眼球不間斷的顫動(dòng)有助于我們更清楚的認(rèn)識(shí)這個(gè)世界。（圖中黃線表示眼球顫動(dòng)軌跡）
生物谷：當(dāng)你一個(gè)人行走在大森林里時(shí)會(huì)有什么感覺(jué),？害怕失去方向？先別慌,，眼睛微小而不自覺(jué)的運(yùn)動(dòng)會(huì)幫你找到前進(jìn)的方向,。美國(guó)科學(xué)家最新的研究表明，凝視物體時(shí)眼球的顫動(dòng)能夠幫助大腦更好地分辨影像的細(xì)節(jié),。該發(fā)現(xiàn)向解決眼動(dòng)的作用這一困擾科學(xué)家50余年的難題邁出了堅(jiān)實(shí)的一步,。相關(guān)研究論文發(fā)表在6月14日的《自然》雜志上,。
我們知道很多種動(dòng)物，比如猴子,、貓,，包括人都具有銳利的中心視覺(jué)（central vision），當(dāng)他們凝視物體時(shí),，眼球會(huì)作出精微的調(diào)整,，這些調(diào)整會(huì)使圖像在視網(wǎng)膜上顫動(dòng)。至于為什么會(huì)這樣,，科學(xué)家知之甚少,。在上世紀(jì)50年代，曾有視覺(jué)專家對(duì)此做過(guò)研究,。他們利用轉(zhuǎn)動(dòng)的鏡子來(lái)抵消受試者盯視圖像時(shí)眼球的顫動(dòng),，這使得受試者開始關(guān)注無(wú)特色的灰暗區(qū)域，而將圖像拋之一邊,。研究人員據(jù)此認(rèn)為,，眼動(dòng)的作用在于保持圖像不消退。但是,，眼動(dòng)是否還有其它功能以及眼球怎樣行使這些功能（如果有的話）仍舊是未解之謎,。
在最新的研究中，美國(guó)波士頓大學(xué)的神經(jīng)科學(xué)家Michele Rucci及其同事利用電腦追蹤方法,，重新對(duì)眼動(dòng)進(jìn)行了研究,。他們?cè)诒O(jiān)控器上對(duì)6名受試者分別示以兩個(gè)不同的圖像。這兩個(gè)圖像均具有灰暗的背景,，不同處在于位于其中間的傾斜線條,，一個(gè)粗大濃密，一個(gè)窄小精細(xì),。在每一個(gè)試驗(yàn)里,，電腦或是保持圖像不動(dòng)，或是令其隨著受試者眼球的顫動(dòng)而前后轉(zhuǎn)動(dòng),。受試者則需要告訴研究人員圖像中的線條向哪一方傾斜,。
結(jié)果與以前的研究完全不同。當(dāng)注視帶有濃密線條的圖像時(shí),，不論圖像轉(zhuǎn)動(dòng)與否,，受試者都能辨別出線條的傾斜方向。而當(dāng)注視轉(zhuǎn)動(dòng)著的線條較細(xì)的圖像時(shí),，他們辨別線條傾斜方向的能力卻下降了16％,。Rucci表示，這一結(jié)果表明，眼動(dòng)能幫助大腦挑選細(xì)節(jié),，例如尋找到森林里某一棵樹以及灌木從中的一個(gè)漿果等,。他說(shuō)：“視覺(jué)不比相機(jī)，拍下一張照片大腦就會(huì)處理它,。觀察的過(guò)程影響著你最終看到的東西,。”
來(lái)自美國(guó)索爾克生物學(xué)研究所（Salk Institute for Biological Studies）的神經(jīng)科學(xué)家Richard Krauzlis表示，此次研究令人信服地說(shuō)明了眼動(dòng)在辨別細(xì)節(jié)上的作用,。他說(shuō),，視覺(jué)專家對(duì)于眼動(dòng)的測(cè)量和歸類很在行，而對(duì)于它們作用的闡釋卻很外行,。所以,，Rucci的研究對(duì)于這一難題的最終解決作出了令人鼓舞的貢獻(xiàn)。（引自科學(xué)網(wǎng) ）
原始出處:
Nature 447, 852-855 (14 June 2007) | doi:10.1038/nature05866; Received 5 March 2007; Accepted 18 April 2007
Miniature eye movements enhance fine spatial detail
Michele Rucci1, Ramon Iovin1, Martina Poletti1 & Fabrizio Santini1
Department of Cognitive and Neural Systems, Boston University, Boston, Massachusetts 02215, USA
Correspondence to: Michele Rucci1 Correspondence and requests for materials should be addressed to M.R. (Email: [email protected]).
Summary
Our eyes are constantly in motion. Even during visual fixation, small eye movements continually jitter the location of gaze1, 2, 3, 4. It is known that visual percepts tend to fade when retinal image motion is eliminated in the laboratory5, 6, 7, 8, 9. However, it has long been debated whether, during natural viewing, fixational eye movements have functions in addition to preventing the visual scene from fading10, 11, 12, 13, 14, 15, 16, 17. In this study, we analysed the influence in humans of fixational eye movements on the discrimination of gratings masked by noise that has a power spectrum similar to that of natural images. Using a new method of retinal image stabilization18, we selectively eliminated the motion of the retinal image that normally occurs during the intersaccadic intervals of visual fixation. Here we show that fixational eye movements improve discrimination of high spatial frequency stimuli, but not of low spatial frequency stimuli. This improvement originates from the temporal modulations introduced by fixational eye movements in the visual input to the retina, which emphasize the high spatial frequency harmonics of the stimulus. In a natural visual world dominated by low spatial frequencies, fixational eye movements appear to constitute an effective sampling strategy by which the visual system enhances the processing of spatial detail.
