經(jīng)常把朋友的名字張冠李戴，或是把事情弄混？這也許是因?yàn)槟愦竽X中神經(jīng)元之間的突觸結(jié)構(gòu)正在經(jīng)歷生生滅滅的變化。一項(xiàng)研究顯示，這種變化會(huì)使得記憶準(zhǔn)確度隨之改變，相關(guān)成果或許可用于治療一些與記憶有關(guān)的疾病。
英國(guó)《自然》雜志刊登報(bào)告說(shuō)，瑞士弗里德里希－米舍研究所等機(jī)構(gòu)研究人員觀察實(shí)驗(yàn)鼠大腦結(jié)構(gòu)變化時(shí)發(fā)現(xiàn)，如果實(shí)驗(yàn)鼠進(jìn)入某個(gè)房間后遭到電擊，它就會(huì)記住這個(gè)遭遇，再進(jìn)入這個(gè)房間時(shí)就會(huì)表現(xiàn)出恐懼，而在其他相似但不同的房間中卻沒(méi)有這種表現(xiàn)。研究發(fā)現(xiàn)，在這個(gè)過(guò)程中，實(shí)驗(yàn)鼠大腦中相關(guān)神經(jīng)元周圍多出了許多突觸結(jié)構(gòu)。
不過(guò)，實(shí)驗(yàn)鼠的記憶準(zhǔn)確度只能維持較短的時(shí)間，在遭電擊兩個(gè)星期后，即使是進(jìn)入相似的房間，它也會(huì)表現(xiàn)出恐懼，這說(shuō)明被電擊的記憶還在，只是大腦開始把相關(guān)環(huán)境混淆了。研究發(fā)現(xiàn)，這時(shí)其大腦中相關(guān)神經(jīng)元周圍的突觸結(jié)構(gòu)逐漸消失。
但如果再讓實(shí)驗(yàn)鼠回到zui初遭電擊的房間，其相關(guān)突觸結(jié)構(gòu)會(huì)重新建立，記憶再次變得準(zhǔn)確，再進(jìn)入其他房間也不再表現(xiàn)出恐懼。研究人員據(jù)此認(rèn)為，突觸結(jié)構(gòu)在大腦記憶中起著確定事件背景、保證記憶準(zhǔn)確度的作用。
原文出處：
Nature doi:10.1038/nature09946
Learning-related feedforward inhibitory connectivity growth required for memory precision
Sarah Ruediger,1, 3 Claudia Vittori,1, 2, 3 Ewa Bednarek,1 Chris Genoud,1 Piergiorgio Strata,2 Benedetto Sacchetti2 & Pico Caroni1
In the adult brain, new synapses are formed and pre-existing ones are lost, but the function of this structural plasticity has remained unclear1, 2, 3, 4, 5. Learning of new skills is correlated with formation of new synapses6, 7, 8. These may directly encode new memories, but they may also have more general roles in memory encoding and retrieval processes2. Here we investigated how mossy fibre terminal complexes at the entry of hippocampal and cerebellar circuits rearrange upon learning in mice, and what is the functional role of the rearrangements. We show that one-trial and incremental learning lead to robust, circuit-specific, long-lasting and reversible increases in the numbers of filopodial synapses onto fast-spiking interneurons that trigger feedforward inhibition. The increase in feedforward inhibition connectivity involved a majority of the presynaptic terminals, restricted the numbers of c-Fos-expressing postsynaptic neurons at memory retrieval, and correlated temporally with the quality of the memory. We then show that for contextual fear conditioning and Morris water maze learning, increased feedforward inhibition connectivity by hippocampal mossy fibres has a critical role for the precision of the memory and the learned behaviour. In the absence of mossy fibre long-term potentiation in Rab3a?/? mice9, c-Fos ensemble reorganization and feedforward inhibition growth were both absent in CA3 upon learning, and the memory was imprecise. By contrast, in the absence of adducin 2 （Add2; also known as β-adducin）10 c-Fos reorganization was normal, but feedforward inhibition growth was abolished. In parallel, c-Fos ensembles in CA3 were greatly enlarged, and the memory was imprecise. Feedforward inhibition growth and memory precision were both rescued by re-expression of Add2 specifically in hippocampal mossy fibres. These results establish a causal relationship between learning-related increases in the numbers of defined synapses and the precision of learning and memory in the adult. The results further relate plasticity and feedforward inhibition growth at hippocampal mossy fibres to the precision of hippocampus-dependent memories.