Krembil Neuroscience Centre, University Health Network, Fell Pavilion, Toronto, Ontario, Canada.
Proc Natl Acad Sci U S A. 2009 Dec 29;106(52):22451-5. doi: 10.1073/pnas.0908651106. Epub 2009 Dec 10.
We examined whether hippocampal activity in recognition relates to the strength of the memory or to recollective experience, a subject of considerable current debate. Participants studied word pairs and then made two successive recognition decisions on each item: first on the uncued target and then on the target presented with the studied cue word. We compared recollection and familiarity patterns of activation in fMRI for these decisions. Critically, our analyses attempted in two ways to equate perceived memory strength while varying the associative information available. First, activity for targets judged familiar before cueing was contrasted with activity for the same items in the second decision as a function of whether the targets converted to recollection or remained familiar when the context cues were provided. We found increased hippocampal activity following cueing only with recollective conversion. Second, we investigated whether hippocampal activity was modulated by the rated familiarity strength of cued items or whether it increased uniquely in recollection. Hippocampal activation was not modulated parametrically by familiarity strength and recollected items were associated with greater activity relative to highly familiar items. Together, our results support the notion that it is recollection of context, rather than memory strength, that underlies hippocampal engagement at retrieval.
我们研究了海马体在识别过程中的活动与记忆强度的关系，或者与回忆体验的关系，这是当前一个相当有争议的话题。参与者学习了单词对，然后对每个项目进行了两次连续的识别决策：第一次是在无提示的目标上，然后是在提示词出现的目标上。我们在 fMRI 中比较了这些决策的回忆和熟悉模式的激活。至关重要的是，我们的分析试图通过两种方式来平衡感知的记忆强度，同时改变可用的联想信息。首先，将提示前判断为熟悉的目标的活动与第二个决策中相同项目的活动进行对比，这取决于目标在提供上下文提示时是转换为回忆还是保持熟悉。我们发现，只有在回忆转换时，提示后才会增加海马体的活动。其次，我们研究了海马体的活动是否受到提示项目的熟悉程度强度的调节，或者它是否仅在回忆中增加。海马体的激活不能通过熟悉程度强度来进行参数调节，并且与高度熟悉的项目相比，回忆的项目与更大的活动相关。总的来说，我们的结果支持这样的观点，即正是背景的回忆，而不是记忆强度，是在检索时引起海马体参与的原因。
