生活中我们经常遇到这样的情形，我们对某一个事件持有非常肯定的答案，结果却证明我们是错的。这是虚假记忆在作怪。美国和韩国科学家近日研究发现，这种逼真的虚假记忆虽然对我们来说难以区分，但实际上它们是由大脑不同的区域进行处理的。这一发现可用来进行阿尔茨海默症（Alzheimer）的早期诊断，以及用来评估证人证词的准确性。相关论文发表在《神经科学杂志》（Journal of Neuroscience）上。
领导此次研究的是美国杜克大学的神经学家Roberto Cabeza和韩国大邱大学的Hongkeun Kim。研究人员先让11个测试者阅读一系列分类的单词，迟些时候让他们回想某个特定的单词是否在最初的系列中出现，并给出对答案的自信程度。实验中用功能核磁共振成像（fMRI）技术监测流向大脑不同区域的血流变化情况。
结果发现，当测试者自信的答案是正确的时候，涌向内颞叶（medial temporal lobes）的血流会增加。而内颞叶所在的大脑部分包含与记忆有重要关系的海马区（hippocampus）。当测试者自信的答案是错误的时候，额顶区（frontoparietal）血流会增加。研究人员认为，这一区域与一种称作“熟悉”的感觉相联系。
研究人员表示，这种“熟悉”的感觉基本上是一种空洞的感觉，它与“回忆”不同，没有真实的记忆细节。在阿尔茨海默症患者身上，这两种记忆方式都存在衰退现象，所以可以通过测量与“熟悉”感觉有关的脑活动来对阿尔茨海默症进行早期诊断。
另外，此次研究结果将来还有望用于辨别证人证词的真假，即用脑部扫描来区分哪些人是在说真话，哪些人则是在撒谎。对此，美国康奈尔大学的认知神经学家Valerie Reyna认为，这一研究结果强调了法官和陪审团不应该轻信证人的证词。她说：“自信与准确性之间并没有多大的联系，这确实让人吃惊。”（科学网 梅进/编译）
原始出处:
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: hongkn1@gmail.com
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
