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(tīng)到過(guò)藍(lán)色么?你曾經(jīng)嘗到過(guò)音符F調(diào)么?對(duì)于大多數(shù)人來(lái)說(shuō),答案是否定的。但是,對(duì)于某些特定人群來(lái)說(shuō),藍(lán)色確實(shí)有一種特定的聲音或形狀,F(xiàn)調(diào)也確實(shí)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(jué)”,一種鮮有的神經(jīng)學(xué)現(xiàn)象,通常十萬(wàn)分之一的人有這種癥狀。
“共同感覺(jué)”
有這種癥狀的人不僅僅會(huì)將聲音與顏色聯(lián)系、味覺(jué)與聲音聯(lián)系,也可能會(huì)在看到某種特定顏色時(shí)設(shè)想聽(tīng)到了某種聲音。更確切地說(shuō),一個(gè)有“共同感覺(jué)”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(huì)聽(tīng)到某種聲音。
類似情況下,某種特定的聲音也會(huì)引發(fā)擁有“共同感覺(jué)”的人能看到某種形狀或特定的顏色,哪怕在他的視覺(jué)范圍內(nèi)并未有這樣的物體出現(xiàn)。對(duì)于味覺(jué)和嗅覺(jué),這種情況也同樣存在。
原因
科學(xué)家們對(duì)于為何會(huì)引發(fā)“共同感覺(jué)”知之甚少。雖然看起來(lái)這是一種遺傳疾病,但事實(shí)上,對(duì)于這種現(xiàn)象的神經(jīng)發(fā)生過(guò)程如何解釋依然成謎。盡管很多科學(xué)家們認(rèn)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(jué)”的癥狀依然不得而知。
另外,目前對(duì)于“共同感覺(jué)”的科學(xué)認(rèn)識(shí)也僅僅是基于幾種有趣的現(xiàn)象觀察。比如,這種連覺(jué)的感知并不會(huì)隨著時(shí)間過(guò)去而消失。換句話說(shuō),如果當(dāng)一個(gè)人在聽(tīng)到C大調(diào)時(shí)看到藍(lán)色與綠色閃過(guò),那么將來(lái)一旦他聽(tīng)到同樣的聲音,眼前就會(huì)浮現(xiàn)出藍(lán)色和綠色。