Addis Donna Rose, McAndrews Mary Pat
Department of Psychology, Harvard University, William James Hall, Rm. 854, 33 Kirkland Street, Cambridge, MA 02138, USA.
Neuroimage. 2006 Dec;33(4):1194-206. doi: 10.1016/j.neuroimage.2006.07.039. Epub 2006 Oct 4.
The ability to form and bind associations between items is an important aspect of successful memory formation. We hypothesize that, during encoding, the left inferior frontal gyrus (IFG) supports generation of associations between items and the hippocampus then binds these associations. This study examined the parametric responses of these regions to varying amounts of generative and relational processing during successful encoding (i.e., for subsequently recognized items). Encoding involved presentation of word triads varying in the number of semantic associations among them (none, one or all); participants judged how many associations were present in each triad. Thus, triads with fewer associations had higher generative load while triads with more associations had higher relational load. Participants later completed a forced-choice recognition test for encoding triads. Successful encoding relative to a control task resulted in activation of bilateral IFG and left hippocampus, and the hippocampus also exhibited a significant subsequent memory effect (hits>misses). Linear parametric analyses revealed that generative load modulated activity in bilateral IFG while relational load correlated with activity in left hippocampus. Although univariate analyses distinguished IFG and hippocampal contributions to the generative and relational stages of encoding, respectively, effective connectivity between these regions did not differ according to condition. Furthermore, this analysis revealed that the left IFG played a pivotal role in coordinating associative encoding processes. Our findings illustrate that modulation of components in a memory network can be independent of patterns of mutual connectivity among those components in mediating successful encoding.
在项目之间形成并绑定关联的能力是成功记忆形成的一个重要方面。我们假设，在编码过程中，左侧额下回（IFG）支持项目之间关联的生成，然后海马体将这些关联绑定起来。本研究考察了在成功编码（即对于随后被识别的项目）过程中，这些区域对不同数量的生成性和关联性加工的参数反应。编码涉及呈现词三元组，其中语义关联的数量各不相同（无、一个或全部）；参与者判断每个三元组中存在多少关联。因此，关联较少的三元组具有更高的生成负荷，而关联较多的三元组具有更高的关系负荷。参与者随后对编码的三元组完成了一个强制选择识别测试。相对于对照任务的成功编码导致双侧IFG和左侧海马体激活，并且海马体也表现出显著的后续记忆效应（命中>未命中）。线性参数分析显示，生成负荷调节双侧IFG的活动，而关系负荷与左侧海马体的活动相关。尽管单变量分析分别区分了IFG和海马体对编码的生成阶段和关系阶段的贡献，但这些区域之间的有效连接性并未因条件而异。此外，该分析表明左侧IFG在协调关联编码过程中起关键作用。我们的研究结果表明，在介导成功编码时，记忆网络中各成分的调节可以独立于这些成分之间的相互连接模式。
