Stark C E, Squire L R
Department of Psychiatry, University of California, San Diego, USA.
Hippocampus. 2000;10(3):329-37. doi: 10.1002/1098-1063(2000)10:3<329::AID-HIPO13>3.0.CO;2-Z.
The phenomenon of temporally graded retrograde amnesia (loss of information acquired before the onset of amnesia) suggests that the hippocampus, and possibly other medial temporal lobe (MTL) structures, have a time-limited role in memory. In three experiments, we made a first attempt to use fMRI to assess activity in the hippocampal region (the CA fields of the hippocampus, the dentate gyrus, and the subiculum) and the adjacent parahippocampal gyrus (parahippocampal, entorhinal, and perirhinal cortices) during recognition memory testing as a function of study-test interval. Experiment 1 (n = 5) demonstrated activity in the hippocampal region and parahippocampal gyrus for targets relative to foils during recognition memory performance following a single study-test delay of about one-half hour. In Experiment 2, 15 participants studied line drawings at each of three different times prior to scanning: one-half hour, 1 day, and 1 week. fMRI data were then collected during recognition memory testing, using targets from all three delays and foils. While an overall effect of targets vs. foils was found in both the hippocampal region and the parahippocampal gyrus, there was no effect of study-test interval on target activity. In Experiment 3 (n = 13), behavioral performance (reaction time and accuracy) was equated across the three delays. Again, no effect of study-test interval was observed. It is possible that the time span sampled in our study (one-half hour to 1 week) was too short to observe changes in activity. Alternatively, activity in the MTL during memory testing may occur even when these structures are not necessary for retrieval.
时间梯度逆行性遗忘（失忆症发作前获取的信息丧失）现象表明，海马体以及可能的其他内侧颞叶（MTL）结构在记忆中具有时间限制作用。在三项实验中，我们首次尝试使用功能磁共振成像（fMRI）来评估在识别记忆测试期间，海马体区域（海马体的CA区、齿状回和下托）以及相邻的海马旁回（海马旁、内嗅和嗅周皮质）的活动，该活动是学习 - 测试间隔的函数。实验1（n = 5）表明，在单次学习 - 测试延迟约半小时后的识别记忆表现中，相对于干扰项，海马体区域和海马旁回对目标有活动。在实验2中，15名参与者在扫描前的三个不同时间分别学习线条图：半小时、1天和1周。然后在识别记忆测试期间收集fMRI数据，使用来自所有三个延迟时间的目标和干扰项。虽然在海马体区域和海马旁回都发现了目标与干扰项的总体效应，但学习 - 测试间隔对目标活动没有影响。在实验3（n = 13）中，在三个延迟时间内使行为表现（反应时间和准确性）相等。同样，未观察到学习 - 测试间隔的影响。有可能我们研究中采样的时间跨度（半小时到1周）太短，无法观察到活动的变化。或者，即使这些结构对检索不是必需的，在记忆测试期间MTL中也可能发生活动。
