Have you ever heard the color blue? Or tasted the musical note F-sharp? For most people, in both cases the answer is no. But for some people blue has a particular sound or shape, and F sharp has a slightly sour taste. This unusual blending of the senses is called synesthesia, a rare neurological phenomenon occurring in roughly 1 in 100,000 people.
Synesthesia
People with this condition do not merely associate sound with color or taste with sound, or imagine hearing a sound when they see a certain color. Rather, when a person with synesthesia encounters a particular sensory stimulus, say seeing the color red, she will hear a sound even when there is no outside source producing the sound.
In a similar manner, a particular sound may cause someone with synesthesia to see certain shapes or certain colors, even when there is no object in that person’s line of sight. The same goes for taste and smell.
Causes
Scientists know very little about what causes synesthesia. While it appears to be hereditary, the actual neurological processes that account for the phenomenon remain a mystery. Although most scientists agree that the hippocampus, an area of the brain responsible for memory, plays a role, exactly how the hippocampus might cause synesthesia is not clear.
Otherwise, scientific knowledge about synesthesia is limited to several interesting observations. For example, synesthetic perceptions remain consistent over time. In other words, if a person with synesthesia sees blue and green flashes when he hears a C-sharp, he will always see those same colors upon hearing that note.
顏色有氣味嗎?
你曾聽到過藍色么?你曾經(jīng)嘗到過音符F調(diào)么?對于大多數(shù)人來說,答案是否定的。但是,對于某些特定人群來說,藍色確實有一種特定的聲音或形狀,F(xiàn)調(diào)也確實有一種酸酸的味道。這種不尋常的感官混淆被稱為“共同感覺”,一種鮮有的神經(jīng)學(xué)現(xiàn)象,通常十萬分之一的人有這種癥狀。
“共同感覺”
有這種癥狀的人不僅僅會將聲音與顏色聯(lián)系、味覺與聲音聯(lián)系,也可能會在看到某種特定顏色時設(shè)想聽到了某種聲音。更確切地說,一個有“共同感覺”的人如果受到了某種特殊的感官刺激,比如看到了紅色,哪怕外界并未有發(fā)音源,她也依然會聽到某種聲音。
類似情況下,某種特定的聲音也會引發(fā)擁有“共同感覺”的人能看到某種形狀或特定的顏色,哪怕在他的視覺范圍內(nèi)并未有這樣的物體出現(xiàn)。對于味覺和嗅覺,這種情況也同樣存在。
原因
科學(xué)家們對于為何會引發(fā)“共同感覺”知之甚少。雖然看起來這是一種遺傳疾病,但事實上,對于這種現(xiàn)象的神經(jīng)發(fā)生過程如何解釋依然成謎。盡管很多科學(xué)家們認為“海馬體”-大腦中用于控制記憶的一片區(qū)域?qū)е麓朔N現(xiàn)象出現(xiàn),但究竟它是如何影響并引發(fā)“共同感覺”的癥狀依然不得而知。
另外,目前對于“共同感覺”的科學(xué)認識也僅僅是基于幾種有趣的現(xiàn)象觀察。比如,這種連覺的感知并不會隨著時間過去而消失。換句話說,如果當(dāng)一個人在聽到C大調(diào)時看到藍色與綠色閃過,那么將來一旦他聽到同樣的聲音,眼前就會浮現(xiàn)出藍色和綠色。