类，重要的一点是你做这一切是有目的的，”普林斯顿大学的神经科学家蒂莫西·布施曼说。“分类的原因是为了支持当前的任务。无论你想要什么，或者你处于什么情境中，你都是根据事物对你的意义来对其进行分类。”
但类别是如何形成的？根据传统观点，随着时间的推移，我们的经验构建出一个概括性的属性清单，形成一个诸如“猫”这样的类别，我们可用它来区分毛茸茸的生物。按照这种模式，我们接收感官信息并将其缩减以匹配记忆中的类别特征：“哦，有个东西形状像尾巴；它有耳朵，有毛——现在我弄清了所有这些特征，”米勒举例说。“现在我在记忆库中查询：哦，是一只猫。”
然而，在巴雷特和米勒的观点中，大脑利用对相似过往情境的记忆来预测一套适合新情境的行为，早于感官确认一个传统类别。
想象你在走路，感觉腿上有东西刮了一下。如果你在一个安全的地方且心态平静，你会继续走，不会多想这一感觉。但假设你正走在一个陌生地方的深草丛中；你的心跳和呼吸比平时快。你感到紧张，因为你的大脑已预测性地为身体分配了资源以备逃离潜在威胁。而因为感到紧张，你已被预设为倾向于认为刮蹭是潜在威胁——虫咬，或者更糟，蛇。
在两种情境中，刮蹭的感觉是相同的，但大脑以截然不同的方式对其进行分类。一个更广泛的信号集——环境和身体的——影响着我们如何形成类别，这一事实为巴雷特和米勒的新框架搭建了舞台。
他们的提议基于他们实验室和其他实验室多年来的解剖学、电生理学和研究。他们构建了一个论点：分类是一种持续的预测工具，神经系统通过它引导行为以维持生物体的存活。
他们的一些证据来自神经元层面。他们引用的研究表明，大脑的连接结构偏向于有利于预测信号而非感官信号。例如，促进内部生成信号反馈流动的神经元之间的连接，远多于处理源自感官的前馈信号的神经元之间的连接。即使在视觉皮层内部，有90%的突触连接促进反馈信号传导。这表明大脑的结构是为了预测类别、感知和行为，而非为了对刺激做出反应式的分类。
在前馈方面，作者描述了携带感官信息的回路在深入大脑时如何经历大量压缩。它们遇到许多体积小、排列密集但连接稀疏的神经元，其信号被削减为通过更少、更大、连接更好的神经元。沿这一梯度行进时，感官信号变得高度抽象——最终到达整合区域，该区域协调来自感官、记忆和身体的信息以指导行为。
随后，作者引用了米勒实验室的电生理学工作，展示反馈和前馈信号如何相互作用。在大脑的宏观视角中，代表许多神经元活动的行波携带着关于目标、计划和身体能量状态的信息。这些波随后遇到并与其他携带感官信息的波合并。
根据巴雷特和米勒的说法，信息波在大脑中级联传播的相互作用可以开始解释为什么同一组外部感官信号在不同情境下可能被不同地分类。如果你筋疲力尽且饥饿，一个碰伤、过熟的苹果会被归类为急需的食物。如果你休息充分且能量充足，它就是一个被略过的次品水果。
“我们的内部状态对我们来说与感官输入同等重要，甚至更重要，”伦敦大学学院的桑德拉·莱纳特说，她研究过啮齿动物的分类。“内部情境如何重新映射我们[形成类别]的规则，这完全是直觉可感的。”
处处同时发生
巴雷特和米勒框架的一个核心组成部分是大脑中预测信号的起源。在大多数关于视觉分类的神经科学文献中，皮层（位于大脑外表面）的整合区域被认为是预测期望的来源。“他们[巴雷特和米勒]做出了不同的选择，”佩索阿说。“他们将边缘核心作为这些预测信号的来源。”
边缘核心包括大脑深部的结构，这些结构整合了携带来自身体、感官、记忆和高级认知功能信息的信号。这个整合网络既靠近下丘脑，又与之高度连接——下丘脑是大脑中一个古老的区域，负责监测基本身体功能，如体温、心率和饥饿感。
由于下丘脑帮助让皮层——大脑折叠的最外层，参与执行控制等高级认知——了解身体的能量状态，作者假设边缘核心促进了大脑预测身体能量需求的能力。
边缘核心是内外信号最压缩化摘要的交汇点。你可以想象神经系统像两个漏斗一样组织，形状像一个领结，在最窄处相遇——边缘核心，即压缩程度最高的点。正如视觉信息在通过视觉皮层并深入大脑时被压缩一样，生理信号在从身体沿迷走神经上行进入大脑时也被压缩。然后它们到达边缘核心，在那里与压缩的感官信息整合。这些信号共同生成一个适当的类别及其相关行为。
取决于类别——视觉类别如“苹果”、抽象类别如“正义”、或情绪类别如“敬畏”——预测反馈信号与压缩感官前馈信号的相互作用可以发生在任意数量的神经区域。这一过程贯穿整个神经系统，作者写道。
巴雷特强调，为这一过程选择任何特定的起点都是任意的。“为了进行科学讨论，你必须说：‘我要选这个点作为起点，’”巴雷特谈到边缘核心时说。“我们本可以轻松选择另一个点。”
米勒同意。“莉萨和我主张的是，这是在每个层面都在发生的事，它发生在很多地方，它是这些对立的、相互作用的信息流——前馈和反馈——相互作用的结果，”他说。“它不是在大脑的一端，而传统上人们认为是这样。”
巴雷特和米勒要求该领域超越一种模式——即类别像文件一样存储在大脑文件柜中的模式。从大脑压缩感官信息的结构方式，到它如何预测并让身体准备好做出反应，分类是被“内置”的，作者写道。它是神经系统的一个核心组织原则，利用记忆、感知和行为来帮助我们在信息丰富的世界中良好地生存。
英文来源：
A New Framework for How the Brain Compresses Our Noisy World
Introduction
Every moment of our lives, our bodies are awash in sensory signals. Photons hit our retinas. Waves of compressed air collide with our eardrums. Volatile molecules bind to receptors in our nostrils, and chemicals slather our taste buds. Pressure and heat activate nerve endings in our skin. We are able to navigate this torrent because the brain does an enormous amount of data compression. Through a process known as categorization, the brain turns the messy, noisy, information-rich world into objects, people, concepts, and emotions that we can understand and act on at the level of experience.
In neuroscience’s traditional view, categorization happens at the very end of sensory processing. The brain passively receives sensory details, then decodes their features and matches them to stored templates in memory, like a clerk shuffling through a neural filing cabinet. But this approach to categorization struggles to account for the extraordinary flexibility in the way we assign labels to features of the world. On a clear day on an open street, a sudden rhythmic patter is a pigeon taking flight, yet when we’re walking down a dimly lit alley at night, the same sound is the shuffle of a stranger’s footsteps. How can the brain categorize similar sets of sensory signals in radically different ways for different situations?
Two of the world’s leading neuroscientists have brought an updated understanding of brain function and structure to this question. In the pages of Nature Reviews Neuroscience, Lisa Feldman Barrett, who studies the psychology and neuroscience of emotion at Northeastern University, and Earl Miller, who studies how the brain carries out goal-directed behavior at the Massachusetts Institute of Technology, collaborated on a new view of categorization. They describe how the brain constantly reconstructs its categories moment to moment based not only on senses and memory, but on the body’s immediate physiological needs.
At the heart of their framework is a counterintuitive insight. While we may have the impression that our categories reflect an objective reality, the researchers argue that the brain projects categories onto the world in response to the body’s survival needs. Before we are even aware of our sensory impressions, the brain is already preparing the body to behave in ways that maintain the energetic resources that power our physiological systems. In this way, the brain’s predictions — rather than the cumulative effects of sensory information — ultimately shape and limit how we categorize objects and features of the world.
The duo’s framework is “a fresh perspective on categorization,” said Luiz Pessoa, a neuroscientist from the University of Maryland. Their idea of “the maintenance of the energetic constraints of life as fundamental to how we structure our categories,” he said, is “really important to pursue.”
Also new in Barrett and Miller’s framework is the hypothesis that categorization doesn’t happen in a particular area of the brain, but across the entire organ and beyond. To understand how organisms form categories, they argued, neuroscientists have to look all over the nervous system, from head to toe.
Heavyweight Match
For many years, these two influential neuroscientists were in the same orbit, but had never collaborated directly.
Miller measures high-level electrical patterns in the brain to better understand the mechanisms driving a model of neural computation known as predictive coding. Predictive coding regards our perceptions as products of the brain’s predictions, rather than a scene built from sensory signals it passively receives.
Typically, if we are experiencing a normal sensory scene (relaxing at home, say) without any novel information, the brain generates predictive signals about the environment (known as feedback signals) that will dominate incoming sensory (or “feedforward”) signals. But if something unexpected happens — an event that deviates from the predictive model — the sensory feedforward signals, such as those arriving in the visual cortex, run up against the predictive feedback signals. This difference creates prediction errors. When sensory signals violate your predictive model, they might enter conscious experience as a feeling of surprise.
“Your brain has to constantly make predictions about what’s going to happen in the next few seconds because it’s got to filter out most of the incoming sensory information,” Miller said. “It can’t process it all, so it’s mainly looking for things that mismatch predictions because it’s more informative.”
In her work, Barrett has applied these ideas of prediction and anticipation to our theoretical understanding of emotions. Central to her work is the concept of allostasis: how an organism predictively regulates its energy use. In her view, emotion categories — fear, happiness, anger — resemble predictive “action plans” that the nervous system generates to activate behaviors that have served us well before. For example, a worked-up bodily state, with elevated heart rate, fast breathing, and tense muscles, in the context of being chased by a dog, would indicate the emotion category “fear” to activate certain behaviors and use our energy resources to fight or run away. Traditionally, emotions were thought to be hardwired in specific circuits present from birth. Barrett has helped show that we construct emotional categories in relation to signals both from within the body and from the external context.
In 2025, Barrett reached out to Miller to see if he’d be interested in putting their ideas together to create a new framework for categorization — one that would move beyond the filing-cabinet model to include their ideas about prediction and allostasis. “Even really brilliant scientists can sometimes be guided by traditional thinking, which can be hard to get beyond,” she said. “He understood what I was saying immediately.” So she asked if he wanted to write a paper together. Miller said yes.
“In our discussions it became clear we were cut from the same cloth,” Miller said. “What I love about Lisa is that she is always thinking in big-picture terms. … Both of us, we are not afraid to say things that run counter to the standard way of looking at things.”
Vivacious Categories
As animals, we are tasked with surviving through change — in the environments we are embedded in, and in our own bodies as well. Because we have limited energy, time, and computational resources, understanding every detail of every situation is impossible. That means we have to take shortcuts to stay alive.
That’s where categories come in. “A category is an event in which different things are treated as similar or equivalent in a particular situation,” Barrett said. Categories might be as basic as “food,” “threat,” or “mate.” Humans have a remarkable ability to form much more detailed categories, including ones that are highly abstract: Visit a philosophy department to hear about categories such as “justice,” “truth,” and “beauty.”
Courtesy of Earl Miller
The function of categorization, Barrett said, is to use past experiences that resemble a new situation to implement behaviors that keep our bodily systems functioning. The category “apple” might be defined through physical features — smooth, round, red, palm-size — but it also includes a set of behavioral policies for how we should interact with it: “good for eating” or “throw out when rotten.”
“The point that is important about categorization is that you do all that for a purpose,” said Timothy Buschman, a neuroscientist from Princeton University. “The reason for categorization is to support the current task. Whatever it is that you want or whatever situation you are in, you are categorizing something according to what meaning it has for you.”
But how are categories formed? According to the traditional view, over time our experiences construct a generalized list of attributes to form a category such as “cat” that we can use to differentiate furry creatures. By this model, we take in sensory information and pare it down to match the categorical features in our memory: “Oh, there’s this thing that’s shaped like a tail; it has ears, it has fur — now I’ve figured out all those features,” Miller suggested. “Now I query my memory banks: Oh, it’s a cat.”
In Barrett and Miller’s view, however, the brain uses memories of similar past situations to predict a set of behaviors that are appropriate for the new situation before the senses have identified a traditional category.
Imagine you are walking, and you feel a scratch on your leg. If you’re in a safe place and are calm, you’ll carry on without giving the sensation a second thought. But let’s say you are walking through tall grass in an unfamiliar place; your heartbeat and breathing are faster than normal. You feel nervous because your brain has predictively allocated resources to your body to flee any potential threats. And by feeling nervous, you have been primed to assume the scratch is a potential threat — an insect bite or, worse, a snake.
In both situations, the sensation of the scratch is the same, but the brain categorizes it in vastly different ways. The fact that a much broader set of signals — environmental and corporeal — influences how we form categories sets the stage for Barrett and Miller’s new framework.
Their proposal is based on years of anatomical, electrophysiological, and brain-imaging research from their labs and others. They have built an argument that categorization is an ongoing predictive tool by which nervous systems guide behavior to keep the organism alive.
Some of their evidence is at the neuronal level. They cite research showing how brain connectivity is structured to favor predictive signals over sensory ones. For example, there are many more connections between neurons that facilitate the feedback flow of internally generated signals than between those handling the feedforward signals that originate from our senses. Even within the visual cortex, 90% of synaptic connections facilitate feedback signaling. That suggests that the brain is structured for predicting categories, perceptions, and behaviors, rather than for categorizing in reaction to stimuli.
On the feedforward side, the authors describe how circuits that carry sensory information undergo extensive compression as they travel deeper into the brain. They encounter many small neurons that are densely packed but scarcely connected, and their signals get whittled down through fewer, bigger, better-connected neurons. Traveling along this gradient, sensory signals become highly abstracted — and eventually reach integrative regions, which coordinate information from the senses, memory, and body to guide behavior.
The authors then draw on electrophysiological work from Miller’s lab to show how feedback and feedforward signals interact. In a zoomed-out view of the brain, traveling waves, which represent the activity of many neurons, carry information about goals, plans, and the energetic state of the body. These waves then encounter and combine with others carrying information from the senses.
According to Barrett and Miller, interaction between waves of information cascading across the brain can start to explain how the same set of external sensory signals might be categorized differently in different situations. If you are exhausted and hungry, a bruised, overripe apple is categorized as much-needed food. If you are well rested and energetically satiated, it’s a piece of subpar fruit to be passed over.
“Our internal state is just as, if not more, important than sensory input to us,” said Sandra Reinert of University College London, who has studied categorization in rodents. “It’s completely intuitive to see how an internal context remaps our rules [for how we form a category].”
Everywhere All at Once
A central component of Barrett and Miller’s framework is the origin of predictive signals in the brain. In most neuroscientific literature on visual categorization, integrative regions of the cortex (located on the outer surface of the brain) are considered the source of predictive expectations. “They [Barrett and Miller] make a different move,” Pessoa said. “They take the limbic core as the source of these predictive signals.”
The limbic core includes structures deep in the brain that combine signals carrying information from the body, senses, memory, and higher-level cognitive functions. This integrative network is both close to and highly connected to the hypothalamus, an ancient part of the brain that monitors basic bodily functions, such as body temperature, heart rate, and hunger.
Because the hypothalamus helps inform the cortex — the folded, outermost layer of the brain, which is involved in high-level cognition such as executive control — about the body’s energetic state, the authors hypothesized that the limbic core facilitates the brain’s ability to anticipate the body’s energy needs.
The limbic core is where the most compressed summaries of internal and external signals intersect. You can imagine the nervous system as being structured like two funnels, shaped like a bow tie, that meet at their narrowest point — the limbic core, the point of highest compression. Just as visual information is compressed as it travels through the visual cortex and deeper into the brain, physiological signals are compressed as they travel from the body up the vagus nerve and into the brain. They then reach the limbic core, where they are integrated with compressed sensory information. Together, these signals generate an appropriate category and its associated behavior.
Depending on the category — a visual category like “apple,” an abstract category like “justice,” or an emotion category like “awe” — the interaction of the predictive feedback signals with the compressed sensory feedforward signals can happen in any number of neural regions. The process spans the entire nervous system, the authors wrote.
Barrett emphasized that selecting any particular starting point for this process is arbitrary. “For the sake of having a scientific discussion, you have to say, ‘I’m going to pick this point as the start,’” Barrett said of the limbic core. “We could’ve easily just picked some other point.”
Miller agreed. “Lisa and I are arguing that this is something that is happening at every level, and it’s happening in lots of places, and it’s happening as a result of these opposing, interacting flows of information — feedforward and feedback,” he said. “It’s not at one end of the brain, which it has traditionally been thought.”
Barrett and Miller are asking the field to move beyond a model in which categories are stored like documents in the brain’s filing cabinet. From the way the brain is structured to compress sensory information, to how it predicts and prepares the body to respond, categorization is “baked” in, the authors wrote. It is a core organizational principle of the nervous system that draws on memory, perception, and behavior to help us survive well in an information-rich world.