An elderly woman named Rosalie was sitting in her nursing home when her room suddenly burst to life with twirling fabrics.
罗萨莉婆婆正坐在养老院的的屋子里，突然，她的房间充满旋转的图形。
Through the elaborate drapings, she could make out animals, children, and costumed characters.
通过精巧的折叠，她能够制作出动物、儿童和一些穿着戏服的角色。
Rosalie was alarmed, not by the intrusion, but because she knew this entourage was an extremely detailed hallucination.
罗萨莉婆婆感到十分震惊，并非这些东西突然出现，而是因为她清楚这些都是细节极其丰富的幻觉。
Her cognitive function was excellent, and she had not taken any medications that might cause hallucinations.
她的认知功能一切正常，也并未服用能够引起幻觉的药物。
Strangest of all, had a real-life crowd of circus performers burst into her room, she wouldn't have been able to see them: she was completely blind.
最奇怪的在于，若在现实中有这样一群马戏团演员冲进她的房间，她也无法看到他们，因为她彻底失去了视觉。
Rosalie had developed a condition known as Charles Bonnet Syndrome,
罗萨莉患有邦纳症候群，
in which patients with either impaired vision or total blindness suddenly hallucinate whole scenes in vivid color.
患者通常视觉受损或是完全丧失视觉，眼前却突然出现色彩缤纷的各种幻觉。
These hallucinations appear suddenly, and can last for mere minutes or recur for years.
这些幻觉的出现很突然，只会持续几分钟或是在几年内反复发作。
We still don't fully understand what causes them to come and go, or why certain patients develop them when others don't.
我们仍然不清楚幻觉出现和消失的原因，也尚不明确为何只有部分患者出现幻觉。
We do know from fMRI studies that these hallucinations activate the same brain areas as sight, areas that are not activated by imagination.
通过功能性磁共振成像，我们发现这些幻觉会激活负责视觉的大脑区域，而想象力并不会激发该区域。
Many other hallucinations, including smells, sights, and sounds, also involve the same brain areas as real sensory experiences.
许多其他的幻觉，包括气味、视觉和声音，都与负责真实感官的大脑区域相同。
Because of this, the cerebral cortex is thought to play a part in hallucinations.
正因为此，大脑皮层被认为与幻觉相关。
This thin layer of grey matter covers the entire cerebrum, with different areas processing information from each of our senses.
这层薄薄的灰质覆盖整个大脑，不同的区域负责处理来自各个感官的信息。
But even in people with completely unimpaired senses, the brain constructs the world we perceive from incomplete information.
但即便对于感官完全正常的人来说，大脑也是通过不完整的信息来构建我们所感知的世界。
For example, our eyes have blind spots where the optic nerve blocks part of the retina.
例如，我们的眼睛有盲点，此处的光学神经会阻挡部分视网膜。
When the visual cortex processes light into coherent images, it fills in these blind spots with information from the surrounding area.
当视觉中枢处理连续图像的光线时，它会用周边区域的信息来填充盲点。
Occasionally, we might notice a glitch, but most of the time we're none the wiser.
有时候，我们或许能发现小错，但绝大多数情况下我们都不够机敏。
When the visual cortex is deprived of input from the eyes, even temporarily,
当视觉中枢不能从眼睛获得信息，即便只持续短暂的时间，
the brain still tries to create a coherent picture, but the limits of its abilities become a lot more obvious.
大脑仍会试图创造出连续的影像，但这种能力的缺陷则更为明显。
The full-blown hallucinations of Charles Bonnet Syndrome are one example.
邦纳症候群中全面爆发的幻觉就是一个例子。
Because Charles Bonnet Syndrome only occurs in people who had normal vision and then lost their sight, not those who were born blind,
由于这种病症只发生在后天失明的人身上，先天失明的人并不会患上该疾病，
scientists think the brain uses remembered images to compensate for the lack of new visual input.
科学家认为大脑使用了记忆中的图像来弥补新视觉信息的缺失。

And the same is true for other senses.
对其他感官来说也是同理。
People with hearing loss often hallucinate music or voices, sometimes as elaborate as the cacophony of an entire marching band.
失聪的人们经常幻听到音乐或说话声，有时声音能够具体到像是整个军乐队在演奏。
In addition to sensory deprivation, recreational and therapeutic drugs,
除了感官功能缺失、服用消遣及治疗性药物之外，
conditions like epilepsy and narcolepsy, and psychiatric disorders like schizophrenia,
癫痫和发作性睡病等疾病，以及精神分裂症等精神失调，
are a few of the many known causes of hallucinations, and we're still finding new ones.
都是已知的能够导致幻觉的原因，而我们仍在探索其他原因。
Some of the most notorious hallucinations are associated with drugs like LSD and psilocybin.
一些众人皆知的幻觉与LSD和赛洛西宾等致幻剂有很大关系。
Their hallmark effects include the sensation that dry objects are wet and that surfaces are breathing.
它们的典型影响包括让我们以为干燥物体是湿润的，物体表面仿佛在呼吸。
At higher doses, the visual world can appear to melt, dissolve into swirls, or burst into fractal-like patterns.
剂量加高之后，眼睛看到的世界则像是融化一般，一切溶解形成漩涡，或是变成分形样式。
Evidence suggests these drugs also act on the cerebral cortex.
证据表明这些药物也会影响大脑皮层。
But while visual impairment typically only causes visual hallucinations,
虽然通常视觉受损只会引发视觉上的幻觉，
and hearing loss auditory ones, substances like LSD cause perceptual disturbances across all the senses.
听力缺失只会导致幻听，但LSD这类物质会干扰所有感官的觉知功能。
That's likely because they activate receptors in a broad range of brain areas, including the cortical regions for all the senses.
这很可能是因为它激发了大脑大片区域的感受器，包括脑皮质区域的所有感官。
LSD and psilocybin both function like serotonin in the brain, binding directly to one type of serotonin receptor in particular.
LSD和赛洛西宾与大脑中的血清素功能相似，可以与一种特定的血清素受体直接结合。
While serotonin's role in the brain is complex and poorly understood,
虽然血清素在大脑中的功能非常复杂，且我们对其知之甚少，
it likely plays an important part in integrating information from the eyes, nose, ears, and other sensory organs.
它可能是在整合信息方面发挥重要作用，这些信息来自于眼睛、鼻子、耳朵以及其他感受器官。
So one theory is that LSD and psilocybin cause hallucinations by disrupting the signaling involved in sensory integration.
有一种理论认为LSD和赛洛西宾会通过扰乱感觉统合时的信号由此导致幻觉。
Hallucinations associated with schizophrenia may share a similar mechanism with those caused by LSD and psilocybin.
与精神分裂症相关的幻觉，可能与由LSD和赛洛西宾造成的幻觉拥有相同的发病机制。
Patients with schizophrenia often have elevated levels of serotonin in the brain.
患有精神分裂症的病人大脑通常拥有较高的血清素的水平。
And antipsychotic drugs relieve symptoms of schizophrenia by blocking the same serotonin receptors LSD and psilocybin bind to.
治疗精神疾病的药物，通过阻断与LSD和赛洛西宾结合的同种血清素受体，来减轻精神分裂症的症状。
And, in some cases, these drugs can even relieve the hallucinations of patients with Charles Bonnet Syndrome.
在某些病例中，这些药物甚至能够减轻邦纳综合征病人的幻觉。
We're still a long way from understanding all the different causes and interconnected mechanisms of hallucinations.
在了解幻觉的全部病因以及相互联系的机制上，我们仍有很长的路要走。
But it's clear that hallucinatory experiences are much more closely tied to ordinary perception than we once thought.
但现已明确的是，幻觉体验与普通感知的关系比我们想象的更近。
And by studying hallucinations, we stand to learn a great deal about how our brains construct the world we see, hear, smell, and touch.
通过研究幻觉，我们能够更多地了解我们的大脑如何通过所看、所听、所闻、所触来构建世界。
As we learn more, we'll likely come to appreciate just how subjective and individual each person's island universe of perception really is.
随着我们不断研究，我们将能够欣赏每个人的感觉世界是多么的主观和独特。