An elderly woman named Rosalie was sitting in her nursing home when her room suddenly burst to life with twirling fabrics. Through the elaborate drapings, she could make out animals, children, and costumed characters. Rosalie was alarmed, not by the intrusion, but because she knew this entourage was an extremely detailed hallucination. Her cognitive function was excellent, and she had not taken any medications that might cause hallucinations. 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.
一位名叫蘿絲莉的老太太, 坐在養老院裡, 她的房間突然間活了起來, 充滿了快速轉動的織物。 透過精密的裝飾, 她能認出動物、 孩童, 以及穿著戲服的角色。 蘿絲莉感到驚恐, 並非因為被這些東西入侵, 而是因為她知道周圍的這些事物, 是非常細緻的幻覺。 她的認知能力很出色, 她沒有服用任何會造成幻覺的藥物。 最奇怪的是,就算真的有一群 馬戲團表演者衝入她的房間, 她也無法看到這些人: 因為她是全盲的。
Rosalie had developed a condition known as Charles Bonnet Syndrome, in which patients with either impaired vision or total blindness suddenly hallucinate whole scenes in vivid color. These hallucinations appear suddenly, and can last for mere minutes or recur for years. We still don’t fully understand what causes them to come and go, or why certain patients develop them when others don’t. We do know from fMRI studies that these hallucinations activate the same brain areas as sight, areas that are not activated by imagination.
蘿絲莉得到了「邦納症候群」, 這種病的病人,不論是視障或全盲, 會突然幻見完整的景象, 充滿鮮明的顏色。 這些幻覺都是突然出現的, 可能持續幾分鐘 或是歷經多年不斷復發。 我們還無法完全了解是什麼 導致幻覺來來去去, 或是為什麼某些病人 會有幻覺,某些卻沒有。 我們根據功能性磁振造影的研究 確知這些幻覺會觸發 和視覺使用區域相同的大腦區域, 而不是想像所使用的區域。
Many other hallucinations, including smells, sights, and sounds, also involve the same brain areas as real sensory experiences. Because of this, the cerebral cortex is thought to play a part in hallucinations. This thin layer of grey matter covers the entire cerebrum, with different areas processing information from each of our senses. But even in people with completely unimpaired senses, the brain constructs the world we perceive from incomplete information. For example, our eyes have blind spots where the optic nerve blocks part of the retina. When the visual cortex processes light into coherent images, it fills in these blind spots with information from the surrounding area. Occasionally, we might notice a glitch, but most of the time we’re none the wiser.
許多其他幻覺,包括嗅覺、 視覺, 和聽覺, 涉及的大腦區域也和真實感官體驗 所使用的大腦區域一樣。 基於這個理由,幻覺被認為 和大腦皮層有部分關係存在。 這一層薄薄的灰質覆蓋了整個大腦, 來自我們各種感官的資訊, 會有不同的區域來負責處理。 但對於感官完全沒有障礙的人來說, 大腦也是用不完整的資訊 來建構出我們所感知到的世界。 比如,我們的眼睛會有盲點, 視神經會阻擋到部分的視網膜。 當視覺皮質把光線 加入到協調連貫的影像中時, 它會用周圍區域的資訊 來填補這些盲點。 偶爾,我們會發現有小差錯, 但大部分的時候,我們都不知道。
When the visual cortex is deprived of input from the eyes, even temporarily, the brain still tries to create a coherent picture, but the limits of its abilities become a lot more obvious. The full-blown hallucinations of Charles Bonnet Syndrome are one example. Because Charles Bonnet Syndrome only occurs in people who had normal vision and then lost their sight, not those who were born blind, scientists think the brain uses remembered images to compensate for the lack of new visual input. And the same is true for other senses. People with hearing loss often hallucinate music or voices, sometimes as elaborate as the cacophony of an entire marching band.
當視覺皮層得不到來自眼睛的 輸入資料時,即使只有一下下, 大腦仍然會試圖創造出 一個協調連貫的圖像, 但就能很明顯發現, 它的能力有限。 邦納症候群的完整幻覺就是一例。 因為只有原本視力正常, 後來才失去視力的人, 才會得到邦納症候群, 出生就失明的人就不會, 科學家認為, 大腦會使用記得的影像, 來補足新的視覺輸入資料中 缺乏的部分。 其他的感官也是一樣的情況。 有聽力障礙的人, 常常會幻聽到音樂或聲音, 有時,聽到的聲音會複雜到 像有一整個軍樂隊一樣。
In addition to sensory deprivation, recreational and therapeutic drugs, conditions like epilepsy and narcolepsy, and psychiatric disorders like schizophrenia, are a few of the many known causes of hallucinations, and we’re still finding new ones.
除了感覺喪失之外, 娛樂性和治療性藥物、 癲癇與猝睡症等病症, 及精神分裂症等精神疾病, 是少數已知的幻覺成因, 且我們還不斷在發現新的成因。
Some of the most notorious hallucinations are associated with drugs like LSD and psilocybin. Their hallmark effects include the sensation that dry objects are wet and that surfaces are breathing. At higher doses, the visual world can appear to melt, dissolve into swirls, or burst into fractal-like patterns. Evidence suggests these drugs also act on the cerebral cortex. But while visual impairment typically only causes visual hallucinations, and hearing loss auditory ones, substances like LSD cause perceptual disturbances across all the senses. That’s likely because they activate receptors in a broad range of brain areas, including the cortical regions for all the senses. LSD and psilocybin both function like serotonin in the brain, binding directly to one type of serotonin receptor in particular. While serotonin’s role in the brain is complex and poorly understood, it likely plays an important part in integrating information from the eyes, nose, ears, and other sensory organs. So one theory is that LSD and psilocybin cause hallucinations by disrupting the signaling involved in sensory integration.
有些最惡名昭彰的幻覺 則是與 LSD 及裸蓋菇素 (都是迷幻藥)等藥物有關。 它們的招牌效應包括 覺得乾燥的物體是濕的, 以及覺得表面在呼吸。 若劑量更高,視覺世界 有可能會像是融化了一樣, 分解成漩渦, 或是突然變成不規則碎片的圖案。 有證據顯示,這些藥物 也會影響大腦皮層。 雖然視覺障礙通常 只會造成視覺的幻覺, 失聰通常只會造成聽覺的幻覺, 但像 LSD 這類物質卻有可能 造成所有感官的知覺混亂。 很有可能是因為它們會啟動 更多大腦區域的接受器, 包括各感官的皮層區域。 LSD 及裸蓋菇素的功能 都像是大腦中的血清素, 特別會直接和一種血清素接受器結合。 雖然血清素在大腦中的角色 很複雜且我們不是很了解, 但它很有可能在整合資訊上 扮演了重要的角色, 整合來自眼睛、鼻子、耳朵, 和其他感覺器官的資訊。 所以,有一種理論是說, LSD 及裸蓋菇素之所以會造成幻覺, 是因為它們會打斷感官整合 所需要用到的相關訊號。 和精神分裂症相關的幻覺
Hallucinations associated with schizophrenia may share a similar mechanism with those caused by LSD and psilocybin. Patients with schizophrenia often have elevated levels of serotonin in the brain. And antipsychotic drugs relieve symptoms of schizophrenia by blocking the same serotonin receptors LSD and psilocybin bind to. And, in some cases, these drugs can even relieve the hallucinations of patients with Charles Bonnet Syndrome.
可能與 LSD 及裸蓋菇素 所造成的幻覺有類似的機制。 精神分裂症病人 通常大腦中的血清素會比較高。 而抗精神病藥物 能緩解精神分裂症的症狀, 因為它們能阻擋與 LSD 及裸蓋菇素 結合的那些血清素接受器。 在某些案例中, 這些藥物甚至可以減輕 邦納症候群病人的幻覺狀況。 對於幻覺的各種成因 以及相關聯的機制,
We’re still a long way from understanding all the different causes and interconnected mechanisms of hallucinations. But it’s clear that hallucinatory experiences are much more closely tied to ordinary perception than we once thought. And by studying hallucinations, we stand to learn a great deal about how our brains construct the world we see, hear, smell, and touch. As we learn more, we’ll likely come to appreciate just how subjective and individual each person’s island universe of perception really is.
我們還有很多要去了解的。 但很清楚的是,幻覺的經歷 和一般感知之間的關係, 遠比我們以前認為的還要密切。 透過研究幻覺, 我們也能準備好去更了解 我們的大腦如何建構出 我們所看見、 聽見、 聞到, 和觸碰到的世界。 當我們懂更多, 就更有可能會開始欣賞 每個人孤立的感知島嶼世界 是有多麼主觀、多麼個人化。