德國(guó)波恩大學(xué)的神經(jīng)學(xué)家25日發(fā)表公報(bào)說,，他們研究揭開了這一現(xiàn)象的生理機(jī)制,。出乎意料的事物能激活大腦的獎(jiǎng)賞中樞,，后者與大腦記憶中樞以電壓信號(hào)互相回應(yīng),，令信息存入長(zhǎng)期記憶區(qū)域,。
研究人員舉例說：“如果所有事都如常發(fā)生（例如某個(gè)早晨你買了一杯咖啡后去上班）,，那么其間的很多細(xì)節(jié)也許你不太可能記?。欢绻l(fā)生了一些意外之事（如你將咖啡潑在褲子上）,，情況就不同了,，你可能很久以后還能清楚記得。”
為解釋這一現(xiàn)象,，波恩大學(xué)研究人員參與的一個(gè)國(guó)際研究小組首先假設(shè)大腦獎(jiǎng)賞中樞的伏隔核與記憶中樞的海馬體之間存在相互作用,，并對(duì)這兩個(gè)區(qū)域進(jìn)行觀察。他們選擇了正在接受治療的8名癲癇癥患者和6名抑郁癥患者作為受檢對(duì)象,。兩組患者的海馬體和伏隔核中置有電極,，能夠方便對(duì)其進(jìn)行測(cè)量。
研究人員選擇了紅色背景的人臉和綠色背景的房屋這兩種反差明顯的圖片,，并讓一種圖片的出現(xiàn)頻率比另一種多得多,，因此后者對(duì)于受檢者來(lái)說就是“意料之外”的。
研究人員在實(shí)驗(yàn)中監(jiān)測(cè)了受檢者的海馬體和伏隔核,，發(fā)現(xiàn)當(dāng)他們觀看圖片時(shí),，海馬體會(huì)釋放一個(gè)持續(xù)187毫秒的電壓信號(hào)刺激伏隔核，后者受激后會(huì)釋放出一個(gè)475毫秒的電壓信號(hào),，最后海馬體又會(huì)以一個(gè)482毫秒的信號(hào)予以回應(yīng),。與此同時(shí)，當(dāng)受檢者看到“意料之外”的圖片時(shí)這些腦部信號(hào)都更強(qiáng)烈,，其對(duì)這些圖片的記憶要比其他圖片強(qiáng)1.5倍,。此研究成果發(fā)表在最新一期的美國(guó)專業(yè)雜志《神經(jīng)元》上。（生物谷Bioon.com）
生物谷推薦原始出處：
Neuron, Volume 65, Issue 4, 541-549, 25 February 2010 | Copyright ? 2010 Elsevier Inc. All rights reserved. | 10.1016/j.neuron.2010.02.006
Intracranial EEG Correlates of Expectancy and Memory Formation in the Human Hippocampus and Nucleus Accumbens
Nikolai Axmacher, Michael X. Cohen, Juergen Fell, Sven Haupt, Matthias Dümpelmann, Christian E. Elger, Thomas E. Schlaepfer, Doris Lenartz, Volker Sturm, Charan Ranganath
Department of Epileptology, University of Bonn, 53105 Bonn, Germany Department of Psychiatry and Psychotherapy, University of Bonn, 53105 Bonn, Germany Life and Brain Center of Academic Research, 53105 Bonn, Germany Center for Neuroscience, University of California, Davis, Davis, CA 95616, USA Department of Psychology, University of California, Davis, Davis, CA 95616, USA Epilepsy Center, University Hospital Freiburg, 79106 Freiburg, Germany Department of Stereotactical Neurosurgery, University of Cologne, 50937 K?ln, Germany Department of Psychology, University of Amsterdam, 1018 WB, Amsterdam, The Netherlands Department of Physiology, University of Arizona, Tucson, AZ 85724, USA Department of Psychiatry, The Johns Hopkins University, Baltimore, MD 21287-7413, USA Department of Mental Health, The Johns Hopkins University, Baltimore, MD 21287-7413, USA Corresponding author
The human brain is adept at anticipating upcoming events, but in a rapidly changing world, it is essential to detect and encode events that violate these expectancies. Unexpected events are more likely to be remembered than predictable events, but the underlying neural mechanisms for these effects remain unclear. We report intracranial EEG recordings from the hippocampus of epilepsy patients, and from the nucleus accumbens of depression patients. We found that unexpected stimuli enhance an early (187 ms) and a late (482 ms) hippocampal potential, and that the late potential is associated with successful memory encoding for these stimuli. Recordings from the nucleus accumbens revealed a late potential (peak at 475 ms), which increases in magnitude during unexpected items, but no subsequent memory effect and no early component. These results are consistent with the hypothesis that activity in a loop involving the hippocampus and the nucleus accumbens promotes encoding of unexpected events.
