躍動的神經

So natural is our capacity for rhythm that most of us take it for granted: when we hear music， we tap our feet to the 2)beat or rock and sway， often unaware that we are even moving. But this instinct is， 3)for all intents and purposes， an evolutionary 4)novelty among humans. Nothing comparable occurs in other mammals nor probably elsewhere in the animal kingdom. Our talent for unconscious 5)entrainment lies at the core of dance， a 6)confluence of movement， rhythm and gestural representation. By far the most synchronized group practice， dance demands a type of interpersonal coordination in space and time that is almost nonexistent in other social contexts.

Even though dance is a fundamental form of human expression， neuroscientists have given it relatively little consideration. Recently， however， researchers have conducted the first brain-imaging studies of both amateur and professional dancers. These investigations address such questions as， How do dancers navigate through space? How do they 7)pace their steps? How do people learn complex series of 8)patterned movements?

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Perhaps the most fascinating question for neuroscientists to explore is why people dance in the first place. Certainly music and dance are closely related; in many instances， dance generates sound. 9)Aztec 10)danzantes in 11)Mexico City wear 12)leggings containing seeds from the 13)ayoyotl tree， called 14)chachayotes， which make a sound with every step. In many other cultures， people put noise-making objects—from 15)taps to 16)castanets to beads—on their bodies or clothes while they dance. In addition， dancers frequently clap， snap and stomp. As a result， we have 17)postulated a “body 18)percussion” hypothesis that dance evolved initially as a sounding phenomenon and that dance and music， especially percussion， evolved together as complementary ways of generating rhythm. The first percussion instruments may well have been components of dancing 19)regalia， not unlike Aztec chachayotes.

Unlike music， however， dance has a strong capacity for representation and imitation， which suggests that dance may have further served as an early form of language. Indeed， dance is the 20)quintessential gesture language. It is interesting to note that during all the movement tasks in our study， we saw activation in a region of the right 21)hemisphere corresponding to what is known as 22)Broca’s area in the left hemisphere. Broca’s area is a part of the 23)frontal lobe classically associated with speech production. In the past decade research has revealed that Broca’s area also contains a representation of the hands.

This finding 24)bolsters the so-called gestural theory of language evolution， whose proponents argue that language evolved initially as a gesture system before becoming vocal. Our study is among the first to show that leg movement activates the right-hemisphere 25)homologue to Broca’s area， which offers more support for the idea that dance began as a form of representational communication.

We view dance as a marriage of the representational capacity of language and the rhythmicity of music. This interaction allows people not only to tell stories using their bodies but to do so while synchronizing their movements with others’ in a way that fosters social 26)cohesion.

我們自然地擁有節奏感，大多數人認為那是理所當然的：聽到音樂時我們會隨著節拍輕輕踏腳，或者搖擺身子，但常常根本沒有意識到自己在動。但實際上，這種本能是人類在進化過程中獲得的新奇稟賦。其他哺乳類動物也好，動物王國的其他領域也好，都沒有可以與之媲美的。人類這種無意識協動的天賦正是舞蹈的神髓所在。一連串的動作、節拍和姿態表現融合成舞蹈。到目前為止，舞蹈可謂是同步程度最高的團體活動，幾乎沒有哪種社會性活動像它一樣需要人們在時間和空間上達到如此精確的協調一致。

雖然舞蹈是人類的一種基本的表達方式，但它一直較少引起神經科學家的關注。而最近，研究人員首次對業余舞者和職業舞者分別進行了腦成像研究。研究針對解答的是這么一些問題：舞者是怎樣駕馭空間的？他們是怎樣調整舞步的？人們是怎么學會一連串復雜的花式動作的？

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也許最令神經科學家們著迷要探究的首要問題就是：人類為什么跳舞？當然，音樂和舞蹈是緊密相連的，很多時候，舞蹈會產生聲響。墨西哥城的阿茲特克舞者，其綁腿（又稱“開心

果”）掛飾里有哈由優特樹的種子，他們每挪動一步，這些種子都會相碰發出聲響。在其他的許多文化里，人們跳舞時都會在身上或衣服上加上諸如金屬片、響板、珠子等等能夠發出聲音的物件。另外，舞者們還會一邊跳舞一邊頻頻拍手，打響指和跺腳。因此，我們提出了一個“軀體打擊樂”的假設，這個假設認為舞蹈最初是從一些發聲現象演化而來，并且舞蹈和音樂特別是打擊樂，相互補充演化發展進而產生了節拍。