來(lái)源:科學(xué)時(shí)報(bào)
斑馬魚(yú)能夠令人驚訝地準(zhǔn)確掌握不同的節(jié)奏。就像一名藍(lán)調(diào)音樂(lè)家不停地用腳和著樂(lè)曲打拍子一樣，斑馬魚(yú)竟然能學(xué)會(huì)隨著閃光燈的節(jié)奏拍打它們的尾巴，并且在燈光熄滅后依然可以記住這些節(jié)奏。這一令人驚訝的發(fā)現(xiàn)為研究動(dòng)物如何測(cè)量時(shí)間提供了線(xiàn)索。研究人員在*近的英國(guó)《自然》（Nature）雜志網(wǎng)絡(luò)版上報(bào)告了這一研究成果。
人類(lèi)和其他動(dòng)物通過(guò)一個(gè)內(nèi)在的生物鐘——即生理節(jié)奏的節(jié)律，負(fù)責(zé)調(diào)節(jié)24小時(shí)的睡眠、進(jìn)食和其他活動(dòng)——來(lái)辨析時(shí)間。但如果是一些更小的時(shí)間增量呢？例如，動(dòng)物必須能夠感知一頭正在接近的食肉動(dòng)物的速度到底有多快。美國(guó)加利福尼亞大學(xué)伯克利分校的神經(jīng)生物學(xué)家Mu-ming Poo表示：“控制分秒生物鐘的機(jī)制依然是個(gè)未解之謎。”
于是，Poo的研究小組開(kāi)始研究大腦中的神經(jīng)細(xì)胞如何在更短的尺度上感知時(shí)間。研究人員將年幼的斑馬魚(yú)——一種常見(jiàn)的實(shí)驗(yàn)室模式動(dòng)物——暴露在不同長(zhǎng)短和頻率的閃光下。他們隨后觀測(cè)了閃光刺激前后頂蓋——負(fù)責(zé)處理視覺(jué)信息的大腦區(qū)域——中的神經(jīng)活動(dòng)。研究人員注意到，當(dāng)閃光停止后，頂蓋中的神經(jīng)活動(dòng)的特殊模式還將持續(xù)20秒鐘，這意味著斑馬魚(yú)記住了這些閃光。事實(shí)上，當(dāng)光線(xiàn)消失后，斑馬魚(yú)能夠以令人驚訝的精準(zhǔn)節(jié)奏繼續(xù)拍打它們的尾巴，就像是一部節(jié)拍器。Poo表示：“在閃光結(jié)束后，斑馬魚(yú)能夠近乎**地復(fù)制節(jié)奏——盡管是在很短的時(shí)間段內(nèi)。”
美國(guó)加利福尼亞大學(xué)洛杉磯分校的神經(jīng)學(xué)家Dean Buonomano認(rèn)為，這項(xiàng)研究提供了后天行為與神經(jīng)活動(dòng)之間的一個(gè)“**的”例證。但是從事大腦辨析時(shí)間研究的Buonomano指出， 由于在這項(xiàng)研究中，斑馬魚(yú)對(duì)人造刺激的響應(yīng)僅僅類(lèi)似于一部節(jié)拍器，因此尚不清楚它們體內(nèi)的生物鐘究竟是如何測(cè)量很短的時(shí)間間隔的。（創(chuàng)賽新聞中心Canspec.com）
原始出處：
Nature，doi:10.1038/nature07351，Germán Sumbre，Mu-ming Poo
Entrained rhythmic activities of neuronal ensembles as perceptual memory of time interval
Germán Sumbre1,3, Akira Muto2,Herwig Baier2 & Mu-ming Poo1
1 Division of Neurobiology,Department of Molecular and Cell Biology, Helen Wills NeuroscienceInstitute, University of California, Berkeley, California 94720,USA
2 Department of Physiology, University of California, SanFrancisco, California 94158, USA
3 Present address: Laboratoire de Neurobiologie, UMR 8544, écoleNormale Supérieure, 46 rue d'Ulm, 75005 Paris,France.
Theability to process temporal information is fundamental to sensoryperception, cognitive processing and motor behaviour of all livingorganisms, from amoebae tohumans1, 2, 3, 4.Neural circuit mechanisms based on neuronal and synaptic propertieshave been shown to process temporal information over the range oftens of microseconds to hundreds ofmilliseconds5, 6, 7.How neural circuits process temporal information in the range ofseconds to minutes is much less understood. Studies of workingmemory in monkeys and rats have shown that neurons in theprefrontal cortex8, 9, 10,the parietal cortex9, 11 andthe thalamus12 exhibitramping activities that linearly correlate with the lapse of timeuntil the end of a specific time interval of several seconds thatthe animal is trained to memorize. Many organisms can also memorizethe time interval of rhythmic sensory stimuli in the timescale ofseconds and can coordinate motor behaviour accordingly, forexample, by keeping the rhythm after exposure to the beat of music.Here we report a form of rhythmic activity among specific neuronalensembles in the zebrafish optic tectum, which retains the memoryof the time interval (in the order of seconds) of repetitivesensory stimuli for a duration of upto 20 s. After repetitive visual conditioning stimulation (CS) ofzebrafish larvae, we observed rhythmic post-CS activities amongspecific tectal neuronal ensembles, with a regular interval thatclosely matched the CS. Visuomotor behaviour of the zebrafishlarvae also showed regular post-CS repetitions at the entrainedtime interval that correlated with rhythmic neuronal ensembleactivities in the tectum. Thus, rhythmic activities among specificneuronal ensembles may act as an adjustable 'metronome' for timeintervals in the order of seconds, and serve as a mechanism for theshort-term perceptual memory of rhythmic sensoryexperience.
