One with the world? A new look at brains transformed by psychedelics.

本文为原文前 6,000 字符的节选翻译，完整内容请查看原文。

For about a decade, the mainstream understanding has been that psychedelics cause chaos in the brain. Brain networks—the stable patterns of communication that handle vision, attention, or our sense of self, and more—loosen and start talking to each other all at once. EEG traces get noisier and more complex. “Think of the networks of the brain as highways,” says Devon Stoliker, a neuroscientist at Monash University. “Under psychedelics, these highways break down into many different directions.”

大约十年来，主流观点一直认为迷幻剂会导致大脑混乱。大脑网络——即处理视觉、注意力、自我意识等功能的稳定通信模式——会变得松散并开始同时相互作用。脑电图（EEG）轨迹变得更加嘈杂和复杂。莫纳什大学的神经科学家德文·斯托利克（Devon Stoliker）说：“把大脑网络想象成高速公路。在迷幻剂的作用下，这些高速公路会分解成许多不同的方向。”

In a recent Nature study, Stoliker’s team designed an experiment to test whether these directions are truly chaotic and random. Researchers gathered 62 people who had never taken a psychedelic before, gave them 19 milligrams of psilocybin, a common psychedelic found in certain fungi, and scanned their brains. Then, they used AI to analyze the drugged and sober brain scans. What emerged was not exactly chaos.

在最近发表于《自然》杂志的一项研究中，斯托利克的团队设计了一个实验，以测试这些方向是否真的混乱且随机。研究人员召集了62名从未服用过迷幻剂的人，给他们服用了19毫克裸盖菇素（一种在某些真菌中常见的迷幻剂），并对他们的大脑进行了扫描。随后，他们利用人工智能分析了受试者在服药和清醒状态下的大脑扫描结果。结果显示，情况并非完全是混乱。

Stoliker thinks chaos is not a satisfactory explanation for psychedelics’ effect on the brain. “It never really explained why an individual would have a meaningful experience, why they might have insight, why they might experience clarity, and why these might translate into positive psychological changes,” Stoliker says. To investigate if there are other explanations, he and his colleagues designed a study called PsiConnect.

斯托利克认为，用“混乱”来解释迷幻剂对大脑的影响并不令人满意。斯托利克说：“它从未真正解释为什么一个人会有有意义的体验，为什么他们可能会产生洞察力，为什么他们会感到清晰，以及为什么这些体验会转化为积极的心理变化。”为了探究是否存在其他解释，他和同事们设计了一项名为“PsiConnect”的研究。

Volunteers went through the same four-part sequence twice, once sober and once on psilocybin. The sequence included putting participants in four different settings or contexts: eight minutes of lying at rest, a guided meditation, an 11-minute curated music playlist, and finally six minutes of eyes-open video of clouds moving across a sky. Each participant did all four inside an MRI scanner about 80 minutes after dosing, and again on EEG about 150 minutes after.

志愿者们两次经历了相同的四个阶段，一次是在清醒状态下，另一次是在服用裸盖菇素后。该过程包括让参与者处于四种不同的环境或情境中：八分钟的静卧休息、引导式冥想、11分钟的精选音乐播放列表，以及最后六分钟观看云朵在天空中飘动的视频。每位参与者在服药后约80分钟内完成了所有四项核磁共振扫描，并在约150分钟后进行了脑电图测试。

There were no cognitive tasks researchers routinely go for in brain studies, but there was a purpose behind this omission. “We wanted ecological validity,” Stoliker says. “We wanted to know what the brain was like when somebody was having an authentic, uninterrupted psychedelic experience. If somebody took a psychedelic in a therapeutic setting, you wouldn’t have them completing tasks.”

研究中没有包含大脑研究中常用的认知任务，但这种省略是有目的的。斯托利克说：“我们想要生态效度。我们想知道当一个人拥有真实、不间断的迷幻体验时，大脑是什么样的。如果有人在治疗环境中服用迷幻剂，你不会让他们去完成任务。”

Stoliker also points out that there’s evidence that giving someone a task mid-trip pulls them out of the state—a phenomenon researchers sometimes call grounding. “Once you introduce these sorts of tasks, you’re actually interrupting the very phenomena you are seeking to measure.” And it worked. Half of the participants ranked their session among the most meaningful experiences of their lives, and 24 put it in their personal top five. Stolkier and his colleagues started analyzing their brain scan data to find out why.

斯托利克还指出，有证据表明，在迷幻过程中给某人布置任务会使他们脱离那种状态——这种现象研究人员有时称之为“接地”。“一旦你引入这些任务，你实际上是在干扰你试图测量的现象。”实验成功了。一半的参与者将这次经历列为他们一生中最有意义的体验之一，24人将其列入个人前五名。斯托利克和他的同事们开始分析大脑扫描数据以找出原因。

Measuring global functional connectivity—how much influence each patch of cortex exerts over the rest—the team found that, when participants had their eyes closed, sensory regions lost sway while associative regions gained. “It seems like the brain’s ability to construct reality, or imagination, or our associations, our beliefs, our sense of self—these faculties had more dominance over sensory areas,” Stoliker says, stressing that the interpretation is a hypothetical.

通过测量全局功能连接性（即大脑皮层的每个区域对其他区域施加多大影响），研究小组发现，当参与者闭上眼睛时，感觉区域的影响力减弱，而联想区域的影响力增强。斯托利克说：“大脑构建现实、想象力、联想、信念或自我意识的能力似乎对感觉区域占据了更多主导地位。”他强调这种解释仅是一个假设。

“This could help explain why people have meaningful, complex imagery experiences, why they have mystical experiences with imagery that is personally relevant to them.” Another observation the team made was that connections within each brain network weakened, connections between networks strengthened. The brain’s modularity, a parameter that describes how cleanly neurons stay sorted into specialist teams, dropped across all four parts of the experimental sequence.

“这有助于解释为什么人们会有有意义的、复杂的意象体验，以及为什么他们会产生与个人相关的神秘意象体验。”研究小组的另一个发现是，每个大脑网络内部的连接减弱了，而网络之间的连接增强了。大脑的模块化（描述神经元如何清晰地分类到专业团队中的参数）在实验过程的四个部分中均有所下降。

What’s more, researchers found that, when sober, activity in a brain with its eyes shut looked very different from a brain watching a movie. Under psilocybin, that difference nearly evaporated. In the visual network, the gap between eyes-open and eyes-closed connectivity shrank by 85 percent. The results from the EEG session independently confirmed that, with alpha-band activity (normally a marker of the brain gating visual input) reduced by nearly half.

此外，研究人员发现，在清醒状态下，闭眼时的大脑活动与观看电影时的大脑活动看起来截然不同。但在裸盖菇素的作用下，这种差异几乎消失了。在视觉网络中，睁眼和闭眼状态下的连接差异缩小了85%。脑电图测试的结果独立证实了这一点，其中阿尔法波段活动（通常是大脑过滤视觉输入的标志）减少了近一半。

“When somebody takes a psychedelic and they’re able to close their eyes and see complex imagery, there seems to be less boundary between the internal and external world than we ordinarily experience,” Stoliker says. Regardless of these details, the results rather accurately reproduced the chaos in the brain so many researchers claimed psychedelics caused. This chaos, though, turned into order when the team processed their data in a slightly unorthodox way.

斯托利克说：“当一个人服用迷幻剂并闭上眼睛看到复杂的意象时，内心世界与外部世界之间的界限似乎比我们平时体验到的要模糊。”尽管有这些细节，但结果相当准确地重现了许多研究人员声称迷幻剂会导致的大脑混乱。然而，当研究小组以一种稍微非正统的方式处理数据时，这种混乱变成了秩序。

Scientists usually do two acts of averaging in a standard brain imaging study. The first is averaging over time. An eight-minute brain scan comprises a few hundred successive images of the whole brain. To understand how two specific regions work together, researchers conventionally average all these images down to a single number describing how well the two regions’ activity matched up across the whole eight minutes.

科学家在标准的脑成像研究中通常会进行两次平均处理。首先是时间上的平均。八分钟的脑部扫描包含数百张连续的全脑图像。为了了解两个特定区域如何协同工作，研究人员通常会将所有这些图像平均为一个单一的数字，用以描述这两个区域的活动在整个八分钟内匹配的程度。

The problem with this analysis is that it runs the risk of missing ordered structures that appear for a brief period and then disappear into chaos. The second analysis is averaging over people. Having produced one such number per participant, the standard approach then pools all of them into a group average, on the assumption that individual differences are noise that will be canceled out.

这种分析的问题在于，它有可能会错过那些短暂出现随后又消失在混乱中的有序结构。第二次分析是人群平均。在为每位参与者得出一个数字后，标准做法是将所有数字汇总为组平均值，假设个体差异是会被抵消的噪音。

Stoliker’s study was focused on individual experiences, so he wanted to avoid that. Instead, the team fed the moment-by-moment activity of 332 brain regions into CEBRA, a machine-learning tool that compressed the data down to its essential structure while preserving the order of events. For each individual, it produced a trajectory—a path traced through a three-dimensional space, one point for each moment of.

斯托利克的研究侧重于个体体验，因此他希望避免这种做法。相反，研究小组将332个大脑区域的实时活动输入到CEBRA中，这是一种机器学习工具，它在保留事件顺序的同时将数据压缩为其基本结构。对于每个人，它生成了一条轨迹——一条在三维空间中追踪的路径，每一个点代表每一个时刻。