對來自外部的信息大腦是如何進行記憶和產(chǎn)生思維的,？這個問題一直像謎一樣困擾著人類,。通過長時間的苦苦探索,，科學(xué)家開始對大腦的記憶和認知過程有了一定的了解，神經(jīng)學(xué)家也在對大腦如何接收外部信息并產(chǎn)生思維的研究中形成了相應(yīng)的理論,。但是,，以色列魏茲曼研究院神經(jīng)生物學(xué)系依蘭拉姆伯博士等人的最新發(fā)現(xiàn)，無疑對當前令人樂觀的腦科學(xué)研究,，提出了新的難題,。
中樞神經(jīng)系統(tǒng)里的細胞，是通過一種沿著神經(jīng)元傳遞的電信號波,，保持著相互間的聯(lián)系的,。在回答大腦是如何將各種信息進行翻譯，以獲得認知和了解眼前世界這個問題時,，目前的理論認為,，這些電信號形成了一種信號模式，在這些模式中包含著不同類型的認知信息,。按照這一理論,，在我們說椅子和桌子這兩個詞時，大腦之所以能夠?qū)ζ溥M行辨別,，因為這些聲音會在神經(jīng)系統(tǒng)中產(chǎn)生截然不同的模式排列,，然后由大腦進行翻譯。如果對上述物體進行重復(fù)表述,，那么,，其模式會以精確和受約束的方式而生成出來。早先的實驗已經(jīng)證明,，重復(fù)模式可以將持續(xù)期延長到1秒鐘,。
但是，依蘭拉姆伯博士領(lǐng)導(dǎo)的研究小組,，在記錄被麻醉的試驗鼠大腦區(qū)（即大腦皮層）神經(jīng)元活動的數(shù)據(jù)并對其進行分析時發(fā)現(xiàn),，生成的模式在數(shù)量上并無差異，或者說，它們重復(fù)某些過程以形成不同模式所占用的時間是一樣的,，并且呈現(xiàn)隨機化的排列順序,。因此他們認為，觀察到的模式,，不可能是由理論上認定的控制機制決定的，而純粹是隨機的,。
這一研究成果可能會對當前關(guān)于神經(jīng)元編碼的爭論產(chǎn)生極大的影響,。拉姆伯說：“從20世紀80年代以來，許多神經(jīng)學(xué)家認為,，他們掌握了最終開啟了解大腦工作原理的鑰匙,，但是，我們獲得的最有力的證據(jù)說明,，大腦可能不是利用精確的活動模式來進行信息編碼的,。”
這一研究成果發(fā)表在近期出版的《神經(jīng)元》雜志上。
部分英文原文：
Neuron, Vol 53, 413-425, 01 February 2007
Article
Stochastic Emergence of Repeating Cortical Motifs in Spontaneous Membrane Potential Fluctuations In Vivo
Alik Mokeichev,1,2 Michael Okun,1,3 Omri Barak,1 Yonatan Katz,1 Ohad Ben-Shahar,2 and Ilan Lampl1,
1 Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel
2 Department of Computer Science and The Zlotowski Center for Neuroscience, Ben Gurion University of the Negev, Beer-Sheva 84105, Israel
3 Department of Computer Science, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
Corresponding author
Ilan Lampl
[email protected]
It was recently discovered that subthreshold membrane potential fluctuations of cortical neurons can precisely repeat during spontaneous activity, seconds to minutes apart, both in brain slices and in anesthetized animals. These repeats, also called cortical motifs, were suggested to reflect a replay of sequential neuronal firing patterns. We searched for motifs in spontaneous activity, recorded from the rat barrel cortex and from the cat striate cortex of anesthetized animals, and found numerous repeating patterns of high similarity and repetition rates. To test their significance, various statistics were compared between physiological data and three different types of stochastic surrogate data that preserve dynamical characteristics of the recorded data. We found no evidence for the existence of deterministically generated cortical motifs. Rather, the stochastic properties of cortical motifs suggest that they appear by chance, as a result of the constraints imposed by the coarse dynamics of subthreshold ongoing activity.
