斑馬魚能夠令人驚訝地準確掌握不同的節(jié)奏。（圖片提供:German Sumbre）
就像一名藍調音樂家不停地用腳和著樂曲打拍子一樣,，斑馬魚竟然能學會隨著閃光燈的節(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)為研究動物如何測量時間提供了線索。研究人員在最近的英國《自然》（Nature）雜志網(wǎng)絡版上報告了這一研究成果,。
人類和其他動物通過一個內在的生物鐘——即生理節(jié)奏的節(jié)律,，負責調節(jié)24小時的睡眠、進食和其他活動——來辨析時間,。但如果是一些更小的時間增量呢,？例如，動物必須能夠感知一頭正在接近的食肉動物的速度到底有多快,。美國加利福尼亞大學伯克利分校的神經生物學家Mu-ming Poo表示：“控制分秒生物鐘的機制依然是個未解之謎,。”
于是，Poo的研究小組開始研究大腦中的神經細胞如何在更短的尺度上感知時間,。研究人員將年幼的斑馬魚——一種常見的實驗室模式動物——暴露在不同長短和頻率的閃光下,。他們隨后觀測了閃光刺激前后頂蓋——負責處理視覺信息的大腦區(qū)域——中的神經活動。研究人員注意到,，當閃光停止后,，頂蓋中的神經活動的特殊模式還將持續(xù)20秒鐘，這意味著斑馬魚記住了這些閃光,。事實上,，當光線消失后，斑馬魚能夠以令人驚訝的精準節(jié)奏繼續(xù)拍打它們的尾巴,，就像是一部節(jié)拍器,。Poo表示：“在閃光結束后，斑馬魚能夠近乎完美地復制節(jié)奏——盡管是在很短的時間段內,。”
美國加利福尼亞大學洛杉磯分校的神經學家Dean Buonomano認為,，這項研究提供了后天行為與神經活動之間的一個“極佳的”例證。但是從事大腦辨析時間研究的Buonomano指出,， 由于在這項研究中,，斑馬魚對人造刺激的響應僅僅類似于一部節(jié)拍器，因此尚不清楚它們體內的生物鐘究竟是如何測量很短的時間間隔的,。（生物谷Bioon.com）
生物谷推薦原始出處：
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 Neuroscience Institute, University of California, Berkeley, California 94720, USA
2 Department of Physiology, University of California, San Francisco, California 94158, USA
3 Present address: Laboratoire de Neurobiologie, UMR 8544, école Normale Supérieure, 46 rue d'Ulm, 75005 Paris, France.
The ability to process temporal information is fundamental to sensory perception, cognitive processing and motor behaviour of all living organisms, from amoebae to humans1, 2, 3, 4. Neural circuit mechanisms based on neuronal and synaptic properties have been shown to process temporal information over the range of tens of microseconds to hundreds of milliseconds5, 6, 7. How neural circuits process temporal information in the range of seconds to minutes is much less understood. Studies of working memory in monkeys and rats have shown that neurons in the prefrontal cortex8, 9, 10, the parietal cortex9, 11 and the thalamus12 exhibit ramping activities that linearly correlate with the lapse of time until the end of a specific time interval of several seconds that the animal is trained to memorize. Many organisms can also memorize the time interval of rhythmic sensory stimuli in the timescale of seconds and can coordinate motor behaviour accordingly, for example, by keeping the rhythm after exposure to the beat of music. Here we report a form of rhythmic activity among specific neuronal ensembles in the zebrafish optic tectum, which retains the memory of the time interval (in the order of seconds) of repetitive sensory stimuli for a duration of up to 20 s. After repetitive visual conditioning stimulation (CS) of zebrafish larvae, we observed rhythmic post-CS activities among specific tectal neuronal ensembles, with a regular interval that closely matched the CS. Visuomotor behaviour of the zebrafish larvae also showed regular post-CS repetitions at the entrained time interval that correlated with rhythmic neuronal ensemble activities in the tectum. Thus, rhythmic activities among specific neuronal ensembles may act as an adjustable 'metronome' for time intervals in the order of seconds, and serve as a mechanism for the short-term perceptual memory of rhythmic sensory experience.
