1月9日,，上海生科院神經(jīng)所張鳴沙課題組,，在Journal of Neuroscience期刊上發(fā)表了題為《后頂葉皮層神經(jīng)活動(dòng)調(diào)控快速眼動(dòng)的產(chǎn)生》的研究成果，通過(guò)在清醒行為猴上進(jìn)行胞外單電極記錄,，該研究組對(duì)后頂葉皮層在快速眼動(dòng)過(guò)程中的作用進(jìn)行了研究,。
通過(guò)快速眼動(dòng)，靈長(zhǎng)類(lèi)動(dòng)物可以將眼球快速轉(zhuǎn)向需要注意的物體,，因此對(duì)其生存有著至關(guān)重要的作用,。通常情況下，靈長(zhǎng)類(lèi)動(dòng)物每秒鐘約做3次快速眼動(dòng),。此外,，當(dāng)快速眼動(dòng)是指向一個(gè)已經(jīng)預(yù)期的位置時(shí)，一部分快速眼動(dòng)可以在極短的反應(yīng)時(shí)間（SRT）內(nèi)產(chǎn)生,，這部分眼動(dòng)被稱(chēng)為急速快速眼動(dòng),。為研究急速快速眼動(dòng)的神經(jīng)機(jī)制，張鳴沙組記錄了恒河猴后頂葉皮層的腦區(qū)之一—后頂葉皮層頂內(nèi)溝外側(cè)區(qū)（LIP）在間隔眼睛運(yùn)動(dòng)任務(wù)（gap task）中的神經(jīng)電活動(dòng),。間隔眼睛運(yùn)動(dòng)任務(wù)是一種特殊的眼睛運(yùn)動(dòng)任務(wù),，在該任務(wù)中，眼動(dòng)目標(biāo)并不是在注視點(diǎn)消失的同時(shí)出現(xiàn),，而是在注視點(diǎn)消失一段時(shí)間后才出現(xiàn),。他們發(fā)現(xiàn)，與沒(méi)有間隔的眼睛運(yùn)動(dòng)任務(wù)相比,，在間隔眼睛運(yùn)動(dòng)任務(wù)中,，約50%的所記錄的神經(jīng)元在間隔期增加了它們的電活動(dòng)。研究者們認(rèn)為,，這部分在眼動(dòng)目標(biāo)出現(xiàn)前就出現(xiàn)的電活動(dòng)增加,，可能代表著某種準(zhǔn)備機(jī)制,，并且可能與間隔眼睛運(yùn)動(dòng)任務(wù)中急速快速眼動(dòng)比率大幅度上升有關(guān)。此外,，該腦區(qū)的一部分在記憶期會(huì)產(chǎn)生持續(xù)放電的神經(jīng)元,，在急速快速眼動(dòng)過(guò)程中的電活動(dòng)高于在普通快速眼動(dòng)過(guò)程中的電活動(dòng)，并且這種電活動(dòng)的增高從眼睛注視注視點(diǎn)開(kāi)始,，一直持續(xù)到目標(biāo)點(diǎn)的出現(xiàn),。這種電活動(dòng)的增高具有空間選擇性，僅限于該神經(jīng)元的感受野,。但是該腦區(qū)的視覺(jué)神經(jīng)元在急速快速眼動(dòng)和普通快速眼動(dòng)過(guò)程中并沒(méi)有表現(xiàn)出電活動(dòng)的不同,。這些研究結(jié)果表明，這種增高的準(zhǔn)備性的活動(dòng)應(yīng)該在決定急速快速眼動(dòng)的產(chǎn)生方面起著至關(guān)重要的作用,。
張鳴沙組第一次提供了直接的電生理證據(jù),，證明頂葉皮層的神經(jīng)元在急速快速眼動(dòng)過(guò)程中的活性不同，該研究支持了前期的后頂葉通路假說(shuō),。在該假說(shuō)中,，研究者推斷后頂葉皮層參與急速快速眼動(dòng)的產(chǎn)生。
該研究由研究生陳默,、劉昱以及合作者魏林郁在張鳴沙教授的指導(dǎo)下完成,。該研究工作受到中國(guó)科學(xué)院“百人計(jì)劃”、 科技部973計(jì)劃和“浦江人才”計(jì)劃等基金資助,。(生物谷Bioon.com)
doi: 10.1523/JNEUROSCI.2675-12.2013
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Parietal Cortical Neuronal Activity Is Selective for Express Saccades
Mo Chen (默 陳)1,*, Yu Liu (昱 劉)1,*, Linyu Wei (郁 魏林)2, and Mingsha Zhang (沙 張鳴)1
Saccadic eye movements are central to primate behavior and serve to move the eyes to visual objects of interest. Express saccades, unlike regular saccades, occur with very short reaction times, a behavior necessary for speeded reactions in goal-directed behavior. Previous studies have shown that introduction of a blank interval (gap) between the fixation point offset and the saccadic target onset leads to an increase in the number of express saccades and that the superior colliculus plays a crucial role in the generation of express saccades. A longstanding hypothesis asserted that express saccades are mediated largely by a subcortical circuit, circumventing extrastriate visual cortex. An alternative “posterior pathway” hypothesis proposed the involvement of posterior parietal cortex. In the present study, using a gap saccade task, we investigated the role of nonhuman primate's lateral intraparietal cortex (LIP) in generation of express saccades. We show that roughly half of recorded LIP neurons were modulated during the gap interval. Moreover, a group of neurons with persistent activity in a memory-guided saccade task enhanced their activity during express saccades relative to that during regular saccades. After reducing the target's certainty by increasing the potential target locations, neuronal activity remained in the similar level during express saccades but markedly reduced during regular saccades that correlated with the increase of saccadic reaction time in the regular saccade. Our results suggest that area LIP is directly involved in generating saccades in express mode.
