生活中我們經(jīng)常遇到這樣的情形，我們對某一個事件持有非?？隙ǖ拇鸢?，結(jié)果卻證明我們是錯的。這是虛假記憶在作怪,。美國和韓國科學(xué)家近日研究發(fā)現(xiàn),，這種逼真的虛假記憶雖然對我們來說難以區(qū)分，但實際上它們是由大腦不同的區(qū)域進(jìn)行處理的,。這一發(fā)現(xiàn)可用來進(jìn)行阿爾茨海默癥（Alzheimer）的早期診斷,，以及用來評估證人證詞的準(zhǔn)確性。相關(guān)論文發(fā)表在《神經(jīng)科學(xué)雜志》（Journal of Neuroscience）上,。
領(lǐng)導(dǎo)此次研究的是美國杜克大學(xué)的神經(jīng)學(xué)家Roberto Cabeza和韓國大邱大學(xué)的Hongkeun Kim,。研究人員先讓11個測試者閱讀一系列分類的單詞，遲些時候讓他們回想某個特定的單詞是否在最初的系列中出現(xiàn),，并給出對答案的自信程度,。實驗中用功能核磁共振成像（fMRI）技術(shù)監(jiān)測流向大腦不同區(qū)域的血流變化情況。
結(jié)果發(fā)現(xiàn),，當(dāng)測試者自信的答案是正確的時候,，涌向內(nèi)顳葉（medial temporal lobes）的血流會增加。而內(nèi)顳葉所在的大腦部分包含與記憶有重要關(guān)系的海馬區(qū)（hippocampus）,。當(dāng)測試者自信的答案是錯誤的時候,，額頂區(qū)（frontoparietal）血流會增加。研究人員認(rèn)為,，這一區(qū)域與一種稱作“熟悉”的感覺相聯(lián)系,。
研究人員表示，這種“熟悉”的感覺基本上是一種空洞的感覺，它與“回憶”不同,，沒有真實的記憶細(xì)節(jié),。在阿爾茨海默癥患者身上，這兩種記憶方式都存在衰退現(xiàn)象,，所以可以通過測量與“熟悉”感覺有關(guān)的腦活動來對阿爾茨海默癥進(jìn)行早期診斷,。
另外，此次研究結(jié)果將來還有望用于辨別證人證詞的真假,，即用腦部掃描來區(qū)分哪些人是在說真話,，哪些人則是在撒謊。對此,，美國康奈爾大學(xué)的認(rèn)知神經(jīng)學(xué)家Valerie Reyna認(rèn)為,，這一研究結(jié)果強(qiáng)調(diào)了法官和陪審團(tuán)不應(yīng)該輕信證人的證詞。她說：“自信與準(zhǔn)確性之間并沒有多大的聯(lián)系,，這確實讓人吃驚,。”（科學(xué)網(wǎng) 梅進(jìn)/編譯）
原始出處:
The Journal of Neuroscience, November 7, 2007, 27(45):12190-12197; doi:10.1523/JNEUROSCI.3408-07.2007
Trusting Our Memories: Dissociating the Neural Correlates of Confidence in Veridical versus Illusory Memories
Hongkeun Kim1 and Roberto Cabeza2
1Department of Rehabilitation Psychology, Daegu University, Daegu 705-714, South Korea, and 2Center for Cognitive Neuroscience, Duke University, Durham, North Carolina 27708-0999
Correspondence should be addressed to Hongkeun Kim, Department of Rehabilitation Psychology, Daegu University, 2288 Daemyung-dong, Nam-gu, Daegu 705-714, South Korea. Email: [email protected]
Although memory confidence and accuracy tend to be positively correlated, people sometimes remember with high confidence events that never happened. How can confidence correlate with accuracy but apply also to illusory memories? One possible explanation is that high confidence in veridical versus illusory memories depends on different neural mechanisms. The present study investigated this possibility using functional magnetic resonance imaging and a modified version of the Deese-Roediger-McDermott false-memory paradigm. Participants read short lists of categorized words, and brain activity was measured while they performed a recognition test with confidence rating. The study yielded three main findings. First, compared with low-confidence responses, high-confidence responses were associated with medial temporal lobe (MTL) activity in the case of true recognition but with frontoparietal activity in the case of false recognition. Second, these regions showed significant confidence-by-veridicality interactions. Finally, only MTL regions showed greater activity for high-confidence true recognition than for high-confidence false recognition, and only frontoparietal regions showed greater activity for high-confidence false recognition than for high-confidence true recognition. These findings indicate that confidence in true recognition is mediated primarily by a recollection-related MTL mechanism, whereas confidence in false recognition reflects mainly a familiarity-related frontoparietal mechanism. This account is consistent with the fuzzy trace theory of false recognition. Correlation analyses revealed that MTL and frontoparietal regions play complementary roles during episodic retrieval. In sum, the present study shows that when one focuses exclusively on high-confidence responses, the neural correlates of true and false memory are clearly different.
Key words: fMRI; false memory; prefrontal cortex; medial temporal lobe; human memory; memory confidence
