Voss Joel L, Paller Ken A
Interdepartmental Neuroscience Program and Department of Psychology, Northwestern University, Evanston, Illinois 60208, USA.
Learn Mem. 2007 Apr 5;14(4):259-67. doi: 10.1101/lm.529807. Print 2007 Apr.
During episodic recognition tests, meaningful stimuli such as words can engender both conscious retrieval (explicit memory) and facilitated access to meaning that is distinct from the awareness of remembering (conceptual implicit memory). Neuroimaging investigations of one type of memory are frequently subject to the confounding influence of the other type of memory, thus posing a serious impediment to theoretical advances in this area. We used minimalist visual shapes (squiggles) to attempt to overcome this problem. Subjective ratings of squiggle meaningfulness varied idiosyncratically, and behavioral indications of conceptual implicit memory were evident only for stimuli given higher ratings. These effects did not result from perceptual-based fluency or from explicit remembering. Distinct event-related brain potentials were associated with conceptual implicit memory and with explicit memory by virtue of contrasts based on meaningfulness ratings and memory judgments, respectively. Frontal potentials from 300 to 500 msec after the onset of repeated squiggles varied systematically with perceived meaningfulness. Explicit memory was held constant in this contrast, so these potentials were taken as neural correlates of conceptual implicit memory. Such potentials can contaminate putative neural correlates of explicit memory, in that they are frequently attributed to the expression of explicit memory known as familiarity. These findings provide the first neural dissociation of these two memory phenomena during recognition testing and underscore the necessity of taking both types of memory into account in order to obtain valid neural correlates of specific memory functions.
在情景识别测试中，诸如单词之类的有意义刺激既能引发有意识的提取（外显记忆），又能促进对意义的获取，这种获取与记忆意识（概念性内隐记忆）不同。对一种记忆类型的神经成像研究经常受到另一种记忆类型的混杂影响，从而对该领域的理论进展构成严重阻碍。我们使用极简主义视觉形状（波形曲线）来试图克服这个问题。对波形曲线意义的主观评分因人而异，并且概念性内隐记忆的行为指标仅在给予较高评分的刺激中才明显。这些效应并非源于基于感知的流畅性或外显记忆。通过分别基于意义评分和记忆判断的对比，不同的事件相关脑电位与概念性内隐记忆和外显记忆相关联。重复呈现波形曲线开始后300至500毫秒的额叶电位随感知到的意义而系统地变化。在这种对比中外显记忆保持不变，因此这些电位被视为概念性内隐记忆的神经关联物。这些电位可能会干扰外显记忆的假定神经关联物，因为它们经常被归因于被称为熟悉度的外显记忆的表现。这些发现首次在识别测试中对这两种记忆现象进行了神经分离，并强调了在获取特定记忆功能的有效神经关联物时同时考虑这两种记忆类型的必要性。
