Buckner R L, Koutstaal W, Schacter D L, Dale A M, Rotte M, Rosen B R
Department of Psychology, Washington University, St. Louis, Missouri 63130, USA.
Neuroimage. 1998 Apr;7(3):163-75. doi: 10.1006/nimg.1998.0328.
In a companion paper (R. L. Buckner et al., 1998, NeuroImage 7, 151-162) we used fMRI to identify brain areas activated by episodic memory retrieval. Prefrontal areas were shown to differentiate component processes related to retrieval success and retrieval effort in block-designed paradigms. Importantly, a right anterior prefrontal area was most active during task blocks involving greatest retrieval success, consistent with an earlier PET study by M. D. Rugg et al. (1996, Brain 119, 2073-2083). However, manipulation of these variables within the context of blocked trials confounds differences related to varying levels of retrieval success with potential shifts in subjects' strategies due to changes in the probability of target events across blocks. To test more rigorously the hypothesis that certain areas are directly related to retrieval success, we adopted recently developed procedures for event-related fMRI. Fourteen subjects studied words under deep encoding and were then tested in a mixed trial paradigm where old and new words were randomly presented. This recognition testing procedure activated similar areas to the blocked trial paradigm, with all areas showing similar levels of activation across old and new items. Of critical importance, significant activation was detected in right anterior prefrontal cortex for new items when subjects correctly indicated they were new (correct rejections). These findings go against the retrieval success hypothesis as formally proposed and provide an important constraint for interpretation of this region's role in episodic retrieval. Furthermore, anterior prefrontal activation was found to occur late, relative to other brain areas, suggesting that it may be involved in retrieval verification or monitoring processes or perhaps even in anticipation of subsequent trial events (although an alternative possibility, that the late onset is mediated by a late vascular response, cannot be ruled out). These findings and their relation to the results obtained in the companion blocked-trial paradigm are discussed.
在一篇相关论文中（R. L. 巴克纳等人，1998年，《神经影像学》第7卷，第151 - 162页），我们使用功能磁共振成像（fMRI）来识别由情景记忆提取所激活的脑区。在组块设计范式中，前额叶区域被证明能够区分与提取成功和提取努力相关的组成过程。重要的是，在涉及最大提取成功的任务组块期间，右侧前额叶前部区域最为活跃，这与M. D. 鲁格等人早期的一项正电子发射断层扫描（PET）研究结果一致（1996年，《大脑》第119卷，第2073 - 2083页）。然而，在组块试验的背景下对这些变量进行操纵，会将与不同提取成功水平相关的差异与由于各块中目标事件概率变化导致的受试者策略潜在转变相混淆。为了更严格地检验某些脑区与提取成功直接相关这一假设，我们采用了最近开发的事件相关功能磁共振成像程序。14名受试者在深度编码下学习单词，然后在一个混合试验范式中进行测试，在该范式中，新旧单词被随机呈现。这种识别测试程序激活的脑区与组块试验范式相似，所有脑区在新旧项目上的激活水平相似。至关重要的是，当受试者正确表明新单词是新的（正确拒绝）时，在右侧前额叶前部皮质中检测到了对新项目的显著激活。这些发现与正式提出的提取成功假设相悖，并为解释该区域在情景提取中的作用提供了重要限制。此外，相对于其他脑区，前额叶前部激活出现得较晚，这表明它可能参与提取验证或监测过程，甚至可能参与对后续试验事件的预期（尽管不能排除另一种可能性，即延迟发作是由延迟的血管反应介导的）。本文讨论了这些发现及其与在相关组块试验范式中获得的结果之间的关系。
