一個(gè)世紀(jì)以來,，科學(xué)家利用電刺激來探索人類大腦,，該方法可以幫組他們識別大腦中每個(gè)特殊神經(jīng)功能區(qū)域,，此外科學(xué)家還利用這種方法治療帕金森癥，抑郁癥等,。盡管這種方法普遍使用,，但研究人員卻從未在細(xì)胞水平上觀察到大腦應(yīng)答電刺激的整個(gè)過程。
最近,，有研究人員利用光學(xué)成像技術(shù)首次觀察到此過程,。他們發(fā)現(xiàn)神經(jīng)元應(yīng)答電刺激并非只在局部發(fā)生應(yīng)答。而是廣泛分布并且分散的神經(jīng)元同時(shí)發(fā)生應(yīng)答,。這項(xiàng)研究報(bào)告發(fā)表在8月27日出版的Neuron雜志上,。
觀察電刺激下神經(jīng)元的應(yīng)答一直以來都是一個(gè)難題，因?yàn)楫?dāng)使用較高電壓進(jìn)行刺激時(shí),，神經(jīng)元產(chǎn)生的電流無法檢測到。
為了回避這個(gè)問題,，該研究的主持者M(jìn)ark Histed通過一種新的光學(xué)成像方法——雙光子顯微鏡法(two-photon microscopy),，跟蹤了小鼠在接受電刺激時(shí)神經(jīng)元中鈣離子水平。研究人員將一種特殊的化學(xué)物質(zhì)引入到組織中,，當(dāng)鈣離子水平升高時(shí)，該物質(zhì)就會變亮,。因此,，研究人員可以看到神經(jīng)元每次被激活時(shí)都會產(chǎn)生光亮,。而且,，研究人員還能夠控制哪一個(gè)神經(jīng)元被激活,。
研究人員懷疑這種分散的神經(jīng)元激活模式并非是神經(jīng)元細(xì)胞體被激活,，只是軸突受到了電刺激。為了證實(shí)這點(diǎn),，研究人員將電極尖端移至遠(yuǎn)離原刺激位點(diǎn)10微米的位置,，10微米差不多為軸突的長度,。研究人員發(fā)現(xiàn)，雖有同等數(shù)量的神經(jīng)元被激活,，但激活的神經(jīng)元并不是原刺激位點(diǎn)周圍的神經(jīng)元,，這說明的確是神經(jīng)元細(xì)胞體接受了電刺激。
這項(xiàng)研究在細(xì)胞水平上揭示了大腦應(yīng)答電刺激的方式,，對未來該領(lǐng)域的試驗(yàn)具有指導(dǎo)意義,。（生物谷Bioon.com）
生物谷推薦原始出處：
Neuron, Volume 63, Issue 4, 508-522, 27 August 2009 doi:10.1016/j.neuron.2009.07.016
Direct Activation of Sparse, Distributed Populations of Cortical Neurons by Electrical Microstimulation
Mark H. Histed1,,,Vincent Bonin1andR. Clay Reid1,,
1 Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
For over a century, electrical microstimulation has been the most direct method for causally linking brain function with behavior. Despite this long history, it is still unclear how the activity of neural populations is affected by stimulation. For example, there is still no consensus on where activated cells lie or on the extent to which neural processes such as passing axons near the electrode are also activated. Past studies of this question have proven difficult because microstimulation interferes with electrophysiological recordings, which in any case provide only coarse information about the location of activated cells. We used two-photon calcium imaging, an optical method, to circumvent these hurdles. We found that microstimulation sparsely activates neurons around the electrode, sometimes as far as millimeters away, even at low currents. Our results indicate that the pattern of activated neurons likely arises from the direct activation of axons in a volume tens of microns in diameter.
